stars viii orbits: Topics by WorldWideScience.org

Sample records for stars viii orbits

Orbiting radiation stars

International Nuclear Information System (INIS)

Foster, Dean P; Langford, John; Perez-Giz, Gabe

2016-01-01

We study a spherically symmetric solution to the Einstein equations in which the source, which we call an orbiting radiation star (OR-star), is a compact object consisting of freely falling null particles. The solution avoids quantum scale regimes and hence neither relies upon nor ignores the interaction of quantum mechanics and gravitation. The OR-star spacetime exhibits a deep gravitational well yet remains singularity free. In fact, it is geometrically flat in the vicinity of the origin, with the flat region being of any desirable scale. The solution is observationally distinct from a black hole because a photon from infinity aimed at an OR-star escapes to infinity with a time delay. (paper)
Local stellar kinematics from RAVE data—VIII. Effects of the Galactic disc perturbations on stellar orbits of red clump stars

Science.gov (United States)

Önal Taş, Ö.; Bilir, S.; Plevne, O.

2018-02-01

We aim to probe the dynamic structure of the extended Solar neighborhood by calculating the radial metallicity gradients from orbit properties, which are obtained for axisymmetric and non-axisymmetric potential models, of red clump (RC) stars selected from the RAdial Velocity Experiment's Fourth Data Release. Distances are obtained by assuming a single absolute magnitude value in near-infrared, i.e. M_{Ks}=-1.54±0.04 mag, for each RC star. Stellar orbit parameters are calculated by using the potential functions: (i) for the MWPotential2014 potential, (ii) for the same potential with perturbation functions of the Galactic bar and transient spiral arms. The stellar age is calculated with a method based on Bayesian statistics. The radial metallicity gradients are evaluated based on the maximum vertical distance (z_{max}) from the Galactic plane and the planar eccentricity (ep) of RC stars for both of the potential models. The largest radial metallicity gradient in the 01 kpc, the radial metallicity gradients have zero or positive values and they do not depend on ep subsamples. There is a large radial metallicity gradient for thin disc, but no radial gradient found for thick disc. Moreover, the largest radial metallicity gradients are obtained where the outer Lindblad resonance region is effective. We claim that this apparent change in radial metallicity gradients in the thin disc is a result of orbital perturbation originating from the existing resonance regions.
The Double Star Orbit Initial Value Problem

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Hensley, Hagan

2018-04-01

Many precise algorithms exist to find a best-fit orbital solution for a double star system given a good enough initial value. Desmos is an online graphing calculator tool with extensive capabilities to support animations and defining functions. It can provide a useful visual means of analyzing double star data to arrive at a best guess approximation of the orbital solution. This is a necessary requirement before using a gradient-descent algorithm to find the best-fit orbital solution for a binary system.
Three Temperate Neptunes Orbiting Nearby Stars

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Fulton, Benjamin J.; Howard, Andrew W.; Weiss, Lauren M.; Sinukoff, Evan; Petigura, Erik A.; Isaacson, Howard; Hirsch, Lea; Marcy, Geoffrey W.; Henry, Gregory W.; Grunblatt, Samuel K.; Huber, Daniel; von Braun, Kaspar; Boyajian, Tabetha S.; Kane, Stephen R.; Wittrock, Justin; Horch, Elliott P.; Ciardi, David R.; Howell, Steve B.; Wright, Jason T.; Ford, Eric B.

2016-10-01

We present the discovery of three modestly irradiated, roughly Neptune-mass planets orbiting three nearby Solar-type stars. HD 42618 b has a minimum mass of 15.4 ± 2.4 {M}\\oplus , a semimajor axis of 0.55 au, an equilibrium temperature of 337 K, and is the first planet discovered to orbit the solar analogue host star, HD 42618. We also discover new planets orbiting the known exoplanet host stars HD 164922 and HD 143761 (ρ CrB). The new planet orbiting HD 164922 has a minimum mass of 12.9 ± 1.6 {M}\\oplus and orbits interior to the previously known Jovian mass planet orbiting at 2.1 au. HD 164922 c has a semimajor axis of 0.34 au and an equilibrium temperature of 418 K. HD 143761 c orbits with a semimajor axis of 0.44 au, has a minimum mass of 25 ± 2 {M}\\oplus , and is the warmest of the three new planets with an equilibrium temperature of 445 K. It orbits exterior to the previously known warm Jupiter in the system. A transit search using space-based CoRoT data and ground-based photometry from the Automated Photometric Telescopes (APTs) at Fairborn Observatory failed to detect any transits, but the precise, high-cadence APT photometry helped to disentangle planetary-reflex motion from stellar activity. These planets were discovered as part of an ongoing radial velocity survey of bright, nearby, chromospherically inactive stars using the Automated Planet Finder (APF) telescope at Lick Observatory. The high-cadence APF data combined with nearly two decades of radial velocity data from Keck Observatory and gives unprecedented sensitivity to both short-period low-mass, and long-period intermediate-mass planets. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time was granted for this project by the University of Hawai‘I, the University of California, and NASA.
STABLE CONIC-HELICAL ORBITS OF PLANETS AROUND BINARY STARS: ANALYTICAL RESULTS

Energy Technology Data Exchange (ETDEWEB)

Oks, E. [Physics Department, 206 Allison Lab., Auburn University, Auburn, AL 36849 (United States)

2015-05-10

Studies of planets in binary star systems are especially important because it was estimated that about half of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges. One-planet binary star systems (OBSS) have a limited analogy to objects studied in atomic/molecular physics: one-electron Rydberg quasimolecules (ORQ). Specifically, ORQ, consisting of two fully stripped ions of the nuclear charges Z and Z′ plus one highly excited electron, are encountered in various plasmas containing more than one kind of ion. Classical analytical studies of ORQ resulted in the discovery of classical stable electronic orbits with the shape of a helix on the surface of a cone. In the present paper we show that despite several important distinctions between OBSS and ORQ, it is possible for OBSS to have stable planetary orbits in the shape of a helix on a conical surface, whose axis of symmetry coincides with the interstellar axis; the stability is not affected by the rotation of the stars. Further, we demonstrate that the eccentricity of the stars’ orbits does not affect the stability of the helical planetary motion if the center of symmetry of the helix is relatively close to the star of the larger mass. We also show that if the center of symmetry of the conic-helical planetary orbit is relatively close to the star of the smaller mass, a sufficiently large eccentricity of stars’ orbits can switch the planetary motion to the unstable mode and the planet would escape the system. We demonstrate that such planets are transitable for the overwhelming majority of inclinations of plane of the stars’ orbits (i.e., the projections of the planet and the adjacent start on the plane of the sky coincide once in a while). This means that conic-helical planetary orbits at binary stars can be detected photometrically. We consider, as an example, Kepler-16 binary stars to provide illustrative numerical data on the possible parameters and the
Neutron stars with orbiting light

International Nuclear Information System (INIS)

Lukacs, B.

1987-11-01

There is a wide-spread belief in the literature of relativistic astrophysics concerning nonsingular final states of the stellar evolution: the external gravitational field of a physically nonsingular central symmetric body (e.g. a neutron star) is asymptotically empty and simple, i.e. there are no closed or trapped light-like causal geodesics. Present paper shows that this belief is false: some examples are presented for nonsingular bodies with various equations of state, around which there are closed light-like trajectories: 'orbiting light'. The reality of the used equations of state is discussed in detail. Present state of particle physics does not establish the existence of matter with such equations of state, but the hypothetical subquark level of matter may have such equation of state, thus 'subquark-stars' may exist with orbiting light around them. So the criterion of 'nonsingularity' must be further analyzed and accurately defined. (D.Gy.) 24 refs.; 5 figs
The Orbit of X Persei and Its Neutron Star Companion

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Delgado-Martí, Hugo; Levine, Alan M.; Pfahl, Eric; Rappaport, Saul A.

2001-01-01

We have observed the Be/X-ray pulsar binary system X Per/4U 0352+30 on 61 occasions spanning an interval of 600 days with the PCA instrument on board the Rossi X-Ray Timing Explorer (RXTE). Pulse timing analyses of the 837 s pulsations yield strong evidence for the presence of orbital Doppler delays. We confirm the Doppler delays by using measurements made with the All Sky Monitor (ASM) on RXTE. We infer that the orbit is characterized by a period Porb=250 days, a projected semimajor axis of the neutron star axsini=454 lt-s, a mass function f(M)=1.61 Msolar, and a modest eccentricity e=0.11. The measured orbital parameters, together with the known properties of the classical Be star X Per, imply a semimajor axis a=1.8-2.2 AU and an orbital inclination i~26deg-33deg. We discuss the formation of the system in the context of the standard evolutionary scenario for Be/X-ray binaries. We find that the system most likely formed from a pair of massive progenitor stars and probably involved a quasi-stable and nearly conservative transfer of mass from the primary to the secondary. We find that the He star remnant of the primary most likely had a mass probability of a system like that of X Per forming with an orbital eccentricity e<~0.11. We speculate that there may be a substantial population of neutron stars formed with little or no kick. Finally, we discuss the connected topics of the wide orbit and accretion by the neutron star from a stellar wind.
A planet in a polar orbit of 1.4 solar-mass star

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Guenther E.W.

2015-01-01

Full Text Available Although more than a thousand transiting extrasolar planets have been discovered, only very few of them orbit stars that are more massive than the Sun. The discovery of such planets is interesting, because they have formed in disks that are more massive but had a shorter life time than those of solar-like stars. Studies of planets more massive than the Sun thus tell us how the properties of the proto-planetary disks effect the formation of planets. Another aspect that makes these planets interesting is that they have kept their original orbital inclinations. By studying them we can thus find out whether the orbital axes planets are initially aligned to the stars rotational axes, or not. Here we report on the discovery of a planet of a 1.4 solar-mass star with a period of 5.6 days in a polar orbit made by CoRoT. This new planet thus is one of the few known close-in planets orbiting a star that is substantially more massive than the Sun.
A Spectroscopic Orbit for the Late-type Be Star β CMi

Energy Technology Data Exchange (ETDEWEB)

Dulaney, Nicholas A.; Richardson, Noel D.; Gerhartz, Cody J.; Bjorkman, J. E.; Bjorkman, K. S.; Morrison, Nancy D.; Bratcher, Allison D.; Greco, Jennifer J.; Hardegree-Ullman, Kevin K.; Lembryk, Ludwik; Oswald, Wayne L.; Trucks, Jesica L. [Ritter Observatory, Department of Physics and Astronomy, The University of Toledo, Toledo, OH 43606-3390 (United States); Carciofi, Alex C. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, SP 05508-900 (Brazil); Klement, Robert [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago (Chile); Wang, Luqian, E-mail: noel.richardson@UToledo.edu [Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, P.O. Box 5060, Atlanta, GA 30302-5060 (United States)

2017-02-10

The late-type Be star β CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. These results showed that the disk is likely truncated at a finite radius from the star, which Klement et al. suggest is evidence for an unseen binary companion in orbit. Here we report on an analysis of the Ritter Observatory spectroscopic archive of β CMi to search for evidence of the elusive companion. We detect periodic Doppler shifts in the wings of the H α line with a period of 170 days and an amplitude of 2.25 km s{sup −1}, consistent with a low-mass binary companion ( M ≈ 0.42 M {sub ⊙}). We then compared small changes in the violet-to-red peak height changes ( V / R ) with the orbital motion. We find weak evidence that it does follow the orbital motion, as suggested by recent Be binary models by Panoglou et al. Our results, which are similar to those for several other Be stars, suggest that β CMi may be a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no direct sign of this companion star is found in the very limited archive of International Ultraviolet Explorer spectra.
Properties of general relativistic irrotational binary neutron stars at the innermost orbit

International Nuclear Information System (INIS)

Uryu, K.; Shibata, M.

2001-01-01

We investigate properties of binary neutron stars around innermost orbits, assuming that the binary is equal mass and in quasiequilibrium. The quasiequilibrium configurations are numerically computed assuming the existence of a helicoidal Killing vector, conformal flatness for spatial components of the metric, and irrotational velocity field for the neutron stars. The computation is performed for the polytropic equation of state with a wide range of the polytropic index n (= 0.5, 0.66667, 0.8, 1, 1.25), and compactness of neutron stars (M/R) ∞ (= 0.03-0.3). Quasiequilibrium sequences of constant rest mass are appropriate models for the final evolution phase of binary neutron stars. It is found that these sequences are always terminated at the innermost orbit where a cusp (inner Lagrange point) appears at the inner edges of the stellar surface. We apply a turning point method to determine the stability of the innermost orbits and found that the innermost stable circular orbit (ISCO) exists for stiff equations of state (n = 0.5 with any (M/R) ∞ and n = 0.66667 with (M/R) ∞ > or ∼ 0.17). The ISCO for n = 0.5 is carefully analyzed. It is clarified that the ISCO are mainly determined by a hydrodynamic instability for realistic compactness of the neutron stars as 0.14 ∞ < or ∼ 0.2. These configurations at the innermost orbits can be used as initial conditions for fully general relativistic simulation for the binary neutron star merger. (author)
Exterior Companions to Hot Jupiters Orbiting Cool Stars Are Coplanar

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Becker, Juliette C.; Vanderburg, Andrew; Adams, Fred C.; Khain, Tali; Bryan, Marta

2017-12-01

The existence of hot Jupiters has challenged theories of planetary formation since the first extrasolar planets were detected. Giant planets are generally believed to form far from their host stars, where volatile materials like water exist in their solid phase, making it easier for giant planet cores to accumulate. Several mechanisms have been proposed to explain how giant planets can migrate inward from their birth sites to short-period orbits. One such mechanism, called Kozai-Lidov migration, requires the presence of distant companions in orbits inclined by more than ˜40° with respect to the plane of the hot Jupiter’s orbit. The high occurrence rate of wide companions in hot-Jupiter systems lends support to this theory for migration. However, the exact orbital inclinations of these detected planetary and stellar companions is not known, so it is not clear whether the mutual inclination of these companions is large enough for the Kozai-Lidov process to operate. This paper shows that in systems orbiting cool stars with convective outer layers, the orbits of most wide planetary companions to hot Jupiters must be well aligned with the orbits of the hot Jupiters and the spins of the host stars. For a variety of possible distributions for the inclination of the companion, the width of the distribution must be less than ˜20° to recreate the observations with good fidelity. As a result, the companion orbits are likely well aligned with those of the hot Jupiters, and the Kozai-Lidov mechanism does not enforce migration in these systems.
On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

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Fleming, David P.; Barnes, Rory; Graham, David E.; Luger, Rodrigo; Quinn, Thomas R.

2018-05-01

We outline a mechanism that explains the observed lack of circumbinary planets (CBPs) via coupled stellar–tidal evolution of isolated binary stars. Tidal forces between low-mass, short-period binary stars on the pre-main sequence slow the stellar rotations transferring rotational angular momentum to the orbit as the stars approach the tidally locked state. This transfer increases the binary orbital period, expanding the region of dynamical instability around the binary, and destabilizing CBPs that tend to preferentially orbit just beyond the initial dynamical stability limit. After the stars tidally lock, we find that angular momentum loss due to magnetic braking can significantly shrink the binary orbit, and hence the region of dynamical stability, over time, impacting where surviving CBPs are observed relative to the boundary. We perform simulations over a wide range of parameter space and find that the expansion of the instability region occurs for most plausible initial conditions and that, in some cases, the stability semimajor axis doubles from its initial value. We examine the dynamical and observable consequences of a CBP falling within the dynamical instability limit by running N-body simulations of circumbinary planetary systems and find that, typically, at least one planet is ejected from the system. We apply our theory to the shortest-period Kepler binary that possesses a CBP, Kepler-47, and find that its existence is consistent with our model. Under conservative assumptions, we find that coupled stellar–tidal evolution of pre-main sequence binary stars removes at least one close-in CBP in 87% of multi-planet circumbinary systems.
Prevalence of Earth-size planets orbiting Sun-like stars.

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Petigura, Erik A; Howard, Andrew W; Marcy, Geoffrey W

2013-11-26

Determining whether Earth-like planets are common or rare looms as a touchstone in the question of life in the universe. We searched for Earth-size planets that cross in front of their host stars by examining the brightness measurements of 42,000 stars from National Aeronautics and Space Administration's Kepler mission. We found 603 planets, including 10 that are Earth size ( ) and receive comparable levels of stellar energy to that of Earth (1 - 2 R[Symbol: see text] ). We account for Kepler's imperfect detectability of such planets by injecting synthetic planet-caused dimmings into the Kepler brightness measurements and recording the fraction detected. We find that 11 ± 4% of Sun-like stars harbor an Earth-size planet receiving between one and four times the stellar intensity as Earth. We also find that the occurrence of Earth-size planets is constant with increasing orbital period (P), within equal intervals of logP up to ~200 d. Extrapolating, one finds 5.7(-2.2)(+1.7)% of Sun-like stars harbor an Earth-size planet with orbital periods of 200-400 d.
The BANANA Survey: Spin-Orbit Alignment in Binary Stars

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Albrecht, Simon; Winn, J. N.; Fabrycky, D. C.; Torres, G.; Setiawan, J.

2012-04-01

Binaries are not always neatly aligned. Previous observations of the DI Herculis system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here, we report on our ongoing survey to measure relative orientations of spin-axes in a number of eclipsing binary systems. These observations will hopefully lead to new insights into star and planet formation, as different formation scenarios predict different degrees of alignment and different dependencies on the system parameters. Measurements of spin-orbit angles in close binary systems will also create a basis for comparison for similar measurements involving close-in planets.
Thermal-orbital coupled tidal heating and habitability of Martian-sized extrasolar planets around M stars

International Nuclear Information System (INIS)

Shoji, D.; Kurita, K.

2014-01-01

M-type stars are good targets in the search for habitable extrasolar planets. Due to their low effective temperatures, the habitable zone of M stars is very close to the stars themselves. For planets that are close to their stars, tidal heating plays an important role in thermal and orbital evolutions, especially when the planet's orbit has a relatively large eccentricity. Although tidal heating interacts with the thermal state and the orbit of the planet, such coupled calculations for extrasolar planets around M stars have not been conducted. We perform coupled calculations using simple structural and orbital models and analyze the thermal state and habitability of a terrestrial planet. Considering this planet to be Martian-sized, the tide heats up and partially melts the mantle, maintaining an equilibrium state if the mass of the star is less than 0.2 times the mass of the Sun and the initial eccentricity of the orbit is more than 0.2. The reduction of heat dissipation due to the melted mantle allows the planet to stay in the habitable zone for more than 10 Gyr even though the orbital distance is small. The surface heat flux at the equilibrium state is between that of Mars and Io. The thermal state of the planet mainly depends on the initial value of the eccentricity and the mass of the star.
Thermal-orbital coupled tidal heating and habitability of Martian-sized extrasolar planets around M stars

Energy Technology Data Exchange (ETDEWEB)

Shoji, D.; Kurita, K. [Earthquake Research Institute, University of Tokyo, Tokyo (Japan)

2014-07-01

M-type stars are good targets in the search for habitable extrasolar planets. Due to their low effective temperatures, the habitable zone of M stars is very close to the stars themselves. For planets that are close to their stars, tidal heating plays an important role in thermal and orbital evolutions, especially when the planet's orbit has a relatively large eccentricity. Although tidal heating interacts with the thermal state and the orbit of the planet, such coupled calculations for extrasolar planets around M stars have not been conducted. We perform coupled calculations using simple structural and orbital models and analyze the thermal state and habitability of a terrestrial planet. Considering this planet to be Martian-sized, the tide heats up and partially melts the mantle, maintaining an equilibrium state if the mass of the star is less than 0.2 times the mass of the Sun and the initial eccentricity of the orbit is more than 0.2. The reduction of heat dissipation due to the melted mantle allows the planet to stay in the habitable zone for more than 10 Gyr even though the orbital distance is small. The surface heat flux at the equilibrium state is between that of Mars and Io. The thermal state of the planet mainly depends on the initial value of the eccentricity and the mass of the star.
Orbital Decay in Binaries with Evolved Stars

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Sun, Meng; Arras, Phil; Weinberg, Nevin N.; Troup, Nicholas; Majewski, Steven R.

2018-01-01

Two mechanisms are often invoked to explain tidal friction in binary systems. The ``dynamical tide” is the resonant excitation of internal gravity waves by the tide, and their subsequent damping by nonlinear fluid processes or thermal diffusion. The ``equilibrium tide” refers to non-resonant excitation of fluid motion in the star’s convection zone, with damping by interaction with the turbulent eddies. There have been numerous studies of these processes in main sequence stars, but less so on the subgiant and red giant branches. Motivated by the newly discovered close binary systems in the Apache Point Observatory Galactic Evolution Experiment (APOGEE-1), we have performed calculations of both the dynamical and equilibrium tide processes for stars over a range of mass as the star’s cease core hydrogen burning and evolve to shell burning. Even for stars which had a radiative core on the main sequence, the dynamical tide may have very large amplitude in the newly radiative core in post-main sequence, giving rise to wave breaking. The resulting large dynamical tide dissipation rate is compared to the equilibrium tide, and the range of secondary masses and orbital periods over which rapid orbital decay may occur will be discussed, as well as applications to close APOGEE binaries.
A hot Saturn on an eccentric orbit around the giant star K2-132

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Jones, M. I.; Brahm, R.; Espinoza, N.; Jordán, A.; Rojas, F.; Rabus, M.; Drass, H.; Zapata, A.; Soto, M. G.; Jenkins, J. S.; Vučković, M.; Ciceri, S.; Sarkis, P.

2018-06-01

Although the majority of radial velocity detected planets have been found orbiting solar-type stars, a fraction of them have been discovered around giant stars. These planetary systems have revealed different orbital properties when compared to solar-type star companions. In particular, radial velocity surveys have shown that there is a lack of giant planets in close-in orbits around giant stars, in contrast to the known population of hot Jupiters orbiting solar-type stars. It has been theorized that the reason for this distinctive feature in the semimajor axis distribution is the result of the stellar evolution and/or that it is due to the effect of a different formation/evolution scenario for planets around intermediate-mass stars. However, in the past few years a handful of transiting short-period planets (P ≲ 10 days) have been found around giant stars, thanks to the high-precision photometric data obtained initially by the Kepler mission, and later by its two-wheel extension K2. These new discoveries have allowed us for the first time to study the orbital properties and physical parameters of these intriguing and elusive substellar companions. In this paper we report on an independent discovery of a transiting planet in field 10 of the K2 mission, also reported recently by Grunblatt et al. (2017, AJ, 154, 254). The host star has recently evolved to the giant phase, and has the following atmospheric parameters: Teff = 4878 ± 70 K, log g = 3.289 ± 0.004, and [Fe/H] = -0.11 ± 0.05 dex. The main orbital parameters of K2-132 b, obtained with all the available data for the system are: P = 9.1708 ± 0.0025 d, e = 0.290 ± 0.049, Mp = 0.495 ± 0.007 MJ and Rp = 1.089 ± 0.006 RJ. This is the fifth known planet orbiting any giant star with a K2-132 b a very interesting object. Tables of the photometry and of the radial velocities are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http
Compact invariant sets of the Bianchi VIII and Bianchi IX Hamiltonian systems

International Nuclear Information System (INIS)

Starkov, Konstantin E.

2011-01-01

In this Letter we prove that all compact invariant sets of the Bianchi VIII Hamiltonian system are contained in the set described by several simple linear equalities and inequalities. Moreover, we describe invariant domains in which the phase flow of this system has no recurrence property and show that there are no periodic orbits and neither homoclinic, nor heteroclinic orbits contained in the zero level set of its Hamiltonian. Similar results are obtained for the Bianchi IX Hamiltonian system. -- Highlights: → Zero level set of Hamiltonian of Bianchi VIII/IX systems contains no periodic orbits. → Similar conditions for homoclinic/heteroclinic orbits are given. → General nonexistence conditions of compact invariant sets are got.
Compact invariant sets of the Bianchi VIII and Bianchi IX Hamiltonian systems

Energy Technology Data Exchange (ETDEWEB)

Starkov, Konstantin E., E-mail: konst@citedi.mx [CITEDI-IPN, Av. del Parque 1310, Mesa de Otay, Tijuana, BC (Mexico)

2011-08-22

In this Letter we prove that all compact invariant sets of the Bianchi VIII Hamiltonian system are contained in the set described by several simple linear equalities and inequalities. Moreover, we describe invariant domains in which the phase flow of this system has no recurrence property and show that there are no periodic orbits and neither homoclinic, nor heteroclinic orbits contained in the zero level set of its Hamiltonian. Similar results are obtained for the Bianchi IX Hamiltonian system. -- Highlights: → Zero level set of Hamiltonian of Bianchi VIII/IX systems contains no periodic orbits. → Similar conditions for homoclinic/heteroclinic orbits are given. → General nonexistence conditions of compact invariant sets are got.

The shortest-known-period star orbiting our Galaxy's supermassive black hole.

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Meyer, L; Ghez, A M; Schödel, R; Yelda, S; Boehle, A; Lu, J R; Do, T; Morris, M R; Becklin, E E; Matthews, K

2012-10-05

Stars with short orbital periods at the center of our Galaxy offer a powerful probe of a supermassive black hole. Over the past 17 years, the W. M. Keck Observatory has been used to image the galactic center at the highest angular resolution possible today. By adding to this data set and advancing methodologies, we have detected S0-102, a star orbiting our Galaxy's supermassive black hole with a period of just 11.5 years. S0-102 doubles the number of known stars with full phase coverage and periods of less than 20 years. It thereby provides the opportunity, with future measurements, to resolve degeneracies in the parameters describing the central gravitational potential and to test Einstein's theory of general relativity in an unexplored regime.
The habitability of planets orbiting M-dwarf stars

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Shields, Aomawa L.; Ballard, Sarah; Johnson, John Asher

2016-12-01

The prospects for the habitability of M-dwarf planets have long been debated, due to key differences between the unique stellar and planetary environments around these low-mass stars, as compared to hotter, more luminous Sun-like stars. Over the past decade, significant progress has been made by both space- and ground-based observatories to measure the likelihood of small planets to orbit in the habitable zones of M-dwarf stars. We now know that most M dwarfs are hosts to closely-packed planetary systems characterized by a paucity of Jupiter-mass planets and the presence of multiple rocky planets, with roughly a third of these rocky M-dwarf planets orbiting within the habitable zone, where they have the potential to support liquid water on their surfaces. Theoretical studies have also quantified the effect on climate and habitability of the interaction between the spectral energy distribution of M-dwarf stars and the atmospheres and surfaces of their planets. These and other recent results fill in knowledge gaps that existed at the time of the previous overview papers published nearly a decade ago by Tarter et al. (2007) and Scalo et al. (2007). In this review we provide a comprehensive picture of the current knowledge of M-dwarf planet occurrence and habitability based on work done in this area over the past decade, and summarize future directions planned in this quickly evolving field.
Tidal Heating of Earth-like Exoplanets around M Stars: Thermal, Magnetic, and Orbital Evolutions.

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Driscoll, P E; Barnes, R

2015-09-01

The internal thermal and magnetic evolution of rocky exoplanets is critical to their habitability. We focus on the thermal-orbital evolution of Earth-mass planets around low-mass M stars whose radiative habitable zone overlaps with the "tidal zone," where tidal dissipation is expected to be a significant heat source in the interior. We develop a thermal-orbital evolution model calibrated to Earth that couples tidal dissipation, with a temperature-dependent Maxwell rheology, to orbital circularization and migration. We illustrate thermal-orbital steady states where surface heat flow is balanced by tidal dissipation and cooling can be stalled for billions of years until circularization occurs. Orbital energy dissipated as tidal heat in the interior drives both inward migration and circularization, with a circularization time that is inversely proportional to the dissipation rate. We identify a peak in the internal dissipation rate as the mantle passes through a viscoelastic state at mantle temperatures near 1800 K. Planets orbiting a 0.1 solar-mass star within 0.07 AU circularize before 10 Gyr, independent of initial eccentricity. Once circular, these planets cool monotonically and maintain dynamos similar to that of Earth. Planets forced into eccentric orbits can experience a super-cooling of the core and rapid core solidification, inhibiting dynamo action for planets in the habitable zone. We find that tidal heating is insignificant in the habitable zone around 0.45 (or larger) solar-mass stars because tidal dissipation is a stronger function of orbital distance than stellar mass, and the habitable zone is farther from larger stars. Suppression of the planetary magnetic field exposes the atmosphere to stellar wind erosion and the surface to harmful radiation. In addition to weak magnetic fields, massive melt eruption rates and prolonged magma oceans may render eccentric planets in the habitable zone of low-mass stars inhospitable for life.
Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star

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Bourrier, Vincent; Lovis, Christophe; Beust, Hervé; Ehrenreich, David; Henry, Gregory W.; Astudillo-Defru, Nicola; Allart, Romain; Bonfils, Xavier; Ségransan, Damien; Delfosse, Xavier; Cegla, Heather M.; Wyttenbach, Aurélien; Heng, Kevin; Lavie, Baptiste; Pepe, Francesco

2018-01-01

The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin–orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere.
A comparison between star products on regular orbits of compact Lie groups

International Nuclear Information System (INIS)

Fioresi, R.; Lledo, M.A.

2002-01-01

In this paper, an algebraic and a differential star product defined on a regular coadjoint orbit of a compact semisimple group are compared. It has been proved that there is an injective algebra homomorphism between the algebra of polynomials with the algebraic star product and the algebra of differential functions with the differential star product structure. (author)
Tidal generation of gravitational waves from orbiting Newtonian stars. I. General formalism

International Nuclear Information System (INIS)

Turner, M.

1977-01-01

A linearized formalism is presented for the calculation of the tidally produced gravitational radiation potential h/sup TT/ from binary systems with arbitrary orbits. The stars are Newtonian, isentropic, and nonrotating. Normal-mode analysis is used to calculate the tidally generated internal motions; the resulting radiation potential h/sup TT/ and its Fourier decomposition are calculated in the Newtonian limit of the multipole formalism. The tidal radiation potential is weaker than that produced by the orbital motion by a factor of order [(stellar radius)/(periastron distance)] 5 . If we assume that the time scale of the tidal perturbation is always much less than the damping time of the star, then if in addition the damping time is much less than the time between periastron passages, the radiation spectrum consists of the l=2 eigenfrequencies of the star near the fundamental l=2 eigenfrequency; if the reverse is true (damping time >> time between periastrons), the spectrum is similar to the orbital gravitational radiation specturm
Advanced Exoplanet Star Tracker for Orbit Self Determination, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal puts forth an innovative star tracker hardware sensor that allows for autonomous calculation of a spacecraft's orbit by employing Doppler Spectroscopy...
On-Orbit Solar Dynamics Observatory (SDO) Star Tracker Warm Pixel Analysis

Science.gov (United States)

Felikson, Denis; Ekinci, Matthew; Hashmall, Joseph A.; Vess, Melissa

2011-01-01

This paper describes the process of identification and analysis of warm pixels in two autonomous star trackers on the Solar Dynamics Observatory (SDO) mission. A brief description of the mission orbit and attitude regimes is discussed and pertinent star tracker hardware specifications are given. Warm pixels are defined and the Quality Index parameter is introduced, which can be explained qualitatively as a manifestation of a possible warm pixel event. A description of the algorithm used to identify warm pixel candidates is given. Finally, analysis of dumps of on-orbit star tracker charge coupled devices (CCD) images is presented and an operational plan going forward is discussed. SDO, launched on February 11, 2010, is operated from the NASA Goddard Space Flight Center (GSFC). SDO is in a geosynchronous orbit with a 28.5 inclination. The nominal mission attitude points the spacecraft X-axis at the Sun, with the spacecraft Z-axis roughly aligned with the Solar North Pole. The spacecraft Y-axis completes the triad. In attitude, SDO moves approximately 0.04 per hour, mostly about the spacecraft Z-axis. The SDO star trackers, manufactured by Galileo Avionica, project the images of stars in their 16.4deg x 16.4deg fields-of-view onto CCD detectors consisting of 512 x 512 pixels. The trackers autonomously identify the star patterns and provide an attitude estimate. Each unit is able to track up to 9 stars. Additionally, each tracker calculates a parameter called the Quality Index, which is a measure of the quality of the attitude solution. Each pixel in the CCD measures the intensity of light and a warns pixel is defined as having a measurement consistently and significantly higher than the mean background intensity level. A warns pixel should also have lower intensity than a pixel containing a star image and will not move across the field of view as the attitude changes (as would a dim star image). It should be noted that the maximum error introduced in the star tracker
Excitation of neutron star oscillations by an orbiting mass

International Nuclear Information System (INIS)

Ruoff, J.

2001-01-01

In this contribution, I present results from a numerical study of the even-parity gravitational radiation generated from a particle orbiting a neutron star. The investigation is focused on those conditions on the orbital parameters that favor the excitation of w-modes. It is found that, for astrophysically realistic conditions, there is practically no w-mode contribution to the emitted radiation. Only for particles with ultra-relativistic orbital speeds ≥ 0.9c, the w-mode does significantly contribute to the total emitted gravitational energy. To obtain reliable results, a way is presented to construct consistent initial data which contain as little as possible initial radiation. (author)
Jupiter Analogs Orbit Stars with an Average Metallicity Close to That of the Sun

DEFF Research Database (Denmark)

Buchhave, Lars A.; Bitsch, Bertram; Johansen, Anders

2018-01-01

Jupiter played an important role in determining the structure and configuration of the Solar System. Whereas hot-Jupiter type exoplanets preferentially form around metal-rich stars, the conditions required for the formation of planets with masses, orbits, and eccentricities comparable to Jupiter...... (Jupiter analogs) are unknown. Using spectroscopic metallicities, we show that stars hosting Jupiter analogs have an average metallicity close to solar, in contrast to their hot-Jupiter and eccentric cool-Jupiter counterparts, which orbit stars with super-solar metallicities. Furthermore......, the eccentricities of Jupiter analogs increase with host-star metallicity, suggesting that planet-planet scatterings producing highly eccentric cool Jupiters could be more common in metal-rich environments. To investigate a possible explanation for these metallicity trends, we compare the observations to numerical...
Chromospherically active stars. VIII - HD 155638 = V792 Herculis: Observational constraints on evolutionary theory

International Nuclear Information System (INIS)

Fekel, F.C.

1991-01-01

V792 Her is an eclipsing RS CVn binary with an orbital period of 27.54 days whose components have spectral types of K0 III and F2 IV. New spectroscopic observations combined with existing photometry have resulted in masses of 1.47 + or - 0.003 solar mass and 1.41 + or - 0.003 solar mass for the K giant and F star, respectively. Additional fundamental parameters are derived. Standard evolutionary models were specifically computed by VandenBerg (1990) for the two stars. The best fit occurs if the components are somewhat metal poor with Fe/H/ = - 0.46. Ages of about 2.3 x 10 to the 9th yr derived for the two components differ by less than 3 percent. Thus, standard evolutionary models with no convective overshoot are able to fit the observed parameters of stars as massive as 1.45 solar mass. However, a definitive comparison is not yet possible since the metal abundance of the stars is unknown and metal-poor convective-overshoot tracks in this mass range are needed. 35 refs
UV SURFACE ENVIRONMENT OF EARTH-LIKE PLANETS ORBITING FGKM STARS THROUGH GEOLOGICAL EVOLUTION

Energy Technology Data Exchange (ETDEWEB)

Rugheimer, S.; Sasselov, D. [Harvard Smithsonian Center for Astrophysics, 60 Garden st., 02138 MA Cambridge (United States); Segura, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México (Mexico); Kaltenegger, L., E-mail: srugheimer@cfa.harvard.edu [Carl Sagan Institute, Cornell University, Ithaca, NY 14853 (United States)

2015-06-10

The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early-Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present-day levels at 2.0 Gyr ago, 0.8 Gyr ago, and modern Earth. In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth–Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5 V) receives 300 times less biologically effective radiation, about 2 times modern Earth–Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments.
UV SURFACE ENVIRONMENT OF EARTH-LIKE PLANETS ORBITING FGKM STARS THROUGH GEOLOGICAL EVOLUTION

International Nuclear Information System (INIS)

Rugheimer, S.; Sasselov, D.; Segura, A.; Kaltenegger, L.

2015-01-01

The UV environment of a host star affects the photochemistry in the atmosphere, and ultimately the surface UV environment for terrestrial planets and therefore the conditions for the origin and evolution of life. We model the surface UV radiation environment for Earth-sized planets orbiting FGKM stars in the circumstellar Habitable Zone for Earth through its geological evolution. We explore four different types of atmospheres corresponding to an early-Earth atmosphere at 3.9 Gyr ago and three atmospheres covering the rise of oxygen to present-day levels at 2.0 Gyr ago, 0.8 Gyr ago, and modern Earth. In addition to calculating the UV flux on the surface of the planet, we model the biologically effective irradiance, using DNA damage as a proxy for biological damage. We find that a pre-biotic Earth (3.9 Gyr ago) orbiting an F0V star receives 6 times the biologically effective radiation as around the early Sun and 3520 times the modern Earth–Sun levels. A pre-biotic Earth orbiting GJ 581 (M3.5 V) receives 300 times less biologically effective radiation, about 2 times modern Earth–Sun levels. The UV fluxes calculated here provide a grid of model UV environments during the evolution of an Earth-like planet orbiting a range of stars. These models can be used as inputs into photo-biological experiments and for pre-biotic chemistry and early life evolution experiments
BINARY STARS WITH COMPONENTS OF SOLAR TYPE: 25 ORBITS AND SYSTEM MASSES

International Nuclear Information System (INIS)

Docobo, J. A.; Ling, J. F.

2009-01-01

Revised orbits and system masses are presented for the following 25 visual double stars: WDS 00593-0040 (A 1902), WDS 00596-0111 (A 1903 AB), WDS 01023+0552 (A 2003), WDS 01049+3649 (A 1515), WDS 01234+5809 (STF 115 AB), WDS 02399+0009 (A 1928), WDS 03310+2937 (A 983), WDS 06573-3530 (I 65), WDS 07043-0303 (A 519), WDS 08267+2432 (A 1746 BC), WDS 10585+1711 (A 2375), WDS 11308+4117 (STT 234), WDS 15370+6426 (HU 1168), WDS 16044-1122 (STF 1998 AB), WDS 16283-1613 (RST 3950), WDS 17324+2848 (A 352), WDS 18466+3821 (HU 1191), WDS 19039+2642 (A 2992), WDS 19055+3352(HU 940), WDS 19282-1209 (SCJ 22), WDS 19487+1504 (A 1658), WDS 22400+0113 (A 2099), WDS 23506-5142 (SLR 14), WDS 23518-0637 (A 2700), and WDS 23529-0309 (FIN 359). In all of these systems, at least one component is of solar type. Total system masses were calculated in each case from the orbital period and semiaxis major together with the Hipparcos parallax, except in the cases for which there are no Hipparcos data or when these values are not precise. Other orbital and physical properties of these stars are also discussed. This paper is the second of three collating the revised double star orbits we have calculated in the past 15 yr.
EUV-driven ionospheres and electron transport on extrasolar giant planets orbiting active stars

Science.gov (United States)

Chadney, J. M.; Galand, M.; Koskinen, T. T.; Miller, S.; Sanz-Forcada, J.; Unruh, Y. C.; Yelle, R. V.

2016-03-01

The composition and structure of the upper atmospheres of extrasolar giant planets (EGPs) are affected by the high-energy spectrum of their host stars from soft X-rays to the extreme ultraviolet (EUV). This emission depends on the activity level of the star, which is primarily determined by its age. In this study, we focus upon EGPs orbiting K- and M-dwarf stars of different ages - ɛ Eridani, AD Leonis, AU Microscopii - and the Sun. X-ray and EUV (XUV) spectra for these stars are constructed using a coronal model. These spectra are used to drive both a thermospheric model and an ionospheric model, providing densities of neutral and ion species. Ionisation - as a result of stellar radiation deposition - is included through photo-ionisation and electron-impact processes. The former is calculated by solving the Lambert-Beer law, while the latter is calculated from a supra-thermal electron transport model. We find that EGP ionospheres at all orbital distances considered (0.1-1 AU) and around all stars selected are dominated by the long-lived H+ ion. In addition, planets with upper atmospheres where H2 is not substantially dissociated (at large orbital distances) have a layer in which H3+ is the major ion at the base of the ionosphere. For fast-rotating planets, densities of short-lived H3+ undergo significant diurnal variations, with the maximum value being driven by the stellar X-ray flux. In contrast, densities of longer-lived H+ show very little day/night variability and the magnitude is driven by the level of stellar EUV flux. The H3+ peak in EGPs with upper atmospheres where H2 is dissociated (orbiting close to their star) under strong stellar illumination is pushed to altitudes below the homopause, where this ion is likely to be destroyed through reactions with heavy species (e.g. hydrocarbons, water). The inclusion of secondary ionisation processes produces significantly enhanced ion and electron densities at altitudes below the main EUV ionisation peak, as
A hot Jupiter orbiting a 2-million-year-old solar-mass T Tauri star.

Science.gov (United States)

Donati, J F; Moutou, C; Malo, L; Baruteau, C; Yu, L; Hébrard, E; Hussain, G; Alencar, S; Ménard, F; Bouvier, J; Petit, P; Takami, M; Doyon, R; Collier Cameron, A

2016-06-30

Hot Jupiters are giant Jupiter-like exoplanets that orbit their host stars 100 times more closely than Jupiter orbits the Sun. These planets presumably form in the outer part of the primordial disk from which both the central star and surrounding planets are born, then migrate inwards and yet avoid falling into their host star. It is, however, unclear whether this occurs early in the lives of hot Jupiters, when they are still embedded within protoplanetary disks, or later, once multiple planets are formed and interact. Although numerous hot Jupiters have been detected around mature Sun-like stars, their existence has not yet been firmly demonstrated for young stars, whose magnetic activity is so intense that it overshadows the radial velocity signal that close-in giant planets can induce. Here we report that the radial velocities of the young star V830 Tau exhibit a sine wave of period 4.93 days and semi-amplitude 75 metres per second, detected with a false-alarm probability of less than 0.03 per cent, after filtering out the magnetic activity plaguing the spectra. We find that this signal is unrelated to the 2.741-day rotation period of V830 Tau and we attribute it to the presence of a planet of mass 0.77 times that of Jupiter, orbiting at a distance of 0.057 astronomical units from the host star. Our result demonstrates that hot Jupiters can migrate inwards in less than two million years, probably as a result of planet–disk interactions.
KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR

International Nuclear Information System (INIS)

Sanchis-Ojeda, Roberto; Winn, Joshua N.; Albrecht, Simon; Marcy, Geoffrey W.; Isaacson, Howard; Howard, Andrew W.; Johnson, John Asher; Torres, Guillermo; Carter, Joshua A.; Dawson, Rebekah I.; Geary, John C.; Campante, Tiago L.; Chaplin, William J.; Davies, Guy R.; Lund, Mikkel N.; Buchhave, Lars A.; Everett, Mark E.; Fischer, Debra A.; Gilliland, Ronald L.; Horch, Elliott P.

2013-01-01

We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, m Kp = 11.6, T eff = 5576 K, M * = 0.98 M ☉ ). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is 6.1 ± 0.2 R ⊕ , based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit, then we can place a rough upper bound of 120 M ⊕ (3σ). The host star has a high obliquity (ψ = 104°), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars
KEPLER-63b: A GIANT PLANET IN A POLAR ORBIT AROUND A YOUNG SUN-LIKE STAR

Energy Technology Data Exchange (ETDEWEB)

Sanchis-Ojeda, Roberto; Winn, Joshua N.; Albrecht, Simon [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Marcy, Geoffrey W.; Isaacson, Howard [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Johnson, John Asher [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Torres, Guillermo; Carter, Joshua A.; Dawson, Rebekah I.; Geary, John C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Campante, Tiago L.; Chaplin, William J.; Davies, Guy R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Lund, Mikkel N. [Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Buchhave, Lars A. [Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Everett, Mark E. [National Optical Astronomy Observatory, 950 N. Cherry Ave, Tucson, AZ 85719 (United States); Fischer, Debra A. [Astronomy Department, Yale University, New Haven, CT (United States); Gilliland, Ronald L. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Horch, Elliott P. [Southern Connecticut State University, New Haven, CT 06515 (United States); and others

2013-09-20

We present the discovery and characterization of a giant planet orbiting the young Sun-like star Kepler-63 (KOI-63, m{sub Kp} = 11.6, T{sub eff} = 5576 K, M{sub *} = 0.98 M{sub ☉}). The planet transits every 9.43 days, with apparent depth variations and brightening anomalies caused by large starspots. The planet's radius is 6.1 ± 0.2 R{sub ⊕}, based on the transit light curve and the estimated stellar parameters. The planet's mass could not be measured with the existing radial-velocity data, due to the high level of stellar activity, but if we assume a circular orbit, then we can place a rough upper bound of 120 M{sub ⊕} (3σ). The host star has a high obliquity (ψ = 104°), based on the Rossiter-McLaughlin effect and an analysis of starspot-crossing events. This result is valuable because almost all previous obliquity measurements are for stars with more massive planets and shorter-period orbits. In addition, the polar orbit of the planet combined with an analysis of spot-crossing events reveals a large and persistent polar starspot. Such spots have previously been inferred using Doppler tomography, and predicted in simulations of magnetic activity of young Sun-like stars.
Optimization method of star tracker orientation for sun-synchronous orbit based on space light distribution.

Science.gov (United States)

Wang, Geng; Xing, Fei; Wei, Minsong; Sun, Ting; You, Zheng

2017-05-20

Star trackers, optical attitude sensors with high precision, are susceptible to space light from the Sun and the Earth albedo. Until now, research in this field has lacked systematic analysis. In this paper, we propose an installation orientation method for a star tracker onboard sun-synchronous-orbit spacecraft and analyze the space light distribution by transforming the complicated relative motion among the Sun, Earth, and the satellite to the body coordinate system of the satellite. Meanwhile, the boundary-curve equations of the areas exposed to the stray light from the Sun and the Earth albedo were calculated by the coordinate-transformation matrix under different maneuver attitudes, and the installation orientation of the star tracker was optimized based on the boundary equations instead of the traditional iterative simulation method. The simulation and verification experiment indicate that this installation orientation method is effective and precise and can provide a reference for the installation of sun-synchronous orbit star trackers free from the stray light.
A Novel Error Model of Optical Systems and an On-Orbit Calibration Method for Star Sensors

Directory of Open Access Journals (Sweden)

Shuang Wang

2015-12-01

Full Text Available In order to improve the on-orbit measurement accuracy of star sensors, the effects of image-plane rotary error, image-plane tilt error and distortions of optical systems resulting from the on-orbit thermal environment were studied in this paper. Since these issues will affect the precision of star image point positions, in this paper, a novel measurement error model based on the traditional error model is explored. Due to the orthonormal characteristics of image-plane rotary-tilt errors and the strong nonlinearity among these error parameters, it is difficult to calibrate all the parameters simultaneously. To solve this difficulty, for the new error model, a modified two-step calibration method based on the Extended Kalman Filter (EKF and Least Square Methods (LSM is presented. The former one is used to calibrate the main point drift, focal length error and distortions of optical systems while the latter estimates the image-plane rotary-tilt errors. With this calibration method, the precision of star image point position influenced by the above errors is greatly improved from 15.42% to 1.389%. Finally, the simulation results demonstrate that the presented measurement error model for star sensors has higher precision. Moreover, the proposed two-step method can effectively calibrate model error parameters, and the calibration precision of on-orbit star sensors is also improved obviously.

A SUPER-EARTH-SIZED PLANET ORBITING IN OR NEAR THE HABITABLE ZONE AROUND A SUN-LIKE STAR

Energy Technology Data Exchange (ETDEWEB)

Barclay, Thomas; Burke, Christopher J.; Howell, Steve B.; Rowe, Jason F.; Huber, Daniel; Jenkins, Jon M.; Quintana, Elisa V.; Still, Martin; Twicken, Joseph D.; Bryson, Stephen T.; Borucki, William J.; Caldwell, Douglas A.; Clarke, Bruce D.; Christiansen, Jessie L; Coughlin, Jeffrey L. [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States); Isaacson, Howard; Kolbl, Rea; Marcy, Geoffrey W. [Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720 (United States); Ciardi, David [NASA Exoplanet Science Institute, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Fischer, Debra A. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others

2013-05-10

We present the discovery of a super-Earth-sized planet in or near the habitable zone of a Sun-like star. The host is Kepler-69, a 13.7 mag G4V-type star. We detect two periodic sets of transit signals in the 3-year flux time series of Kepler-69, obtained with the Kepler spacecraft. Using the very high precision Kepler photometry, and follow-up observations, our confidence that these signals represent planetary transits is >99.3%. The inner planet, Kepler-69b, has a radius of 2.24{sup +0.44}{sub -0.29} R{sub Circled-Plus} and orbits the host star every 13.7 days. The outer planet, Kepler-69c, is a super-Earth-sized object with a radius of 1.7{sup +0.34}{sub -0.23} R{sub Circled-Plus} and an orbital period of 242.5 days. Assuming an Earth-like Bond albedo, Kepler-69c has an equilibrium temperature of 299 {+-} 19 K, which places the planet close to the habitable zone around the host star. This is the smallest planet found by Kepler to be orbiting in or near the habitable zone of a Sun-like star and represents an important step on the path to finding the first true Earth analog.
A Neptune-sized transiting planet closely orbiting a 5–10-million-year-old star.

Science.gov (United States)

David, Trevor J; Hillenbrand, Lynne A; Petigura, Erik A; Carpenter, John M; Crossfield, Ian J M; Hinkley, Sasha; Ciardi, David R; Howard, Andrew W; Isaacson, Howard T; Cody, Ann Marie; Schlieder, Joshua E; Beichman, Charles A; Barenfeld, Scott A

2016-06-30

Theories of the formation and early evolution of planetary systems postulate that planets are born in circumstellar disks, and undergo radial migration during and after dissipation of the dust and gas disk from which they formed. The precise ages of meteorites indicate that planetesimals—the building blocks of planets—are produced within the first million years of a star’s life. Fully formed planets are frequently detected on short orbital periods around mature stars. Some theories suggest that the in situ formation of planets close to their host stars is unlikely and that the existence of such planets is therefore evidence of large-scale migration. Other theories posit that planet assembly at small orbital separations may be common. Here we report a newly born, transiting planet orbiting its star with a period of 5.4 days. The planet is 50 per cent larger than Neptune, and its mass is less than 3.6 times that of Jupiter (at 99.7 per cent confidence), with a true mass likely to be similar to that of Neptune. The star is 5–10 million years old and has a tenuous dust disk extending outward from about twice the Earth–Sun separation, in addition to the fully formed planet located at less than one-twentieth of the Earth–Sun separation.
AN ANALYTIC METHOD TO DETERMINE HABITABLE ZONES FOR S-TYPE PLANETARY ORBITS IN BINARY STAR SYSTEMS

International Nuclear Information System (INIS)

Eggl, Siegfried; Pilat-Lohinger, Elke; Gyergyovits, Markus; Funk, Barbara; Georgakarakos, Nikolaos

2012-01-01

With more and more extrasolar planets discovered in and around binary star systems, questions concerning the determination of the classical habitable zone have arisen. Do the radiative and gravitational perturbations of the second star influence the extent of the habitable zone significantly, or is it sufficient to consider the host star only? In this article, we investigate the implications of stellar companions with different spectral types on the insolation a terrestrial planet receives orbiting a Sun-like primary. We present time-independent analytical estimates and compare them to insolation statistics gained via high precision numerical orbit calculations. Results suggest a strong dependence of permanent habitability on the binary's eccentricity, as well as a possible extension of habitable zones toward the secondary in close binary systems.
Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone.

Science.gov (United States)

Joshi, Manoj M; Haberle, Robert M

2012-01-01

M stars comprise 80% of main sequence stars, so their planetary systems provide the best chance for finding habitable planets, that is, those with surface liquid water. We have modeled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M stars), using spectrally resolved data of Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 μm, combined with M stars emitting a significant fraction of their radiation at these same longer wavelengths, means that the albedos of ice and snow on planets orbiting M stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M stars may be 10-30% farther away from the parent star than previously thought.
Richest Planetary System Discovered - Up to seven planets orbiting a Sun-like star

Science.gov (United States)

2010-08-01

Astronomers using ESO's world-leading HARPS instrument have discovered a planetary system containing at least five planets, orbiting the Sun-like star HD 10180. The researchers also have tantalising evidence that two other planets may be present, one of which would have the lowest mass ever found. This would make the system similar to our Solar System in terms of the number of planets (seven as compared to the Solar System's eight planets). Furthermore, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System. "We have found what is most likely the system with the most planets yet discovered," says Christophe Lovis, lead author of the paper reporting the result. "This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system." The team of astronomers used the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla, Chile, for a six-year-long study of the Sun-like star HD 10180, located 127 light-years away in the southern constellation of Hydrus (the Male Water Snake). HARPS is an instrument with unrivalled measurement stability and great precision and is the world's most successful exoplanet hunter. Thanks to the 190 individual HARPS measurements, the astronomers detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets. The five strongest signals correspond to planets with Neptune-like masses - between 13 and 25 Earth masses [1] - which orbit the star with periods ranging from about 6 to 600 days. These planets are located between 0.06 and 1.4 times the Earth-Sun distance from their central star. "We also have
TURBOVELOCITY STARS: KICKS RESULTING FROM THE TIDAL DISRUPTION OF SOLITARY STARS

International Nuclear Information System (INIS)

Manukian, Haik; Guillochon, James; Ramirez-Ruiz, Enrico; O'Leary, Ryan M.

2013-01-01

The centers of most known galaxies host supermassive black holes (SMBHs). In orbit around these black holes are a centrally concentrated distribution of stars, both in single and in binary systems. Occasionally, these stars are perturbed onto orbits that bring them close to the SMBH. If the star is in a binary system, the three-body interaction with the SMBH can lead to large changes in orbital energy, depositing one of the two stars on a tightly-bound orbit, and its companion into a hyperbolic orbit that may escape the galaxy. In this Letter, we show that the disruption of solitary stars can also lead to large positive increases in orbital energy. The kick velocity depends on the amount of mass the star loses at pericenter, but not on the ratio of black hole to stellar mass, and are at most the star's own escape velocity. We find that these kicks are usually too small to result in the ejection of stars from the Milky Way, but can eject the stars from the black hole's sphere of influence, reducing their probability of being disrupted again. We estimate that ∼ 10 5 stars, ∼ 1% of all stars within 10 pc of the galactic center, are likely to have had mass removed by the central black hole through tidal interaction, and speculate that these 'turbovelocity' stars will at first be redder, but eventually bluer, and always brighter than their unharassed peers.
A TEMPORAL MAP IN GEOSTATIONARY ORBIT: THE COVER ETCHING ON THE EchoStar XVI ARTIFACT

Energy Technology Data Exchange (ETDEWEB)

Weisberg, Joel M., E-mail: jweisber@carleton.edu [Department of Physics and Astronomy, Carleton College, Northfield, MN 55057 (United States); Paglen, Trevor, E-mail: trevor@paglen.com

2012-10-01

Geostationary satellites are unique among orbital spacecraft in that they experience no appreciable atmospheric drag. After concluding their respective missions, geostationary spacecraft remain in orbit virtually in perpetuity. As such, they represent some of human civilization's longest lasting artifacts. With this in mind, the EchoStar XVI satellite, to be launched in fall 2012, will play host to a time capsule intended as a message for the deep future. Inspired in part by the Pioneer Plaque and Voyager Golden Records, the EchoStar XVI Artifact is a pair of gold-plated aluminum jackets housing a small silicon disk containing 100 photographs. The Cover Etching, the subject of this paper, is etched onto one of the two jackets. It is a temporal map consisting of a star chart, pulsar timings, and other information describing the epoch from which EchoStar XVI came. The pulsar sample consists of 13 rapidly rotating objects, 5 of which are especially stable, having spin periods <10 ms and extremely small spin-down rates. In this paper, we discuss our approach to the time map etched onto the cover and the scientific data shown on it, and we speculate on the uses that future scientists may have for its data. The other portions of the EchoStar XVI Artifact will be discussed elsewhere.
A TEMPORAL MAP IN GEOSTATIONARY ORBIT: THE COVER ETCHING ON THE EchoStar XVI ARTIFACT

International Nuclear Information System (INIS)

Weisberg, Joel M.; Paglen, Trevor

2012-01-01

Geostationary satellites are unique among orbital spacecraft in that they experience no appreciable atmospheric drag. After concluding their respective missions, geostationary spacecraft remain in orbit virtually in perpetuity. As such, they represent some of human civilization's longest lasting artifacts. With this in mind, the EchoStar XVI satellite, to be launched in fall 2012, will play host to a time capsule intended as a message for the deep future. Inspired in part by the Pioneer Plaque and Voyager Golden Records, the EchoStar XVI Artifact is a pair of gold-plated aluminum jackets housing a small silicon disk containing 100 photographs. The Cover Etching, the subject of this paper, is etched onto one of the two jackets. It is a temporal map consisting of a star chart, pulsar timings, and other information describing the epoch from which EchoStar XVI came. The pulsar sample consists of 13 rapidly rotating objects, 5 of which are especially stable, having spin periods <10 ms and extremely small spin-down rates. In this paper, we discuss our approach to the time map etched onto the cover and the scientific data shown on it, and we speculate on the uses that future scientists may have for its data. The other portions of the EchoStar XVI Artifact will be discussed elsewhere.
X-rays from HD 100546- A Young Herbig Star Orbited by Giant Protoplanets

Science.gov (United States)

Skinner, Stephen

A protoplanetary system consisting of at least two giant planets has beendetected orbiting the young nearby Herbig Be star HD 100546. The inner protoplanet orbits inside a gap within 14 AU of the star and is exposed to strong stellar UV and X-ray radiation. The detection of very warm disk gas provides evidence that stellar heating is affecting physical conditions in the planet-forming environment. We obtained a deep 74 ksec X-ray observation of HD 100546 in 2015 with XMM-Newton yielding an excellent-quality spectrum. We propose here to analyze the XMM-Newton data to determine the X-ray ionization and heating rates in the disk. X-ray ionization and heating affect the thermal and chemical structure of the disk and are key parameters for constructing realistic planet formation models. We are requesting ADAP funding to support the analysis and publication of this valuable XMM-Newton data set, which is now in the public archive.
S2 like Star Orbits near the Galactic Center in Rn and Yukawa Gravity

Science.gov (United States)

Borka, Dusko; Jovanović, Predrag; Jovanović Vesna Borka; Zakharov, Alexander F.

2015-01-01

In this chapter we investigate the possibility to provide theoretical explanation for the observed deviations of S2 star orbit around the Galactic Center using gravitational potentials derived from extended gravity models, but in absence of dark matter. Extended Theories of Gravity are alternative theories of gravitational interaction developed from the exact starting points investigated first by Einstein and Hilbert and aimed from one side to extend the positive results of General Relativity and, on the other hand, to cure its shortcomings. One of the aims of these theories is to explain galactic and extragalactic dynamics without introduction of dark matter. They are based on straightforward generalizations of the Einstein theory where the gravitational action (the Hilbert-Einstein action) is assumed to be linear in the Ricci curvature scalar R. The f(R) gravity is a type of modified gravity which generalizes Einstein's General Relativity, i.e. the simplest case is just the General Relativity. It is actually a family of models, each one defined by a different function of the Ricci scalar. Here, we consider Rn (power-law fourth-order theories of gravity) and Yukawa-like modified gravities in the weak field limit and discuss the constrains on these theories. For that purpose we simulate the orbit of S2 star around the Galactic Center in Rn and Yukawa-like gravity potentials and compare it with New Technology Telescope/Very Large Telescope (NTT/VLT) as well as by Keck telescope observations. Our simulations result in strong constraints on the range of gravity interaction and showed that both Rn and Yukawa gravity could satisfactorily explain the observed orbits of S2 star. However, we concluded that parameters of Rn and Yukawa gravity theories must be very close to those corresponding to the Newtonian limit of the theory. Besides, in contrast to Newtonian gravity, these two modified theories induce orbital precession, even in the case of point-like central mass. The
A BINARY ORBIT FOR THE MASSIVE, EVOLVED STAR HDE 326823, A WR+O SYSTEM PROGENITOR

International Nuclear Information System (INIS)

Richardson, N. D.; Gies, D. R.; Williams, S. J.

2011-01-01

The hot star HDE 326823 is a candidate transition-phase object that is evolving into a nitrogen-enriched Wolf-Rayet star. It is also a known low-amplitude, photometric variable with a 6.123 day period. We present new, high- and moderate-resolution spectroscopy of HDE 326823, and we show that the absorption lines show coherent Doppler shifts with this period while the emission lines display little or no velocity variation. We interpret the absorption line shifts as the orbital motion of the apparently brighter star in a close, interacting binary. We argue that this star is losing mass to a mass gainer star hidden in a thick accretion torus and to a circumbinary disk that is the source of the emission lines. HDE 326823 probably belongs to a class of objects that produce short-period WR+O binaries.
Kinematic and spatial distributions of barium stars - are the barium stars and Am stars related?

International Nuclear Information System (INIS)

Hakkila, J.

1989-01-01

The possibility of an evolutionary link between Am stars and barium stars is considered, and an examination of previous data suggests that barium star precursors are main-sequence stars of intermediate mass, are most likely A and/or F dwarfs, and are intermediate-mass binaries with close to intermediate orbital separations. The possible role of mass transfer in the later development of Am systems is explored. Mass transfer and loss from systems with a range of masses and orbital separations may explain such statistical peculiarities of barium stars as the large dispersion in absolute magnitude, the large range of elemental abundances from star to star, and the small number of stars with large peculiar velocities. 93 refs
Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars. I. Classifying Low-Mass Host Stars Observed During Campaigns 1-7

Science.gov (United States)

Dressing, Courtney D.; Newton, Elisabeth R.; Schlieder, Joshua E.; Charbomeau, David; Krutson, Heather A.; Vanderburg, Andrew; Sinukoff, Evan

2017-01-01

We present near-infrared spectra for 144 candidate planetary systems identified during Campaigns 1-7 of the NASA K2 Mission. The goal of the survey was to characterize planets orbiting low-mass stars, but our Infrared Telescope Facility/SpeX and Palomar/TripleSpec spectroscopic observations revealed that 49% of our targets were actually giant stars or hotter dwarfs reddened by interstellar extinction. For the 72 stars with spectra consistent with classification as cool dwarfs (spectral types K3-M4), we refined their stellar properties by applying empirical relations based on stars with interferometric radius measurements. Although our revised temperatures are generally consistent with those reported in the Ecliptic Plane Input Catalog (EPIC), our revised stellar radii are typically 0.13 solar radius (39%) larger than the EPIC values, which were based on model isochrones that have been shown to underestimate the radii of cool dwarfs. Our improved stellar characterizations will enable more efficient prioritization of K2 targets for follow-up studies.
INTERACTION OF CLOSE-IN PLANETS WITH THE MAGNETOSPHERE OF THEIR HOST STARS. II. SUPER-EARTHS AS UNIPOLAR INDUCTORS AND THEIR ORBITAL EVOLUTION

International Nuclear Information System (INIS)

Laine, Randy O.; Lin, Douglas N. C.

2012-01-01

Planets with several Earth masses and orbital periods of a few days have been discovered through radial velocity and transit surveys. Regardless of their formation mechanism, an important evolution issue is the efficiency of their retention in the proximity of their host stars. If these 'super-Earths' attained their present-day orbits during or shortly after the T Tauri phase of their host stars, a large fraction of these planets would have encountered an intense stellar magnetic field. These rocky planets have a higher conductivity than the atmosphere of their host stars and, therefore, the magnetic flux tube connecting them would slip though the envelope of the host stars faster than across the planets. The induced electromotive force across the planet's diameter leads to a potential drop which propagates along a flux tube away from the planet with an Alfvén speed. The foot of the flux tube would sweep across the stellar surface and the potential drop across the field lines drives a DC current analogous to that proposed for the electrodynamics of the Io-Jupiter system. The ohmic dissipation of this current produces potentially observable hot spots in the star envelope. It also heats the planet and leads to a torque which drives the planet's orbit to evolve toward both circularization and a state of synchronization with the spin of the star. The net effect is the damping of the planet's orbital eccentricity. Around slowly (or rapidly) spinning stars, this process also causes rocky planets with periods less than a few days to undergo orbital decay (or expansion/stagnation) within a few Myr. In principle, this effect can determine the retention efficiency of short-period hot Earths. We also estimate the ohmic dissipation interior to these planets and show that it can lead to severe structure evolution and potential loss of volatile material in them. However, these effects may be significantly weakened by the reconnection of the induced field.
K2-232 b: a transiting warm Saturn on an eccentric P = 11.2 d orbit around a V = 9.9 star

Science.gov (United States)

Brahm, R.; Espinoza, N.; Jordán, A.; Rojas, F.; Sarkis, P.; Díaz, M. R.; Rabus, M.; Drass, H.; Lachaume, R.; Soto, M. G.; Jenkins, J. S.; Jones, M. I.; Henning, Th; Pantoja, B.; Vučković, M.

2018-06-01

We report the discovery of K2-232 b using photometric data of the Kepler K2 satellite coupled with ground-based spectroscopic observations. K2-232 b has a mass of MP = 0.397 ± 0.037 MJ, a radius of RP = 1.00 ± 0.020 RJ, and a moderately low equilibrium temperature of Teq = 1030 ± 15 K due to its relatively large star-planet separation of a = 0.1036 au. K2-232 b orbits its bright (V = 9.9) late F-type host star in an eccentric orbit (e = 0.258 ± 0.025) every 11.2 d, and is one of only four well-characterized warm Jupiters having host stars brighter than V = 10. We estimate a heavy element content of 20 ± 7 M⊕ for K2-232 b, which is consistent with standard models of giant planet formation. The bright host star of K2-232 b makes this system a well-suited target for detailed follow-up observations that will aid in the study of the atmospheres and orbital evolution of giant planets at moderate separations from their host stars.
Ultracompact X-ray binary stars

NARCIS (Netherlands)

Haaften, L.M. van

2013-01-01

Ultracompact X-ray binary stars usually consist of a neutron star and a white dwarf, two stars bound together by their strong gravity and orbiting each other very rapidly, completing one orbit in less than one hour. Neutron stars are extremely compact remnants of the collapsed cores of massive stars
THE OCCURRENCE RATE OF EARTH ANALOG PLANETS ORBITING SUN-LIKE STARS

International Nuclear Information System (INIS)

Catanzarite, Joseph; Shao, Michael

2011-01-01

Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine η Earth , the fraction of Sun-like stars that have planets like Earth. When a planet 'transits' or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler's Science Team has determined sizes, surface temperatures, orbit sizes, and periods for over a thousand new planet candidates. In this paper, we characterize the period probability distribution function of the super-Earth and Neptune planet candidates with periods up to 132 days, and find three distinct period regimes. For candidates with periods below 3 days, the density increases sharply with increasing period; for periods between 3 and 30 days, the density rises more gradually with increasing period, and for periods longer than 30 days, the density drops gradually with increasing period. We estimate that 1%-3% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of 2011 February. This estimate of η Earth is based on extrapolation from a fiducial subsample of the Kepler planet candidates that we chose to be nominally 'complete' (i.e., no missed detections) to the realm of the Earth-like planets, by means of simple power-law models. The accuracy of the extrapolation will improve as more data from the Kepler mission are folded in. Accurate knowledge of η Earth is essential for the planning of future missions that will image and take spectra of Earth-like planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions.
NEW PRECISION ORBITS OF BRIGHT DOUBLE-LINED SPECTROSCOPIC BINARIES. V. THE AM STARS HD 434 AND 41 SEXTANTIS

International Nuclear Information System (INIS)

Fekel, Francis C.; Williamson, Michael H.

2010-01-01

We have detected the secondary component in two previously known spectroscopic binaries, HD 434 and 41 Sex, and for the first time determined double-lined orbits for them. Despite the relatively long period of 34.26 days and a moderate eccentricity of 0.32, combined with the components' rotationally broadened lines, measurement of the primary and secondary radial velocities of HD 434 has enabled us to obtain significantly improved orbital elements. While the 41 Sex system has a much shorter period of 6.167 days and a circular orbit, the estimated V mag difference of 3.2 between its components also makes this a challenging system. The new orbital dimensions (a 1 sin i and a 2 sin i) and minimum masses (m 1 sin 3 i and m 2 sin 3 i) of HD 434 have accuracies of 0.8% or better, while the same quantities for 41 Sex are good to 0.5% or better. Both components of HD 434 are Am stars while the Am star primary of 41 Sex has a late-F or early-G companion. All four stars are on the main sequence. The two components of HD 434 are rotating much faster than their predicted pseudosynchronous velocities, while both components of 41 Sex are synchronously rotating. For the primary of 41 Sex, the spectrum line depth changes noted by Sreedhar Rao et al. were not detected.
INFRARED SPECTROSCOPY OF SYMBIOTIC STARS. VIII. ORBITS FOR THREE S-TYPE SYSTEMS: AE ARAE, Y CORONAE AUSTRALIS, AND SS 73-147

International Nuclear Information System (INIS)

Fekel, Francis C.; Hinkle, Kenneth H.; Joyce, Richard R.; Wood, Peter R.

2010-01-01

With new infrared radial velocities we have computed orbits of the M giants in three southern S-type symbiotic systems. AE Ara and SS 73-147 have circular orbits with periods of 803 and 820 days, respectively. The eccentric orbit of Y CrA has a period that is about twice as long, 1619 days. Except for CH Cyg it is currently the S-type symbiotic system with the longest period for which a spectroscopic orbit has been determined. The Paschen δ emission line velocities of AE Ara are nearly in antiphase with the M giant absorption feature velocities and result in a mass ratio of 2.7. Emission lines in the 1.005 μm region for the other two symbiotic systems are not good proxies for the hot components in those systems. There is no evidence that these three symbiotics are eclipsing. With spectral classes of M5.5 or M6, the three giants presumably also have velocity variations that result from pulsations, but we have been unable to identify specific pulsation periods in the absorption line velocity residuals.
Orbital and epicyclic frequencies around neutron and strange stars in R{sup 2} gravity

Energy Technology Data Exchange (ETDEWEB)

Staykov, Kalin V., E-mail: kstaykov@phys.uni-sofia.bg [Department of Theoretical Physics, Faculty of Physics, Sofia University, 1164, Sofia (Bulgaria); Doneva, Daniela D., E-mail: daniela.doneva@uni-tuebingen.de [Theoretical Astrophysics, Eberhard Karls University of Tübingen, 72076, Tübingen (Germany); INRNE-Bulgarian Academy of Sciences, 1784, Sofia (Bulgaria); Yazadjiev, Stoytcho S., E-mail: yazad@phys.uni-sofia.bg [Department of Theoretical Physics, Faculty of Physics, Sofia University, 1164, Sofia (Bulgaria); Theoretical Astrophysics, Eberhard Karls University of Tübingen, 72076, Tübingen (Germany)

2015-12-21

According to various models, the orbital and the epicyclic frequencies of particles moving on a circular orbit around compact objects are related to the quasi-periodic oscillations observed in the X-ray flux of some pulsars or black hole candidates. It is expected that they originate from the inner edge of the accretion discs, deep into the gravitational field of the compact objects. Considering the planned new generation X-ray timing observatories with large collective areas, the quasi-periodic oscillations might be an excellent tool for testing gravity in strong field regime and, respectively, alternative gravitational theories. We examine the orbital and the epicyclic frequencies of a particle moving on a circular orbit around neutron or strange stars in R{sup 2} gravity. The case of slow rotation is considered too. The R{sup 2} gravity results are compared to the general relativistic case. We comment on the deviations from general relativity, as well as the deviations due to rotation in both theories.

Orbital and epicyclic frequencies around neutron and strange stars in R{sup 2} gravity

Energy Technology Data Exchange (ETDEWEB)

Staykov, Kalin V. [Sofia University, Department of Theoretical Physics, Faculty of Physics, Sofia (Bulgaria); Doneva, Daniela D. [Eberhard Karls University of Tuebingen, Theoretical Astrophysics, Tuebingen (Germany); INRNE-Bulgarian Academy of Sciences, Sofia (Bulgaria); Yazadjiev, Stoytcho S. [Sofia University, Department of Theoretical Physics, Faculty of Physics, Sofia (Bulgaria); Eberhard Karls University of Tuebingen, Theoretical Astrophysics, Tuebingen (Germany)

2015-12-15

According to various models, the orbital and the epicyclic frequencies of particles moving on a circular orbit around compact objects are related to the quasi-periodic oscillations observed in the X-ray flux of some pulsars or black hole candidates. It is expected that they originate from the inner edge of the accretion discs, deep into the gravitational field of the compact objects. Considering the planned new generation X-ray timing observatories with large collective areas, the quasi-periodic oscillations might be an excellent tool for testing gravity in strong field regime and, respectively, alternative gravitational theories. We examine the orbital and the epicyclic frequencies of a particle moving on a circular orbit around neutron or strange stars in R{sup 2} gravity. The case of slow rotation is considered too. The R{sup 2} gravity results are compared to the general relativistic case. We comment on the deviations from general relativity, as well as the deviations due to rotation in both theories. (orig.)
Extreme secular excitation of eccentricity inside mean motion resonance. Small bodies driven into star-grazing orbits by planetary perturbations

Science.gov (United States)

Pichierri, Gabriele; Morbidelli, Alessandro; Lai, Dong

2017-09-01

Context. It is well known that asteroids and comets fall into the Sun. Metal pollution of white dwarfs and transient spectroscopic signatures of young stars like β-Pic provide growing evidence that extra solar planetesimals can attain extreme orbital eccentricities and fall into their parent stars. Aims: We aim to develop a general, implementable, semi-analytical theory of secular eccentricity excitation of small bodies (planetesimals) in mean motion resonances with an eccentric planet valid for arbitrary values of the eccentricities and including the short-range force due to General Relativity. Methods: Our semi-analytic model for the restricted planar three-body problem does not make use of series expansion and therefore is valid for any eccentricity value and semi-major axis ratio. The model is based on the application of the adiabatic principle, which is valid when the precession period of the longitude of pericentre of the planetesimal is much longer than the libration period in the mean motion resonance. In resonances of order larger than 1 this is true except for vanishingly small eccentricities. We provide prospective users with a Mathematica notebook with implementation of the model allowing direct use. Results: We confirm that the 4:1 mean motion resonance with a moderately eccentric (e' ≲ 0.1) planet is the most powerful one to lift the eccentricity of planetesimals from nearly circular orbits to star-grazing ones. However, if the planet is too eccentric, we find that this resonance is unable to pump the planetesimal's eccentricity to a very high value. The inclusion of the General Relativity effect imposes a condition on the mass of the planet to drive the planetesimals into star-grazing orbits. For a planetesimal at 1 AU around a solar mass star (or white dwarf), we find a threshold planetary mass of about 17 Earth masses. We finally derive an analytical formula for this critical mass. Conclusions: Planetesimals can easily fall into the central star
Stellar orbits around Sgr A*

International Nuclear Information System (INIS)

Trippe, S; Gillessen, S; Ott, T; Eisenhauer, F; Paumard, T; Martins, F; Genzel, R; Schoedel, R; Eckart, A; Alexander, T

2006-01-01

In this article we present and discuss the latest results from the observations of stars (''S-stars'') orbiting Sgr A* . With improving data quality the number of observed S-stars has increased substantially in the last years. The combination of radial velocity and proper motion information allows an ever more precise determination of orbital parameters and of the mass of and the distance to the supermassive black hole in the centre of the Milky Way. Additionally, the orbital solutions allow us to verify an agreement between the NIR source Sgr A* and the dynamical centre of the stellar orbits to within 2 mas
RADIAL VELOCITY MONITORING OF KEPLER HEARTBEAT STARS

Energy Technology Data Exchange (ETDEWEB)

Shporer, Avi [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Fuller, Jim [TAPIR, Walter Burke Institute for Theoretical Physics, Mailcode 350-17, Caltech, Pasadena, CA 91125 (United States); Isaacson, Howard [Department of Astronomy, University of California, Berkeley CA 94720 (United States); Hambleton, Kelly; Prša, Andrej [Department of Astrophysics and Planetary Science, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085 (United States); Thompson, Susan E. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Kurtz, Donald W. [Jeremiah Horrocks Institute, University of Central Lancashire, Preston, PR1 2HE (United Kingdom); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); O’Leary, Ryan M. [JILA, University of Colorado and NIST, 440 UCB, Boulder, 80309-0440 (United States)

2016-09-20

Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars in order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity–period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories.
RADIAL VELOCITY MONITORING OF KEPLER HEARTBEAT STARS

International Nuclear Information System (INIS)

Shporer, Avi; Fuller, Jim; Isaacson, Howard; Hambleton, Kelly; Prša, Andrej; Thompson, Susan E.; Kurtz, Donald W.; Howard, Andrew W.; O’Leary, Ryan M.

2016-01-01

Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars in order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity–period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories.
The Possibility of Multiple Habitable Worlds Orbiting Binary Stars

Science.gov (United States)

Mason, P. A.

2014-03-01

Are there planetary systems for which there is life on multiple worlds? Where are these fruitful planetary systems and how do we detect them? In order to address these questions; conditions which enable life and those that prevent or destroy it must be considered. Many constraints are specific to planetary systems, independent of the number of worlds in habitable zones. For instance, life on rocky planets or moons likely requires the right abundance of volatiles and radiogenic elements for prolonged geologic activity. Catastrophic sterilization events such as nearby supernovae and gamma-ray bursts affect entire planetary systems not just specific worlds. Giant planets may either enhance or disrupt the development of complex life within a given system. It might be rare for planetary systems to possess qualities that promote life and lucky enough to avoid cataclysm. However, multiple habitable planets may provide enhanced chances for advanced life to develop. The best predictor of life on one habitable zone planet might be the presence of life on its neighbor as panspermia may occur in planetary systems with several habitable worlds. Circumbinary habitability may go hand in hand with habitability of multiple worlds. The circumstances in which the Binary Habitability Mechanism (BHM) operates are reviewed. In some cases, the early synchronization of the primary's rotation with the binary period results in a reduction of XUV flux and stellar winds. Main sequence binaries with periods in the 10-50 days provide excellent habitable environments, within which multiple worlds may thrive. Planets and moons in these habitable zones need less magnetic protection than their single star counterparts. Exomoons orbiting a Neptune-like planet, within a BHM protected habitable zone, are expected to be habitable over a wide range of semimajor axes due to a larger planetary Hill radius. A result confirmed by numerical orbital calculations. Binaries containing a solar type star with a
INFRARED SPECTROSCOPY OF SYMBIOTIC STARS. VII. BINARY ORBIT AND LONG SECONDARY PERIOD VARIABILITY OF CH CYGNI

International Nuclear Information System (INIS)

Hinkle, Kenneth H.; Joyce, Richard R.; Fekel, Francis C.

2009-01-01

High-dispersion spectroscopic observations are used to refine orbital elements for the symbiotic binary CH Cyg. The current radial velocities, added to a previously published 13 year time series of infrared velocities for the M giant in the CH Cyg symbiotic system, more than double the length of the time series to 29 years. The two previously identified velocity periods are confirmed. The long period, revised to 15.6 ± 0.1 yr, is shown to result from a binary orbit with a 0.7 M sun white dwarf and 2 M sun M giant. Mass transfer to the white dwarf is responsible for the symbiotic classification. CH Cyg is the longest period S-type symbiotic known. Similarities with the longer period D-type systems are noted. The 2.1 year period is shown to be on Wood's sequence D, which contains stars identified as having long secondary periods (LSP). The cause of the LSP variation in CH Cyg and other stars is unknown. From our review of possible causes, we identify g-mode nonradial pulsation as the leading mechanism for LSP variation in CH Cyg. If g-mode pulsation is the cause of the LSPs, a radiative region is required near the photosphere of pulsating asymptotic giant branch stars.
Neutron Stars and NuSTAR

Science.gov (United States)

Bhalerao, Varun

2012-05-01

My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses
LONG-ORBITAL-PERIOD PREPOLARS CONTAINING EARLY K-TYPE DONOR STARS. BOTTLENECK ACCRETION MECHANISM IN ACTION

International Nuclear Information System (INIS)

Tovmassian, G.; González–Buitrago, D.; Zharikov, S.; Reichart, D. E.; Haislip, J. B.; Ivarsen, K. M.; LaCluyze, A. P.; Moore, J. P.; Miroshnichenko, A. S.

2016-01-01

We studied two objects identified as cataclysmic variables (CVs) with periods exceeding the natural boundary for Roche-lobe-filling zero-age main sequence (ZAMS) secondary stars. We present observational results for V1082 Sgr with a 20.82 hr orbital period, an object that shows a low luminosity state when its flux is totally dominated by a chromospherically active K star with no signs of ongoing accretion. Frequent accretion shutoffs, together with characteristics of emission lines in a high state, indicate that this binary system is probably detached, and the accretion of matter on the magnetic white dwarf takes place through stellar wind from the active donor star via coupled magnetic fields. Its observational characteristics are surprisingly similar to V479 And, a 14.5 hr binary system. They both have early K-type stars as donor stars. We argue that, similar to the shorter-period prepolars containing M dwarfs, these are detached binaries with strong magnetic components. Their magnetic fields are coupled, allowing enhanced stellar wind from the K star to be captured and channeled through the bottleneck connecting the two stars onto the white dwarf’s magnetic pole, mimicking a magnetic CV. Hence, they become interactive binaries before they reach contact. This will help to explain an unexpected lack of systems possessing white dwarfs with strong magnetic fields among detached white+red dwarf systems
LONG-ORBITAL-PERIOD PREPOLARS CONTAINING EARLY K-TYPE DONOR STARS. BOTTLENECK ACCRETION MECHANISM IN ACTION

Energy Technology Data Exchange (ETDEWEB)

Tovmassian, G.; González–Buitrago, D.; Zharikov, S. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 877, Ensenada, Baja California, 22800 México (Mexico); Reichart, D. E.; Haislip, J. B.; Ivarsen, K. M.; LaCluyze, A. P.; Moore, J. P. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Campus Box 3255, Chapel Hill, NC 27599 (United States); Miroshnichenko, A. S., E-mail: gag@astro.unam.mx, E-mail: dgonzalez@astro.unam.mx, E-mail: zhar@astro.unam.mx [Department of Physics and Astronomy, University of North Carolina at Greensboro, Greensboro, NC 27402-6170 (United States)

2016-03-01

We studied two objects identified as cataclysmic variables (CVs) with periods exceeding the natural boundary for Roche-lobe-filling zero-age main sequence (ZAMS) secondary stars. We present observational results for V1082 Sgr with a 20.82 hr orbital period, an object that shows a low luminosity state when its flux is totally dominated by a chromospherically active K star with no signs of ongoing accretion. Frequent accretion shutoffs, together with characteristics of emission lines in a high state, indicate that this binary system is probably detached, and the accretion of matter on the magnetic white dwarf takes place through stellar wind from the active donor star via coupled magnetic fields. Its observational characteristics are surprisingly similar to V479 And, a 14.5 hr binary system. They both have early K-type stars as donor stars. We argue that, similar to the shorter-period prepolars containing M dwarfs, these are detached binaries with strong magnetic components. Their magnetic fields are coupled, allowing enhanced stellar wind from the K star to be captured and channeled through the bottleneck connecting the two stars onto the white dwarf’s magnetic pole, mimicking a magnetic CV. Hence, they become interactive binaries before they reach contact. This will help to explain an unexpected lack of systems possessing white dwarfs with strong magnetic fields among detached white+red dwarf systems.
Seth Nicholson's First Satellite Discovery: Jupiter IX and His Orbit for It

Science.gov (United States)

Osterbrock, Donald E.

2006-12-01

Seth B. Nicholson was a graduate astronomy student at the University of California in Berkeley when he discovered his first satellite in 1914. He was later to discover three more, after he had joined the Mount Wilson Observatory staff following his PhD in 1915. Nicholson had begun his thesis on the problem of computing an improved orbit for J VIII, which had been discovered by Melotte in England in 1908, a distant irregular satellite like J VI and J VII. Nicholson was taking photographic plates to measure the position of J VIII in the summer of 1914 with the Crossley 36-inch reflector of Lick Observatory. He was a teaching assistant at Berkeley that summer, but would go up to Mount Hamilton to observe on weekends in the dark of the moon, traveling by rail, stage (an automobile on a regular schedule between San Jose and the observatory) and interurban trolley car, and sleeping in a shed near the Crossley dome. He first saw J IX as a much fainter object with the same motion as J VIII on a plate he took in late July 1914, and realized it must be another satellite of the giant planet. Nicholson obtained his first orbit of J IX, which had by then become his new thesis topic, in September, and published a paper on it in early 1915. Its orbit, like that of J VIII, was retrograde and irregular, but it was considerably fainter. Nicholson, a loyal student of Armin O. Leuschner, the head of the Berkeley Astronomy Division, used his teacher's "short method" (or analytic method) to calculate the orbit.
SOFT X-RAY TEMPERATURE TIDAL DISRUPTION EVENTS FROM STARS ON DEEP PLUNGING ORBITS

Energy Technology Data Exchange (ETDEWEB)

Dai, Lixin; McKinney, Jonathan C.; Miller, M. Coleman, E-mail: cosimo@umd.edu [Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States)

2015-10-20

One of the puzzles associated with tidal disruption event candidates (TDEs) is that there is a dichotomy between the color temperatures of a few × 10{sup 4} K for TDEs discovered with optical and UV telescopes and the color temperatures of a few × 10{sup 5}–10{sup 6} K for TDEs discovered with X-ray satellites. Here, we propose that high-temperature TDEs are produced when the tidal debris of a disrupted star self-intersects relatively close to the supermassive black hole, in contrast to the more distant self-intersection that leads to lower color temperatures. In particular, we note from simple ballistic considerations that greater apsidal precession in an orbit is the key to closer self-intersection. Thus, larger values of β, the ratio of the tidal radius to the pericenter distance of the initial orbit, are more likely to lead to higher temperatures of more compact disks that are super-Eddington and geometrically and optically thick. For a given star and β, apsidal precession also increases for larger black hole masses, but larger black hole masses imply a lower temperature at the Eddington luminosity. Thus, the expected dependence of the temperature on the mass of the black hole is non-monotonic. We find that in order to produce a soft X-ray temperature TDE, a deep plunging stellar orbit with β > 3 is needed and a black hole mass of ≲5 × 10{sup 6}M{sub ⊙} is favored. Although observations of TDEs are comparatively scarce and are likely dominated by selection effects, it is encouraging that both expectations are consistent with current data.
THE PHASES DIFFERENTIAL ASTROMETRY DATA ARCHIVE. II. UPDATED BINARY STAR ORBITS AND A LONG PERIOD ECLIPSING BINARY

International Nuclear Information System (INIS)

Muterspaugh, Matthew W.; O'Connell, J.; Hartkopf, William I.; Lane, Benjamin F.; Williamson, M.; Kulkarni, S. R.; Konacki, Maciej; Burke, Bernard F.; Colavita, M. M.; Shao, M.; Wiktorowicz, Sloane J.

2010-01-01

Differential astrometry measurements from the Palomar High-precision Astrometric Search for Exoplanet Systems have been combined with lower precision single-aperture measurements covering a much longer timespan (from eyepiece measurements, speckle interferometry, and adaptive optics) to determine improved visual orbits for 20 binary stars. In some cases, radial velocity observations exist to constrain the full three-dimensional orbit and determine component masses. The visual orbit of one of these binaries-α Com (HD 114378)-shows that the system is likely to have eclipses, despite its very long period of 26 years. The next eclipse is predicted to be within a week of 2015 January 24.
Structural Instability in Ice VIII under Pressure

International Nuclear Information System (INIS)

Besson, J.; Klotz, S.; Hamel, G.; Marshall, W.; Nelmes, R.; Loveday, J.

1997-01-01

Below 125K, tetragonal ice VIII remains in a metastable form at ambient pressure. This form has long been considered to be identical to ice VIII, although unexplained discrepancies exist between their vibrational spectra. Neutron diffraction studies reveal an isostructural phase transformation below 2GPa related to a weakening of the bonds between the two D 2 O sublattices of ice VIII. In this new phase, ice VIII ' , the tetragonal distortion is 20% larger than in ice VIII, which accounts for the differences between the vibrational frequencies of the two phases. copyright 1997 The American Physical Society
Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds

Science.gov (United States)

Zakharov, A. F.; Jovanović, P.; Borka, D.; Borka Jovanović, V.

2018-04-01

Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as mg advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume that trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. In contrast with our previous studies, where we present current constraints on parameters of Yukawa gravity [5] and graviton mass [6] from observations of S2 star, in the paper we express expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations. We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around 5 × 10‑23 eV or slightly better than current estimates obtained with LIGO observations.
Orbit elements and kinematics of the halo stars and the old disk population: evidence for active phases in the evolution of the Galaxy

International Nuclear Information System (INIS)

Marsakov, V.A.; Suchkov, A.A.

1978-01-01

The distributions of orbits eccentricities and of angular momenta for the halo stars and for the old disk population are considered. The distributions have gaps separating the halo from the disk and diving the halo population into three groups. From the point of view of star formation during the collapse at the earliy stages of evolution the gaps evidence that threre were in the Galaxy long periods of suppression of star formation. The kinematics and the orbit elements of the halo stars and of the old disk population allow to conclude that there was no significant relaxation in the halo; the halo subsystems are not stationary, they perform radial oscillations with respect to the galactic centre; the velocity dispersion in the galactic rotation direction for the halo stars having the same age does not exceed 20-40 km/s; the dispersion of the velocity component along the galactic radius is symmetrically higher for the subsystems with a greater eccentrically and reaches 215 km/s for the stars with the greatest eccentricaities; the sing of the angular momentum in the protogalactic gas cloud probably changed at some distance form the galactic centre
ORBITAL VARIATION OF THE X-RAY EMISSION FROM THE DOUBLE NEUTRON STAR BINARY J1537+1155

International Nuclear Information System (INIS)

Durant, Martin; Kargaltsev, Oleg; Volkov, Igor; Pavlov, George G.

2011-01-01

We observed the double neutron star binary (DNSB) containing PSR J1537+1155 (also known as B1534+12) with the Chandra X-Ray Observatory. This is one of the two DNSBs detected in X-rays and the only one where a hint of variability with orbital phase was found (in the previous Chandra observation). Our follow-up observation supports the earlier result: the distribution of photon arrival times with orbital phase again shows a deficit around apastron. The significance of the deficit in the combined data set exceeds 99%. Such an orbital light curve suggests that the X-ray emission is seen only when neutron star (NS) B passes through the equatorial pulsar wind of NS A. We describe statistical tests that we used to determine the significance of the deficit, and conclusions that can be drawn from its existence, such as interaction of the pulsar wind with the NS companion. We also provide better constrained spectral model parameters obtained from the joint spectral fits to the data from both observations. A power law successfully fits the data, with best-fit photon index Γ = 3.1 ± 0.4 and unabsorbed flux f = (3.2 ± 0.8) × 10 –15 erg s –1 cm –2 (0.3-8 keV range).
Some properties of spectral binary stars

International Nuclear Information System (INIS)

Krajcheva, Z.T.; Popova, E.I.; Tutukov, A.V.; Yungel'son, L.R.; AN SSSR, Moscow. Astronomicheskij Sovet)

1978-01-01

Statistical investigations of spectra binary stars are carried out. Binary systems consisting of main sequence stars are considered. For 826 binary stars masses of components, ratios of component masses, semiaxes of orbits and orbital angular momenta are calculated. The distributions of these parameters and their correlations are analyzed. The dependences of statistical properties of spectral binary stars on their origin and evolution are discussed
Development and characterization of recombinant ovine coagulation factor VIII.

Directory of Open Access Journals (Sweden)

Philip M Zakas

Full Text Available Animal models of the bleeding disorder, hemophilia A, have been an integral component of the biopharmaceutical development process and have facilitated the development of recombinant coagulation factor VIII (fVIII products capable of restoring median survival of persons with hemophilia A to that of the general population. However, there remain several limitations to recombinant fVIII as a biotherapeutic, including invasiveness of intravenous infusion, short half-life, immunogenicity, and lack of availability to the majority of the world's population. The recently described ovine model of hemophilia A is the largest and most accurate phenocopy. Affected sheep die prematurely due to bleeding-related pathogenesis and display robust adaptive humoral immunity to non-ovine fVIII. Herein, we describe the development and characterization of recombinant ovine fVIII (ofVIII to support further the utility of the ovine hemophilia A model. Full-length and B-domain deleted (BDD ofVIII cDNAs were generated and demonstrated to facilitate greater biosynthetic rates than their human fVIII counterparts while both BDD constructs showed greater expression rates than the same-species full-length versions. A top recombinant BDD ofVIII producing baby hamster kidney clone was identified and used to biosynthesize raw material for purification and biochemical characterization. Highly purified recombinant BDD ofVIII preparations possess a specific activity nearly 2-fold higher than recombinant BDD human fVIII and display a differential glycosylation pattern. However, binding to the carrier protein, von Willebrand factor, which is critical for stability of fVIII in circulation, is indistinguishable. Decay of thrombin-activated ofVIIIa is 2-fold slower than human fVIII indicating greater intrinsic stability. Furthermore, intravenous administration of ofVIII effectively reverses the bleeding phenotype in the murine model of hemophilia A. Recombinant ofVIII should facilitate
A HOT URANUS ORBITING THE SUPER METAL-RICH STAR HD 77338 AND THE METALLICITY-MASS CONNECTION

International Nuclear Information System (INIS)

Jenkins, J. S.; Hoyer, S.; Jones, M. I.; Rojo, P.; Day-Jones, A. C.; Ruiz, M. T.; Jones, H. R. A.; Tuomi, M.; Barnes, J. R.; Pavlenko, Y. V.; Pinfield, D. J.; Murgas, F.; Ivanyuk, O.; Jordán, A.

2013-01-01

We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD 77338 as part of our ongoing Calan-Hertfordshire Extrasolar Planet Search. The best-fit planet solution has an orbital period of 5.7361 ± 0.0015 days and with a radial velocity semi-amplitude of only 5.96 ± 1.74 ms –1 , we find a minimum mass of 15.9 +4.7 -5.3 M ⊕ . The best-fit eccentricity from this solution is 0.09 +0.25 -0.09 , and we find agreement for this data set using a Bayesian analysis and a periodogram analysis. We measure a metallicity for the star of +0.35 ± 0.06 dex, whereas another recent work finds +0.47 ± 0.05 dex. Thus HD 77338b is one of the most metal-rich planet-host stars known and the most metal-rich star hosting a sub-Neptune-mass planet. We searched for a transit signature of HD 77338b but none was detected. We also highlight an emerging trend where metallicity and mass seem to correlate at very low masses, a discovery that would be in agreement with the core accretion model of planet formation. The trend appears to show that for Neptune-mass planets and below, higher masses are preferred when the host star is more metal-rich. Also a lower boundary is apparent in the super metal-rich regime where there are no very low mass planets yet discovered in comparison to the sub-solar metallicity regime. A Monte Carlo analysis shows that this low-mass planet desert is statistically significant with the current sample of 36 planets at the ∼4.5σ level. In addition, results from Kepler strengthen the claim for this paucity of the lowest-mass planets in super metal-rich systems. Finally, this discovery adds to the growing population of low-mass planets around low-mass and metal-rich stars and shows that very low mass planets can now be discovered with a relatively small number of data points using stable instrumentation.

The diskmass survey. VIII. On the relationship between disk stability and star formation

Energy Technology Data Exchange (ETDEWEB)

Westfall, Kyle B.; Verheijen, Marc A. W. [Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen (Netherlands); Andersen, David R. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Martinsson, Thomas P. K. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Swaters, Robert A., E-mail: westfall@astro.rug.nl [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

2014-04-10

We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo and Wiegert (Q {sub RW}), incorporating stellar kinematic data for the first time, and the star-formation rate estimated from 21 cm continuum emission. We determine the stability level of each disk probabilistically using a Bayesian analysis of our data and a simple dynamical model. Our method incorporates the shape of the stellar velocity ellipsoid (SVE) and yields robust SVE measurements for over 90% of our sample. Averaging over this subsample, we find a meridional shape of σ{sub z}/σ{sub R}=0.51{sub −0.25}{sup +0.36} for the SVE and, at 1.5 disk scale lengths, a stability parameter of Q {sub RW} = 2.0 ± 0.9. We also find that the disk-averaged star-formation-rate surface density ( Σ-dot {sub e,∗}) is correlated with the disk-averaged gas and stellar mass surface densities (Σ {sub e,} {sub g} and Σ {sub e,} {sub *}) and anti-correlated with Q {sub RW}. We show that an anti-correlation between Σ-dot {sub e,∗} and Q {sub RW} can be predicted using empirical scaling relations, such that this outcome is consistent with well-established statistical properties of star-forming galaxies. Interestingly, Σ-dot {sub e,∗} is not correlated with the gas-only or star-only Toomre parameters, demonstrating the merit of calculating a multi-component stability parameter when comparing to star-formation activity. Finally, our results are consistent with the Ostriker et al. model of self-regulated star-formation, which predicts Σ-dot {sub e,∗}/Σ{sub e,g}∝Σ{sub e,∗}{sup 1/2}. Based on this and other theoretical expectations, we discuss the possibility of a physical link between disk stability level and star-formation rate in light of our empirical results.
Shooting stars

International Nuclear Information System (INIS)

Maurette, M.; Hammer, C.

1985-01-01

A shooting star passage -even a star shower- can be sometimes easily seen during moonless black night. They represent the partial volatilization in earth atmosphere of meteorites or micrometeorites reduced in cosmic dusts. Everywhere on earth, these star dusts are searched to be gathered. This research made one year ago on the Greenland ice-cap is this article object; orbit gathering projects are also presented [fr
Over 100 Validated and Candidate Planets Orbiting Bright Stars in K2 Campaigns 0-10

Science.gov (United States)

Mayo, Andrew; Vanderburg, Andrew; Latham, David; Bieryla, Allyson; Morton, Timothy

2018-01-01

Since 2014, NASA's K2 mission has observed large portions of the ecliptic plane in search of transiting planets and has detected hundreds of planet candidates. With observations planned until at least early 2018, K2 will continue to identify more planet candidates. We present here over 250 planet candidates observed during Campaigns 0-10 of the K2 mission that are orbiting stars brighter than 13th magnitude and for which we have obtained high-resolution spectra. We analyze these candidates using the VESPA package in order to calculate the false positive probability (FPP), and find that more than half are validated with a FPP less than 0.1%. We show that like the population of planets found during the original Kepler mission, large planets discovered by K2 tend to orbit metal-rich stars. We also show tentative evidence of a gap in the planet radius distribution. We compare our sample to the Kepler candidate sample investigated by Fulton and collaborators and conclude that more planets are required to confirm the gap. This work, in addition to increasing the population of validated K2 planets and providing new targets for follow-up observations, will also serve as a framework for validating candidates from upcoming K2 campaigns and the Transiting Exoplanet Survey Satellite (TESS), expected to launch in 2018.
New binary pulsar in a highy eccentric orbit

International Nuclear Information System (INIS)

Stokes, G.H.; Taylor, J.H.; Dewey, R.J.

1985-01-01

We report the discovery of PSR 2303+46, the fifth radio pulsar known to be in a gravitationally bound orbit around another star. The pulsar period (1.066 s) and the orbital eccentricity (0.658) are the largest amount the five binary systems, while the orbital period (12./sup d/34) lies near the middle of the range. Evolutionary considerations suggest strongly that the companion is another neutron star. The general relativistic precession of periastron should be observable within 1 or 2 yr and, when measured, will specify the total mass of the two stars
Barium and Tc-poor S stars: Binary masqueraders among carbon stars

OpenAIRE

Jorissen, A.; Van Eck, S.

1997-01-01

The current understanding of the origin of barium and S stars is reviewed, based on new orbital elements and binary frequencies. The following questions are addressed: (i) Is binarity a necessary condition to produce a barium star? (ii) What is the mass transfer mode (wind accretion or RLOF?) responsible for their formation? (iii) Do barium stars form as dwarfs or as giants? (iv) Do barium stars evolve into Tc-poor S stars? (v) What is the relative frequency of Tc-rich and Tc-poor S stars?
PROBABILITY OF CME IMPACT ON EXOPLANETS ORBITING M DWARFS AND SOLAR-LIKE STARS

Energy Technology Data Exchange (ETDEWEB)

Kay, C. [Solar Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Opher, M.; Kornbleuth, M., E-mail: ckay@bu.edu [Astronomy Department, Boston University, Boston, MA 02215 (United States)

2016-08-01

Solar coronal mass ejections (CMEs) produce adverse space weather effects at Earth. Planets in the close habitable zone of magnetically active M dwarfs may experience more extreme space weather than at Earth, including frequent CME impacts leading to atmospheric erosion and leaving the surface exposed to extreme flare activity. Similar erosion may occur for hot Jupiters with close orbits around solar-like stars. We have developed a model, Forecasting a CME's Altered Trajectory (ForeCAT), which predicts a CME's deflection. We adapt ForeCAT to simulate CME deflections for the mid-type M dwarf V374 Peg and hot Jupiters with solar-type hosts. V374 Peg's strong magnetic fields can trap CMEs at the M dwarfs's Astrospheric Current Sheet, that is, the location of the minimum in the background magnetic field. Solar-type CMEs behave similarly, but have much smaller deflections and do not become trapped at the Astrospheric Current Sheet. The probability of planetary impact decreases with increasing inclination of the planetary orbit with respect to the Astrospheric Current Sheet: 0.5–5 CME impacts per day for M dwarf exoplanets, 0.05–0.5 CME impacts per day for solar-type hot Jupiters. We determine the minimum planetary magnetic field necessary to shield a planet's atmosphere from CME impacts. M dwarf exoplanets require values between tens and hundreds of Gauss. Hot Jupiters around a solar-type star, however, require a more reasonable <30 G. These values exceed the magnitude required to shield a planet from the stellar wind, suggesting that CMEs may be the key driver of atmospheric losses.
PROBABILITY OF CME IMPACT ON EXOPLANETS ORBITING M DWARFS AND SOLAR-LIKE STARS

International Nuclear Information System (INIS)

Kay, C.; Opher, M.; Kornbleuth, M.

2016-01-01

Solar coronal mass ejections (CMEs) produce adverse space weather effects at Earth. Planets in the close habitable zone of magnetically active M dwarfs may experience more extreme space weather than at Earth, including frequent CME impacts leading to atmospheric erosion and leaving the surface exposed to extreme flare activity. Similar erosion may occur for hot Jupiters with close orbits around solar-like stars. We have developed a model, Forecasting a CME's Altered Trajectory (ForeCAT), which predicts a CME's deflection. We adapt ForeCAT to simulate CME deflections for the mid-type M dwarf V374 Peg and hot Jupiters with solar-type hosts. V374 Peg's strong magnetic fields can trap CMEs at the M dwarfs's Astrospheric Current Sheet, that is, the location of the minimum in the background magnetic field. Solar-type CMEs behave similarly, but have much smaller deflections and do not become trapped at the Astrospheric Current Sheet. The probability of planetary impact decreases with increasing inclination of the planetary orbit with respect to the Astrospheric Current Sheet: 0.5–5 CME impacts per day for M dwarf exoplanets, 0.05–0.5 CME impacts per day for solar-type hot Jupiters. We determine the minimum planetary magnetic field necessary to shield a planet's atmosphere from CME impacts. M dwarf exoplanets require values between tens and hundreds of Gauss. Hot Jupiters around a solar-type star, however, require a more reasonable <30 G. These values exceed the magnitude required to shield a planet from the stellar wind, suggesting that CMEs may be the key driver of atmospheric losses.
MASCARA-1 b. A hot Jupiter transiting a bright mV = 8.3 A-star in a misaligned orbit

Science.gov (United States)

Talens, G. J. J.; Albrecht, S.; Spronck, J. F. P.; Lesage, A.-L.; Otten, G. P. P. L.; Stuik, R.; Van Eylen, V.; Van Winckel, H.; Pollacco, D.; McCormac, J.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Snellen, I. A. G.

2017-10-01

We report the discovery of MASCARA-1 b, which is the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). This exoplanet is a hot Jupiter orbiting a bright mV = 8.3, rapidly rotating (vsini⋆ > 100 km s-1) A8 star with a period of 2.148780 ± 8 × 10-6 days. The planet has a mass and radius of 3.7 ± 0.9 MJup and 1.5 ± 0.3 RJup, respectively. As with most hot Jupiters transiting early-type stars, we find a misalignment between the planet orbital axis and the stellar spin axis, which may be a signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of 1.5 ± 0.9 g cm-3 and an equilibrium temperature of 2570+50-30K, that is one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA. Tables of the photometry and the reduced spectra as FITS files are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A73
The influence of prophylactic factor VIII in severe hemophilia A

Science.gov (United States)

Gissel, Matthew; Whelihan, Matthew F; Ferris, Lauren A; Mann, Kenneth G; Rivard, Georges E; Brummel-Ziedins, Kathleen E

2013-01-01

Introduction Hemophilia A individuals displaying a similar genetic defect have heterogeneous clinical phenotypes. Aim To evaluate the underlying effect of exogenous factor (f)VIII on tissue factor (Tf)-initiated blood coagulation in severe hemophilia utilizing both empirical and computational models. Methods We investigated twenty-five clinically severe hemophilia A patients. All individuals were on fVIII prophylaxis and had not received fVIII from 0.25 to 4 days prior to phlebotomy. Coagulation was initiated by the addition of Tf to contact-pathway inhibited whole blood ± an anti-fVIII antibody. Aliquots were quenched over 20 min and analyzed for thrombin generation and fibrin formation. Coagulation factor levels were obtained and used to computationally predict thrombin generation with fVIII set to either zero or its value at the time of the draw. Results Due to prophylactic fVIII, at the time of the blood draw, the individuals had fVIII levels that ranged from hemophilia A. The combination of each individual's coagulation factors (outside of fVIII) determine each individual's baseline thrombin potential and may affect bleeding risk. PMID:21899664
Stars get dizzy after lunch

International Nuclear Information System (INIS)

Zhang, Michael; Penev, Kaloyan

2014-01-01

Exoplanet searches have discovered a large number of h ot Jupiters — high-mass planets orbiting very close to their parent stars in nearly circular orbits. A number of these planets are sufficiently massive and close-in to be significantly affected by tidal dissipation in the parent star, to a degree parameterized by the tidal quality factor Q * . This process speeds up their star's rotation rate while reducing the planet's semimajor axis. In this paper, we investigate the tidal destruction of hot Jupiters. Because the orbital angular momenta of these planets are a significant fraction of their star's rotational angular momenta, they spin up their stars significantly while spiraling to their deaths. Using the Monte Carlo simulation, we predict that for Q * = 10 6 , 3.9 × 10 –6 of stars with the Kepler Target Catalog's mass distribution should have a rotation period shorter than 1/3 day (8 hr) due to accreting a planet. Exoplanet surveys such as SuperWASP, HATnet, HATsouth, and KELT have already produced light curves of millions of stars. These two facts suggest that it may be possible to search for tidally destroyed planets by looking for stars with extremely short rotational periods, then looking for remnant planet cores around those candidates, anomalies in the metal distribution, or other signatures of the recent accretion of the planet.
Masses, radii, and orbits of small Kepler planets

DEFF Research Database (Denmark)

Marcy, Geoffrey W.; Isaacson, Howard; Howard, Andrew W.

2014-01-01

We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurement...
Environmental effects on star formation in dwarf galaxies and star clusters

Science.gov (United States)

Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

2015-08-01

We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in an external environment.Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. The two-fluids instability at the interface between a stellar system and its surrounding hotter and less dense environment is related to the star formation processes through a set of differential equations. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in theoretical interpretations of numerical results as well as observational applications. We show how spherical coordinates naturally enlighten the interpretation of the two-fluids instability in a geometry that directly applies to astrophysical case. Finally, we consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.
Factor VIII assay

Science.gov (United States)

... this page: //medlineplus.gov/ency/article/003678.htm Factor VIII assay To use the sharing features on ... M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health ...
Roto-translation motion of the stars in close binary systems

International Nuclear Information System (INIS)

Medvedeva, A A

2013-01-01

This article has to show that the model of p-h which is used to determine the change of the semi major axis of the relative orbit stars is incorrect and leads to large errors in the determination of semi-major axis. The new model, suitable for the elliptical orbits of the stars. To determine relative motion of stars in a close binary system in this paper uses a numerical integration of the equations of motion with the reactive forces, including the rotational component of attraction between the stars and the stream flows into the substance. The calculations of elliptical orbits of close binary stars show that the effect of the reactive force on the evolution of the orbits of stars may be different. The results can be refined by introducing other disturbing factors and making new assumptions based on observations
An Earth-mass planet orbiting α Centauri B.

Science.gov (United States)

Dumusque, Xavier; Pepe, Francesco; Lovis, Christophe; Ségransan, Damien; Sahlmann, Johannes; Benz, Willy; Bouchy, François; Mayor, Michel; Queloz, Didier; Santos, Nuno; Udry, Stéphane

2012-11-08

Exoplanets down to the size of Earth have been found, but not in the habitable zone--that is, at a distance from the parent star at which water, if present, would be liquid. There are planets in the habitable zone of stars cooler than our Sun, but for reasons such as tidal locking and strong stellar activity, they are unlikely to harbour water-carbon life as we know it. The detection of a habitable Earth-mass planet orbiting a star similar to our Sun is extremely difficult, because such a signal is overwhelmed by stellar perturbations. Here we report the detection of an Earth-mass planet orbiting our neighbour star α Centauri B, a member of the closest stellar system to the Sun. The planet has an orbital period of 3.236 days and is about 0.04 astronomical units from the star (one astronomical unit is the Earth-Sun distance).
The stars: an absolute radiometric reference for the on-orbit calibration of PLEIADES-HR satellites

Science.gov (United States)

Meygret, Aimé; Blanchet, Gwendoline; Mounier, Flore; Buil, Christian

2017-09-01

The accurate on-orbit radiometric calibration of optical sensors has become a challenge for space agencies who gather their effort through international working groups such as CEOS/WGCV or GSICS with the objective to insure the consistency of space measurements and to reach an absolute accuracy compatible with more and more demanding scientific needs. Different targets are traditionally used for calibration depending on the sensor or spacecraft specificities: from on-board calibration systems to ground targets, they all take advantage of our capacity to characterize and model them. But achieving the in-flight stability of a diffuser panel is always a challenge while the calibration over ground targets is often limited by their BDRF characterization and the atmosphere variability. Thanks to their agility, some satellites have the capability to view extra-terrestrial targets such as the moon or stars. The moon is widely used for calibration and its albedo is known through ROLO (RObotic Lunar Observatory) USGS model but with a poor absolute accuracy limiting its use to sensor drift monitoring or cross-calibration. Although the spectral irradiance of some stars is known with a very high accuracy, it was not really shown that they could provide an absolute reference for remote sensors calibration. This paper shows that high resolution optical sensors can be calibrated with a high absolute accuracy using stars. The agile-body PLEIADES 1A satellite is used for this demonstration. The star based calibration principle is described and the results are provided for different stars, each one being acquired several times. These results are compared to the official calibration provided by ground targets and the main error contributors are discussed.
Star formation: Cosmic feast

Science.gov (United States)

Scaringi, Simone

2017-03-01

Low-mass stars form through a process known as disk accretion, eating up material that orbits in a disk around them. It turns out that the same mechanism also describes the formation of more massive stars.
[Ehler-Danlos syndrome type VIII].

Science.gov (United States)

Ciarloni, L; Perrigouard, C; Lipsker, D; Cribier, B

2010-03-01

Ehlers-Danlos syndrome (EDS) comprises a heterogeneous group of diseases involving genetic collagen fibre impairment. We describe a case of a patient presenting the rare type VIII, in which dermatitis ocre was associated with parodontal disease, and which was diagnosed late. A 29-year-old man consulted for a pretibial ulcer present for seven years, resulting from a post-traumatic haematoma that had failed to heal. In view of the longiliner morphology, it had previously been diagnosed as Marfan syndrome. Subsequently, edentation was observed as well as "alveolar bone fragility". Examination revealed a marfanoid morphotype, a pretibial ulcer set within long-standing bilateral dermatitis ocre and papyraceous scars, but no joint hyperlaxity or cutaneous hyperelasticity. The diagnosis was consequently corrected to EDS type VIII. Type VIII is a rare form of EDS, and the molecular mechanism is poorly understood. The involvement of parodontal connective tissue suggests impairment of collagen I and III proteins. It is important to identify this type of the disease since it involves parodontal disease for which early treatment is required in order to try to prevent edentation. The present case demonstrates the importance of diagnosis, which may be based upon appearance of bilateral dermatitis ocre from the age of 15 years associated with skin fragility. This sign is not part of the classical picture of Marfan syndrome, with which EDS type VIII is often confounded. Copyright 2009 Elsevier Masson SAS. All rights reserved.
Retired A Stars and Their Companions. III. Comparing the Mass-Period Distributions of Planets Around A-Type Stars and Sun-Like Stars

Science.gov (United States)

Bowler, Brendan P.; Johnson, John Asher; Marcy, Geoffrey W.; Henry, Gregory W.; Peek, Kathryn M. G.; Fischer, Debra A.; Clubb, Kelsey I.; Liu, Michael C.; Reffert, Sabine; Schwab, Christian; Lowe, Thomas B.

2010-01-01

We present an analysis of ~5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 lsim M */M sunlsim 2.0) with the goal of measuring the occurrence rate of Jovian planets around (evolved) A-type stars and comparing the distributions of their orbital and physical characteristics to those of planets around Sun-like stars. We provide updated orbital solutions incorporating new radial velocity measurements for five known planet-hosting stars in our sample; uncertainties in the fitted parameters are assessed using a Markov-Chain Monte Carlo method. The frequency of Jovian planets interior to 3 AU is 26+9 -8%, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to {0.2, 0.3, 0.5, 0.6, 1.3} M Jup within {0.1, 0.3, 0.6, 1.0, 3.0} AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN vprop M α P β dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of α and β for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4σ level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (~50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets. Based on observations obtained at the Lick Observatory, which is operated by the University of California.
Optimal Target Stars in the Search for Life

Science.gov (United States)

Lingam, Manasvi; Loeb, Abraham

2018-04-01

The selection of optimal targets in the search for life represents a highly important strategic issue. In this Letter, we evaluate the benefits of searching for life around a potentially habitable planet orbiting a star of arbitrary mass relative to a similar planet around a Sun-like star. If recent physical arguments implying that the habitability of planets orbiting low-mass stars is selectively suppressed are correct, we find that planets around solar-type stars may represent the optimal targets.

Differential proteolytic activation of factor VIII-von Willebrand factor complex by thrombin

International Nuclear Information System (INIS)

Hill-Eubanks, D.C.; Parker, C.G.; Lollar, P.

1989-01-01

Blood coagulation factor VIII (fVIII) is a plasma protein that is decreased or absent in hemophilia A. It is isolated as a mixture of heterodimers that contain a variably sized heavy chain and a common light chain. Thrombin catalyzes the activation of fVIII in a reaction that is associated with cleavages in both types of chain. The authors isolated a serine protease from Bothrops jararacussu snake venom that catalyzes thrombin-like heavy-chain cleavage but not light-chain cleavage in porcine fVIII as judged by NaDodSO 4 /PAGE and N-terminal sequence analysis. Using a plasma-free assay of the ability of activated 125 I-fVIII to function as a cofactor in the activation of factor X by factor IXa, they found that fVIII is activated by the venom enzyme. The venom enzyme-activated fVIII was isolated in stable form by cation-exchange HPLC. von Willebrand factor inhibited venom enzyme-activated fVIII but not thrombin-activated fVIII. These results suggest that the binding of fVIII to von Willebrand factor depends on the presence of an intact light chain and that activated fVIII must dissociate from von Willebrand factor to exert its cofactor effect. Thus, proteolytic activation of fVIII-von Willebrand factor complex appears to be differentially regulated by light-chain cleavage to dissociate the complex and heavy-chain cleavage to activate the cofactor function
Stars on Local Time: A Personal Almanac

Science.gov (United States)

Gottlieb-Roberts, M.

2016-01-01

First presented at INSAP VIII, the artwork A Personal Almanac is my interpretation of the familiar seasons-of-life allegory. The booklet's eight pairs of seasonal pages— spring equinox through the cross-quarter Groundhog Day—portray a life in the decades from the 1940s to the 2010s under the stars of rural Georgia, France, Miami, West Africa and the other places I have lived. A Personal Almanac is included in the art book A Durable Tale, the illustrated story of my thirty-year search in the Southeast United States and in West Africa for living memories of old star almanacs. In that odyssey I uncovered some very deep roots for an oral literature of the African desert, the nomadic bard's star story that I believe inspired creation of the first nine tablets of the standard version Babylonian Gilgamesh.
77 FR 64401 - Order of Succession for HUD Region VIII

Science.gov (United States)

2012-10-19

... Region VIII AGENCY: Office of Field Policy and Management, HUD. ACTION: Notice of Order of Succession... Field Offices (Region VIII). This Order of Succession supersedes all previous Orders of Succession for HUD Region VIII. DATES: Effective Date: October 9, 2012. FOR FURTHER INFORMATION CONTACT: Lawrence D...
Finding binaries from phase modulation of pulsating stars with Kepler

Science.gov (United States)

Shibahashi, Hiromoto; Murphy, Simon; Bedding, Tim

2017-09-01

Binary orbital motion causes a periodic variation in the path length travelled by light emitted from a star towards us. Hence, if the star is pulsating, the observed phase of the pulsation varies over the orbit. Conversely, once we have observed such phase variation, we can extract information about the binary orbit from photometry alone. Continuous and precise space-based photometry has made it possible to measure these light travel time effects on the pulsating stars in binary systems. This opens up a new way of finding unseen brown dwarfs, planets, or massive compact stellar remnants: neutron stars and black holes.
Evaluation of parameters of Black Hole, stellar cluster and dark matter distribution from bright star orbits in the Galactic Center

Science.gov (United States)

Zakharov, Alexander

It is well-known that one can evaluate black hole (BH) parameters (including spin) analyz-ing trajectories of stars around BH. A bulk distribution of matter (dark matter (DM)+stellar cluster) inside stellar orbits modifies trajectories of stars, namely, generally there is a apoas-tron shift in direction which opposite to GR one, even now one could put constraints on DM distribution and BH parameters and constraints will more stringent in the future. Therefore, an analyze of bright star trajectories provides a relativistic test in a weak gravitational field approximation, but in the future one can test a strong gravitational field near the BH at the Galactic Center with the same technique due to a rapid progress in observational facilities. References A. Zakharov et al., Phys. Rev. D76, 062001 (2007). A.F. Zakharov et al., Space Sci. Rev. 148, 301313(2009).
The DiskMass Survey. VIII. On the Relationship between Disk Stability and Star Formation

NARCIS (Netherlands)

Westfall, Kyle B.; Andersen, David R.; Bershady, Matthew A.; Martinsson, Thomas P. K.; Swaters, Robert A.; Verheijen, Marc A. W.

2014-01-01

We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo & Wiegert (Q RW), incorporating stellar
The Spacelab IPS Star Simulator

Science.gov (United States)

Wessling, Francis C., III

The cost of doing business in space is very high. If errors occur while in orbit the costs grow and desired scientific data may be corrupted or even lost. The Spacelab Instrument Pointing System (IPS) Star Simulator is a unique test bed that allows star trackers to interface with simulated stars in a laboratory before going into orbit. This hardware-in-the loop testing of equipment on earth increases the probability of success while in space. The IPS Star Simulator provides three fields of view 2.55 x 2.55 degrees each for input into star trackers. The fields of view are produced on three separate monitors. Each monitor has 4096 x 4096 addressable points and can display 50 stars (pixels) maximum at a given time. The pixel refresh rate is 1000 Hz. The spectral output is approximately 550 nm. The available relative visual magnitude range is 2 to 8 visual magnitudes. The star size is less than 100 arc seconds. The minimum star movement is less than 5 arc seconds and the relative position accuracy is approximately 40 arc seconds. The purpose of this paper is to describe the LPS Star Simulator design and to provide an operational scenario so others may gain from the approach and possible use of the system.
Factoring in Factor VIII With Acute Ischemic Stroke.

Science.gov (United States)

Siegler, James E; Samai, Alyana; Albright, Karen C; Boehme, Amelia K; Martin-Schild, Sheryl

2015-10-01

There is growing research interest into the etiologies of cryptogenic stroke, in particular as it relates to hypercoagulable states. An elevation in serum levels of the procoagulant factor VIII is recognized as one such culprit of occult cerebral infarctions. It is the objective of the present review to summarize the molecular role of factor VIII in thrombogenesis and its clinical use in the diagnosis and prognosis of acute ischemic stroke. We also discuss the utility of screening for serum factor VIII levels among patients at risk for, or those who have experienced, ischemic stroke. © The Author(s) 2015.
The dance of the double stars

International Nuclear Information System (INIS)

Theokas, A.

1985-01-01

The paper concerns pairs of stars orbiting one another. The evolutionary path model for close binary stars, involving a mass transfer of gases between the stars, is described. The life history of a single star; cataclysmic variables; the algol paradox, matter and lagranges' point; x-ray binaries and bursters; and pulsars; are all briefly discussed. (U.K.)
Relaxation near Supermassive Black Holes Driven by Nuclear Spiral Arms: Anisotropic Hypervelocity Stars, S-stars, and Tidal Disruption Events

Energy Technology Data Exchange (ETDEWEB)

Hamers, Adrian S. [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States); Perets, Hagai B., E-mail: hamers@ias.edu [Technion—Israel Institute of Technology, Haifa 32000 (Israel)

2017-09-10

Nuclear spiral arms are small-scale transient spiral structures found in the centers of galaxies. Similarly to their galactic-scale counterparts, nuclear spiral arms can perturb the orbits of stars. In the case of the Galactic center (GC), these perturbations can affect the orbits of stars and binaries in a region extending to several hundred parsecs around the supermassive black hole (SMBH), causing diffusion in orbital energy and angular momentum. This diffusion process can drive stars and binaries to close approaches with the SMBH, disrupting single stars in tidal disruption events (TDEs), or disrupting binaries, leaving a star tightly bound to the SMBH and an unbound star escaping the galaxy, i.e., a hypervelocity star (HVS). Here, we consider diffusion by nuclear spiral arms in galactic nuclei, specifically the Milky Way GC. We determine nuclear-spiral-arm-driven diffusion rates using test-particle integrations and compute disruption rates. Our TDE rates are up to 20% higher compared to relaxation by single stars. For binaries, the enhancement is up to a factor of ∼100, and our rates are comparable to the observed numbers of HVSs and S-stars. Our scenario is complementary to relaxation driven by massive perturbers. In addition, our rates depend on the inclination of the binary with respect to the Galactic plane. Therefore, our scenario provides a novel potential source for the observed anisotropic distribution of HVSs. Nuclear spiral arms may also be important for accelerating the coalescence of binary SMBHs and for supplying nuclear star clusters with stars and gas.
Extended analyses of Se VII and Se VIII

International Nuclear Information System (INIS)

Vankleef, Th.A.M.; Joshi, Y.N.

1984-01-01

Joshi et al. (1984) have conducted an analysis of the 3d8 4s-3d8 4p transitions in As VII. The present investigation is concerned with an analysis of similar transitions in Se VIII. The selenium spectrum was photographed in the 400-1200-A wavelength region on a variety of normal-incidence spectrographs. Attention is given to least-squares-fit (LSF) and Hartree-Fock (HF) parameter values for the 3d9 4d configuration of Se VII, LSF and HF parameter values for the 3d8 4s and 3d8 4p configurations of Se VIII, the energy and composition of the levels of the 3d9 4d configuration of Se VII, classified lines in Se VII, energy levels and composition of the 3d8 4s configuration and the revised and newly determined levels of the 3d8 4p configuration of Se VIII, and newly classified lines of Se VIII. 15 references
POET: A Model for Planetary Orbital Evolution Due to Tides on Evolving Stars

Science.gov (United States)

Penev, Kaloyan; Zhang, Michael; Jackson, Brian

2014-06-01

We make publicly available an efficient, versatile, easy to use and extend tool for calculating the evolution of circular aligned planetary orbits due to the tidal dissipation in the host star. This is the first model to fully account for the evolution of the angular momentum of the stellar convective envelope by the tidal coupling, the transfer of angular momentum between the stellar convective and radiative zones, the effects of the stellar evolution on the tidal dissipation efficiency and stellar core and envelope spins, the loss of stellar convective zone angular momentum to a magnetically launched wind and frequency dependent tidal dissipation. This is only a first release and further development is under way to allow calculating the evolution of inclined and eccentric orbits, with the latter including the tidal dissipation in the planet and its feedback on planetary structure. Considerable effort has been devoted to providing extensive documentation detailing both the usage and the complete implementation details, in order to make it as easy as possible for independent groups to use and/or extend the code for their purposes. POET represents a significant improvement over some previous models for planetary tidal evolution and so has many astrophysical applications. In this article, we describe and illustrate several key examples.
PLANET HUNTERS. VIII. CHARACTERIZATION OF 41 LONG-PERIOD EXOPLANET CANDIDATES FROM KEPLER ARCHIVAL DATA

International Nuclear Information System (INIS)

Wang, Ji; Fischer, Debra A.; Picard, Alyssa; Schmitt, Joseph R.; Boyajian, Tabetha S.; Barclay, Thomas; Ma, Bo; Bowler, Brendan P.; Riddle, Reed; Jek, Kian J.; LaCourse, Daryll; Simister, Dean Joseph; Grégoire, Boscher; Babin, Sean P.; Poile, Trevor; Jacobs, Thomas Lee; Baranec, Christoph; Law, Nicholas M.; Lintott, Chris; Schawinski, Kevin

2015-01-01

The census of exoplanets is incomplete for orbital distances larger than 1 AU. Here, we present 41 long-period planet candidates in 38 systems identified by Planet Hunters based on Kepler archival data (Q0–Q17). Among them, 17 exhibit only one transit, 14 have two visible transits, and 10 have more than three visible transits. For planet candidates with only one visible transit, we estimate their orbital periods based on transit duration and host star properties. The majority of the planet candidates in this work (75%) have orbital periods that correspond to distances of 1–3 AU from their host stars. We conduct follow-up imaging and spectroscopic observations to validate and characterize planet host stars. In total, we obtain adaptive optics images for 33 stars to search for possible blending sources. Six stars have stellar companions within 4″. We obtain high-resolution spectra for 6 stars to determine their physical properties. Stellar properties for other stars are obtained from the NASA Exoplanet Archive and the Kepler Stellar Catalog by Huber et al. We validate 7 planet candidates that have planet confidence over 0.997 (3σ level). These validated planets include 3 single-transit planets (KIC-3558849b, KIC-5951458b, and KIC-8540376c), 3 planets with double transits (KIC-8540376b, KIC-9663113b, and KIC-10525077b), and 1 planet with four transits (KIC-5437945b). This work provides assessment regarding the existence of planets at wide separations and the associated false positive rate for transiting observation (17%–33%). More than half of the long-period planets with at least three transits in this paper exhibit transit timing variations up to 41 hr, which suggest additional components that dynamically interact with the transiting planet candidates. The nature of these components can be determined by follow-up radial velocity and transit observations
PLANET HUNTERS. VIII. CHARACTERIZATION OF 41 LONG-PERIOD EXOPLANET CANDIDATES FROM KEPLER ARCHIVAL DATA

Energy Technology Data Exchange (ETDEWEB)

Wang, Ji; Fischer, Debra A.; Picard, Alyssa; Schmitt, Joseph R.; Boyajian, Tabetha S. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Barclay, Thomas [NASA Ames Research Center, M/S 244-30, Moffett Field, CA 94035 (United States); Ma, Bo [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Bowler, Brendan P.; Riddle, Reed [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91101 (United States); Jek, Kian J.; LaCourse, Daryll; Simister, Dean Joseph; Grégoire, Boscher; Babin, Sean P.; Poile, Trevor; Jacobs, Thomas Lee; Baranec, Christoph [Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700 (United States); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States); Lintott, Chris [Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); and others

2015-12-20

The census of exoplanets is incomplete for orbital distances larger than 1 AU. Here, we present 41 long-period planet candidates in 38 systems identified by Planet Hunters based on Kepler archival data (Q0–Q17). Among them, 17 exhibit only one transit, 14 have two visible transits, and 10 have more than three visible transits. For planet candidates with only one visible transit, we estimate their orbital periods based on transit duration and host star properties. The majority of the planet candidates in this work (75%) have orbital periods that correspond to distances of 1–3 AU from their host stars. We conduct follow-up imaging and spectroscopic observations to validate and characterize planet host stars. In total, we obtain adaptive optics images for 33 stars to search for possible blending sources. Six stars have stellar companions within 4″. We obtain high-resolution spectra for 6 stars to determine their physical properties. Stellar properties for other stars are obtained from the NASA Exoplanet Archive and the Kepler Stellar Catalog by Huber et al. We validate 7 planet candidates that have planet confidence over 0.997 (3σ level). These validated planets include 3 single-transit planets (KIC-3558849b, KIC-5951458b, and KIC-8540376c), 3 planets with double transits (KIC-8540376b, KIC-9663113b, and KIC-10525077b), and 1 planet with four transits (KIC-5437945b). This work provides assessment regarding the existence of planets at wide separations and the associated false positive rate for transiting observation (17%–33%). More than half of the long-period planets with at least three transits in this paper exhibit transit timing variations up to 41 hr, which suggest additional components that dynamically interact with the transiting planet candidates. The nature of these components can be determined by follow-up radial velocity and transit observations.
General Relativity and Compact Stars

International Nuclear Information System (INIS)

Glendenning, Norman K.

2005-01-01

Compact stars--broadly grouped as neutron stars and white dwarfs--are the ashes of luminous stars. One or the other is the fate that awaits the cores of most stars after a lifetime of tens to thousands of millions of years. Whichever of these objects is formed at the end of the life of a particular luminous star, the compact object will live in many respects unchanged from the state in which it was formed. Neutron stars themselves can take several forms--hyperon, hybrid, or strange quark star. Likewise white dwarfs take different forms though only in the dominant nuclear species. A black hole is probably the fate of the most massive stars, an inaccessible region of spacetime into which the entire star, ashes and all, falls at the end of the luminous phase. Neutron stars are the smallest, densest stars known. Like all stars, neutron stars rotate--some as many as a few hundred times a second. A star rotating at such a rate will experience an enormous centrifugal force that must be balanced by gravity or else it will be ripped apart. The balance of the two forces informs us of the lower limit on the stellar density. Neutron stars are 10 14 times denser than Earth. Some neutron stars are in binary orbit with a companion. Application of orbital mechanics allows an assessment of masses in some cases. The mass of a neutron star is typically 1.5 solar masses. They can therefore infer their radii: about ten kilometers. Into such a small object, the entire mass of our sun and more, is compressed
K2-139 b: a low-mass warm Jupiter on a 29-d orbit transiting an active K0 V star

Science.gov (United States)

Barragán, O.; Gandolfi, D.; Smith, A. M. S.; Deeg, H. J.; Fridlund, M. C. V.; Persson, C. M.; Donati, P.; Endl, M.; Csizmadia, Sz; Grziwa, S.; Nespral, D.; Hatzes, A. P.; Cochran, W. D.; Fossati, L.; Brems, S. S.; Cabrera, J.; Cusano, F.; Eigmüller, Ph; Eiroa, C.; Erikson, A.; Guenther, E.; Korth, J.; Lorenzo-Oliveira, D.; Mancini, L.; Pätzold, M.; Prieto-Arranz, J.; Rauer, H.; Rebollido, I.; Saario, J.; Zakhozhay, O. V.

2018-04-01

We announce the discovery of K2-139 b (EPIC 218916923 b), a transiting warm-Jupiter (Teq = 547 ± 25 K) on a 29-d orbit around an active (log R^' _HK = -4.46 ± 0.06) K0 V star in K2 Campaign 7. We derive the system's parameters by combining the K2 photometry with ground-based follow-up observations. With a mass of 0.387 _{ - 0.075 } ^ {+ 0.083 }MJ and radius of 0.808 _{ - 0.033 } ^ {+ 0.034 }RJ, K2-139 b is one of the transiting warm Jupiters with the lowest mass known to date. The planetary mean density of 0.91 _{ - 0.20} ^ { + 0.24 } g cm-3can be explained with a core of ˜50 M⊕. Given the brightness of the host star (V = 11.653 mag), the relatively short transit duration (˜5 h), and the expected amplitude of the Rossiter-McLaughlin effect (˜25m s-1), K2-139 is an ideal target to measure the spin-orbit angle of a planetary system hosting a warm Jupiter.
The quantum anomalous Hall effect on a star lattice with spin-orbit coupling and an exchange field

International Nuclear Information System (INIS)

Chen Mengsu; Wan Shaolong

2012-01-01

We study a star lattice with Rashba spin-orbit coupling and an exchange field and find that there is a quantum anomalous Hall effect in this system, and that there are five energy gaps at Dirac points and quadratic band crossing points. We calculate the Berry curvature distribution and obtain the Hall conductivity (Chern number ν) quantized as integers, and find that ν =- 1,2,1,1,2 when the Fermi level lies in these five gaps. Our model can be viewed as a general quantum anomalous Hall system and, in limit cases, can give what the honeycomb lattice and kagome lattice give. We also find that there is a nearly flat band with ν = 1 which may provide an opportunity for realizing the fractional quantum anomalous Hall effect. Finally, the chiral edge states on a zigzag star lattice are given numerically, to confirm the topological property of this system. (paper)
New planet hints at life in the stars

CERN Multimedia

Dalton, A W

2002-01-01

Astronomers have detected a distant planet 100 light years from Earth, circling Tau1 Gruis, its star, in the constellation of Grus (the crane). The planet, similar in appearance to Jupiter, is three times as far away from its star as the Earth is from the Sun and takes four years to revolve around the star, in a roughly circular orbit. Scientists believe this type of planetary orbit is the most promising for finding worlds that contain life (1 page).
Evidence for a solar companion star

International Nuclear Information System (INIS)

Muller, R.A.

1984-08-01

Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future
Evidence for a solar companion star

Energy Technology Data Exchange (ETDEWEB)

Muller, R.A.

1984-08-01

Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future.

Idiopathic Acquired Hemophilia A with Undetectable Factor VIII Inhibitor

Directory of Open Access Journals (Sweden)

Nicholas B. Abt

2014-01-01

Full Text Available Objective. We present the case of a 73-year-old female, with no family or personal history of a bleeding disorder, who had a classic presentation for acquired hemophilia A. Factor VIII activity was low but detectable and a factor VIII inhibitor was undetectable. Methods. The patient’s plasma was comprehensively studied to determine the cause of the acquired coagulopathy. Using the Nijmegen modification of the Bethesda assay, no factor VIII autoantibody was measureable despite varying the incubation time from 1 to 3 hours. Results. The aPTT was prolonged at 46.8 seconds, which did not correct in the 4 : 1 mix but did with 1 : 1 mix. Using a one stage factor VIII activity assay, the FVIII activity was 16% and chromogenic FVIII activity was also 16%. The patient was treated with recombinant FVII and transfusion, significantly reducing bleeding. Long-term therapy was initiated with cyclophosphamide and prednisone with normalization of FVIII activity. Conclusions. Physicians can be presented with the challenging clinical picture of an acquired factor VIII inhibitor without a detectable inhibitor by the Bethesda assay. Standard therapy for an acquired hemophilia A should be considered.
4p-5s transitions in YVII, VIII, ZrVIII, IX, NbIX, X and MoX, XI

International Nuclear Information System (INIS)

Rahimullah, K.; Chaghtai, M.S.Z.; Khatoon, S.

1976-01-01

The spectra of Y VII, VIII, Zr VIII, IX, Nb X and Mo X, XI are studied for the first time and the 1971 analysis of Nb IX is improved. By analyses of the transitions 4s 2 4psup(k)-4s 2 4psup(k-1)5s all the levels of the configurations 4p 3 , 4p 2 5s, 4p 2 and 4p5s are established in the spectra concerned. (Auth.)
RADIAL VELOCITY OBSERVATIONS AND LIGHT CURVE NOISE MODELING CONFIRM THAT KEPLER-91b IS A GIANT PLANET ORBITING A GIANT STAR

International Nuclear Information System (INIS)

Barclay, Thomas; Huber, Daniel; Rowe, Jason F.; Quintana, Elisa V.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Foreman-Mackey, Daniel

2015-01-01

Kepler-91b is a rare example of a transiting hot Jupiter around a red giant star, providing the possibility to study the formation and composition of hot Jupiters under different conditions compared to main-sequence stars. However, the planetary nature of Kepler-91b, which was confirmed using phase-curve variations by Lillo-Box et al., was recently called into question based on a re-analysis of Kepler data. We have obtained ground-based radial velocity observations from the Hobby-Eberly Telescope and unambiguously confirm the planetary nature of Kepler-91b by simultaneously modeling the Kepler and radial velocity data. The star exhibits temporally correlated noise due to stellar granulation which we model as a Gaussian Process. We hypothesize that it is this noise component that led previous studies to suspect Kepler-91b to be a false positive. Our work confirms the conclusions presented by Lillo-Box et al. that Kepler-91b is a 0.73 ± 0.13 M Jup planet orbiting a red giant star
Differential rotation of stars with multiple transiting planets

Science.gov (United States)

Netto, Yuri; Valio, Adriana

2017-10-01

If a star hosts a planet in an orbit such that it eclipses the star periodically, can be estimated the rotation profile of this star. If planets in multiplanetary system occult different stellar areas, spots in more than one latitude of the stellar disc can be detected. The monitored study of theses starspots in different latitudes allow us to infer the rotation profile of the star. We use the model described in Silva (2003) to characterize the starspots of Kepler-210, an active star with two planets. Kepler-210 is a late K star with an estimated age of 350 +/- 50 Myrs, average rotation period of 12.33 days, mass of 0.63 M⊙ and radius of 0.69 R⊙. The planets that eclipses this star have radii of 0.0498 R s and 0.0635 R s with orbital periods of 2.4532 +/- 0.0007 days and 7.9725 +/- 0.0014 days, respectively, where R s is the star radius.
Distances of Dwarf Carbon Stars

Science.gov (United States)

Harris, Hugh C.; Dahn, Conard C.; Subasavage, John P.; Munn, Jeffrey A.; Canzian, Blaise J.; Levine, Stephen E.; Monet, Alice B.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy M.; Hartkopf, William I.

2018-06-01

Parallaxes are presented for a sample of 20 nearby dwarf carbon stars. The inferred luminosities cover almost two orders of magnitude. Their absolute magnitudes and tangential velocities confirm prior expectations that some originate in the Galactic disk, although more than half of this sample are halo stars. Three stars are found to be astrometric binaries, and orbital elements are determined; their semimajor axes are 1–3 au, consistent with the size of an AGB mass-transfer donor star.
Orbital motion in pre-main sequence binaries

Energy Technology Data Exchange (ETDEWEB)

Schaefer, G. H. [The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023 (United States); Prato, L. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Simon, M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Patience, J., E-mail: schaefer@chara-array.org [Astrophysics Group, School of Physics, University of Exeter, Exeter, EX4 4QL (United Kingdom)

2014-06-01

We present results from our ongoing program to map the visual orbits of pre-main sequence (PMS) binaries in the Taurus star forming region using adaptive optics imaging at the Keck Observatory. We combine our results with measurements reported in the literature to analyze the orbital motion for each binary. We present preliminary orbits for DF Tau, T Tau S, ZZ Tau, and the Pleiades binary HBC 351. Seven additional binaries show curvature in their relative motion. Currently, we can place lower limits on the orbital periods for these systems; full solutions will be possible with more orbital coverage. Five other binaries show motion that is indistinguishable from linear motion. We suspect that these systems are bound and might show curvature with additional measurements in the future. The observations reported herein lay critical groundwork toward the goal of measuring precise masses for low-mass PMS stars.
Pioneer Venus Star Sensor. [active despin control application

Science.gov (United States)

Gutshall, R. L.; Thomas, G.

1979-01-01

The design predictions and orbital performance verification of the solid state star scanner used in the Onboard Attitude Control of the Pioneer Venus Orbiter and Multiprobe are presented. The star sensor extended the scanner use to active despin control, and it differs from previous sensors in solid state detection, redundant electronics for reliability, larger field of view, and large dynamic spin range. The star scanner hardware and design performance based on the ability to predict all noise sources, signal magnitudes, and expected detection probability are discussed. In-flight data collected to verify sensor ground calibration are tabulated and plotted in predicted accuracy curves. It is concluded that the Pioneer Venus Star Sensor has demonstrated predictable star calibration in the range of .1 magnitude uncertainties and usable star catalogs of 100 stars with very high probabilities of detection, which were much better than expected and well within the mission requirements.
POET: Planetary Orbital Evolution due to Tides

Science.gov (United States)

Penev, Kaloyan

2014-08-01

POET (Planetary Orbital Evolution due to Tides) calculates the orbital evolution of a system consisting of a single star with a single planet in orbit under the influence of tides. The following effects are The evolutions of the semimajor axis of the orbit due to the tidal dissipation in the star and the angular momentum of the stellar convective envelope by the tidal coupling are taken into account. In addition, the evolution includes the transfer of angular momentum between the stellar convective and radiative zones, effect of the stellar evolution on the tidal dissipation efficiency, and stellar core and envelope spins and loss of stellar convective zone angular momentum to a magnetically launched wind. POET can be used out of the box, and can also be extended and modified.
Featured Image: Orbiting Stars Share an Envelope

Science.gov (United States)

Kohler, Susanna

2016-03-01

This beautiful series of snapshots from a simulation (click for a better look!) shows what happens when two stars in a binary system become enclosed in the same stellar envelope. In this binary system, one of the stars has exhausted its hydrogen fuel and become a red giant, complete with an expanding stellar envelope composed of hydrogen and helium. Eventually, the envelope expands so much that the companion star falls into it, where it releases gravitational potential energy into the common envelope. A team led by Sebastian Ohlmann (Heidelberg Institute for Theoretical Studies and University of Wrzburg) recently performed hydrodynamic simulations of this process. Ohlmann and collaborators discovered that the energy release eventually triggers large-scale flow instabilities, which leads to turbulence within the envelope. This process has important consequences for how these systems next evolve (for instance, determining whether or not a supernova occurs!). You can check out the authors video of their simulated stellar inspiral below, or see their paper for more images and results from their study.CitationSebastian T. Ohlmann et al 2016 ApJ 816 L9. doi:10.3847/2041-8205/816/1/L9
Tidal stripping of stars near supermassive black holes

Directory of Open Access Journals (Sweden)

Blandford R.

2012-12-01

Full Text Available In a binary system composed of a supermassive black hole and a star orbiting the hole in an equatorial, circular orbit, the stellar orbit will shrink due to the action of gravitational radiation, until the star fills its Roche lobe outside the Innermost Stable Circular Orbit (ISCO of the hole or plunges into the hole. In the former case, gas will flow through the inner Lagrange point (L1 to the hole. If this tidal stripping process happens on a time scale faster than the thermal time scale but slower than the dynamical time scale, the entropy as a function of the interior mass is conserved. The star will evolve adiabatically, and, in most cases, will recede from the hole while filling its Roche lobe. We calculate how the stellar equilibrium properties change, which determines how the stellar orbital period and mass-transfer rate change through the “Roche evolution” for various types of stars in the relativistic regime. We envisage that the mass stream eventually hits the accretion disc, where it forms a hot spot orbiting the hole and may ultimately modulate the luminosity with the stellar orbital frequency. The ultimate goal is to probe the mass and spin of the hole and provide a test of general relativity in the strong-field regime from the resultant quasi-periodic signals. The observability of such a modulation is discussed along with a possible interpretation of an intermittent 1 hour period in the X-ray emission of RE J1034+ 396.
THERMAL EFFECTS ON CAMERA FOCAL LENGTH IN MESSENGER STAR CALIBRATION AND ORBITAL IMAGING

Directory of Open Access Journals (Sweden)

S. Burmeister

2018-04-01

Full Text Available We analyse images taken by the MErcury Surface, Space ENviorment, GEochemistry, and Ranging (MESSENGER spacecraft for the camera’s thermal response in the harsh thermal environment near Mercury. Specifically, we study thermally induced variations in focal length of the Mercury Dual Imaging System (MDIS. Within the several hundreds of images of star fields, the Wide Angle Camera (WAC typically captures up to 250 stars in one frame of the panchromatic channel. We measure star positions and relate these to the known star coordinates taken from the Tycho-2 catalogue. We solve for camera pointing, the focal length parameter and two non-symmetrical distortion parameters for each image. Using data from the temperature sensors on the camera focal plane we model a linear focal length function in the form of f(T = A0 + A1 T. Next, we use images from MESSENGER’s orbital mapping mission. We deal with large image blocks, typically used for the production of a high-resolution digital terrain models (DTM. We analyzed images from the combined quadrangles H03 and H07, a selected region, covered by approx. 10,600 images, in which we identified about 83,900 tiepoints. Using bundle block adjustments, we solved for the unknown coordinates of the control points, the pointing of the camera – as well as the camera’s focal length. We then fit the above linear function with respect to the focal plane temperature. As a result, we find a complex response of the camera to thermal conditions of the spacecraft. To first order, we see a linear increase by approx. 0.0107 mm per degree temperature for the Narrow-Angle Camera (NAC. This is in agreement with the observed thermal response seen in images of the panchromatic channel of the WAC. Unfortunately, further comparisons of results from the two methods, both of which use different portions of the available image data, are limited. If leaving uncorrected, these effects may pose significant difficulties in
Evolving ONe WD+He star systems to intermediate-mass binary pulsars

Science.gov (United States)

Liu, D.; Wang, B.; Chen, W.; Zuo, Z.; Han, Z.

2018-06-01

It has been suggested that accretion-induced collapse (AIC) is a non-negligible path for the formation of the observed neutron stars (NSs). An ONe white dwarf (WD) that accretes material from a He star may experience AIC process and eventually produce intermediate-mass binary pulsars (IMBPs), named as the ONe WD+He star scenario. Note that previous studies can only account for part of the observed IMBPs with short orbital periods. In this work, we investigate the evolution of about 900 ONe WD+He star binaries to explore the distribution of IMBPs. We found that the ONe WD+He star scenario could form IMBPs including pulsars with 5-340 ms spin periods and 0.75-1.38 M_{⊙} WD companions, in which the orbital periods range from 0.04 to 900 d. Compared with the 20 observed IMBPs, this scenario can cover the parameters of 13 sources in the final orbital period-WD mass plane and the Corbet diagram, most of which have short orbital periods. We found that the ONe WD+He star scenario can explain almost all the observed IMBPs with short orbital periods. This work can well match the observed parameters of PSR J1802-2124 (one of the two precisely observed IMBPs), providing a possible evolutional path for its formation. We also speculate that the compact companion of HD 49798 (a hydrogen depleted sdO6 star) may be not a NS based on this work.
Jonckheere Double Star Photometry â Part VIII: Sextans

Science.gov (United States)

Knapp, Wilfried

2018-01-01

If any double star discoverer is in urgent need of photometry then it is Jonckheere. There are over 3000 Jonckheere objects listed in the WDS catalog and a good part of them with magnitudes obviously far too bright. This report covers the Jonckheere objects in the constellation Sextans. One image per object was taken with V-filter to allow for visual magnitude measurement by differential photometry. All objects were additionally checked for common proper motion and a good part of the objects qualify indeed as potential CPM pairs.
40 CFR Appendix Viii to Part 600 - Fuel Economy Label Formats

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel Economy Label Formats VIII... POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Pt. 600, App. VIII Appendix VIII to Part 600—Fuel Economy Label Formats EC01MY92.117 EC01MY92.118 EC01MY92.119 EC01MY92.120...
The stellar orbit distribution in present-day galaxies inferred from the CALIFA survey

Science.gov (United States)

Zhu, Ling; van de Ven, Glenn; Bosch, Remco van den; Rix, Hans-Walter; Lyubenova, Mariya; Falcón-Barroso, Jesús; Martig, Marie; Mao, Shude; Xu, Dandan; Jin, Yunpeng; Obreja, Aura; Grand, Robert J. J.; Dutton, Aaron A.; Macciò, Andrea V.; Gómez, Facundo A.; Walcher, Jakob C.; García-Benito, Rubén; Zibetti, Stefano; Sánchez, Sebastian F.

2018-03-01

Galaxy formation entails the hierarchical assembly of mass, along with the condensation of baryons and the ensuing, self-regulating star formation1,2. The stars form a collisionless system whose orbit distribution retains dynamical memory that can constrain a galaxy's formation history3. The orbits dominated by ordered rotation, with near-maximum circularity λz ≈ 1, are called kinematically cold, and the orbits dominated by random motion, with low circularity λz ≈ 0, are kinematically hot. The fraction of stars on `cold' orbits, compared with the fraction on `hot' orbits, speaks directly to the quiescence or violence of the galaxies' formation histories4,5. Here we present such orbit distributions, derived from stellar kinematic maps through orbit-based modelling for a well-defined, large sample of 300 nearby galaxies. The sample, drawn from the CALIFA survey6, includes the main morphological galaxy types and spans a total stellar mass range from 108.7 to 1011.9 solar masses. Our analysis derives the orbit-circularity distribution as a function of galaxy mass and its volume-averaged total distribution. We find that across most of the considered mass range and across morphological types, there are more stars on `warm' orbits defined as 0.25 ≤ λz ≤ 0.8 than on either `cold' or `hot' orbits. This orbit-based `Hubble diagram' provides a benchmark for galaxy formation simulations in a cosmological context.
In Orbit Performance of a Fully Autonomous Star Tracker

DEFF Research Database (Denmark)

Jørgensen, John Leif

1999-01-01

The Department of Automation at DTU has developed the Advanced Stellar Compass (ASC), a fully autonomous star tracker, for use as high precision attitude reference onboard spacecrafts. The ASC is composed of a CCD-based camera and a powerful microprocessor containing star catalogue, image......-analysis software and a search engine. The unit autonomously performs all tasks necessary to calculate the inertial attitude from a star image. To allow for flexible attitude manoeuvres, the ASC can, simultaneously, drive from one to four cameras, efficiently removing dropouts from, e.g., sun blinding of one camera......, it is difficult to test and verify the true robustness and accuracy of a star tracker on ground. This is caused by the fact that only real-sky tests offer high fidelity stimulation of the sensor, while the atmosphere instabilities result in a dominant noise source intrinsically limiting the achievable accuracy...
Two planetary systems with transiting Earth-size and super-Earth planets orbiting late-type dwarf stars

Science.gov (United States)

Alonso, E. Díez; Hernández, J. I. González; Suárez Gómez, S. L.; Aguado, D. S.; González Gutiérrez, C.; Suárez Mascareño, A.; Cabrera-Lavers, A.; González-Nuevo, J.; Toledo-Padrón, B.; Gracia, J.; de Cos Juez, F. J.; Rebolo, R.

2018-06-01

We present two new planetary systems found around cool dwarf stars with data from the K2 mission. The first system was found in K2-XX1 (EPIC 248545986), characterized in this work as M3.0V and observed in the 14th campaign of K2. It consists of three Earth-size transiting planets with radii of 1.1, 1.0 and 1.1 R⊕, showing a compact configuration with orbital periods of 5.24, 7.78 and 10.1 days, close to 2:3:4 resonance. The second was found in K2-XX2 (EPIC 249801827), characterized in this work as M0.5V and observed in the 15th campaign. It consists of two transiting super-Earths with radii 2.0 and 1.8 R⊕ and orbital periods of 6.03 and 20.5 days. The equilibrium temperatures of the atmospheres of these planets are estimated to be in the range of 380-600 K and the amplitudes of signals in transmission spectroscopy are estimated at ˜ 10 ppm.
Ehlers-Danlos Syndrome Type VIII: A Rare Cause of Leg Ulcers in Young Patients

Directory of Open Access Journals (Sweden)

Sophie Ronceray

2013-01-01

Full Text Available Ehlers-Danlos syndrome type VIII (EDS-VIII is a very rare autosomal dominant disease characterized by early-onset periodontitis associated with features of Ehlers-Danlos syndrome. We report a 32-year-old man whose chronic leg ulcer led to the diagnosis of EDS-VIII. He had severe periodontitis with complete loss of permanent teeth and skin fragility with thin skin, atrophic scars, and brownish atrophic pretibial plaques. Leg ulcer is not a prominent feature of EDS-VIII. We suggest adding EDS-VIII to the list of rare diseases accounting for chronic leg ulcers, if this case report prompts others to report leg ulcers associated with EDS-VIII.
Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets

NARCIS (Netherlands)

Marcy, G.W.; et al., [Unknown; Hekker, S.

2014-01-01

We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements,
BINARY DISRUPTION BY MASSIVE BLACK HOLES: HYPERVELOCITY STARS, S STARS, AND TIDAL DISRUPTION EVENTS

Energy Technology Data Exchange (ETDEWEB)

Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J.; Geller, Margaret J.; Brown, Warren R., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: wbrown@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-04-20

We examine whether disrupted binary stars can fuel black hole growth. In this mechanism, tidal disruption produces a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole. After a cluster of bound stars forms, orbital diffusion allows the black hole to accrete stars by tidal disruption at a rate comparable to the capture rate. In the Milky Way, HVSs and the S star cluster imply similar rates of 10{sup -5} to 10{sup -3} yr{sup -1} for binary disruption. These rates are consistent with estimates for the tidal disruption rate in nearby galaxies and imply significant black hole growth from disrupted binaries on 10 Gyr timescales.

Hypervelocity stars from young stellar clusters in the Galactic Centre

Science.gov (United States)

Fragione, G.; Capuzzo-Dolcetta, R.; Kroupa, P.

2017-05-01

The enormous velocities of the so-called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of HVSs as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pericentre. High-velocity stars will move close to the initial cluster orbital plane and in the direction of the cluster orbital motion at the pericentre. The binary fraction of these HVS jets depends on the primordial binary fraction in the young cluster. The level of initial mass segregation determines the value of the average mass of the ejected stars. Some binary stars will merge, continuing their travel across and out of the Galaxy as blue stragglers.
AAV5-Factor VIII Gene Transfer in Severe Hemophilia A.

Science.gov (United States)

Rangarajan, Savita; Walsh, Liron; Lester, Will; Perry, David; Madan, Bella; Laffan, Michael; Yu, Hua; Vettermann, Christian; Pierce, Glenn F; Wong, Wing Y; Pasi, K John

2017-12-28

Patients with hemophilia A rely on exogenous factor VIII to prevent bleeding in joints, soft tissue, and the central nervous system. Although successful gene transfer has been reported in patients with hemophilia B, the large size of the factor VIII coding region has precluded improved outcomes with gene therapy in patients with hemophilia A. We infused a single intravenous dose of a codon-optimized adeno-associated virus serotype 5 (AAV5) vector encoding a B-domain-deleted human factor VIII (AAV5-hFVIII-SQ) in nine men with severe hemophilia A. Participants were enrolled sequentially into one of three dose cohorts (low dose [one participant], intermediate dose [one participant], and high dose [seven participants]) and were followed through 52 weeks. Factor VIII activity levels remained at 3 IU or less per deciliter in the recipients of the low or intermediate dose. In the high-dose cohort, the factor VIII activity level was more than 5 IU per deciliter between weeks 2 and 9 after gene transfer in all seven participants, and the level in six participants increased to a normal value (>50 IU per deciliter) that was maintained at 1 year after receipt of the dose. In the high-dose cohort, the median annualized bleeding rate among participants who had previously received prophylactic therapy decreased from 16 events before the study to 1 event after gene transfer, and factor VIII use for participant-reported bleeding ceased in all the participants in this cohort by week 22. The primary adverse event was an elevation in the serum alanine aminotransferase level to 1.5 times the upper limit of the normal range or less. Progression of preexisting chronic arthropathy in one participant was the only serious adverse event. No neutralizing antibodies to factor VIII were detected. The infusion of AAV5-hFVIII-SQ was associated with the sustained normalization of factor VIII activity level over a period of 1 year in six of seven participants who received a high dose, with
The spectroscopic orbit of Capella revisited

Science.gov (United States)

Weber, M.; Strassmeier, K. G.

2011-07-01

Context. Capella is among the few binary stars with two evolved giant components. The hotter component is a chromospherically active star within the Hertzsprung gap, while the cooler star is possibly helium-core burning. Aims: The known inclination of the orbital plane from astrometry in combination with precise radial velocities will allow very accurate masses to be determined for the individual Capella stars. This will constrain their evolutionary stage and possibly the role of the active star's magnetic field on the dynamical evolution of the binary system. Methods: We obtained a total of 438 high-resolution échelle spectra during the years 2007-2010 and used the measured velocities to recompute the orbital elements. Our double-lined orbital solution yields average residuals of 64 m s-1 for the cool component and 297 m s-1 for the more rapidly rotating hotter component. Results: The semi-amplitude of the cool component is smaller by 0.045 km s-1 than the orbit determination of Torres et al. from data taken during 1996-1999 but more precise by a factor of 5.5, while for the hotter component it is larger by 0.580 km s-1 and more precise by a factor of 3.6. This corresponds to masses of 2.573 ± 0.009 M⊙ and 2.488 ± 0.008 M⊙ for the cool and hot component, respectively. Their relative errors of 0.34% and 0.30% are about half of the values given in Torres et al. for a combined literature-data solution but with absolute values different by 4% and 2% for the two components, respectively. The mass ratio of the system is therefore q = MA/MB = 0.9673 ± 0.0020. Conclusions: Our orbit is the most precise and also likely to be the most accurate ever obtained for Capella. Based on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC.Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A89
Orbital parameters of extrasolar planets derived from polarimetry

Science.gov (United States)

Fluri, D. M.; Berdyugina, S. V.

2010-03-01

Context. Polarimetry of extrasolar planets becomes a new tool for their investigation, which requires the development of diagnostic techniques and parameter case studies. Aims: Our goal is to develop a theoretical model which can be applied to interpret polarimetric observations of extrasolar planets. Here we present a theoretical parameter study that shows the influence of the various involved parameters on the polarization curves. Furthermore, we investigate the robustness of the fitting procedure. We focus on the diagnostics of orbital parameters and the estimation of the scattering radius of the planet. Methods: We employ the physics of Rayleigh scattering to obtain polarization curves of an unresolved extrasolar planet. Calculations are made for two cases: (i) assuming an angular distribution for the intensity of the scattered light as from a Lambert sphere and for polarization as from a Rayleigh-type scatterer; and (ii) assuming that both the intensity and polarization of the scattered light are distributed according to the Rayleigh law. We show that the difference between these two cases is negligible for the shapes of the polarization curves. In addition, we take the size of the host star into account, which is relevant for hot Jupiters orbiting giant stars. Results: We discuss the influence of the inclination of the planetary orbit, the position angle of the ascending node, and the eccentricity on the linearly polarized light curves both in Stokes Q/I and U/I. We also analyze errors that arise from the assumption of a point-like star in numerical modeling of polarization as compared to consistent calculations accounting for the finite size of the host star. We find that errors due to the point-like star approximation are reduced with the size of the orbit, but still amount to about 5% for known hot Jupiters. Recovering orbital parameters from simulated data is shown to be very robust even for very noisy data because the polarization curves react
Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.

Science.gov (United States)

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-08-03

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.
Blood coagulation factor VIII

Indian Academy of Sciences (India)

Factor VIII (FVIII) functions as a co-factor in the blood coagulation cascade for the proteolytic activation of factor X by factor IXa. Deficiency of FVIII causes hemophilia A, the most commonly inherited bleeding disorder. This review highlights current knowledge on selected aspects of FVIII in which both the scientist and the ...
The Origin of Runaway Stars

Science.gov (United States)

Hoogerwerf, R.; de Bruijne, J. H. J.; de Zeeuw, P. T.

2000-12-01

Milliarcsecond astrometry provided by Hipparcos and by radio observations makes it possible to retrace the orbits of some of the nearest runaway stars and pulsars to determine their site of origin. The orbits of the runaways AE Aurigae and μ Columbae and of the eccentric binary ι Orionis intersected each other ~2.5 Myr ago in the nascent Trapezium cluster, confirming that these runaways were formed in a binary-binary encounter. The path of the runaway star ζ Ophiuchi intersected that of the nearby pulsar PSR J1932+1059, ~1 Myr ago, in the young stellar group Upper Scorpius. We propose that this neutron star is the remnant of a supernova that occurred in a binary system that also contained ζ Oph and deduce that the pulsar received a kick velocity of ~350 km s-1 in the explosion. These two cases provide the first specific kinematic evidence that both mechanisms proposed for the production of runaway stars, the dynamical ejection scenario and the binary-supernova scenario, operate in nature.
SPIN-PRECESSION: BREAKING THE BLACK HOLE-NEUTRON STAR DEGENERACY

Energy Technology Data Exchange (ETDEWEB)

Chatziioannou, Katerina; Cornish, Neil; Klein, Antoine; Yunes, Nicolás [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2015-01-01

Mergers of compact stellar remnants are prime targets for the LIGO/Virgo gravitational wave detectors. The gravitational wave signals from these merger events can be used to study the mass and spin distribution of stellar remnants, and provide information about black hole horizons and the material properties of neutron stars. However, it has been suggested that degeneracies in the way that the star's mass and spin are imprinted in the waveforms may make it impossible to distinguish between black holes and neutron stars. Here we show that the precession of the orbital plane due to spin-orbit coupling breaks the mass-spin degeneracy, and allows us to distinguish between standard neutron stars and alternative possibilities, such as black holes or exotic neutron stars with large masses and spins.
The great escape - II. Exoplanet ejection from dying multiple-star systems

Science.gov (United States)

Veras, Dimitri; Tout, Christopher A.

2012-05-01

Extrasolar planets and belts of debris orbiting post-main-sequence single stars may become unbound as the evolving star loses mass. In multiple-star systems, the presence or co-evolution of the additional stars can significantly complicate the prospects for orbital excitation and escape. Here, we investigate the dynamical consequences of multi-phasic, non-linear mass loss and establish a criterion for a system of any stellar multiplicity to retain a planet whose orbit surrounds all of the parent stars. For single stars which become white dwarfs, this criterion can be combined with the Chandrasekhar Limit to establish the maximum allowable mass-loss rate for planet retention. We then apply the criterion to circumbinary planets in evolving binary systems over the entire stellar mass phase space. Through about 105 stellar evolutionary track realizations, we characterize planetary ejection prospects as a function of binary separation, stellar mass and metallicity. This investigation reveals that planets residing at just a few tens of au from a central concentration of stars are susceptible to escape in a wide variety of multiple systems. Further, planets are significantly more susceptible to ejection from multiple-star systems than from single-star systems for a given system mass. For system masses greater than about 2 M⊙, multiple-star systems represent the greater source of free-floating planets.
Why do we find ourselves around a yellow star instead of a red star?

Science.gov (United States)

Haqq-Misra, Jacob; Kopparapu, Ravi Kumar; Wolf, Eric T.

2018-01-01

M-dwarf stars are more abundant than G-dwarf stars, so our position as observers on a planet orbiting a G-dwarf raises questions about the suitability of other stellar types for supporting life. If we consider ourselves as typical, in the anthropic sense that our environment is probably a typical one for conscious observers, then we are led to the conclusion that planets orbiting in the habitable zone of G-dwarf stars should be the best place for conscious life to develop. But such a conclusion neglects the possibility that K-dwarfs or M-dwarfs could provide more numerous sites for life to develop, both now and in the future. In this paper we analyse this problem through Bayesian inference to demonstrate that our occurrence around a G-dwarf might be a slight statistical anomaly, but only the sort of chance event that we expect to occur regularly. Even if M-dwarfs provide more numerous habitable planets today and in the future, we still expect mid G- to early K-dwarfs stars to be the most likely place for observers like ourselves. This suggests that observers with similar cognitive capabilities as us are most likely to be found at the present time and place, rather than in the future or around much smaller stars.
Iron Abundance in the Prototype PG 1159 Star, GW Vir Pulsator PG 1159-035, and Related Objects

Science.gov (United States)

Werner, K.; Rauch, T.; Kruk, J. W.; Kurucz, R. L.

2011-01-01

We performed an iron abundance determination of the hot, hydrogen deficient post-AGB star PG 1159-035. which is the prototype of the PG 1159 spectral class and the GW Vir pulsators, and of two related objects (PG 1520+525, PG 1144+005), based on the first detection of Fe VIII lines in stellar photospheres. In another PG 1159 star. PG 1424+535. we detect Fe VII lines. In all four stars, each within T(sub eff) = 110,000-150,000 K, we find a solar iron abundance. This result agrees with our recent abundance analysis of the hottest PG 1159 stars (T(sub eff) = 150,000-200,000 K) that exhibit Fe x lines. On the whole, we find that the PG 1159 stars are not significantly iron deficient, in contrast to previous notions.
SPIN-ORBIT ALIGNMENT FOR THE CIRCUMBINARY PLANET HOST KEPLER-16 A

International Nuclear Information System (INIS)

Winn, Joshua N.; Albrecht, Simon; Johnson, John Asher; Torres, Guillermo; Carter, Joshua A.; Ragozzine, Darin; Quinn, Samuel N.; Latham, David W.; Cochran, William D.; Marcy, Geoffrey W.; Howard, Andrew W.; Isaacson, Howard; Fischer, Debra; Doyle, Laurance; Welsh, William; Orosz, Jerome; Fabrycky, Daniel C.; Shporer, Avi; Howell, Steve B.; Prsa, Andrej

2011-01-01

Kepler-16 is an eccentric low-mass eclipsing binary with a circumbinary transiting planet. Here, we investigate the angular momentum of the primary star, based on Kepler photometry and Keck spectroscopy. The primary star's rotation period is 35.1 ± 1.0 days, and its projected obliquity with respect to the stellar binary orbit is 1. 0 6 ± 2. 0 4. Therefore, the three largest sources of angular momentum-the stellar orbit, the planetary orbit, and the primary's rotation-are all closely aligned. This finding supports a formation scenario involving accretion from a single disk. Alternatively, tides may have realigned the stars despite their relatively wide separation (0.2 AU), a hypothesis that is supported by the agreement between the measured rotation period and the 'pseudosynchronous' period of tidal evolution theory. The rotation period, chromospheric activity level, and fractional light variations suggest a main-sequence age of 2-4 Gyr. Evolutionary models of low-mass stars can match the observed masses and radii of the primary and secondary stars to within about 3%.
Extrasolar Giant Planet in Earth-like Orbit

Science.gov (United States)

1999-07-01

Discovery from a Long-term Project at La Silla A new extrasolar planet has been found at the ESO La Silla Observatory as a companion to iota Horologii (iota Hor) . This 5.4-mag solar-type star is located at a distance of 56 light-years and is just visible to the unaided eye in the southern constellation Horologium (The Pendulum Clock). The discovery is the result of a long-term survey of forty solar-type stars that was begun in November 1992. It is based on highly accurate measurements of stellar radial velocities, i.e. the speed with which a star moves along the line of sight. The presence of a planet in orbit around a star is inferred from observed, regular changes of this velocity, as the host star and its planet revolve around a common center of gravity. Since in all cases the star is much heavier than the planet, the resulting velocity variations of the star are always quite small. The team that found the new planet, now designated iota Hor b , consists of Martin Kürster , Michael Endl and Sebastian Els (ESO-Chile), Artie P. Hatzes and William D. Cochran (University of Texas, Austin, USA), and Stefan Döbereiner and Konrad Dennerl (Max-Planck-Institut für extraterrestrische Physik, Garching, Germany). Iodine cell provides very accurate velocity measurements iota Hor b represents the first discovery of an extrasolar planet with an ESO instrument [1]. The finding is based on data obtained with ESO's highest-resolution spectrograph, the Coudé Echelle Spectrometer (CES) at the 1.4-m Coudé Auxiliary Telescope (CAT). While this telescope has recently been decommissioned, the CES instrument is now coupled via an optical fiber link to the larger ESO 3.6-m telescope, thus permitting the continuation of this survey. The high precision radial velocity measurements that are necessary for a study of this type were achieved by means of a special calibration technique. It incorporates an iodine gas absorption cell and sophisticated data modelling. The cell is used like
Agnostic stacking of intergalactic doublet absorption: measuring the Ne VIII population

Science.gov (United States)

Frank, Stephan; Pieri, Matthew M.; Mathur, Smita; Danforth, Charles W.; Shull, J. Michael

2018-05-01

We present a blind search for doublet intergalactic metal absorption with a method dubbed `agnostic stacking'. Using a forward-modelling framework, we combine this with direct detections in the literature to measure the overall metal population. We apply this novel approach to the search for Ne VIII absorption in a set of 26 high-quality COS spectra. We probe to an unprecedented low limit of log N>12.3 at 0.47≤z ≤1.34 over a path-length Δz = 7.36. This method selects apparent absorption without requiring knowledge of its source. Stacking this mixed population dilutes doublet features in composite spectra in a deterministic manner, allowing us to measure the proportion corresponding to Ne VIII absorption. We stack potential Ne VIII absorption in two regimes: absorption too weak to be significant in direct line studies (12.3 13.7). We do not detect Ne VIII absorption in either regime. Combining our measurements with direct detections, we find that the Ne VIII population is reproduced with a power-law column density distribution function with slope β = -1.86 ^{+0.18 }_{ -0.26} and normalization log f_{13.7} = -13.99 ^{+0.20 }_{ -0.23}, leading to an incidence rate of strong Ne VIII absorbers dn/dz =1.38 ^{+0.97 }_{ -0.82}. We infer a cosmic mass density for Ne VIII gas with 12.3 value significantly lower that than predicted by recent simulations. We translate this density into an estimate of the baryon density Ωb ≈ 1.8 × 10-3, constituting 4 per cent of the total baryonic mass.
Environmental effects on stellar populations of star clusters and dwarf galaxies

Science.gov (United States)

Pasetto, Stefano; Cropper, Mark; Fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

2017-03-01

We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation of gravitationally bound systems in an external environment. Ram pressure, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, and tidal forces are accounted for separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment. We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance. The developed theoretical framework has direct applications to the cases of massive star clusters, dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.
Evolution of a massive binary in a star field

International Nuclear Information System (INIS)

Baranov, A.S.

1984-01-01

The orbital evolution of a massive binary system interacting with a background field of single stars whose phase density is homogeneous in configuration space is considered. The velocity distribution is assumed isotropic up to some limiting value, and a typical field star is regarded as having a velocity much higher than the orbital speed of the pair components. An expression is derived for the transfer of energy from the binary to the field stars. The time evolution of the orbit parameters a, e is established, and the evolution rate is estimated for Kardashev's (1983) model galactic nucleus containing a central black-hole binary. On the above assumptions the components should become twice as close together within only a few tens of millennia, although the picture may change fundamentally if the nucleus is rotating. 13 references
THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS

International Nuclear Information System (INIS)

Dressing, Courtney D.; Charbonneau, David

2013-01-01

We use the optical and near-infrared photometry from the Kepler Input Catalog to provide improved estimates of the stellar characteristics of the smallest stars in the Kepler target list. We find 3897 dwarfs with temperatures below 4000 K, including 64 planet candidate host stars orbited by 95 transiting planet candidates. We refit the transit events in the Kepler light curves for these planet candidates and combine the revised planet/star radius ratios with our improved stellar radii to revise the radii of the planet candidates orbiting the cool target stars. We then compare the number of observed planet candidates to the number of stars around which such planets could have been detected in order to estimate the planet occurrence rate around cool stars. We find that the occurrence rate of 0.5-4 R ⊕ planets with orbital periods shorter than 50 days is 0.90 +0.04 -0.03 planets per star. The occurrence rate of Earth-size (0.5-1.4 R ⊕ ) planets is constant across the temperature range of our sample at 0.51 -0.05 +0.06 Earth-size planets per star, but the occurrence of 1.4-4 R ⊕ planets decreases significantly at cooler temperatures. Our sample includes two Earth-size planet candidates in the habitable zone, allowing us to estimate that the mean number of Earth-size planets in the habitable zone is 0.15 +0.13 -0.06 planets per cool star. Our 95% confidence lower limit on the occurrence rate of Earth-size planets in the habitable zones of cool stars is 0.04 planets per star. With 95% confidence, the nearest transiting Earth-size planet in the habitable zone of a cool star is within 21 pc. Moreover, the nearest non-transiting planet in the habitable zone is within 5 pc with 95% confidence.
A Brightness-Referenced Star Identification Algorithm for APS Star Trackers

Science.gov (United States)

Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

2014-01-01

Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid and geometric voting methods. All three methods were tested with simulation data and actual in orbit data from the APS star tracker of ZY-3. Using a catalog composed of 1500 stars, the results show that without false stars the efficiency of this new method is 4∼5 times that of the pyramid method and 35∼37 times that of the geometric method. PMID:25299950
The habitable zone and extreme planetary orbits.

Science.gov (United States)

Kane, Stephen R; Gelino, Dawn M

2012-10-01

The habitable zone for a given star describes the range of circumstellar distances from the star within which a planet could have liquid water on its surface, which depends upon the stellar properties. Here we describe the development of the habitable zone concept, its application to our own solar system, and its subsequent application to exoplanetary systems. We further apply this to planets in extreme eccentric orbits and show how they may still retain life-bearing properties depending upon the percentage of the total orbit which is spent within the habitable zone. Key Words: Extrasolar planets-Habitable zone-Astrobiology.
Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities

Energy Technology Data Exchange (ETDEWEB)

Carter, J. A.; Agol, E.; Chaplin, W. J.; Basu, S.; Bedding, T. R.; Buchhave, L. A.; Christensen-Dalsgaard, J.; Deck, K. M.; Elsworth, Y.; Fabrycky, D. C.; Ford, E. B.; Fortney, J. J.; Hale, S. J.; Handberg, R.; Hekker, S.; Holman, M. J.; Huber, D.; Karoff, C.; Kawaler, S. D.; Kjeldsen, H.; Lissauer, J. J.; Lopez, E. D.; Lund, M. N.; Lundkvist, M.; Metcalfe, T. S.; Miglio, A.; Rogers, L. A.; Stello, D.; Borucki, W. J.; Bryson, S.; Christiansen, J. L.; Cochran, W. D.; Geary, J. C.; Gilliland, R. L.; Haas, M. R.; Hall, J.; Howard, A. W.; Jenkins, J. M.; Klaus, T.; Koch, D. G.; Latham, D. W.; MacQueen, P. J.; Sasselov, D.; Steffen, J. H.; Twicken, J. D.; Winn, J. N.

2012-06-21

In the Solar system the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal, and that planets' orbits can change substantially after their formation. Here we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10%, and densities differing by a factor of 8. One planet is likely a rocky `super-Earth', whereas the other is more akin to Neptune. These planets are thirty times more closely spaced--and have a larger density contrast--than any adjacent pair of planets in the Solar system.

Statistical investigation of spectroscopic binary stars

International Nuclear Information System (INIS)

Tutukov, A.V.; Yungelson, L.R.

1980-01-01

A catalog of physical parameters of about 1000 spectroscopic binary stars (SB), based on the Batten catalog, its extensions, and newly published data has been compiled. Masses of stars' components (M 1 and M 2 ), mass ratios of components (q=M 1 /M 2 ) and orbital angular momenta are computed, wherever possible. It is probable that the initial mass function of the primaries is non-monotonic and is described only approximately by a power-law. A number of assumed 'initial' distributions of M 1 , q and the semiaxes of orbits were transformed with the aim of obtaining 'observed' distributions taking into account the observational selection due to the luminosities of the components, their radial velocities, inclinations of the orbits, and the effects of matter exchange between the components. (Auth.)
A Search for Exoplanets in Short-Period Binary Star Systems

Directory of Open Access Journals (Sweden)

Ronald Kaitchuck

2012-03-01

Full Text Available This paper reports the progress of a search for exoplanets with S-type orbits in short-period binary star systems. The selected targets have stellar orbital periods of just a few days. These systems are eclipsing binaries so that exoplanet transits, if planets exist, will be highly likely. We report the results for seven binary star systems.
The Nuclear Spectroscopic Telescope Array (NuSTAR)

DEFF Research Database (Denmark)

Harrison, Fiona A.; Boggs, Steve; Christensen, Finn Erland

2010-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (6 - 80 keV) telescope to orbit. NuSTAR will offer a factor 50 - 100 sensitivity improvement compared to previous collimated or coded mask imagers that have operated...... in this energy band. In addition, NuSTAR provides sub-arcminute imaging with good spectral resolution over a 12-arcminute eld of view. After launch, NuSTAR will carry out a two-year primary science mission that focuses on four key programs: studying the evolution of massive black holes through surveys carried...... on-orbit deployment of an extendable mast. An aspect and alignment metrology system enable reconstruction of the absolute aspect and variations in the telescope alignment resulting from mast exure during ground data processing. Data will be publicly available at GSFC's High Energy Archive Research...
The labour ward analgesic service at King Edward VIII Hospital ...

African Journals Online (AJOL)

The labour ward analgesic service at King Edward VIII. Hospital, Durban. D. A. ROCKE, C. C. ROUT, H. D. RUSSELL, S. SINGH. Abstract The provision of analgesic services to the labour ward at King Edward VIII Hospital was studied during a I-week period. Of249 patients, 113 (45%) received no analgesia whatsoever.
KIC 8164262: a heartbeat star showing tidally induced pulsations with resonant locking

Science.gov (United States)

Hambleton, K.; Fuller, J.; Thompson, S.; Prša, A.; Kurtz, D. W.; Shporer, A.; Isaacson, H.; Howard, A. W.; Endl, M.; Cochran, W.; Murphy, S. J.

2018-02-01

We present the analysis of KIC 8164262, a heartbeat star with a high-amplitude (∼1 mmag), tidally resonant pulsation (a mode in resonance with the orbit) at 229 times the orbital frequency and a plethora of tidally induced g-mode pulsations (modes excited by the orbit). The analysis combines Kepler light curves with follow-up spectroscopic data from the Keck telescope, KPNO (Kitt Peak National Observatory) 4-m Mayall telescope and the 2.7-m telescope at the McDonald observatory. We apply the binary modelling software, PHOEBE, to the Kepler light curve and radial velocity data to determine a detailed binary star model that includes the prominent pulsation and Doppler boosting, alongside the usual attributes of a binary star model (including tidal distortion and reflection). The results show that the system contains a slightly evolved F star with an M secondary companion in a highly eccentric orbit (e = 0.886). We use the results of the binary star model in a companion paper (Fuller) where we show that the prominent pulsation can be explained by a tidally excited oscillation mode held near resonance by a resonance locking mechanism.
Young and Waltzing Binary Stars

Science.gov (United States)

2001-10-01

ADONIS Observes Low-mass Eclipsing System in Orion Summary A series of very detailed images of a binary system of two young stars have been combined into a movie . In merely 3 days, the stars swing around each other. As seen from the earth, they pass in front of each other twice during a full revolution, producing eclipses during which their combined brightness diminishes . A careful analysis of the orbital motions has now made it possible to deduce the masses of the two dancing stars . Both turn out to be about as heavy as our Sun. But while the Sun is about 4500 million years old, these two stars are still in their infancy. They are located some 1500 light-years away in the Orion star-forming region and they probably formed just 10 million years ago . This is the first time such an accurate determination of the stellar masses could be achieved for a young binary system of low-mass stars . The new result provides an important piece of information for our current understanding of how young stars evolve. The observations were obtained by a team of astronomers from Italy and ESO [1] using the ADaptive Optics Near Infrared System (ADONIS) on the 3.6-m telescope at the ESO La Silla Observatory. PR Photo 29a/01 : The RXJ 0529.4+0041 system before primary eclipse PR Photo 29b/01 : The RXJ 0529.4+0041 system at mid-primary eclipse PR Photo 29c/01 : The RXJ 0529.4+0041 system after primary eclipse PR Photo 29d/01 : The RXJ 0529.4+0041 system before secondary eclipse PR Photo 29e/01 : The RXJ 0529.4+0041 system at mid-secondary eclipse PR Photo 29f/01 : The RXJ 0529.4+0041 system after secondary eclipse PR Video Clip 06/01 : Video of the RXJ 0529.4+0041 system Binary stars and stellar masses Since some time, astronomers have noted that most stars seem to form in binary or multiple systems. This is quite fortunate, as the study of binary stars is the only way in which it is possible to measure directly one of the most fundamental quantities of a star, its mass. The mass of a
Motion-blurred star acquisition method of the star tracker under high dynamic conditions.

Science.gov (United States)

Sun, Ting; Xing, Fei; You, Zheng; Wei, Minsong

2013-08-26

The star tracker is one of the most promising attitude measurement devices used in spacecraft due to its extremely high accuracy. However, high dynamic performance is still one of its constraints. Smearing appears, making it more difficult to distinguish the energy dispersive star point from the noise. An effective star acquisition approach for motion-blurred star image is proposed in this work. The correlation filter and mathematical morphology algorithm is combined to enhance the signal energy and evaluate slowly varying background noise. The star point can be separated from most types of noise in this manner, making extraction and recognition easier. Partial image differentiation is then utilized to obtain the motion parameters from only one image of the star tracker based on the above process. Considering the motion model, the reference window is adopted to perform centroid determination. Star acquisition results of real on-orbit star images and laboratory validation experiments demonstrate that the method described in this work is effective and the dynamic performance of the star tracker could be improved along with more identified stars and guaranteed position accuracy of the star point.
The spectroscopic orbits and physical parameters of GG Carinae

Science.gov (United States)

Marchiano, P.; Brandi, E.; Muratore, M. F.; Quiroga, C.; Ferrer, O. E.; García, L. G.

2012-04-01

Aims: GG Car is an eclipsing binary classified as a B[e] supergiant star. The aims of our study are to improve the orbital elements of the binary system in order to obtain the actual orbital period of this system. We also compare the spectral energy distribution of the observed fluxes over a wide wavelength range with a model of a circumstellar envelope composed of gas and dust. This fitting allows us to derive the physical parameters of the system and its environment, as well as to obtain an estimation of the distance to GG Car. Methods: We analyzed about 55 optical and near infrared spectrograms taken during 1996-2010. The spectroscopic orbits were obtained by measuring the radial velocities of the blueshifted absorptions of the He I P-Cygni profiles, which are very representative of the orbital motion of both stars. On the other hand, we modeled the spectral energy distribution of GG Car, proposing a simple model of a spherical envelope consisting of a layer close to the central star composed of ionized gas and other outermost layers composed of dust. Its effect on the spectral energy distribution considering a central B-type star is presented. Comparing the model with the observed continuum energy distribution of GG Car, we can derive fundamental parameters of the system, as well as global physical properties of the gas and dust envelope. It is also possible to estimate the distance taking the spectral regions into account where the theoretical data fit the observational data very well and using the set of parameters obtained and the value of the observed flux for different wavelengths. Results: For the first time, we have determined the orbits for both components of the binary through a detailed study of the He I lines, at λλ4471, 5875, 6678, and 7065 Å, thereby obtaining an orbital period of 31.033 days. An eccentric orbit with e = 0.28 and a mass ratio q = 2.2 ± 0.9 were calculated. Comparing the model with the observed continuum energy distribution of
Lightweight Double Neutron Star Found

Science.gov (United States)

Kohler, Susanna

2018-02-01

More than forty years after the first discovery of a double neutron star, we still havent found many others but a new survey is working to change that.The Hunt for PairsThe observed shift in the Hulse-Taylor binarys orbital period over time as it loses energy to gravitational-wave emission. [Weisberg Taylor, 2004]In 1974, Russell Hulse and Joseph Taylor discovered the first double neutron star: two compact objects locked in a close orbit about each other. Hulse and Taylors measurements of this binarys decaying orbit over subsequent years led to a Nobel prize and the first clear evidence of gravitational waves carrying energy and angular momentum away from massive binaries.Forty years later, we have since confirmed the existence of gravitational waves directly with the Laser Interferometer Gravitational-Wave Observatory (LIGO). Nonetheless, finding and studying pre-merger neutron-star binaries remains a top priority. Observing such systems before they merge reveals crucial information about late-stage stellar evolution, binary interactions, and the types of gravitational-wave signals we expect to find with current and future observatories.Since the Hulse-Taylor binary, weve found a total of 16 additional double neutron-star systems which represents only a tiny fraction of the more than 2,600 pulsars currently known. Recently, however, a large number of pulsar surveys are turning their eyes toward the sky, with a focus on finding more double neutron stars and at least one of them has had success.The pulse profile for PSR J1411+2551 at 327 MHz. [Martinez et al. 2017]A Low-Mass DoubleConducted with the 1,000-foot Arecibo radio telescope in Puerto Rico, the Arecibo 327 MHz Drift Pulsar Survey has enabled the recent discovery of dozens of pulsars and transients. Among them, as reported by Jose Martinez (Max Planck Institute for Radio Astronomy) and coauthors in a recent publication, is PSR J1411+2551: a new double neutron star with one of the lowest masses ever measured
Orbital Motion of Young Binaries in Ophiuchus and Upper Centaurus–Lupus

Science.gov (United States)

Schaefer, G. H.; Prato, L.; Simon, M.

2018-03-01

We present measurements of the orbital positions and flux ratios of 17 binary and triple systems in the Ophiuchus star-forming region and the Upper Centaurus–Lupus cluster based on adaptive optics imaging at the Keck Observatory. We report the detection of visual companions in MML 50 and MML 53 for the first time, as well as the possible detection of a third component in WSB 21. For six systems in our sample, our measurements provide a second orbital position following their initial discoveries over a decade ago. For eight systems with sufficient orbital coverage, we analyze the range of orbital solutions that fit the data. Ultimately, these observations will help provide the groundwork toward measuring precise masses for these pre-main-sequence stars and understanding the distribution of orbital parameters in young multiple systems.
HABITABLE ZONES OF POST-MAIN SEQUENCE STARS

International Nuclear Information System (INIS)

Ramirez, Ramses M.; Kaltenegger, Lisa

2016-01-01

Once a star leaves the main sequence and becomes a red giant, its Habitable Zone (HZ) moves outward, promoting detectable habitable conditions at larger orbital distances. We use a one-dimensional radiative-convective climate and stellar evolutionary models to calculate post-MS HZ distances for a grid of stars from 3700 to 10,000 K (∼M1 to A5 stellar types) for different stellar metallicities. The post-MS HZ limits are comparable to the distances of known directly imaged planets. We model the stellar as well as planetary atmospheric mass loss during the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) phases for super-Moons to super-Earths. A planet can stay between 200 million years up to 9 Gyr in the post-MS HZ for our hottest and coldest grid stars, respectively, assuming solar metallicity. These numbers increase for increased stellar metallicity. Total atmospheric erosion only occurs for planets in close-in orbits. The post-MS HZ orbital distances are within detection capabilities of direct imaging techniques.
HABITABLE ZONES OF POST-MAIN SEQUENCE STARS

Energy Technology Data Exchange (ETDEWEB)

Ramirez, Ramses M.; Kaltenegger, Lisa [Carl Sagan Institute, Cornell University, Ithaca, NY (United States)

2016-05-20

Once a star leaves the main sequence and becomes a red giant, its Habitable Zone (HZ) moves outward, promoting detectable habitable conditions at larger orbital distances. We use a one-dimensional radiative-convective climate and stellar evolutionary models to calculate post-MS HZ distances for a grid of stars from 3700 to 10,000 K (∼M1 to A5 stellar types) for different stellar metallicities. The post-MS HZ limits are comparable to the distances of known directly imaged planets. We model the stellar as well as planetary atmospheric mass loss during the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) phases for super-Moons to super-Earths. A planet can stay between 200 million years up to 9 Gyr in the post-MS HZ for our hottest and coldest grid stars, respectively, assuming solar metallicity. These numbers increase for increased stellar metallicity. Total atmospheric erosion only occurs for planets in close-in orbits. The post-MS HZ orbital distances are within detection capabilities of direct imaging techniques.
Thermoelectrical properties of the compounds ScM{sup VIII}Sb and YM{sup VIII}Sb (M{sup VIII} = Ni, Pd, Pt)

Energy Technology Data Exchange (ETDEWEB)

Oestreich, J; Probst, U; Richardt, F; Bucher, E [University of Konstanz, PO Box X916, D-78457 Konstanz (Germany)

2003-02-05

The research into new materials with good thermoelectric properties has revealed new compounds consisting of metallic elements (Bando Y, Suemitsu T, Takagi K, Tokushima H, Echizen Y, Katoh K, Umeo K, Maeda Y and Takabatake T 2000 J. Alloys Compounds 313 1-6, Ghelani N, Loo S, Chung D, Sportouch S, Nardi S, Kanatzidis M, Hogan T and Nolas G 2000 Mater. Res. Soc. 626 Z8.6.1). The half-Heusler compound ZrNiSn, in particular, shows promising thermoelectric properties and has been studied by many scientists during recent years (Uher C, Hu S, Yang J, Meisner G P and Morelli D T 1997 Proc. ICT'97: 16th Int. Conf. on Thermoelectrics pp 485-8, Romaka L P, Stadnyk Yu V, Goryn A M, Gorelenko Yu K and Skolozdra R V 1997 Proc. ICT'97: 16th Int. Conf. on Thermoelectrics pp 516-19, Hohl H, Ramirez A P, Goldmann C, Ernst G, Woelfing B and Bucher E 1998 J. Phys.: Condens. Matter 11 1697-709, Oestreich J, Kaefer W, Richardt F, Probst U and Bucher E 1999 Proc. 5th European Workshop on Thermoelectrics pp 192-5). In an effort to find new thermoelectric materials, the half-Heusler compounds of the groups ScM{sup VIII}Sb and YM{sup VIII}Sb (M{sup VIII} = Ni, Pd, Pt) were synthesized by arc melting and the thermoelectric properties were examined by standard characterization methods. Doping experiments showed that it is possible to change the electrical properties of the compounds while retaining the half-Heusler structure. Within the two groups, YPtSb showed the best thermoelectrical properties. At a temperature of 400 K the electrical conductivity of YPtSb is 748{omega}{sup -1} cm{sup -1} and the Seebeck coefficient is 116.3{mu}V K{sup -1}. The thermal conductivity at 400 K extrapolated using the Wiedemann-Franz law is 2.87 W K{sup -1} m{sup -1}. This leads to a dimensionless figure of merit of 0.14.
The Updated Multiple Star Catalog

Science.gov (United States)

Tokovinin, Andrei

2018-03-01

The catalog of hierarchical stellar systems with three or more components is an update of the original 1997 version. For 2000 hierarchies, the new Multiple Star Catalog (MSC) provides distances, component masses and periods, and supplementary information (astrometry, photometry, identifiers, orbits, notes). The MSC content and format are explained, and its incompleteness and strong observational selection are stressed. Nevertheless, the MSC can be used for statistical studies and is a valuable source for planning observations of multiple stars. Rare classes of stellar hierarchies found in the MSC (with six or seven components, extremely eccentric orbits, planar and possibly resonant orbits, hosting planets) are briefly presented. High-order hierarchies have smaller velocity dispersion compared to triples and are often associated with moving groups. The paper concludes with an analysis of the ratio of periods and separations between inner and outer subsystems. In wide hierarchies, the ratio of semimajor axes, estimated statistically, is distributed between 3 and 300, with no evidence of dynamically unstable systems.
Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler

DEFF Research Database (Denmark)

Howard, A.W.; Geoffrey, G.W.; Bryson, S.T.

2012-01-01

We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that include...... a nearly complete set of detected planets as small as 2 R ⊕. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R p, and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability...... of transit, R /a. We consider first Kepler target stars within the "solar subset" having T eff = 4100-6100 K, log g = 4.0-4.9, and Kepler magnitude Kp planets down to 2 R...
Mapping the Region in the Nearest Star System to Search for Habitable Planets

Science.gov (United States)

Lissauer, Jack J.; Quarles, B.

2015-01-01

Circumstellar planets within the alpha Centauri AB star system have been suggested through formation models and recent observations, and ACESat (Belikov et al. AAS Meeting #225, #311.01, 2015) is a proposed space mission designed to directly image Earth-sized planets in the habitable zones of both of these stars. The alpha Centauri system is billions of years old, so planets are only expected to be found in regions where their orbits are long-lived. We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales and we map the positions in the sky plane where planets on stable orbits about either stellar component may appear. We confirm the qualitative results of Wiegert & Holman (Astron. J. 113, 1445, 1997) regarding the approximate size of the regions of stable orbits, which are larger for retrograde orbits relative to the binary than for prograde orbits. Additionally, we find that mean motion resonances with the binary orbit leave an imprint on the limits of orbital stability, and the effects of the Lidov-Kozai mechanism are also readily apparent. Overall, orbits in the habitable zones near the plane of the binary are stable, whereas high-inclination orbits are short-lived.
TIDAL BREAKUP OF BINARY STARS AT THE GALACTIC CENTER. II. HYDRODYNAMIC SIMULATIONS

International Nuclear Information System (INIS)

Antonini, Fabio; Merritt, David; Lombardi, James C. Jr

2011-01-01

In Paper I, we followed the evolution of binary stars as they orbited near the supermassive black hole (SMBH) at the Galactic center, noting the cases in which the two stars would come close enough together to collide. In this paper, we replace the point-mass stars by fluid realizations, and use a smoothed-particle hydrodynamics code to follow the close interactions. We model the binary components as main-sequence stars with initial masses of 1, 3, and 6 solar masses, and with chemical composition profiles taken from stellar evolution codes. Outcomes of the close interactions include mergers, collisions that leave both stars intact, and ejection of one star at high velocity accompanied by capture of the other star into a tight orbit around the SMBH. For the first time, we follow the evolution of the collision products for many (∼> 100) orbits around the SMBH. Stars that are initially too small to be tidally disrupted by the SMBH can be puffed up by close encounters or collisions, with the result that tidal stripping occurs in subsequent periapse passages. In these cases, mass loss occurs episodically, sometimes for hundreds of orbits before the star is completely disrupted. Repeated tidal flares, of either increasing or decreasing intensity, are a predicted consequence. In collisions involving a low-mass and a high-mass star, the merger product acquires a high core hydrogen abundance from the smaller star, effectively resetting the nuclear evolution 'clock' to a younger age. Elements like Li, Be, and B that can exist only in the outermost envelope of a star are severely depleted due to envelope ejection during collisions and due to tidal forces from the SMBH. Tidal spin-up can occur due to either a collision or tidal torque by the SMBH at periapsis. However, in the absence of collisions, tidal spin-up of stars is only important in a narrow range of periapse distances, r t /2 ∼ per ∼ t , with r t the tidal disruption radius. We discuss the implications of
Prevalence of Earth-size planets orbiting Sun-like stars

OpenAIRE

Petigura, Erik A.; Howard, Andrew W.; Marcy, Geoffrey W.

2013-01-01

Determining whether Earth-like planets are common or rare looms as a touchstone in the question of life in the universe. We searched for Earth-size planets that cross in front of their host stars by examining the brightness measurements of 42,000 stars from National Aeronautics and Space Administration's Kepler mission. We found 603 planets, including 10 that are Earth size (1-2 Earth-radii) and receive comparable levels of stellar energy to that of Earth (within a factor of four). We account...
OGLE-2017-BLG-0482Lb: A Microlensing Super-Earth Orbiting a Low-mass Host Star

Science.gov (United States)

Han, C.; Hirao, Y.; Udalski, A.; Lee, C.-U.; Bozza, V.; Gould, A.; and; Abe, F.; Barry, R.; Bond, I. A.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Evans, P.; Fukui, A.; Itow, Y.; Kawasaki, K.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Matsubara, Y.; Miyazaki, S.; Munakata, H.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Ranc, C.; Rattenbury, N.; Saito, T.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yamada, T.; Yonehara, A.; The MOA Collaboration; Mróz, P.; Poleski, R.; Kozłowski, S.; Soszyński, I.; Pietrukowicz, P.; Skowron, J.; Szymański, M. K.; Ulaczyk, K.; Pawlak, M.; Rybicki, K.; Iwanek, P.; The OGLE Collaboration; Albrow, M. D.; Chung, S.-J.; Hwang, K.-H.; Jung, Y. K.; Kim, D.; Kim, W.-T.; Kim, H.-W.; Ryu, Y.-H.; Shin, I.-G.; Shvartzvald, Y.; Yee, J. C.; Zhu, W.; Cha, S.-M.; Kim, S.-L.; Kim, D.-J.; Lee, D.-J.; Lee, Y.; Park, B.-G.; Pogge, R. W.; The KMTNet Collaboration

2018-05-01

We report the discovery of a planetary system in which a super-Earth orbits a late M-dwarf host. The planetary system was found from the analysis of the microlensing event OGLE-2017-BLG-0482, wherein the planet signal appears as a short-term anomaly to the smooth lensing light curve produced by the host. Despite its weak signal and short duration, the planetary signal was firmly detected from the dense and continuous coverage by three microlensing surveys. We find a planet/host mass ratio of q ∼ 1.4 × 10‑4. We measure the microlens parallax {π }{{E}} from the long-term deviation in the observed lensing light curve, but the angular Einstein radius {θ }{{E}} cannot be measured because the source trajectory did not cross the planet-induced caustic. Using the measured event timescale and the microlens parallax, we find that the masses of the planet and the host are {M}{{p}}={9.0}-4.5+9.0 {M}\\oplus and {M}host}={0.20}-0.10+0.20 {M}ȯ , respectively, and the projected separation between them is {a}\\perp ={1.8}-0.7+0.6 au. The estimated distance to the lens is {D}{{L}}={5.8}-2.1+1.8 kpc. The discovery of the planetary system demonstrates that microlensing provides an important method to detect low-mass planets orbiting low-mass stars.
Searching for Rapid Orbital Decay of WASP-18b

Science.gov (United States)

Wilkins, Ashlee N.; Delrez, Laetitia; Barker, Adrian J.; Deming, Drake; Hamilton, Douglas; Gillon, Michael; Jehin, Emmanuel

2017-02-01

The WASP-18 system, with its massive and extremely close-in planet, WASP-18b (M p = 10.3M J , a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q‧, the modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q‧ being larger than was inferred from solar-type stars and find that Q‧ ≥ 1 × 106, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.

Environmental effects on stellar populations of dwarf galaxies and star clusters

Science.gov (United States)

Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

2015-08-01

We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in an external environment. Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in observational applications as well as theoretical interpretations of numerical results.We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.
New study on the XeVIII spectrum

International Nuclear Information System (INIS)

Gallardo, M.; Raineri, M.; Giuliani, M.; Lagorio, C.; Padilla, S.; Sarmiento, R.; Reyna Almandos, J.G.

2005-01-01

Capillary light sources were used to observe the spectrum of seven-times-ionized xenon, XeVIII, in the 300-6000 A wavelength range. Twenty-eight energy levels belonging to the 5s-9s, 5d-9d, 5g-9g, 7i-10i, 9l, 5p-9p, 4f-9f, 6h-9h and 8k-10k configurations were adjusted and 38 new spectral lines were classified. The XeVIII ionization energy was determined with improved accuracy using the polarization model. The analysis was supported by Hartree-Fock calculations. The weighted oscillator strengths for all the observed spectral lines were also calculated considering the fitted values for the energy parameters
New study on the XeVIII spectrum

Energy Technology Data Exchange (ETDEWEB)

Gallardo, M. [Centro de Investigaciones Opticas (CIOp) Casilla de Correo 124, 1900 La Plata (Argentina)]. E-mail: gallardom@ciop.unlp.edu.ar; Raineri, M. [Centro de Investigaciones Opticas (CIOp) Casilla de Correo 124, 1900 La Plata (Argentina)]. E-mail: monicar@ciop.unlp.edu.ar; Giuliani, M. [Dto. de Fisica, Fac. de C. Exactas y Naturales, Universidad Nacional de Mar del Plata Funes 3350 (7600) Mar del Plata (Argentina); Lagorio, C. [Dto. de Fisica, Fac. de C. Exactas y Naturales, Universidad Nacional de Mar del Plata Funes 3350 (7600) Mar del Plata (Argentina); Padilla, S. [Dto. de Fisica, Fac. de C. Exactas y Naturales, Universidad Nacional de Mar del Plata Funes 3350 (7600) Mar del Plata (Argentina); Sarmiento, R. [Dto. De Fisica, Universidad del Atlantico, A.A 1890 Barranquilla (Colombia); Reyna Almandos, J.G. [Centro de Investigaciones Opticas (CIOp) Casilla de Correo 124, 1900 La Plata (Argentina)]. E-mail: jreyna@ciop.unlp.edu.ar

2005-10-15

Capillary light sources were used to observe the spectrum of seven-times-ionized xenon, XeVIII, in the 300-6000 A wavelength range. Twenty-eight energy levels belonging to the 5s-9s, 5d-9d, 5g-9g, 7i-10i, 9l, 5p-9p, 4f-9f, 6h-9h and 8k-10k configurations were adjusted and 38 new spectral lines were classified. The XeVIII ionization energy was determined with improved accuracy using the polarization model. The analysis was supported by Hartree-Fock calculations. The weighted oscillator strengths for all the observed spectral lines were also calculated considering the fitted values for the energy parameters.
Southern high-velocity stars

International Nuclear Information System (INIS)

Augensen, H.J.; Buscombe, W.

1978-01-01

Using the model of the Galaxy presented by Eggen, Lynden-Bell and Sandage (1962), plane galactic orbits have been calculated for 800 southern high-velocity stars which possess parallax, proper motion, and radial velocity data. The stars with trigonometric parallaxes were selected from Buscombe and Morris (1958), supplemented by more recent spectroscopic data. Photometric parallaxes from infrared color indices were used for bright red giants studied by Eggen (1970), and for red dwarfs for which Rodgers and Eggen (1974) determined radial velocities. A color-color diagram based on published values of (U-B) and (B-V) for most of these stars is shown. (Auth.)
Binary Star Fractions from the LAMOST DR4

Science.gov (United States)

Tian, Zhi-Jia; Liu, Xiao-Wei; Yuan, Hai-Bo; Chen, Bing-Qiu; Xiang, Mao-Sheng; Huang, Yang; Wang, Chun; Zhang, Hua-Wei; Guo, Jin-Cheng; Ren, Juan-Juan; Huo, Zhi-Ying; Yang, Yong; Zhang, Meng; Bi, Shao-Lan; Yang, Wu-Ming; Liu, Kang; Zhang, Xian-Fei; Li, Tan-Da; Wu, Ya-Qian; Zhang, Jing-Hua

2018-05-01

Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multi-epoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions, are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with T eff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy.
The impact of galaxy geometry and mass evolution on the survival of star clusters

International Nuclear Information System (INIS)

Madrid, Juan P.; Hurley, Jarrod R.; Martig, Marie

2014-01-01

Direct N-body simulations of globular clusters in a realistic Milky-Way-like potential are carried out using the code NBODY6 to determine the impact of the host galaxy disk mass and geometry on the survival of star clusters. A relation between disk mass and star-cluster dissolution timescale is derived. These N-body models show that doubling the mass of the disk from 5 × 10 10 M ☉ to 10 × 10 10 M ☉ halves the dissolution time of a satellite star cluster orbiting the host galaxy at 6 kpc from the galactic center. Different geometries in a disk of identical mass can determine either the survival or dissolution of a star cluster orbiting within the inner 6 kpc of the galactic center. Furthermore, disk geometry has measurable effects on the mass loss of star clusters up to 15 kpc from the galactic center. N-body simulations performed with a fine output time step show that at each disk crossing the outer layers of star clusters experiences an increase in velocity dispersion of ∼5% of the average velocity dispersion in the outer section of star clusters. This leads to an enhancement of mass loss—a clearly discernable effect of disk shocking. By running models with different inclinations, we determine that star clusters with an orbit that is perpendicular to the Galactic plane have larger mass loss rates than do clusters that evolve in the Galactic plane or in an inclined orbit.
Magnetospheric structure and atmospheric Joule heating of habitable planets orbiting M-dwarf stars

Energy Technology Data Exchange (ETDEWEB)

Cohen, O.; Drake, J. J.; Garraffo, C.; Poppenhaeger, K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Glocer, A. [NASA/GSFC, Code 673, Greenbelt, MD 20771 (United States); Bell, J. M. [Center for Planetary Atmospheres and Flight Sciences, National Institute of Aerospace, Hampton, VA 23666 (United States); Ridley, A. J.; Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

2014-07-20

We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvénic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvénic sectors, while no bow shock forms in the sub-Alfvénic sectors. The planets reside most of the time in the sub-Alfvénic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the intense stellar wind. For the steady-state solution, the heating is about 0.1%-3% of the total incoming stellar irradiation, and it is enhanced by 50% for the time-dependent case. The significant Joule Heating obtained here should be considered in models for the atmospheres of habitable planets in terms of the thickness of the atmosphere, the top-side temperature and density, the boundary conditions for the atmospheric pressure, and particle radiation and transport. Here we assume constant ionospheric Pedersen conductance similar to that of the Earth. The conductance could be greater due to the intense EUV radiation leading to smaller heating rates. We plan to quantify the ionospheric conductance in future study.
RADIAL VELOCITIES OF GALACTIC O-TYPE STARS. II. SINGLE-LINED SPECTROSCOPIC BINARIES

International Nuclear Information System (INIS)

Williams, S. J.; Gies, D. R.; Hillwig, T. C.; McSwain, M. V.; Huang, W.

2013-01-01

We report on new radial velocity measurements of massive stars that are either suspected binaries or lacking prior observations. This is part of a survey to identify and characterize spectroscopic binaries among O-type stars with the goal of comparing the binary fraction of field and runaway stars with those in clusters and associations. We present orbits for HDE 308813, HD 152147, HD 164536, BD–16°4826, and HDE 229232, Galactic O-type stars exhibiting single-lined spectroscopic variation. By fitting model spectra to our observed spectra, we obtain estimates for effective temperature, surface gravity, and rotational velocity. We compute orbital periods and velocity semiamplitudes for each system and note the lack of photometric variation for any system. These binaries probably appear single-lined because the companions are faint and because their orbital Doppler shifts are small compared to the width of the rotationally broadened lines of the primary.
Limits on stellar companions to exoplanet host stars with eccentric planets

International Nuclear Information System (INIS)

Kane, Stephen R.; Hinkel, Natalie R.; Howell, Steve B.; Horch, Elliott P.; Feng, Ying; Wright, Jason T.; Ciardi, David R.; Everett, Mark E.; Howard, Andrew W.

2014-01-01

Though there are now many hundreds of confirmed exoplanets known, the binarity of exoplanet host stars is not well understood. This is particularly true of host stars that harbor a giant planet in a highly eccentric orbit since these are more likely to have had a dramatic dynamical history that transferred angular momentum to the planet. Here we present observations of four exoplanet host stars that utilize the excellent resolving power of the Differential Speckle Survey Instrument on the Gemini North telescope. Two of the stars are giants and two are dwarfs. Each star is host to a giant planet with an orbital eccentricity >0.5 and whose radial velocity (RV) data contain a trend in the residuals to the Keplerian orbit fit. These observations rule out stellar companions 4-8 mag fainter than the host star at passbands of 692 nm and 880 nm. The resolution and field of view of the instrument result in exclusion radii of 0.''05-1.''4, which excludes stellar companions within several AU of the host star in most cases. We further provide new RVs for the HD 4203 system that confirm that the linear trend previously observed in the residuals is due to an additional planet. These results place dynamical constraints on the source of the planet's eccentricities, place constraints on additional planetary companions, and inform the known distribution of multiplicity amongst exoplanet host stars.
Cataclysmic Variable Stars

Science.gov (United States)

Hellier, Coel

2001-01-01

Cataclysmic variable stars are the most variable stars in the night sky, fluctuating in brightness continually on timescales from seconds to hours to weeks to years. The changes can be recorded using amateur telescopes, yet are also the subject of intensive study by professional astronomers. That study has led to an understanding of cataclysmic variables as binary stars, orbiting so closely that material transfers from one star to the other. The resulting process of accretion is one of the most important in astrophysics. This book presents the first account of cataclysmic variables at an introductory level. Assuming no previous knowledge of the field, it explains the basic principles underlying the variability, while providing an extensive compilation of cataclysmic variable light curves. Aimed at amateur astronomers, undergraduates, and researchers, the main text is accessible to those with no mathematical background, while supplementary boxes present technical details and equations.
Kepler-36: a pair of planets with neighboring orbits and dissimilar densities

NARCIS (Netherlands)

Carter, J.A.; Agol, E.; Chaplin, W.J.; Basu, S.; Bedding, T.R.; Buchhave, L.A.; Christensen-Dalsgaard, J.; Deck, K.M.; Elsworth, Y.; Fabrycky, D.C.; Ford, E.B.; Fortney, J.J.; Hale, S.J.; Handberg, R.; Hekker, S.; Holman, M.J.; Huber, D.; Karoff, C.; Kawaler, S.D.; Kjeldsen, H.; Lissauer, J.J.; Lopez, E.D.; Lund, M.N.; Lundkvist, M.; Metcalfe, T.S.; Miglio, A.; Rogers, L.A.; Stello, D.; Borucki, W.J.; Bryson, S.; Christiansen, J.L.; Cochran, W.D.; Geary, J.C.; Gilliland, R.L.; Haas, M.R.; Hall, J.; Howard, A.W.; Jenkins, J.M.; Klaus, T.; Koch, D.G.; Latham, D.W.; MacQueen, P.J.; Sasselov, D.; Steffen, J.H.; Twicken, J.D.; Winn, J.N.

2012-01-01

In the solar system, the planets’ compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets’ orbits can
Ages of M Dwarf Stars from their Alpha Enhancement

Science.gov (United States)

Muirhead, Philip Steven; Veyette, Mark

2018-01-01

M dwarf stars dominate stellar populations, and recent results from NASA's Kepler Mission suggest rocky planets are abundant around M dwarf stars. With so many planets orbiting M dwarfs, exoplanet scientists can now turn to questions about their history and evolution. Unfortunately, measuring fundamental properties of M dwarfs is challenging for a variety of reasons. I will discuss the importance of near-infrared spectroscopy in this effort. With high-resolution near-infrared spectroscopy covering Y to K band, we can measure detailed fundamental properties of low-mass stars. With new techniques to measure stellar alpha and iron abundances, we can begin to measure the most challenging fundamental property of M dwarfs: their age. These efforts are even more exciting in the coming years, when the TESS spacecraft is expected to discover five times as many planets orbiting low-mass stars as Kepler.
Orbital Instabilities in a Triaxial Cusp Potential

Science.gov (United States)

Adams, Fred C.; Bloch, Anthony M.; Butler, Suzanne C.; Druce, Jeffrey M.; Ketchum, Jacob A.

2007-12-01

This paper constructs an analytic form for a triaxial potential that describes the dynamics of a wide variety of astrophysical systems, including the inner portions of dark matter halos, the central regions of galactic bulges, and young embedded star clusters. Specifically, this potential results from a density profile of the form ρ(m)~m-1, where the radial coordinate is generalized to triaxial form so that m2=x2/a2+y2/b2+z2/c2. Using the resulting analytic form of the potential and the corresponding force laws, we construct orbit solutions and show that a robust orbit instability exists in these systems. For orbits initially confined to any of the three principal planes, the motion in the perpendicular direction can be unstable. We discuss the range of parameter space for which these orbits are unstable, find the growth rates and saturation levels of the instability, and develop a set of analytic model equations that elucidate the essential physics of the instability mechanism. This orbit instability has a large number of astrophysical implications and applications, including understanding the formation of dark matter halos, the structure of galactic bulges, the survival of tidal streams, and the early evolution of embedded star clusters.
Hot Jupiters and cool stars

International Nuclear Information System (INIS)

Villaver, Eva; Mustill, Alexander J.; Livio, Mario; Siess, Lionel

2014-01-01

Close-in planets are in jeopardy, as their host stars evolve off the main sequence (MS) to the subgiant and red giant phases. In this paper, we explore the influences of the stellar mass (in the range 1.5-2 M ☉ ), mass-loss prescription, planet mass (from Neptune up to 10 Jupiter masses), and eccentricity on the orbital evolution of planets as their parent stars evolve to become subgiants and red giants. We find that planet engulfment along the red giant branch is not very sensitive to the stellar mass or mass-loss rates adopted in the calculations, but quite sensitive to the planetary mass. The range of initial separations for planet engulfment increases with decreasing mass-loss rates or stellar masses and increasing planetary masses. Regarding the planet's orbital eccentricity, we find that as the star evolves into the red giant phase, stellar tides start to dominate over planetary tides. As a consequence, a transient population of moderately eccentric close-in Jovian planets is created that otherwise would have been expected to be absent from MS stars. We find that very eccentric and distant planets do not experience much eccentricity decay, and that planet engulfment is primarily determined by the pericenter distance and the maximum stellar radius.
Incorporation of star measurements for the determination of orbit and attitude parameters of a geosynchronous satellite: An iterative application of linear regression

Science.gov (United States)

Phillips, D.

1980-01-01

Currently on NOAA/NESS's VIRGS system at the World Weather Building star images are being ingested on a daily basis. The image coordinates of the star locations are measured and stored. Subsequently, the information is used to determine the attitude, the misalignment angles between the spin axis and the principal axis of the satellite, and the precession rate and direction. This is done for both the 'East' and 'West' operational geosynchronous satellites. This orientation information is then combined with image measurements of earth based landmarks to determine the orbit of each satellite. The method for determining the orbit is simple. For each landmark measurement one determines a nominal position vector for the satellite by extending a ray from the landmark's position towards the satellite and intersecting the ray with a sphere with center coinciding with the Earth's center and with radius equal to the nominal height for a geosynchronous satellite. The apparent motion of the satellite around the Earth's center is then approximated with a Keplerian model. In turn the variations of the satellite's height, as a function of time found by using this model, are used to redetermine the successive satellite positions by again using the Earth based landmark measurements and intersecting rays from these landmarks with the newly determined spheres. This process is performed iteratively until convergence is achieved. Only three iterations are required.
THE ORBIT OF THE ORPHAN STREAM

International Nuclear Information System (INIS)

Newberg, Heidi Jo; Willett, Benjamin A.; Yanny, Brian; Xu Yan

2010-01-01

We use recent Sloan Extension for Galactic Understanding and Exploration (SEGUE) spectroscopy and the Sloan Digital Sky Survey (SDSS) and SEGUE imaging data to measure the sky position, distance, and radial velocities of stars in the tidal debris stream that is commonly referred to as the 'Orphan Stream'. We fit orbital parameters to the data and find a prograde orbit with an apogalacticon, perigalacticon, and eccentricity of 90 kpc, 16.4 kpc, and e = 0.7, respectively. Neither the dwarf galaxy UMa II nor the Complex A gas cloud has velocities consistent with a kinematic association with the Orphan Stream. It is possible that Segue-1 is associated with the Orphan Stream, but no other known Galactic clusters or dwarf galaxies in the Milky Way lie along its orbit. The detected portion of the stream ranges from 19 to 47 kpc from the Sun and is an indicator of the mass interior to these distances. There is a marked increase in the density of Orphan Stream stars near (l, b) = (253 0 , 49 0 ), which could indicate the presence of the progenitor at the edge of the SDSS data. If this is the progenitor, then the detected portion of the Orphan Stream is a leading tidal tail. We find blue horizontal branch (BHB) stars and F turnoff stars associated with the Orphan Stream. The turnoff color is (g - r) 0 = 0.22. The BHB stars have a low metallicity of [Fe/H] WBG = -2.1. The orbit is best fit to a halo potential with a halo plus disk mass of about 2.6 x 10 11 M sun , integrated to 60 kpc from the Galactic center. Our fits are done to orbits rather than full N-body simulations; we show that if N-body simulations are used, the inferred mass of the galaxy would be slightly smaller. Our best fit is found with a logarithmic halo speed of v halo = 73 ± 24 km s -1 , a disk+bulge mass of M(R 11 M sun , and a halo mass of M(R 11 M sun . However, we can find similar fits to the data that use a Navarro-Frenk-White halo profile or that have smaller disk masses and correspondingly larger
Effectiveness of Mind Mapping in English Teaching among VIII Standard Students

Science.gov (United States)

Hallen, D.; Sangeetha, N.

2015-01-01

The aim of the study is to find out the effectiveness of mind mapping technique over conventional method in teaching English at high school level (VIII), in terms of Control and Experimental group. The sample of the study comprised, 60 VIII Standard students in Tiruchendur Taluk. Mind Maps and Achievement Test (Pretest & Posttest) were…
Population pharmacokinetics of recombinant coagulation factor VIII-SingleChain in patients with severe hemophilia A.

Science.gov (United States)

Zhang, Y; Roberts, J; Tortorici, M; Veldman, A; St Ledger, K; Feussner, A; Sidhu, J

2017-06-01

Essentials rVIII-SingleChain is a unique recombinant factor VIII (FVIII) molecule. A population pharmacokinetic model was based on FVIII activity of severe hemophilia A patients. The model was used to simulate factor VIII activity-time profiles for various dosing scenarios. The model supports prolonged dosing of rVIII-SingleChain with intervals of up to twice per week. Background Single-chain recombinant coagulation factor VIII (rVIII-SingleChain) is a unique recombinant coagulation factor VIII molecule. Objectives To: (i) characterize the population pharmacokinetics (PK) of rVIII-SingleChain in patients with severe hemophilia A; (ii) identify correlates of variability in rVIII-SingleChain PK; and (iii) simulate various dosing scenarios of rVIII-SingleChain. Patients/Methods A population PK model was developed, based on FVIII activity levels of 130 patients with severe hemophilia A (n = 91 for ≥ 12-65 years; n = 39 for 85% and > 93% of patients were predicted to maintain FVIII activity level above 1 IU dL -1 , at all times with three-times-weekly dosing (given on days 0, 2, and 4.5) at the lowest (20 IU kg -1 ) and highest (50 IU kg -1 ) doses, respectively. For twice weekly dosing (days 0 and 3.5) of 50 IU kg -1 rVIII-SingleChain, 62-80% of patients across all ages were predicted to maintain a FVIII activity level above 1 IU dL -1 at day 7. Conclusions The population PK model adequately characterized rVIII-SingleChain PK, and the model can be utilized to simulate FVIII activity-time profiles for various dosing scenarios. © 2017 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and Haemostasis.
Chemical abundances of primary stars in the Sirius-like binary systems

Science.gov (United States)

Kong, X. M.; Zhao, G.; Zhao, J. K.; Shi, J. R.; Kumar, Y. Bharat; Wang, L.; Zhang, J. B.; Wang, Y.; Zhou, Y. T.

2018-05-01

Study of primary stars lying in Sirius-like systems with various masses of white dwarf (WD) companions and orbital separations is one of the key aspects to understand the origin and nature of barium (Ba) stars. In this paper, based on high-resolution and high-S/N spectra, we present systematic analysis of photospheric abundances for 18 FGK primary stars of Sirius-like systems including six giants and 12 dwarfs. Atmospheric parameters, stellar masses, and abundances of 24 elements (C, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, and Nd) are determined homogeneously. The abundance patterns in these sample stars show that most of the elements in our sample follow the behaviour of field stars with similar metallicity. As expected, s-process elements in four known Ba giants show overabundance. A weak correlation was found between anomalies of s-process elemental abundance and orbital separation, suggesting that the orbital separation of the binaries could not be the main constraint to differentiate strong Ba stars from mild Ba stars. Our study shows that the large mass (>0.51 M⊙) of a WD companion in a binary system is not a sufficient condition to form a Ba star, even if the separation between the two components is small. Although not sufficient, it seems to be a necessary condition since Ba stars with lower mass WDs in the observed sample were not found. Our results support that [s/Fe] and [hs/ls] ratios of Ba stars are anti-correlated with the metallicity. However, the different levels of s-process overabundance among Ba stars may not be dominated mainly by the metallicity.
The Influence of Orbital Resonances on the Water Transport to Objects in the Circumprimary Habitable Zone of Binary Star Systems

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Bancelin, David; Pilat-Lohinger, Elke; Maindl, Thomas I.; Ragossnig, Florian; Schäfer, Christoph

2017-06-01

We investigate the role of secular and mean motion resonances on the water transport from a belt of icy asteroids onto planets or embryos orbiting inside the circumprimary habitable zone (HZ) of a binary star system. In addition, the host-star has an accompanying gas giant planet. For a comparison, we perform two case studies where a secular resonance (SR) is located either inside the HZ close to 1.0 au (causing eccentric motion of a planet or embryos therein) or in the asteroid belt, beyond the snow line. In the latter case, a higher flux of icy objects moving toward the HZ is expected. Collisions between asteroids and objects in the HZ are treated analytically. Our purely dynamical study shows that the SR in the HZ boosts the water transport however, collisions can occur at very high impact speeds. In this paper, we treat for the first time, realistic collisions using a GPU 3D-SPH code to assess the water loss in the projectile. Including the water loss into the dynamical results, we get more realistic values for the water mass fraction of the asteroid during an impact. We highlight that collisions occurring at high velocities greatly reduce the water content of the projectile and thus the amount of water transported to planets or embryos orbiting inside the HZ. Moreover, we discuss other effects that could modify our results, namely the asteroid’s surface rate recession due to ice sublimation and the atmospheric drag contribution on the asteroids’ mass loss.

The variable Herbig Ae star HR 5999: VIII. Spectroscopic observations 1975 - 1985 and correlations with simulataneous photometry

International Nuclear Information System (INIS)

Tjin, A.; Djie, H.R.E.; The, P.S.; Andersen, J.; Nordstroem, B.; Finkenzeller, U.; Jankovics, I.

1989-01-01

Visual spectroscopy of the irregularly variable Herbig Ae star HR 5999 over the past 15 years is summarised. The general features of the spectrum indicate that HR 5999 is an A5-7 III-IVe star with an extended circumstellar atmosphere. Typical lines have a rotationally broadened photospheric component and one or two blue-shifted ''shell'' components. The average radial velocity of the photospheric components, together with the common proper motions of the stars strongly suggest that HR 5999 and the peculiar B6 star HR 6000 from a physical pair, with common age. In order to study the relation between variations in the spectrum and in the brightness of the star, three sequences of simultaneous spectroscopic and photometric observations have been obtained during the past decade. From these and other (isolated) simultaneous observations we concluded that: (a) the photospheric radial velocity component is variable, possibly with a period of about 14 days, which could point to the presence of a close companion, (b) occasionally, sudden variations may occur (within one night) either in the photospheric line components,or in the shell (absorption or emission) components or both; (c) a decreasing brightness is correlated with increasing Hα-emission flux and a decreasing wind velocity in the shell region. An interpretation of these correlations in terms of magnetic activity is proposed
Searching for Rapid Orbital Decay of WASP-18b

Energy Technology Data Exchange (ETDEWEB)

Wilkins, Ashlee N.; Deming, Drake; Hamilton, Douglas [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Delrez, Laetitia [Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Barker, Adrian J. [Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom); Gillon, Michael; Jehin, Emmanuel, E-mail: awilkins@astro.umd.edu [Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, allée du 6 Août 19C, B-4000 Lige (Belgium)

2017-02-20

The WASP-18 system, with its massive and extremely close-in planet, WASP-18b ( M{sub p} = 10.3 M{sub J}, a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q ′, the modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer ) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope ) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q ′ being larger than was inferred from solar-type stars and find that Q ′ ≥ 1 × 10{sup 6}, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.
Radiative Hydrodynamic Simulations of In Situ Star Formation in the Galactic Center

Science.gov (United States)

Frazer, Chris; Heitsch, Fabian

2018-01-01

Many stars observed in the Galactic Center (GC) orbit the supermassive black hole (SMBH), Sagittarius A*, in a region where the extreme gravitational field is expected to inhibit star formation. Yet, many of these stars are young which favors an in situ formation scenario. Previous numerical work on this topic has focused on two possible solutions. First, the tidal capture of a > 10^4 Msun infalling molecular cloud by an SMBH may result in the formation of a surrounding gas disk which then rapidly cools and forms stars. This process results in stellar populations that are consistent with the observed stellar disk in the GC. Second, dense gas clumps of approximately 100 Msun on highly eccentric orbits about an SMBH can experience sparks of star formation via orbital compressions occurring during pericenter passage. In my dissertation, I build upon these models using a series of grid-based radiative hydrodynamic simulations, including the effects of both ionizing ultraviolet light from existing stars as well as X-ray radiation emanating from the central black hole. Radiation is treated with an adaptive ray-tracing routine, including appropriate heating and cooling for both neutral and ionized gas. These models show that ultraviolet radiation is sufficiently strong to heat low mass gas clouds, thus suppressing star formation from clump compression. Gas disks that form from cloud capture become sufficiently dense to provide shielding from the radiation of existing central stars, thus allowing star formation to continue. Conversely, X-rays easily penetrate and heat the potentially star forming gas. For sufficiently high radiation fields, this provides a mechanism to disrupt star formation for both scenarios considered above.
THE SYNERGY OF DIRECT IMAGING AND ASTROMETRY FOR ORBIT DETERMINATION OF EXO-EARTHS

International Nuclear Information System (INIS)

Shao, Michael; Catanzarite, Joseph; Pan Xiaopei

2010-01-01

The holy grail of exoplanet searches is an exo-Earth, an Earth mass planet in the habitable zone (HZ) around a nearby star. Mass is one of the most important characteristics of a planet and can only be measured by observing the motion of the star around the planet-star center of gravity. The planet's orbit can be measured either by imaging the planet at multiple epochs or by measuring the position of the star at multiple epochs by space-based astrometry. The measurement of an exoplanet's orbit by direct imaging is complicated by a number of factors. One is the inner working angle (IWA). A space coronagraph or interferometer imaging an exo-Earth can separate the light from the planet from the light from the star only when the star-planet separation is larger than the IWA. Second, the apparent brightness of a planet depends on the orbital phase. A single image of a planet cannot tell us whether the planet is in the HZ or distinguish whether it is an exo-Earth or a Neptune-mass planet. Third is the confusion that may arise from the presence of multiple planets. With two images of a multiple planet system, it is not possible to assign a dot to a planet based only on the photometry and color of the planet. Finally, the planet-star contrast must exceed a certain minimum value in order for the planet to be detected. The planet may be unobservable even when it is outside the IWA, such as when the bright side of the planet is facing away from us in a 'crescent' phase. In this paper we address the question: 'Can a prior astrometric mission that can identify which stars have Earth-like planets significantly improve the science yield of a mission to image exo-Earths?' In the case of the Occulting Ozone Observatory, a small external occulter mission that cannot measure spectra, we find that the occulter mission could confirm the orbits of ∼4 to ∼5 times as many exo-Earths if an astrometric mission preceded it to identify which stars had such planets. In the case of an
The Maui International Double Star Conference

Science.gov (United States)

Genet, Russell

2013-04-01

A three-day double star conference in February, 2013, covered double star observations from simple eyepiece astrometry of wide binaries, with orbital periods of centuries, to amplitude interferometry of binaries with periods measured in days or even hours. A wide range of participants, from students and amateurs to professionals shared their perspectives in panel discussions. This was the first conference of the newly-formed International Association of Double Star Observers (IADSO). PDFs of 22 of the talks and YouTube links to 23 of the talks and panels are available at www.IADSO.org.
NuSTAR Observation of the Symbiotic System GX 1+4

Science.gov (United States)

Wolff, Michael Thomas; Becker, Peter A.; Enoto, Teruaki; Pottschmidt, Katja; Wood, Kent

2017-08-01

We report on a NuSTAR observation of the symbiotic binary system GX 1+4. GX 1+4 is one of a small number of systems with a red giant mass donor and a magnetic neutron star in orbit around each other. The accreting pulsar in GX 1+4 has a spin period of ~150 seconds with epochs of both spin-up and spin-down. The orbital period that has not been determined. Magnetic accretion theory in such systems suggests that the neutron star has a magnetic field in the range 1013-1014 Gauss although this is not settled because no cyclotron absorption feature has been observed in the X-ray spectrum. The NuSTAR spectrum shows broad Fe-line emission near ~6.5 keV and also shows a broad power law shape detected up to ~60 keV. We analyze and discuss the NuSTAR X-ray data with particular attention to the question of what can the spectrum tell us about the structure of the accretion flow onto the neutron star and the magnetic field strength.
The Double Star mission

Directory of Open Access Journals (Sweden)

Liu

2005-11-01

Full Text Available The Double Star Programme (DSP was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances in conjunction with the Cluster mission. The first spacecraft, TC-1 (Tan Ce means "Explorer", was launched on 29 December 2003, and the second one, TC-2, on 25 July 2004 on board two Chinese Long March 2C rockets. TC-1 was injected in an equatorial orbit of 570x79000 km altitude with a 28° inclination and TC-2 in a polar orbit of 560x38000 km altitude. The orbits have been designed to complement the Cluster mission by maximizing the time when both Cluster and Double Star are in the same scientific regions. The two missions allow simultaneous observations of the Earth magnetosphere from six points in space. To facilitate the comparison of data, half of the Double Star payload is made of spare or duplicates of the Cluster instruments; the other half is made of Chinese instruments. The science operations are coordinated by the Chinese DSP Scientific Operations Centre (DSOC in Beijing and the European Payload Operations Service (EPOS at RAL, UK. The spacecraft and ground segment operations are performed by the DSP Operations and Management Centre (DOMC and DSOC in China, using three ground station, in Beijing, Shanghai and Villafranca.
Star Masses and Star-Planet Distances for Earth-like Habitability.

Science.gov (United States)

Waltham, David

2017-01-01

This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M ⊙ planets with at least simple life is 0.57 M ⊙ < M < 1.64 M ⊙ . Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.
Confirmation of Earth-Mass Planets Orbiting the Millisecond Pulsar PSR B1257 + 12.

Science.gov (United States)

Wolszczan, A

1994-04-22

The discovery of two Earth-mass planets orbiting an old ( approximately 10(9) years), rapidly spinning neutron star, the 6.2-millisecond radio pulsar PSR B1257+12, was announced in early 1992. It was soon pointed out that the approximately 3:2 ratio of the planets' orbital periods should lead to accurately predictable and possibly measurable gravitational perturbations of their orbits. The unambiguous detection of this effect, after 3 years of systematic timing observations of PSR B1257+12 with the 305-meter Arecibo radiotelescope, as well as the discovery of another, moon-mass object in orbit around the pulsar, constitutes irrefutable evidence that the first planetary system around a star other than the sun has been identified.
HATS-50b through HATS-53b: Four Transiting Hot Jupiters Orbiting G-type Stars Discovered by the HATSouth Survey

Science.gov (United States)

Henning, Th.; Mancini, L.; Sarkis, P.; Bakos, G. Á.; Hartman, J. D.; Bayliss, D.; Bento, J.; Bhatti, W.; Brahm, R.; Ciceri, S.; Csubry, Z.; de Val-Borro, M.; Espinoza, N.; Fulton, B. J.; Howard, A. W.; Isaacson, H. T.; Jordán, A.; Marcy, G. W.; Penev, K.; Rabus, M.; Suc, V.; Tan, T. G.; Tinney, C. G.; Wright, D. J.; Zhou, G.; Durkan, S.; Lazar, J.; Papp, I.; Sari, P.

2018-02-01

We report the discovery of four close-in transiting exoplanets (HATS-50b through HATS-53b), discovered using the HATSouth three-continent network of homogeneous and automated telescopes. These new exoplanets belong to the class of hot Jupiters and orbit G-type dwarf stars, with brightness in the range V = 12.5–14.0 mag. While HATS-53 has many physical characteristics similar to the Sun, the other three stars appear to be metal-rich ([{Fe}/{{H}}]=0.2{--}0.3), larger, and more massive. Three of the new exoplanets, namely HATS-50b, HATS-51b, and HATS-53b, have low density (HATS-50b: 0.39+/- 0.10 {M}{{J}}, 1.130+/- 0.075 {R}{{J}}; HATS-51b: 0.768+/- 0.045 {M}{{J}}, 1.41+/- 0.19 {R}{{J}}; HATS-53b: 0.595+/- 0.089 {M}{{J}}, 1.340+/- 0.056 {R}{{J}}) and similar orbital periods (3.8297 days, 3.3489 days, 3.8538 days, respectively). Instead, HATS-52b is more dense (mass 2.24+/- 0.15 {M}{{J}} and radius 1.382+/- 0.086 {R}{{J}}) and has a shorter orbital period (1.3667 days). It also receives an intensive radiation from its parent star and, consequently, presents a high equilibrium temperature ({T}{eq}=1834+/- 73 K). HATS-50 shows a marginal additional transit feature consistent with an ultra-short-period hot super Neptune (upper mass limit 0.16 {M}{{J}}), which will be able to be confirmed with TESS photometry. The HATSouth network is operated by a collaboration consisting of Princeton University (PU), the Max Planck Institute für Astronomie (MPIA), the Australian National University (ANU), and the Pontificia Universidad Católica de Chile (PUC). The station at Las Campanas Observatory (LCO) of the Carnegie Institute is operated by PU in conjunction with PUC, the station at the High Energy Spectroscopic Survey (H.E.S.S.) site is operated in conjunction with MPIA, and the station at Siding Spring Observatory (SSO) is operated jointly with ANU. Based in part on observations made with the ESO 3.6 m, the NTT, the MPG 2.2 m and Euler 1.2 m Telescopes at the ESO Observatory in
DISCERNING EXOPLANET MIGRATION MODELS USING SPIN-ORBIT MEASUREMENTS

International Nuclear Information System (INIS)

Morton, Timothy D.; Johnson, John Asher

2011-01-01

We investigate the current sample of exoplanet spin-orbit measurements to determine whether a dominant planet migration channel can be identified, and at what confidence. We use the predictions of Kozai migration plus tidal friction and planet-planet scattering as our misalignment models, and we allow for a fraction of intrinsically aligned systems, explainable by disk migration. Bayesian model comparison demonstrates that the current sample of 32 spin-orbit measurements strongly favors a two-mode migration scenario combining planet-planet scattering and disk migration over a single-mode Kozai migration scenario. Our analysis indicates that between 34% and 76% of close-in planets (95% confidence) migrated via planet-planet scattering. Separately analyzing the subsample of 12 stars with T eff >6250 K-which Winn et al. predict to be the only type of stars to maintain their primordial misalignments-we find that the data favor a single-mode scattering model over Kozai with 85% confidence. We also assess the number of additional hot star spin-orbit measurements that will likely be necessary to provide a more confident model selection, finding that an additional 20-30 measurement has a >50% chance of resulting in a 95% confident model selection, if the current model selection is correct. While we test only the predictions of particular Kozai and scattering migration models in this work, our methods may be used to test the predictions of any other spin-orbit misaligning mechanism.
AN ORBIT FIT FOR THE GRILLMAIR DIONATOS COLD STELLAR STREAM

International Nuclear Information System (INIS)

Willett, Benjamin A.; Newberg, Heidi Jo; Zhang Haotong; Yanny, Brian; Beers, Timothy C.

2009-01-01

We use velocity and metallicity information from Sloan Digital Sky Survey and Sloan Extension for Galactic Understanding and Exploration stellar spectroscopy to fit an orbit to the narrow 63 deg. stellar stream of Grillmair and Dionatos. The stars in the stream have a retrograde orbit with eccentricity e = 0.33 (perigalacticon of 14.4 kpc and apogalacticon of 28.7 kpc) and inclination approximately i ∼ 35 deg. In the region of the orbit which is detected, it has a distance of about 7-11 kpc from the Sun. Assuming a standard disk plus bulge and logarithmic halo potential for the Milky Way stars plus dark matter, the stream stars are moving with a large space velocity of approximately 276 km s -1 at perigalacticon. Using this stream alone, we are unable to determine if the dark matter halo is oblate or prolate. The metallicity of the stream is [Fe/H] = -2.1 ± 0.1. Observed proper motions for individual stream members above the main sequence turnoff are consistent with the derived orbit. None of the known globular clusters in the Milky Way have positions, radial velocities, and metallicities that are consistent with being the progenitor of the GD-1 stream.
An Orbit Fit for the Grillmair Dionatos Cold Stellar Stream

Energy Technology Data Exchange (ETDEWEB)

Willett, Benjamin A.; Newberg, Heidi Jo; Zhang, Haotong; Yanny, Brian; Beers, Timothy C.

2009-01-01

We use velocity and metallicity information from Sloan Digital Sky Survey and Sloan Extension for Galactic Understanding and Exploration stellar spectroscopy to fit an orbit to the narrow 63{sup o} stellar stream of Grillmair and Dionatos. The stars in the stream have a retrograde orbit with eccentricity e = 0.33 (perigalacticon of 14.4 kpc and apogalacticon of 28.7 kpc) and inclination approximately i {approx} 35{sup o}. In the region of the orbit which is detected, it has a distance of about 7-11 kpc from the Sun. Assuming a standard disk plus bulge and logarithmic halo potential for the Milky Way stars plus dark matter, the stream stars are moving with a large space velocity of approximately 276 km s{sup -1} at perigalacticon. Using this stream alone, we are unable to determine if the dark matter halo is oblate or prolate. The metallicity of the stream is [Fe/H] = -2.1 {+-} 0.1. Observed proper motions for individual stream members above the main sequence turnoff are consistent with the derived orbit. None of the known globular clusters in the Milky Way have positions, radial velocities, and metallicities that are consistent with being the progenitor of the GD-1 stream.
Astrometric detectability of systems with unseen companions: effects of the Earth orbital motion

Science.gov (United States)

Butkevich, Alexey G.

2018-06-01

The astrometric detection of an unseen companion is based on an analysis of the apparent motion of its host star around the system's barycentre. Systems with an orbital period close to 1 yr may escape detection if the orbital motion of their host stars is observationally indistinguishable from the effects of parallax. Additionally, an astrometric solution may produce a biased parallax estimation for such systems. We examine the effects of the orbital motion of the Earth on astrometric detectability in terms of a correlation between the Earth's orbital position and the position of the star relative to its system barycentre. The χ2 statistic for parallax estimation is calculated analytically, leading to expressions that relate the decrease in detectability and accompanying parallax bias to the position correlation function. The impact of the Earth's motion critically depends on the exoplanet's orbital period, diminishing rapidly as the period deviates from 1 yr. Selection effects against 1-yr-period systems is, therefore, expected. Statistical estimation shows that the corresponding loss of sensitivity results in a typical 10 per cent increase in the detection threshold. Consideration of eccentric orbits shows that the Earth's motion has no effect on detectability for e≳ 0.5. The dependence of the detectability on other parameters, such as orbital phases and inclination of the orbital plane to the ecliptic, are smooth and monotonic because they are described by simple trigonometric functions.
Infrared Spectroscopy of the Late-Type Star in the Neutron Star X-ray Symbiotic System 4U 1700+24 = V934 Herculis

Science.gov (United States)

Hinkle, Kenneth; Fekel, Francis; Joyce, Richard; Mikolajewska, Joanna; Galan, Cezary

2018-01-01

V934 Her = 4U 1700+24 is a previously known M giant - neutron star X-ray symbiotic system. Employing newly measured optical and infrared radial velocities spanning 29 years plus the extensive set of velocities in the literature, we have computed the orbit of the M III in that system. We determine an orbital period of 4391 days or 12.0 yr, far longer than the 404 day orbit commonly cited in the literature. In addition to the 12.0 yr orbital period we find a shorter period of 420 days, similar to that previously found. Instead of orbital motion, we attribute this shorter period to a long secondary pulsation (LSP) period in the SRb variable M3 III. The orbit is seen nearly pole on explaining why X-ray pulsations associated with the neutron star have not been detected. Arguments are made that this orientation supports a pulsation origin for LSP. We also measure CNO and Fe peak abundances of the M giant. Basic properties of the M giant are derived. We discuss the possible evolutionary paths this system has taken to get to its current state.
PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER

Energy Technology Data Exchange (ETDEWEB)

Howard, Andrew W.; Marcy, Geoffrey W. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Bryson, Stephen T.; Rowe, Jason F.; Borucki, William J.; Koch, David G.; Lissauer, Jack J. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Jenkins, Jon M.; Van Cleve, Jeffrey; Caldwell, Douglas A. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States); Batalha, Natalie M. [Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States); Dunham, Edward W. [Lowell Observatory, Flagstaff, AZ 86001 (United States); Gautier, Thomas N. [Jet Propulsion Laboratory/Caltech, Pasadena, CA 91109 (United States); Cochran, William D. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Latham, David W.; Torres, Guillermo [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brown, Timothy M. [Las Cumbres Observatory Global Telescope, Goleta, CA 93117 (United States); Gilliland, Ronald L. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Buchhave, Lars A. [Niels Bohr Institute, Copenhagen University (Denmark); Christensen-Dalsgaard, Jorgen, E-mail: howard@astro.berkeley.edu [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); and others

2012-08-01

We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally 'planet candidates') from the Kepler mission that include a nearly complete set of detected planets as small as 2 R{sub Circled-Plus }. For each of the 156,000 target stars, we assess the detectability of planets as a function of planet radius, R{sub p}, and orbital period, P, using a measure of the detection efficiency for each star. We also correct for the geometric probability of transit, R{sub *}/a. We consider first Kepler target stars within the 'solar subset' having T{sub eff} = 4100-6100 K, log g 4.0-4.9, and Kepler magnitude Kp < 15 mag, i.e., bright, main-sequence GK stars. We include only those stars having photometric noise low enough to permit detection of planets down to 2 R{sub Circled-Plus }. We count planets in small domains of R{sub p} and P and divide by the included target stars to calculate planet occurrence in each domain. The resulting occurrence of planets varies by more than three orders of magnitude in the radius-orbital period plane and increases substantially down to the smallest radius (2 R{sub Circled-Plus }) and out to the longest orbital period (50 days, {approx}0.25 AU) in our study. For P < 50 days, the distribution of planet radii is given by a power law, df/dlog R = k{sub R}R{sup {alpha}} with k{sub R} = 2.9{sup +0.5}{sub -0.4}, {alpha} = -1.92 {+-} 0.11, and R {identical_to} R{sub p}/R{sub Circled-Plus }. This rapid increase in planet occurrence with decreasing planet size agrees with the prediction of core-accretion formation but disagrees with population synthesis models that predict a desert at super-Earth and Neptune sizes for close-in orbits. Planets with orbital periods shorter than 2 days are extremely rare; for R{sub p} > 2 R{sub Circled-Plus} we measure an
PG 0308 + 096 and PG 1026 + 002 - Two new short period binary stars resulting from common-envelope evolution

Science.gov (United States)

Saffer, Rex A.; Wade, Richard A.; Liebert, James; Green, Richard F.; Sion, Edward M.; Bechtold, J.; Foss, Diana; Kidder, K.

1993-01-01

Ultraviolet spectroscopy, optical spectroscopy, and spectrophotometry have been used to study the excess UV stars PG 0308 + 096 and PG 1026 + 002. Both objects are short-period binary systems, each containing a DA white dwarf star and a dM star. Orbital periods of approximately 0.284 day for PG 0308 + 096, and aproximately 0.597 day for PG 1026, have been found by spectroscopic analysis of the H-alpha emission line. Ly-alpha and Balmer line profile fitting were used to estimate the mass of white dwarf stars; mass estimates for the dM stars are based on their spectral types. The orbital inclinations are derived from these masses, the periods, and amplitudes of the H-alpha radial velocity curves. The equivalent width of the H-alpha emission line, in each binary system, varies with the orbital phase in such a manner as to imply that it arises, in large part at least, from the hemisphere of the M star that faces the white dwarf star.
The formation of retrograde planetary orbits by close stellar encounters

Directory of Open Access Journals (Sweden)

Ford E. B.

2011-02-01

Full Text Available We consider the growing number of observations of the RossiterMcLaughlin eﬀect in transiting planets, which seem to suggest that ~30% of transiting planets are in highly inclined or retrograde orbits. We consider the dense cluster environment in which stars are born and investigate whether perturbations from passing stars can drive planetary systems into retrograde conﬁgurations. We ﬁnd that ﬂy-bys can result in signiﬁcantly more inclination excitation than might naively be expected from impulse approximations, leading to several percent of stellar systems possessing planets in retrograde orbits.
55 CANCRI: A COPLANAR PLANETARY SYSTEM THAT IS LIKELY MISALIGNED WITH ITS STAR

International Nuclear Information System (INIS)

Kaib, Nathan A.; Duncan, Martin J.; Raymond, Sean N.

2011-01-01

Although the 55 Cnc system contains multiple, closely packed planets that are presumably in a coplanar configuration, we use numerical simulations to demonstrate that they are likely to be highly inclined to their parent star's spin axis. Due to perturbations from its distant binary companion, this planetary system precesses like a rigid body about its parent star. Consequently, the parent star's spin axis and the planetary orbit normal likely diverged long ago. Because only the projected separation of the binary is known, we study this effect statistically, assuming an isotropic distribution for wide binary orbits. We find that the most likely projected spin-orbit angle is ∼50°, with a ∼30% chance of a retrograde configuration. Transit observations of the innermost planet—55 Cnc e—may be used to verify these findings via the Rossiter-McLaughlin effect. 55 Cancri may thus represent a new class of planetary systems with well-ordered, coplanar orbits that are inclined with respect to the stellar equator.
A new interpretation of luminous blue stars

International Nuclear Information System (INIS)

Stothers, R.

1976-01-01

A major revision of current theoretical ideas about the brightest blue stars must be made if Carson's new radiative opacities are adopted in stellar models. Unlike earlier opacities, the new opacities exhibit a large ''bump'' due to CNO ionization, which leads to very strong central condensation, convective instability, and pulsational instability in hot, diffuse stellar envelopes (typically those in which L/M>10 3 solar units). Despite a number of theoretical uncertainties, the new picture of the structure of very luminous stars is reasonably successful in accounting for a variety of previously unexplained observations. Thus, the new stellar models for the phase of core hydrogen burning predict large radii and rather cool effective temperatures (which are yet to be observationally confirmed) for O stars, and a spreading out of the main-sequence band in the H-R diagram toward luminous cool supergiants for masses higher than approx.20 M/sub sun/, beginning at M/sub v/=-4.5 and Sp=B1. They also predict slower surface rotations for O stars compared with B stars; and, in binary systems, slower apsidal motions, closer rotational-revolutional synchronism, and smaller orbital eccentricities. In massive X-ray binary systems, circular orbits and supergiant-like visual companions are expected to be quite common. Radial pulsations of the models have been calculated by employing linearized nonadiabatic pulsation theory. Long-period variability is predicted to exist for massive blue supergiants of luminosity class Ia. The new models for helium stars predict large radii and rather cool effective temperatures for Wolf-Rayet stars, as well as multimodal pulsational instability and, possibly, surface turbulence for these stars. Ultrashort-period variability, observed in many classes of hot luminous stars, may be due, in part, to high radial overtone pulsations (or, possibly, to nonradial pulsation or convective modes)

NICER Discovers the Ultracompact Orbit of the Accreting Millisecond Pulsar IGR J17062–6143

DEFF Research Database (Denmark)

Strohmayer, T. E.; Arzoumanian, Z.; Bogdanov, S.

2018-01-01

We present results of recent Neutron Star Interior Composition Explorer (NICER) observations of the accreting millisecond X-ray pulsar (AMXP) IGR J17062−6143 that show that it resides in a circular, ultracompact binary with a 38-minute orbital period. NICER observed the source for ≈26 ks over a 5...... of the neutron star. A coherent search for the orbital solution using the Z2 method finds a best-fitting circular orbit with a period of 2278.21 s (37.97 minutes), a projected semimajor axis of 0.00390 lt-s, and a barycentric pulsar frequency of 163.6561105 Hz. This is currently the shortest known orbital period...
275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0–10

DEFF Research Database (Denmark)

Mayo, Andrew W.; Vanderburg, Andrew; Latham, David W.

2018-01-01

Since 2014, NASA’s K2 mission has observed large portions of the ecliptic plane in search of transiting planets and has detected hundreds of planet candidates. With observations planned until at least early 2018, K2 will continue to identify more planet candidates. We present here 275 planet...... candidates observed during Campaigns 0–10 of the K2 mission that are orbiting stars brighter than 13 mag (in Kepler band) and for which we have obtained high-resolution spectra ( R = 44,000). These candidates are analyzed using the vespa package in order to calculate their false-positive probabilities (FPP......). We find that 149 candidates are validated with an FPP lower than 0.1%, 39 of which were previously only candidates and 56 of which were previously undetected. The processes of data reduction, candidate identification, and statistical validation are described, and the demographics of the candidates...
Acquired high titre factor VIII inhibitor with underlying polyarteritis nodosa.

Science.gov (United States)

Snowden, J A; Hutchings, M; Spearing, R; Patton, W N

1997-05-01

We here present the case of a 70-year-old woman referred to our unit for investigation of bleeding. Investigations confirmed a high titre acquired Factor VIII inhibitor. In association there was relapse of systemic illness associated with anti-neutrophil cytoplasmic antibodies (atypical pattern) for which she had been treated five years previously. Immunosuppression was attempted, but it failed to have an impact both on the inhibitor titre and on the underlying disorder. The patient died from multi-organ failure and massive chest hemorrhage. Post-mortem showed necrotizing vasculitis of medium sized vessels at several sites, including the kidney, consistent with a diagnosis of polyarteritis nodosa. Although it is well recognised that Factor VIII inhibitors are found in conjunction with autoimmune disorders, this case is significant in that it is the first associated with histologically proven polyarteritis nodosa type vasculitis. The case illustrates the difficulties in the investigation and management of patients with acquired high titre Factor VIII inhibitors.
Chromogenic Factor VIII Assays for Improved Diagnosis of Hemophilia A.

Science.gov (United States)

Rodgers, Susan; Duncan, Elizabeth

2017-01-01

Hemophilia A is an inherited bleeding disorder caused by a reduced level of factor VIII coagulant activity (FVIII:C) in blood. Bleeding episodes may occur spontaneously in the severe form of hemophilia or after trauma in the milder forms. It is important that patients are diagnosed correctly, which includes placing them into the correct severity category of the disorder so that appropriate treatment can be given. Diagnosis is made by determination of the amount of FVIII:C in the blood, usually using a one-stage factor VIII:C assay. However, approximately one third of patients with mild or moderate hemophilia will have much lower results by the chromogenic assay, with some of them having normal results by the one-stage assay. The chromogenic factor VIII assay is used in some specialized hemophilia reference centers and is recommended for the diagnosis of mild hemophilia A, as this assay is considered to better reflect the severity status of hemophilia patients than the one-stage assay.
Impacts of WIMP dark matter upon stellar evolution: main-sequence stars

CERN Document Server

Scott, Pat; Edsjo, Joakim

2008-01-01

The presence of large amounts of WIMP dark matter in stellar cores has been shown to have significant effects upon models of stellar evolution. We present a series of detailed grids of WIMP-influenced stellar models for main sequence stars, computed using the DarkStars code. We describe the changes in stellar structure and main sequence evolution which occur for masses ranging from 0.3 to 2.0 solar masses and metallicities from Z = 0.0003-0.02, as a function of the rate of energy injection by WIMPs. We then go on to show what rates of energy injection can be obtained using realistic orbital parameters for stars near supermassive black holes, including detailed considerations of dark matter halo velocity and density profiles. Capture and annihilation rates are strongly boosted when stars follow elliptical rather than circular orbits, causing WIMP annihilation to provide up to 100 times the energy of hydrogen fusion in stars at the Galactic centre.
The MACHO Project LMC Variable Star Inventory. VIII. The Recent Star Formation History of the Large Magellanic Cloud from the Cepheid Period Distribution

International Nuclear Information System (INIS)

Alcock, C.; Allsman, R.A.; Alves, D.R.; Axelrod, T.S.; Becker, A.C.; Bennett, D.P.; Bersier, D.F.; Cook, K.H.; Freeman, K.C.; Griest, K.; Guern, J.A.; Lehner, M.; Marshall, S.L.; Minniti, D.; Peterson, B.A.; Pratt, M.R.; Quinn, P.J.; Rodgers, A.W.; Stubbs, C.W.

1999-01-01

We present an analysis of the period distribution of about 1800 Cepheids in the LMC, based on data obtained by the MACHO microlensing experiment and on a previous catalog by C. H. Payne Gaposchkin. Using stellar evolution and pulsation models, we construct theoretical period-frequency distributions that are compared with the observations. These models reveal that a significant burst of star formation has occurred recently in the LMC (∼1.15x10 8 yr). We also show that during the last ∼10 8 yr, the main center of star formation has been propagating from southeast to northwest along the bar. We find that the evolutionary masses of Cepheids are still smaller than pulsation masses by ∼7% and that the red edge of the Cepheid instability strip could be slightly bluer than indicated by theory. There are approximately 600 Cepheids with periods below ∼2.5 days that cannot be explained by evolution theory. We suggest that they are anomalous Cepheids and that a number of these stars are double-mode Cepheids. copyright copyright 1999. The American Astronomical Society
Observations of southern Wolf-Rayet stars. I

International Nuclear Information System (INIS)

Niemela, V.S.

1976-01-01

The Wolf-Rayet star HD 90657 is found to be a spectroscopic binary with a WN5+O6 spectrum and a period of 6.456 days. Preliminary orbital elements show an elliptic orbit and a mass ratio Msub(WR)/Msub(O) approximately 0.5. Evidence is presented for the Wolf-Rayet atmosphere being accelerated outwards and not being spherically symmetric. (Auth.)
Type VIII collagen is elevated in diseases associated with angiogenesis and vascular remodeling

DEFF Research Database (Denmark)

Hansen, N. U. B.; Willumsen, N.; Bülow Sand, Jannie Marie

2016-01-01

Objectives Type VIII collagen is involved in angiogenesis and remodeling of arteries. We hypothesized that type VIII collagen was upregulated in diseases associated with vascular remodeling, e.g. pulmonary fibrosis and cancer. In this paper we present the development and validation of a competitive...
Weighing the Smallest Stars

Science.gov (United States)

2005-01-01

VLT Finds Young, Very Low Mass Objects Are Twice As Heavy As Predicted Summary Thanks to the powerful new high-contrast camera installed at the Very Large Telescope, photos have been obtained of a low-mass companion very close to a star. This has allowed astronomers to measure directly the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its host star, is still 93 times as massive as Jupiter. And it appears to be almost twice as heavy as theory predicts it to be. This discovery therefore suggests that, due to errors in the models, astronomers may have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. PR Photo 03/05: Near-infrared image of AB Doradus A and its companion (NACO SDI/VLT) A winning combination A star can be characterised by many parameters. But one is of uttermost importance: its mass. It is the mass of a star that will decide its fate. It is thus no surprise that astronomers are keen to obtain a precise measure of this parameter. This is however not an easy task, especially for the least massive ones, those at the border between stars and brown dwarf objects. Brown dwarfs, or "failed stars", are objects which are up to 75 times more massive than Jupiter, too small for major nuclear fusion processes to have ignited in its interior. To determine the mass of a star, astronomers generally look at the motion of stars in a binary system. And then apply the same method that allows determining the mass of the Earth, knowing the distance of the Moon and the time it takes for its satellite to complete one full orbit (the so-called "Kepler's Third Law"). In the same way, they have also measured the mass of the Sun by knowing the Earth-Sun distance and the time - one year - it takes our planet to make a tour around the Sun. The problem with low-mass objects is that they are very faint and will often be hidden in the glare of the brighter star they orbit, also when viewed
The F309S mutation increases factor VIII secretion in human cell line

Directory of Open Access Journals (Sweden)

Daianne Maciely Carvalho Fantacini

2016-06-01

Full Text Available ABSTRACT OBJECTIVES: The capacity of a human cell line to secrete recombinant factor VIII with a F309S point mutation was investigated, as was the effect of the addition of chemical chaperones (betaine and sodium-4-phenylbutyrate on the secretion of factor VIII. METHODS: This work used a vector with a F309S mutation in the A1 domain to investigate FVIII production in the HEK 293 human cell line. Factor VIII activity was measured by chromogenic assay. Furthermore, the effects of chemical drugs on the culture were evaluated. RESULTS: The addition of the F309S mutation to a previously described FVIII variant increased FVIII secretion by 4.5 fold. Moreover, the addition of betaine or sodium-4-phenylbutyrate increased the secretion rate of FVIIIΔB proteins in HEK 293 cells, but the same effect was not seen for FVIIIΔB-F309S indicating that all the recombinant protein produced had been efficiently secreted. CONCLUSION: Bioengineering factor VIII expressed in human cells may lead to an efficient production of recombinant factor VIII and contribute toward low-cost coagulation factor replacement therapy for hemophilia A. FVIII-F309S produced in human cells can be effective in vivo.
Myosin VIII regulates protonemal patterning and developmental timing in the moss Physcomitrella patens.

Science.gov (United States)

Wu, Shu-Zon; Ritchie, Julie A; Pan, Ai-Hong; Quatrano, Ralph S; Bezanilla, Magdalena

2011-09-01

Plants have two classes of myosins. While recent work has focused on class XI myosins showing that myosin XI is responsible for organelle motility and cytoplasmic streaming, much less is known about the role of myosin VIII in plant growth and development. We have used a combination of RNAi and insertional knockouts to probe myosin VIII function in the moss Physcomitrella patens. We isolated Δmyo8ABCDE plants demonstrating that myosin VIII is not required for plant viability. However, myosin VIII mutants are smaller than wild-type plants in part due to a defect in cell size. Additionally, Δmyo8ABCDE plants produce more side branches and form gametophores much earlier than wild-type plants. In the absence of nutrient media, Δmyo8ABCDE plants exhibit significant protonemal patterning defects, including highly curved protonemal filaments, morphologically defective side branches, as well as an increase in the number of branches. Exogenous auxin partially rescues protonemal defects in Δmyo8ABCDE plants grown in the absence of nutrients. This result, together with defects in protonemal branching, smaller caulonemal cells, and accelerated development in the Δmyo8ABCDE plants, suggests that myosin VIII is involved in hormone homeostasis in P. patens.
Specific membrane binding of factor VIII is mediated by O-phospho-L-serine, a moiety of phosphatidylserine.

Science.gov (United States)

Gilbert, G E; Drinkwater, D

1993-09-21

Phosphatidylserine, a negatively charged lipid, is exposed on the platelet membrane following cell stimulation, correlating with the expression of factor VIII receptors. We have explored the importance of the negative electrostatic potential of phosphatidylserine vs chemical moieties of phosphatidylserine for specific membrane binding of factor VIII. Fluorescein-labeled factor VIII bound to membranes containing 15% phosphatidic acid, a negatively charged phospholipid, with low affinity compared to phosphatidylserine-containing membranes. Binding was not specific as it was inhibited by other proteins in plasma. Factor VIII bound to membranes containing 10% phosphatidylserine in spite of a varying net charge provided by 0-15% stearylamine, a positively charged lipid. The soluble phosphatidylserine moiety, O-phospho-L-serine, inhibited factor VIII binding to phosphatidylserine-containing membranes with a Ki of 20 mM, but the stereoisomer, O-phospho-D-serine, was 5-fold less effective. Furthermore, binding of factor VIII to membranes containing synthetic phosphatidyl-D-serine was 5-fold less than binding to membranes containing phosphatidyl-L-serine. Membranes containing synthetic phosphatidyl-L-homoserine, differing from phosphatidylserine by a single methylene, supported high-affinity binding, but it was not specific as factor VIII was displaced by other plasma proteins. O-Phospho-L-serine also inhibited the binding of factor VIII to platelet-derived microparticles with a Ki of 20 mM, and the stereoisomer was 4-fold less effective. These results indicate that membrane binding of factor VIII is mediated by a stereoselective recognition O-phospho-L-serine of phosphatidylserine and that negative electrostatic potential is of lesser importance.
DETECTION OF KOI-13.01 USING THE PHOTOMETRIC ORBIT

International Nuclear Information System (INIS)

Shporer, Avi; Jenkins, Jon M.; Seader, Shawn E.; Smith, Jeffrey C.; Thompson, Susan E.; Twicken, Joseph D.; Rowe, Jason F.; Sanderfer, Dwight T.; Still, Martin D.; Welsh, William F.

2011-01-01

We use the KOI-13 transiting star-planet system as a test case for the recently developed BEER algorithm, aimed at identifying non-transiting low-mass companions by detecting the photometric variability induced by the companion along its orbit. Such photometric variability is generated by three mechanisms: the beaming effect, tidal ellipsoidal distortion, and reflection/heating. We use data from three Kepler quarters, from the first year of the mission, while ignoring measurements within the transit and occultation, and show that the planet's ephemeris is clearly detected. We fit for the amplitude of each of the three effects and use the beaming effect amplitude to estimate the planet's minimum mass, which results in M p sin i = 9.2 ± 1.1 M J (assuming the host star parameters derived by Szabo et al.). Our results show that non-transiting star-planet systems similar to KOI-13.01 can be detected in Kepler data, including a measurement of the orbital ephemeris and the planet's minimum mass. Moreover, we derive a realistic estimate of the amplitudes uncertainties, and use it to show that data obtained during the entire lifetime of the Kepler mission of 3.5 years will allow detecting non-transiting close-in low-mass companions orbiting bright stars, down to the few Jupiter mass level. Data from the Kepler Extended Mission, if funded by NASA, will further improve the detection capabilities.
VIII Olimpíada Brasileira de Astronomia e Astronáutica

Science.gov (United States)

Garcia Canalle, João Batista; Villas da Rocha, Jaime Fernando; Wuensche de Souza, Carlos Alexandre; Pereira Ortiz, Roberto; Aguilera, Nuricel Villalonga; Padilha, Maria De Fátima Catta Preta; Pessoa Filho, José Bezerra; Soares Rodrigues, Ivette Maria

2007-07-01

Neste trabalho apresentamos as motivações pelas quais organizamos, em conjunto, pela primeira vez, a Olimpíada Brasileira de Astronomia incluindo a Astronáutica, em colaboração com a Agência Espacial Brasileira. Esta ampliação contribuiu para atrair ainda mais alunos, professores, escolas e patrocinadores para participarem desta Olimpíada. Em 2005 participaram da VIII Olimpíada Brasileira de Astronomia e Astronáutica (VIII OBA) 187.726 alunos distribuídos por 3.229 escolas, pertencentes a todos os estados brasileiros, incluindo o Distrito Federal. O crescimento em número de alunos participantes foi 52,4% maior do que em 2004. Em abril de 2005 organizamos, em Itapecerica da Serra, SP, um curso para os 50 alunos previamente selecionados e participantes da VII OBA e ao final selecionamos, dentre eles, uma equipe de 5 alunos, os quais representaram o Brasil na X Olimpíada Internacional de Astronomia, na China, em outubro de 2005. Ganhamos, pela primeira vez, uma medalha de ouro naquele evento. Em Agosto de 2005, organizamos a VIII Escola de Agosto para 50 alunos e respectivos professores, em Águas de Lindóia, SP, juntamente com a XXXI reunião anual da Sociedade Astronômica Brasileira (SAB). Em novembro de 2005 realizamos a I Jornada Espacial, em São José dos Campos, com 22 alunos e 22 professores selecionados dentre os participantes que melhores resultados obtiveram nas questões de Astronáutica da VIII OBA. Neste trabalho detalhamos os resultados da VIII OBA bem como as ações subseqüentes.
Analysis of mutations in the entire coding sequence of the factor VIII gene

Energy Technology Data Exchange (ETDEWEB)

Bidichadani, S.I.; Lanyon, W.G.; Connor, J.M. [Glascow Univ. (United Kingdom)] [and others

1994-09-01

Hemophilia A is a common X-linked recessive disorder of bleeding caused by deleterious mutations in the gene for clotting factor VIII. The large size of the factor VIII gene, the high frequency of de novo mutations and its tissue-specific expression complicate the detection of mutations. We have used a combination of RT-PCR of ectopic factor VIII transcripts and genomic DNA-PCRs to amplify the entire essential sequence of the factor VIII gene. This is followed by chemical mismatch cleavage analysis and direct sequencing in order to facilitate a comprehensive search for mutations. We describe the characterization of nine potentially pathogenic mutations, six of which are novel. In each case, a correlation of the genotype with the observed phenotype is presented. In order to evaluate the pathogenicity of the five missense mutations detected, we have analyzed them for evolutionary sequence conservation and for their involvement of sequence motifs catalogued in the PROSITE database of protein sites and patterns.
Planet Formation in Disks with Inclined Binary Companions: Can Primordial Spin-Orbit Misalignment be Produced?

Science.gov (United States)

Zanazzi, J. J.; Lai, Dong

2018-04-01

Many hot Jupiter (HJ) systems have been observed to have their stellar spin axis misaligned with the planet's orbital angular momentum axis. The origin of this spin-orbit misalignment and the formation mechanism of HJs remain poorly understood. A number of recent works have suggested that gravitational interactions between host stars, protoplanetary disks, and inclined binary companions may tilt the stellar spin axis with respect to the disk's angular angular momentum axis, producing planetary systems with misaligned orbits. These previous works considered idealized disk evolution models and neglected the gravitational influence of newly formed planets. In this paper, we explore how disk photoevaporation and planet formation and migration affect the inclination evolution of planet-star-disk-binary systems. We take into account planet-disk interactions and the gravitational spin-orbit coupling between the host star and the planet. We find that the rapid depletion of the inner disk via photoevaporation reduces the excitation of stellar obliquities. Depending on the formation and migration history of HJs, the spin-orbit coupling between the star and the planet may reduces and even completely suppress the excitation of stellar obliquities. Our work constrains the formation/migration history of HJs. On the other hand, planetary systems with "cold" Jupiters or close-in super-earths may experience excitation of stellar obliquities in the presence of distant inclined companions.
A systematic search for brown dwarfs orbiting nearby stars

International Nuclear Information System (INIS)

Henry, T.J.; Mccarthy, D.W. Jr.

1990-01-01

Survey data for brown dwarf and stellar companions relative to known M dwarf stars within 5 pc north of -30 deg are analyzed. A region 0.2 to 5 arcsec in radius around 27 stars at the IR H and K bands are examined using IR speckle interferometry. The frequency of binary versus single M dwarfs in the solar neighborhood is examined. The IR mass-magnitude relations and mass-luminosity-age relation are studied. The data reveal that there are 19 single M dwarfs, 8 M dwarf binaries, 1 M dwarf triple system, and 1 M dwarf in a triple system for M dwarfs within 5 pc north of -30 deg. Also of the 27 M dwarfs studied none was found to have a brown dwarf companion. 64 refs
Tidal formation of Hot Jupiters in binary star systems

Science.gov (United States)

Bataille, M.; Libert, A.-S.; Correia, A. C. M.

2015-10-01

More than 150 Hot Jupiters with orbital periods less than 10 days have been detected. Their in-situ formation is physically unlikely. We need therefore to understand the migration of these planets from high distance (several AUs). Three main models are currently extensively studied: disk-planet interactions (e.g. [3]), planet-planet scattering (e.g. [4]) and Kozai migration (e.g. [2]). Here we focus on this last mechanism, and aim to understand which dynamical effects are the most active in the accumulation of planetary companions with low orbital periods in binary star systems. To do so, we investigate the secular evolution of Hot Jupiters in binary star systems. Our goal is to study analytically the 3-day pile-up observed in their orbital period. Our framework is the hierarchical three-body problem, with the effects of tides, stellar oblateness, and general relativity. Both the orbital evolution and the spin evolution are considered. Using the averaged equations of motion in a vectorial formalism of [1], we have performed # 100000 numerical simulations of well diversified three-body systems, reproducing and generalizing the numerical results of [2]. Based on a thorough analysis of the initial and final configurations of the systems, we have identified different categories of secular evolutions present in the simulations, and proposed for each one a simplified set of equations reproducing the evolution. Statistics about spin-orbit misalignements and mutual inclinations between the orbital planes of the Hot Jupiter and the star companion are also provided. Finally, we show that the extent of the 3 day pile-up is very dependent on the initial parameters of the simulations.
POSSIBLE ORIGIN OF THE G2 CLOUD FROM THE TIDAL DISRUPTION OF A KNOWN GIANT STAR BY SGR A*

International Nuclear Information System (INIS)

Guillochon, James; Loeb, Abraham; MacLeod, Morgan; Ramirez-Ruiz, Enrico

2014-01-01

The discovery of the gas cloud G2 on a near-radial orbit about Sgr A* has prompted much speculation on its origin. In this Letter, we propose that G2 formed out of the debris stream produced by the removal of mass from the outer envelope of a nearby giant star. We perform hydrodynamical simulations of the returning tidal debris stream with cooling and find that the stream condenses into clumps that fall periodically onto Sgr A*. We propose that one of these clumps is the observed G2 cloud, with the rest of the stream being detectable at lower Brγ emissivity along a trajectory that would trace from G2 to the star that was partially disrupted. By simultaneously fitting the orbits of S2, G2, and ∼2000 candidate stars, and by fixing the orbital plane of each candidate star to G2 (as is expected for a tidal disruption), we find that several stars have orbits that are compatible with the notion that one of them was tidally disrupted to produce G2. If one of these stars were indeed disrupted, it last encountered Sgr A* hundreds of years ago and has likely encountered Sgr A* repeatedly. However, while these stars are compatible with the giant disruption scenario given their measured positions and proper motions, their radial velocities are currently unknown. If one of these stars' radial velocity is measured to be compatible with a disruptive orbit, it would strongly suggest that its disruption produced G2
The Habitable Zone and Extreme Planetary Orbits

OpenAIRE

Kane, Stephen R.; Gelino, Dawn M.

2012-01-01

The habitable zone for a given star describes the range of circumstellar distances from the star within which a planet could have liquid water on its surface, which depends upon the stellar properties. Here we describe the development of the habitable zone concept, its application to our own solar system, and its subsequent application to exoplanetary systems. We further apply this to planets in extreme eccentric orbits and show how they may still retain life-bearing properties depending upon...

Modelling the ionosphere of gas-giant exoplanets irradiated by low-mass stars

Science.gov (United States)

Chadney, J.; Galand, M.; Unruh, Y.; Koskinen, T.; Sanz-Forcada, J.

2015-10-01

The composition and structure of the upper atmosphere of Extrasolar Giant Planets (EGPs) are affected by the high-energy spectrum of the host star from soft X-rays to Extreme UltraViolet (EUV) (0.1-10 nm). This emission depends on the activity level of the star, which is primarily determined by its age [1]. In this study, we focus upon EGPs orbiting K- and M-dwarf stars of different ages. XUV spectra for these stars are constructed using a coronal model [2]. These spectra are used to drive both a thermospheric [3] and an ionospheric model, providing densities of neutral and ion species. Ionisation is included through photo-ionisation and electronimpact processes. The former is calculated by solving the Lambert-Beer law, while the latter is calculated from a supra-thermal electron transport model [4]. Planets orbiting far from the star are found to undergo Jeans escape, whereas close-orbiting planets undergo hydrodynamic escape. The critical orbital distance of transition between the two regimes is dependent on the level of stellar activity. We also find that EGP ionospheres at all orbital distances considered (0.1-1 AU) and around all stars selected (eps Eri, AD Leo, AU Mic) are dominated by the long-lived H+ ion. In addition, planets in the Jeans escape regime also have a layer in which H3 + is the major ion at the base of the ionosphere. For fast-rotating planets, densities of short-lived H3 + undergo significant diurnal variations, their peak value being determined by the stellar X-ray flux. In contrast, densities of longer-lived H+ show very little day/night variability and their value is determined by the level of stellar EUV flux. The H3 + peak in EGPs in the hydrodynamic escape regime under strong stellar illumination is pushed to altitudes below the homopause, where this ion is likely to be destroyed through reactions with heavy species (e.g., hydrocarbons, water). Infrared emissions from H3 + shall also be discussed, as well as the impact of stellar
White-dwarf rotational equilibria in magnetic cataclysmic variable stars

Energy Technology Data Exchange (ETDEWEB)

Warner, B. (Cape Town Univ. (South Africa). Dept. of Astronomy Australian National Univ., Canberra (Australia). Dept. of Mathematics); Wickramasinghe, D.T. (Australian National Univ., Canberra (Australia). Dept. of Mathematics)

1991-02-01

The magnetic cataclysmic variable stars (polars, intermediate polars and DQ Her stars) are grouped about three lines in the orbital period-spin period diagram. This segregation is shown to be the consequence of competition between braking and accretion torques when combined with the effects of cyclical variations in rate of mass transfer. (author).
The vestibulocochlear nerve (VIII).

Science.gov (United States)

Benoudiba, F; Toulgoat, F; Sarrazin, J-L

2013-10-01

The vestibulocochlear nerve (8th cranial nerve) is a sensory nerve. It is made up of two nerves, the cochlear, which transmits sound and the vestibular which controls balance. It is an intracranial nerve which runs from the sensory receptors in the internal ear to the brain stem nuclei and finally to the auditory areas: the post-central gyrus and superior temporal auditory cortex. The most common lesions responsible for damage to VIII are vestibular Schwannomas. This report reviews the anatomy and various investigations of the nerve. Copyright © 2013. Published by Elsevier Masson SAS.
Observing Double Stars

Science.gov (United States)

Genet, Russell M.; Fulton, B. J.; Bianco, Federica B.; Martinez, John; Baxter, John; Brewer, Mark; Carro, Joseph; Collins, Sarah; Estrada, Chris; Johnson, Jolyon; Salam, Akash; Wallen, Vera; Warren, Naomi; Smith, Thomas C.; Armstrong, James D.; McGaughey, Steve; Pye, John; Mohanan, Kakkala; Church, Rebecca

2012-05-01

Double stars have been systematically observed since William Herschel initiated his program in 1779. In 1803 he reported that, to his surprise, many of the systems he had been observing for a quarter century were gravitationally bound binary stars. In 1830 the first binary orbital solution was obtained, leading eventually to the determination of stellar masses. Double star observations have been a prolific field, with observations and discoveries - often made by students and amateurs - routinely published in a number of specialized journals such as the Journal of Double Star Observations. All published double star observations from Herschel's to the present have been incorporated in the Washington Double Star Catalog. In addition to reviewing the history of visual double stars, we discuss four observational technologies and illustrate these with our own observational results from both California and Hawaii on telescopes ranging from small SCTs to the 2-meter Faulkes Telescope North on Haleakala. Two of these technologies are visual observations aimed primarily at published "hands-on" student science education, and CCD observations of both bright and very faint doubles. The other two are recent technologies that have launched a double star renaissance. These are lucky imaging and speckle interferometry, both of which can use electron-multiplying CCD cameras to allow short (30 ms or less) exposures that are read out at high speed with very low noise. Analysis of thousands of high speed exposures allows normal seeing limitations to be overcome so very close doubles can be accurately measured.
Tatooines Future: The Eccentric Response of Keplers Circumbinary Planets to Common-Envelope Evolution of their Host Stars

Science.gov (United States)

Kostov, Veselin B.; Moore, Keavin; Tamayo, Daniel; Jayawardhana, Ray; Rinehart, Stephen A.

2016-01-01

Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and common-envelope stages (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the common-envelope phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-common-envelope, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and non-adiabatic) if their host binaries undergo more than one common-envelope stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same common-envelope stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semi-major axis can survive the common envelope evolution of a close binary star with a total mass of 1 Solar Mass.
Practical experience and lessons learned through implementation of Appendix VIII performance demonstration requirements

International Nuclear Information System (INIS)

Ashwin, P.J.; Becker, F.L.; Latiolais, C.L.; Spanner, J.C.

1996-01-01

To provide the US nuclear industry with a uniform implementation of the Performance Demonstration requirements within the 1989 edition of ASME Section XI, Appendix VIII, representatives from all US nuclear utilities formed the Performance Demonstration Initiative (PDI). The PDI recognized the potential benefits that Appendix VIII offered the nuclear industry and initiated a proactive approach to implement the requirements. In doing so it was expected that performance demonstration of ultrasonic examination procedures would allow for improvement in the efficiency and credibility of inservice inspection to be realized. Explicit within the performance demonstration requirements of Appendix VIII is the need for a Performance Demonstration Administrator, a difficult requirement to fulfill. Not only must the administrator exhibit the attributes of understanding the demonstration requirements, but also have solid technical knowledge, integrity and be able to interface with the industry at all levels, from operations to regulatory. For the nuclear industry, the EPRI NDE Center is an obvious choice to fulfill this position. This paper provides a brief background of the PDI, a nuclear industry-wide initiative to implement the performance demonstration requirements of Appendix VIII. Even though the consensus approach adopted by the PDI is discussed, the paper's primary objective is to provide examples of the lessons learned by the Center through the specific requirements of Appendix VIII
A planet orbiting an sdB star and an M dwarf in 2M 1938+4603

Directory of Open Access Journals (Sweden)

Blokesz Adam

2015-01-01

Full Text Available We present a preliminary analysis of the 2M 1938+4603 star. It is an eclipsing binary system consisting of a primary sdB component and a secondary M dwarf. The photometric data are dominated by mutual eclipses and a very strong reflection effect. The primary has a fairly rich pulsation spectrum which can be used to study its interior. On the other hand, the pulsations affect the binary trend and vice versa what makes the analysis very difficult. Therefore, we attempted at proper modeling of the light variation due to eclipses and reflection and their removal from the data so it does not affect the Fourier analysis of stellar pulsations. We focus on mid-times of over 16 000 primary and secondary minima, which were used to verify stability of the orbital period. The O-C diagram indicates possible parabolic and sinusoidal variations, commonly explained by period changes caused by evolution and a presence of a third body, respectively.
Unravelling the escape dynamics and the nature of the normally hyperbolic invariant manifolds in tidally limited star clusters

Science.gov (United States)

Zotos, Euaggelos E.; Jung, Christof

2017-02-01

The escape mechanism of orbits in a star cluster rotating around its parent galaxy in a circular orbit is investigated. A three degrees of freedom model is used for describing the dynamical properties of the Hamiltonian system. The gravitational field of the star cluster is represented by a smooth and spherically symmetric Plummer potential. We distinguish between ordered and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. The Smaller ALignment Index (SALI) method is used for determining the regular or chaotic nature of the orbits. The basins of escape are located and they are also correlated with the corresponding escape time of the orbits. Areas of bounded regular or chaotic motion and basins of escape were found to coexist in the (x, z) plane. The properties of the normally hyperbolic invariant manifolds (NHIMs), located in the vicinity of the index-1 Lagrange points L1 and L2, are also explored. These manifolds are of paramount importance as they control the flow of stars over the saddle points, while they also trigger the formation of tidal tails observed in star clusters. Bifurcation diagrams of the Lyapunov periodic orbits as well as restrictions of the Poincaré map to the NHIMs are deployed for elucidating the dynamics in the neighbourhood of the saddle points. The extended tidal tails, or tidal arms, formed by stars with low velocity which escape through the Lagrange points are monitored. The numerical results of this work are also compared with previous related work.
Optimized Trajectories to the Nearest Stars Using Lightweight High-velocity Photon Sails

Science.gov (United States)

Heller, René; Hippke, Michael; Kervella, Pierre

2017-09-01

New means of interstellar travel are now being considered by various research teams, assuming lightweight spaceships to be accelerated via either laser or solar radiation to a significant fraction of the speed of light (c). We recently showed that gravitational assists can be combined with the stellar photon pressure to decelerate an incoming lightsail from Earth and fling it around a star or bring it to rest. Here, we demonstrate that photogravitational assists are more effective when the star is used as a bumper (I.e., the sail passes “in front of” the star) rather than as a catapult (I.e., the sail passes “behind” or “around” the star). This increases the maximum deceleration at α Cen A and B and reduces the travel time of a nominal graphene-class sail (mass-to-surface ratio 8.6× {10}-4 {{g}} {{{m}}}-2) from 95 to 75 years. The maximum possible velocity reduction upon arrival depends on the required deflection angle from α Cen A to B and therefore on the binary’s orbital phase. Here, we calculate the variation of the minimum travel times from Earth into a bound orbit around Proxima for the next 300 years and then extend our calculations to roughly 22,000 stars within about 300 lt-yr. Although α Cen is the most nearby star system, we find that Sirius A offers the shortest possible travel times into a bound orbit: 69 years assuming 12.5% c can be obtained at departure from the solar system. Sirius A thus offers the opportunity of flyby exploration plus deceleration into a bound orbit of the companion white dwarf after relatively short times of interstellar travel.
AN INTERFEROMETRIC AND SPECTROSCOPIC ANALYSIS OF THE MULTIPLE STAR SYSTEM HD 193322

International Nuclear Information System (INIS)

Ten Brummelaar, Theo A.; Farrington, Christopher D.; Schaefer, Gail H.

2011-01-01

The star HD 193322 is a remarkable multiple system of massive stars that lies at the heart of the cluster Collinder 419. Here we report on new spectroscopic observations and radial velocities of the narrow-lined component Ab1 which we use to determine its orbital motion around a close companion Ab2 (P = 312 days) and around a distant third star Aa (P = 35 years). We have also obtained long baseline interferometry of the target in the K' band with the CHARA Array which we use in two ways. First, we combine published speckle interferometric measurements with CHARA separated fringe packet measurements to improve the visual orbit for the wide Aa,Ab binary. Second, we use measurements of the fringe packet from Aa to calibrate the visibility of the fringes of the Ab1,Ab2 binary, and we analyze these fringe visibilities to determine the visual orbit of the close system. The two most massive stars, Aa and Ab1, have masses of approximately 21 and 23 M sun , respectively, and their spectral line broadening indicates that they represent extremes of fast and slow projected rotational velocity, respectively.
Evolution of Neutron Stars and Observational Constraints

Directory of Open Access Journals (Sweden)

Lattimer J.

2010-10-01

Full Text Available The structure and evolution of neutron stars is discussed with a view towards constraining the properties of high density matter through observations. The structure of neutron stars is illuminated through the use of several analytical solutions of Einstein’s equations which, together with the maximally compact equation of state, establish extreme limits for neutron stars and approximations for binding energies, moments of inertia and crustal properties as a function of compactness. The role of the nuclear symmetry energy is highlighted and constraints from laboratory experiments such as nuclear masses and heavy ion collisions are presented. Observed neutron star masses and radius limits from several techniques, such as thermal emissions, X-ray bursts, gammaray ﬂares, pulsar spins and glitches, spin-orbit coupling in binary pulsars, and neutron star cooling, are discussed. The lectures conclude with a discusson of proto-neutron stars and their neutrino signatures.
Pulsar-irradiated stars in dense globular clusters

Science.gov (United States)

Tavani, Marco

1992-01-01

We discuss the properties of stars irradiated by millisecond pulsars in 'hard' binaries of dense globular clusters. Irradiation by a relativistic pulsar wind as in the case of the eclipsing millisecond pulsar PSR 1957+20 alter both the magnitude and color of the companion star. Some of the blue stragglers (BSs) recently discovered in dense globular clusters can be irradiated stars in binaries containing powerful millisecond pulsars. The discovery of pulsar-driven orbital modulations of BS brightness and color with periods of a few hours together with evidence for radio and/or gamma-ray emission from BS binaries would valuably contribute to the understanding of the evolution of collapsed stars in globular clusters. Pulsar-driven optical modulation of cluster stars might be the only observable effect of a new class of binary pulsars, i.e., hidden millisecond pulsars enshrouded in the evaporated material lifted off from the irradiated companion star.
Long-term captures of low-mass intruders by binary stars

International Nuclear Information System (INIS)

Hills, J.G.

1983-01-01

Intensive computer simulations were made of three families of encounters between a binary star and a low-mass intruder which previous work indicated have a high probability of producing long-lived triple-star systems. For comparison, a fourth family which produces few long-lived trinaries was also studied. In the first two families, the binary components are equally massive and the closest approach of the intruder to the center of mass of the binary is about two times its semimajor axis, a 0 . In Family 1, the orbit of the original binary is circular, e = 0, while in Family 2, e 0 = 0.95. In Family 3 one binary component is 100 times as massive as the other, the orbit is circular, and the low-mass intruder enters the binary at nearly zero impact parameter. The probability that the intruder is trapped for at least one revolution around the binary is 0.24, 0.46, and 0.51, respectively, for these three families of encounters. The fraction of the intruders surviving successive revolutions drops rapidly. However, one encounter in Family 1 and two in Family 3 resulted in the intruder making more than 300 revolutions around the inner binary before escaping. Some intruders remained bound for more than 20 000 revolutions of the inner binary. The longest duration captures occur when the intruder is thrown into an orbit with a very large semimajor axis. About 20% of the encounters in the three families result in the intruder being thrown into an orbit with a semimajor axis a>100 a 0 , while about 2% result in the intruder going into an orbit with a>1000 a 0 . Intruders thrown into these large semimajor axis orbits have the best chance of having their orbits stabilized by passing stars
Stars defy theories of stellar matter

CERN Multimedia

2002-01-01

Two bizarre objects called RXJ1856 and 3C58, found by an orbiting X-ray telescope may represent a new class of star and may contain a new form of matter, defying current particle physics theories (1/2 page).
Light-Time Effect and Mass Transfer in the Triple Star SW Lyncis

Directory of Open Access Journals (Sweden)

Chun-Hwey Kim

1999-06-01

Full Text Available In this paper all the photoelectric times of minimum for the triple star SW Lyn have been analyzed in terms of light-time e ect due to the third-body and secular period decreases induced by mass transfer process. The light-time orbit determined recently by Ogloza et al.(1998 were modi ed and improved. And it is found that the orbital period of SW Lyn have been decreasing secularly. The third-body revolves around the mass center of triple stars every 5y.77 in a highly eccentric elliptical orbit(e=0.61. The third-body with a minimum mass of 1.13M may be a binary or a white dwarf. The rate of secular period-decrease were obtained as ¡âP/P = -12.45 x 10^-11, implying the mass-transfer from the massive primary star to the secondary. The mass losing rate from the primary were calculated as about 1.24 x 10^-8M /y. It is noticed that the mass-transfer in SW Lyn system is opposite in direction to that deduced from it's Roche geometry by previous investigators.
Biomarker response to galactic cosmic ray-induced NOx and the methane greenhouse effect in the atmosphere of an Earth-like planet orbiting an M dwarf star.

Science.gov (United States)

Grenfell, John Lee; Griessmeier, Jean-Mathias; Patzer, Beate; Rauer, Heike; Segura, Antigona; Stadelmann, Anja; Stracke, Barbara; Titz, Ruth; Von Paris, Philip

2007-02-01

Planets orbiting in the habitable zone of M dwarf stars are subject to high levels of galactic cosmic rays (GCRs), which produce nitrogen oxides (NOx) in Earth-like atmospheres. We investigate to what extent these NO(Mx) species may modify biomarker compounds such as ozone (O3) and nitrous oxide (N2O), as well as related compounds such as water (H2O) (essential for life) and methane (CH4) (which has both abiotic and biotic sources). Our model results suggest that such signals are robust, changing in the M star world atmospheric column due to GCR NOx effects by up to 20% compared to an M star run without GCR effects, and can therefore survive at least the effects of GCRs. We have not, however, investigated stellar cosmic rays here. CH4 levels are about 10 times higher on M star worlds than on Earth because of a lowering in hydroxyl (OH) in response to changes in the ultraviolet. The higher levels of CH4 are less than reported in previous studies. This difference arose partly because we used different biogenic input. For example, we employed 23% lower CH4 fluxes compared to those studies. Unlike on Earth, relatively modest changes in these fluxes can lead to larger changes in the concentrations of biomarker and related species on the M star world. We calculate a CH4 greenhouse heating effect of up to 4K. O3 photochemistry in terms of the smog mechanism and the catalytic loss cycles on the M star world differs considerably compared with that of Earth.
Investigation of superflares frequency variability of solar-type stars

International Nuclear Information System (INIS)

Akopian, A.A.

2015-01-01

Statistical study of the variability of the superflares frequency of 46 solar-type stars detected by orbital observatory 'Kepler' is presented. Two possible scenarios for changes in frequency are considered. In the first, the temporal sequence of superflares is regarded as a piecewise stationary Poissonian process. Statistically significant change in the frequency of superflares by several times is revealed at five stars. Moments of change of frequency are accompanied by sudden changes in the behavior of the star's brightness. Brightness of a star for a short time becomes irregular, with a significant decrease in the amplitude
Igor Zabel 14. VIII 1958 - 23. VII 2005

Index Scriptorium Estoniae

2005-01-01

Igor Zabel oli Ida-Euroopa tuntumaid kunstiteoreetikuid ja kuraatoreid. Töötas 1986. aastast Ljubljana moodsa kunsti muuseumi kuraatorina. 9. VIII avatakse seal viimane I. Zabeli kureeritud näitus "Territories, Identities, Nets-Slovene Art 1995-2005"
THE FORMATION MECHANISM OF GAS GIANTS ON WIDE ORBITS

International Nuclear Information System (INIS)

Dodson-Robinson, Sarah E.; Veras, Dimitri; Ford, Eric B.; Beichman, C. A.

2009-01-01

The recent discoveries of massive planets on ultra-wide orbits of HR 8799 and Fomalhaut present a new challenge for planet formation theorists. Our goal is to figure out which of three giant planet formation mechanisms-core accretion (with or without migration), scattering from the inner disk, or gravitational instability-could be responsible for Fomalhaut b, HR 8799 b, c and d, and similar planets discovered in the future. This paper presents the results of numerical experiments comparing the long-period planet formation efficiency of each possible mechanism in model A star, G star, and M star disks. First, a simple core accretion simulation shows that planet cores forming beyond 35 AU cannot reach critical mass, even under the most favorable conditions one can construct. Second, a set of N-body simulations demonstrates that planet-planet scattering does not create stable, wide-orbit systems such as HR 8799. Finally, a linear stability analysis verifies previous work showing that global spiral instabilities naturally arise in high-mass disks. We conclude that massive gas giants on stable orbits with semimajor axes a ∼> 35 AU form by gravitational instability in the disk. We recommend that observers examine the planet detection rate as a function of stellar age, controlling for the planets' dimming with time. Any age trend would indicate that planets on wide orbits are transient relics of scattering from the inner disk. If planet detection rate is found to be independent of stellar age, it would confirm our prediction that gravitational instability is the dominant mode of producing detectable planets on wide orbits. We also predict that the occurrence ratio of long-period to short-period gas giants should be highest for M dwarfs due to the inefficiency of core accretion and the expected small fragment mass (∼10 M Jup ) in their disks.
Photometric Observations of 6000 Stars in the Cygnus Field

Science.gov (United States)

Borucki, W.; Caldwell, D.; Koch, D.; Jenkins, J.; Ninkov, Z.

1999-01-01

A small photometer to detect transits by extrasolar planets has been assembled and is being tested at Lick Observatory on Mt. Hamilton, California. The Vulcan photometer is constructed from a 30 cm focal length, F/2.5 AeroEktar reconnaissance lens and Photometrics PXL16800 CCD camera. A spectral filter is used to confine the pass band from 480 to 763 mn. It simultaneously monitors 6000 stars brighter than 12th magnitude within a single star field in the galactic plane. When the data are folded and phased to discover low amplitude transits, the relative precision of one-hour samples is about 1 part per thousand (10 x l0(exp -3)) for many of the brighter stars. This precision is sufficient to find jovian-size planets orbiting solar-like stars, which have signal amplitudes from 5 to 30 x l0(exp -3) depending on the inflation of the planet and the size of the star. Based on the frequency of giant inner-planets discovered by Doppler-velocity method, one or two planets should be detectable in a rich star field. The goal of the observations is to obtain the sizes of giant extrasolar planets in short-period orbits and to combine these with masses determined from Doppler velocity measurements to determine the densities of these planets. A further goal is to compare the measured planetary diameters with those predicted from theoretical models. From August 10 through September 30 of 1998, a forty nine square degree field in the Cygnus constellation centered at RA and DEC of 19 hr 47 min, +36 deg 55 min was observed. Useful data were obtained on twenty-nine nights. Nearly fifty stars showed some evidence of transits with periods between 0.3 and 8 days. Most had amplitudes too large to be associated with planetary transits. However, several stars showed low amplitude transits. The data for several transits of each of these two stars have been folded and been folded into 30 minute periods. Only Cygl433 shows any evidence of a flattened bottom that is expected when a small object

Home therapy with continuous infusion of factor VIII after minor surgery or serious haemorrhage.

Science.gov (United States)

Varon, D; Schulman, S; Bashari, D; Martinowitz, U

1996-10-01

Administration of factor VIII (F VIII) concentrates by continuous infusion is now routinely used at several haemophilia centers but almost exclusively for hospitalized patients. We evaluated various aspects of home therapy with continuous infusion of an immunoaffinity purified F VIII concentrate (Monoclate P®, Armour) in patients who would normally have been treated with high doses in bolus injections or with continuous infusion as in-patients. Twenty haemophilia A patients, eight after minor surgery and 12 for serious haemorrhage, received continuous infusion with undiluted F VIII by a minipump for a mean of 0.9 days in the hospital, followed by 3.3 days at home. Infusion bags were exchanged every 2.5 days. No haemorrhagic complications occurred, and five haemorrhages that had been resistant to treatment with bolus injections responded promptly to the continuous infusion. There were no technical problems and patient compliance and acceptance was good. We find this mode of therapy safe, efficacious and convenient for the patients as well as for the staff.
RETIRED A STARS AND THEIR COMPANIONS. III. COMPARING THE MASS-PERIOD DISTRIBUTIONS OF PLANETS AROUND A-TYPE STARS AND SUN-LIKE STARS

International Nuclear Information System (INIS)

Bowler, Brendan P.; Johnson, John Asher; Liu, Michael C.; Marcy, Geoffrey W.; Peek, Kathryn M. G.; Henry, Gregory W.; Fischer, Debra A.; Clubb, Kelsey I.; Reffert, Sabine; Schwab, Christian; Lowe, Thomas B.

2010-01-01

We present an analysis of ∼5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 ∼ * /M sun ∼ +9 -8 %, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to {0.2, 0.3, 0.5, 0.6, 1.3} M Jup within {0.1, 0.3, 0.6, 1.0, 3.0} AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN ∝ M α P β dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of α and β for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4σ level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (∼50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets.
Social stars: Modeling the interactive lives of stars in dense clusters and binary systems in the era of time domain astronomy

Science.gov (United States)

MacLeod, Morgan Elowe

This thesis uses computational modeling to study of phases of dramatic interaction that intersperse stellar lifetimes. In galactic centers stars trace dangerously wandering orbits dictated by the combined gravitational force of a central, supermassive black hole and all of the surrounding stars. In binary systems, stars' evolution -- which causes their radii to increase substantially -- can bring initially non-interacting systems into contact. Moments of strong stellar interaction transform stars, their subsequent evolution, and the stellar environments they inhabit. In tidal disruption events, a star is partially or completely destroyed as tidal forces from a supermassive black hole overwhelm the star's self gravity. A portion of the stellar debris falls back to the black hole powering a luminous flare as it accretes. This thesis studies the relative event rates and properties of tidal disruption events for stars across the stellar evolutionary spectrum. Tidal disruptions of giant stars occur with high specific frequency; these objects' extended envelopes make them vulnerable to disruption. More-compact white dwarf stars are tidally disrupted relatively rarely. Their transients are also of very different duration and luminosity. Giant star disruptions power accretion flares with timescales of tens to hundreds of years; white dwarf disruption flares take hours to days. White dwarf tidal interactions can additionally trigger thermonuclear burning and lead to transients with signatures similar to type I supernovae. In binary star systems, a phase of hydrodynamic interaction called a common envelope episode occurs when one star evolves to swallow its companion. Dragged by the surrounding gas, the companion star spirals through the envelope to tighter orbits. This thesis studies accretion and flow morphologies during this phase. Density gradients across the gravitationally-focussed material lead to a strong angular momentum barrier to accretion during common envelope
RED RUNAWAYS II: LOW-MASS HILLS STARS IN SDSS STRIPE 82

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yanqiong; Smith, Martin C. [Key Laboratory of Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Carlin, Jeffrey L., E-mail: zhangyq@shao.ac.cn, E-mail: msmith@shao.ac.cn [Rensselaer Polytechnic Institute, Troy (United States)

2016-11-20

Stars ejected from the Galactic Center can be used to place important constraints on the Milky Way potential. Since existing hypervelocity stars are too distant to accurately determine orbits, we have conducted a search for nearby candidates using full three-dimensional velocities. Since the efficacy of such studies is often hampered by deficiencies in proper motion catalogs, we have chosen to utilize the reliable, high-precision Sloan Digital Sky Survey (SDSS) Stripe 82 proper motion catalog. Although we do not find any candidates which have velocities in excess of the escape speed, we identify 226 stars on orbits that are consistent with Galactic Center ejection. This number is significantly larger than what we would expect for halo stars on radial orbits and cannot be explained by disk or bulge contamination. If we restrict ourselves to metal-rich stars, we find 29 candidates with [Fe/H] > −0.8 dex and 10 with [Fe/H] > −0.6 dex. Their metallicities are more consistent with what we expect for bulge ejecta, and so we believe these candidates are especially deserving of further study. We have supplemented this sample using our own radial velocities, developing an algorithm to use proper motions for optimizing candidate selection. This technique provides considerable improvement on the blind spectroscopic sample of SDSS, being able to identify candidates with an efficiency around 20 times better than a blind search.
RED RUNAWAYS II: LOW-MASS HILLS STARS IN SDSS STRIPE 82

International Nuclear Information System (INIS)

Zhang, Yanqiong; Smith, Martin C.; Carlin, Jeffrey L.

2016-01-01

Stars ejected from the Galactic Center can be used to place important constraints on the Milky Way potential. Since existing hypervelocity stars are too distant to accurately determine orbits, we have conducted a search for nearby candidates using full three-dimensional velocities. Since the efficacy of such studies is often hampered by deficiencies in proper motion catalogs, we have chosen to utilize the reliable, high-precision Sloan Digital Sky Survey (SDSS) Stripe 82 proper motion catalog. Although we do not find any candidates which have velocities in excess of the escape speed, we identify 226 stars on orbits that are consistent with Galactic Center ejection. This number is significantly larger than what we would expect for halo stars on radial orbits and cannot be explained by disk or bulge contamination. If we restrict ourselves to metal-rich stars, we find 29 candidates with [Fe/H] > −0.8 dex and 10 with [Fe/H] > −0.6 dex. Their metallicities are more consistent with what we expect for bulge ejecta, and so we believe these candidates are especially deserving of further study. We have supplemented this sample using our own radial velocities, developing an algorithm to use proper motions for optimizing candidate selection. This technique provides considerable improvement on the blind spectroscopic sample of SDSS, being able to identify candidates with an efficiency around 20 times better than a blind search.
FUNDAMENTAL PROPERTIES OF KEPLER PLANET-CANDIDATE HOST STARS USING ASTEROSEISMOLOGY

Energy Technology Data Exchange (ETDEWEB)

Huber, Daniel; Lissauer, Jack J.; Rowe, Jason F. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Chaplin, William J. [School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT (United Kingdom); Christensen-Dalsgaard, Jorgen; Kjeldsen, Hans; Handberg, Rasmus; Karoff, Christoffer; Lund, Mikkel N.; Lundkvist, Mia [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Gilliland, Ronald L. [Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Buchhave, Lars A. [Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Fischer, Debra A.; Basu, Sarbani [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Sanchis-Ojeda, Roberto [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Hekker, Saskia [Astronomical Institute ' ' Anton Pannekoek' ' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Isaacson, Howard; Marcy, Geoffrey W. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Latham, David W., E-mail: daniel.huber@nasa.gov [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); and others

2013-04-20

We have used asteroseismology to determine fundamental properties for 66 Kepler planet-candidate host stars, with typical uncertainties of 3% and 7% in radius and mass, respectively. The results include new asteroseismic solutions for four host stars with confirmed planets (Kepler-4, Kepler-14, Kepler-23 and Kepler-25) and increase the total number of Kepler host stars with asteroseismic solutions to 77. A comparison with stellar properties in the planet-candidate catalog by Batalha et al. shows that radii for subgiants and giants obtained from spectroscopic follow-up are systematically too low by up to a factor of 1.5, while the properties for unevolved stars are in good agreement. We furthermore apply asteroseismology to confirm that a large majority of cool main-sequence hosts are indeed dwarfs and not misclassified giants. Using the revised stellar properties, we recalculate the radii for 107 planet candidates in our sample, and comment on candidates for which the radii change from a previously giant-planet/brown-dwarf/stellar regime to a sub-Jupiter size or vice versa. A comparison of stellar densities from asteroseismology with densities derived from transit models in Batalha et al. assuming circular orbits shows significant disagreement for more than half of the sample due to systematics in the modeled impact parameters or due to planet candidates that may be in eccentric orbits. Finally, we investigate tentative correlations between host-star masses and planet-candidate radii, orbital periods, and multiplicity, but caution that these results may be influenced by the small sample size and detection biases.
DIRECT IMAGING IN THE HABITABLE ZONE AND THE PROBLEM OF ORBITAL MOTION

International Nuclear Information System (INIS)

Males, Jared R.; Skemer, Andrew J.; Close, Laird M.

2013-01-01

High contrast imaging searches for exoplanets have been conducted on 2.4-10 m telescopes, typically at H band (1.6 μm) and used exposure times of ∼1 hr to search for planets with semi-major axes of ∼> 10 AU. We are beginning to plan for surveys using extreme-AO systems on the next generation of 30 m class telescopes, where we hope to begin probing the habitable zones (HZs) of nearby stars. Here we highlight a heretofore ignorable problem in direct imaging: planets orbit their stars. Under the parameters of current surveys, orbital motion is negligible over the duration of a typical observation. However, this motion is not negligible when using large diameter telescopes to observe at relatively close stellar distances (1-10 pc), over the long exposure times (10-20 hr) necessary for direct detection of older planets in the HZ. We show that this motion will limit our achievable signal-to-noise ratio and degrade observational completeness. Even on current 8 m class telescopes, orbital motion will need to be accounted for in an attempt to detect HZ planets around the nearest Sun-like stars α Cen A and B, a binary system now known to harbor at least one planet. Here we derive some basic tools for analyzing this problem, and ultimately show that the prospects are good for de-orbiting a series of shorter exposures to correct for orbital motion.
VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. I. A LOW-MASS RATIO STELLAR COMPANION TO TYC 4110-01037-1 IN A 79 DAY ORBIT

International Nuclear Information System (INIS)

Wisniewski, John P.; Agol, Eric; Barnes, Rory; Ge, Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Chang, Liang; Crepp, Justin R.; Eastman, Jason; Gaudi, B. Scott; Esposito, Massimiliano; Gonzalez Hernandez, Jonay I.; Prieto, Carlos Allende; Ghezzi, Luan; Da Costa, Luiz N.; Porto De Mello, G. F.; Stassun, Keivan G.; Cargile, Phillip; Bizyaev, Dmitry

2012-01-01

TYC 4110-01037-1 has a low-mass stellar companion, whose small mass ratio and short orbital period are atypical among binary systems with solar-like (T eff ∼ ☉ and radius of 0.99 ± 0.18 R ☉ . We analyze 32 radial velocity (RV) measurements from the SDSS-III MARVELS survey as well as 6 supporting RV measurements from the SARG spectrograph on the 3.6 m Telescopio Nazionale Galileo telescope obtained over a period of ∼2 years. The best Keplerian orbital fit parameters were found to have a period of 78.994 ± 0.012 days, an eccentricity of 0.1095 ± 0.0023, and a semi-amplitude of 4199 ± 11 m s –1 . We determine the minimum companion mass (if sin i = 1) to be 97.7 ± 5.8 M Jup . The system's companion to host star mass ratio, ≥0.087 ± 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (T eff ∼< 6000 K) stars. One possible way to create such a system would be if a triple-component stellar multiple broke up into a short period, low q binary during the cluster dispersal phase of its lifetime. A candidate tertiary body has been identified in the system via single-epoch, high contrast imagery. If this object is confirmed to be comoving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of low-mass stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.
Atmospheric mass-loss of extrasolar planets orbiting magnetically active host stars

Science.gov (United States)

Lalitha, Sairam; Schmitt, J. H. M. M.; Dash, Spandan

2018-06-01

Magnetic stellar activity of exoplanet hosts can lead to the production of large amounts of high-energy emission, which irradiates extrasolar planets, located in the immediate vicinity of such stars. This radiation is absorbed in the planets' upper atmospheres, which consequently heat up and evaporate, possibly leading to an irradiation-induced mass-loss. We present a study of the high-energy emission in the four magnetically active planet-bearing host stars, Kepler-63, Kepler-210, WASP-19, and HAT-P-11, based on new XMM-Newton observations. We find that the X-ray luminosities of these stars are rather high with orders of magnitude above the level of the active Sun. The total XUV irradiation of these planets is expected to be stronger than that of well-studied hot Jupiters. Using the estimated XUV luminosities as the energy input to the planetary atmospheres, we obtain upper limits for the total mass- loss in these hot Jupiters.
HOT STARS WITH HOT JUPITERS HAVE HIGH OBLIQUITIES

International Nuclear Information System (INIS)

Winn, Joshua N.; Albrecht, Simon; Fabrycky, Daniel; Johnson, John Asher

2010-01-01

We show that stars with transiting planets for which the stellar obliquity is large are preferentially hot (T eff > 6250 K). This could explain why small obliquities were observed in the earliest measurements, which focused on relatively cool stars drawn from Doppler surveys, as opposed to hotter stars that emerged more recently from transit surveys. The observed trend could be due to differences in planet formation and migration around stars of varying mass. Alternatively, we speculate that hot-Jupiter systems begin with a wide range of obliquities, but the photospheres of cool stars realign with the orbits due to tidal dissipation in their convective zones, while hot stars cannot realign because of their thinner convective zones. This in turn would suggest that hot Jupiters originate from few-body gravitational dynamics and that disk migration plays at most a supporting role.
EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS

Energy Technology Data Exchange (ETDEWEB)

Rugheimer, S. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kaltenegger, L. [Carl Sagan Institute, Cornell University, Ithaca, NY 14853 (United States); Segura, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México (Mexico); Linsky, J. [JILA, University of Colorado and NIST, 440 UCB, Boulder, CO 80309-0440 (United States); Mohanty, S. [Imperial College London, 1010 Blackett Lab, Prince Consort Road, London SW7 2AZ (United Kingdom)

2015-08-10

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T{sub eff} = 2300 K to T{sub eff} = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H{sub 2}O, O{sub 3}, CH{sub 4}, N{sub 2}O, and CH{sub 3}Cl. To observe signatures of life—O{sub 2}/O{sub 3} in combination with reducing species like CH{sub 4}—we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O{sub 2} spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N{sub 2}O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH{sub 3}Cl could become detectable, depending on the depth of the overlapping N{sub 2}O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities.
EFFECT OF UV RADIATION ON THE SPECTRAL FINGERPRINTS OF EARTH-LIKE PLANETS ORBITING M STARS

International Nuclear Information System (INIS)

Rugheimer, S.; Kaltenegger, L.; Segura, A.; Linsky, J.; Mohanty, S.

2015-01-01

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T eff = 2300 K to T eff = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H 2 O, O 3 , CH 4 , N 2 O, and CH 3 Cl. To observe signatures of life—O 2 /O 3 in combination with reducing species like CH 4 —we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O 2 spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N 2 O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH 3 Cl could become detectable, depending on the depth of the overlapping N 2 O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities
Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia a

NARCIS (Netherlands)

C.L. Eckhardt (Corien); A.S. van Velzen (Alice); M.A.D. Peters (Marjolein); J. Astermark (Jan); P.P. Brons; G. Castaman (Giancarlo); M.H. Cnossen (Marjon); N. Dors (N.); C. Escuriola-Ettingshausen (Carmen); K. Hamulyák (K.); D.P. Hart (Daniel); C.R.M. Hay (Charles R.); S. Haya (Saturnino); W.L. van Heerde; C. Hermans (Cédric); M. Holmström (Margareta); V. Jimenez-Yuste (Victor); R.D. Keenan (Russell); R. Klamroth (Robert); B.A.P. Laros-Van Gorkom (Britta); F.W.G. Leebeek (Frank); R. Liesner (Ri); A. Mäkipernaa (Anne); C. Male (Christoph); E.P. Mauser-Bunschoten (Eveline); M.G. Mazzucconi (Maria); S. McRae (Simon); K. Meijer (K.); M. Mitchell (Michael); M. Morfini (Massimo); M.R. Nijziel (Marten); J. Oldenburg (Jan); K. Peerlinck; P. Petrini (Pia); H. Platokouki (Helena); S.E. Reitter-Pfoertner (Sylvia); E. Santagostino (Elena); P. Schinco (Piercarla); F.J.W. Smiers (Frans); K.D. Siegmund (Kimberly); A. Tagliaferri (Annarita); T.T. Yee (Thynn); P.W. Kamphuisen (Pieter Willem); J.G. van der Bom (Anske); K. Fijnvandraat

2013-01-01

textabstractNeutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into
A New Orbit for the Eclipsing Binary V577 Oph

Energy Technology Data Exchange (ETDEWEB)

Jeffery, Elizabeth J. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Barnes, Thomas G. III; Montemayor, Thomas J. [The University of Texas at Austin, McDonald Observatory, 1 University Station, C1402, Austin, TX 78712-0259 (United States); Skillen, Ian, E-mail: ejjeffer@calpoly.edu, E-mail: tgb@astro.as.utexas.edu, E-mail: tm@astro.as.utexas.edu, E-mail: wji@ing.iac.es [Isaac Newton Group, Apartado de Correos 321, E-38700 Santa Cruz de La Palma, Canary Islands (Spain)

2017-09-01

Pulsating stars in eclipsing binary systems are unique objects for providing constraints on stellar models. To fully leverage the information available from the binary system, full orbital radial velocity curves must be obtained. We report 23 radial velocities for components of the eclipsing binary V577 Oph, whose primary star is a δ Sct variable. The velocities cover a nearly complete orbit and a time base of 20 years. We computed orbital elements for the binary and compared them to the ephemeris computed by Creevey et al. The comparison shows marginally different results. In particular, a change in the systemic velocity by −2 km s{sup −1} is suggested by our results. We compare this systemic velocity difference to that expected due to reflex motion of the binary in response to the third body in the system. The systemic velocity difference is consistent with reflex motion, given our mass determination for the eclipsing binary and the orbital parameters determined by Volkov and Volkova for the three-body orbit. We see no evidence for the third body in our spectra, but we do see strong interstellar Na D lines that are consistent in strength with the direction and expected distance of V577 Oph.
A New Orbit for the Eclipsing Binary V577 Oph

Science.gov (United States)

Jeffery, Elizabeth J.; Barnes, Thomas G., III; Skillen, Ian; Montemayor, Thomas J.

2017-09-01

Pulsating stars in eclipsing binary systems are unique objects for providing constraints on stellar models. To fully leverage the information available from the binary system, full orbital radial velocity curves must be obtained. We report 23 radial velocities for components of the eclipsing binary V577 Oph, whose primary star is a δ Sct variable. The velocities cover a nearly complete orbit and a time base of 20 years. We computed orbital elements for the binary and compared them to the ephemeris computed by Creevey et al. The comparison shows marginally different results. In particular, a change in the systemic velocity by -2 km s-1 is suggested by our results. We compare this systemic velocity difference to that expected due to reflex motion of the binary in response to the third body in the system. The systemic velocity difference is consistent with reflex motion, given our mass determination for the eclipsing binary and the orbital parameters determined by Volkov & Volkova for the three-body orbit. We see no evidence for the third body in our spectra, but we do see strong interstellar Na D lines that are consistent in strength with the direction and expected distance of V577 Oph.
Characterization of five partial deletions of the factor VIII gene

International Nuclear Information System (INIS)

Youssoufian, H.; Antonarakis, S.E.; Aronis, S.; Tsiftis, G.; Phillips, D.G.; Kazazian, H.H. Jr.

1987-01-01

Hemophilia A is an X-linked disorder of coagulation caused by a deficiency of factor VIII. By using cloned DNA probes, the authors have characterized the following five different partial deletions of the factor VIII gene from a panel of 83 patients with hemophilia A: (i) a 7-kilobase (kb) deletion that eliminates exon 6; (ii) a 2.5-kb deletion that eliminates 5' sequences of exon 14; (iii) a deletion of at least 7 kb that eliminates exons 24 and 25; (iv) a deletion of at least 16 kb that eliminates exons 23-25; and (v) a 5.5-kb deletion that eliminates exon 22. The first four deletions are associated with severe hemophilia A. By contrast, the last deletion is associated with moderate disease, possibly because of in-frame splicing from adjacent exons. None of those patients with partial gene deletions had circulating inhibitors to factor VIII. One deletion occurred de novo in a germ cell of the maternal grandmother, while a second deletion occurred in a germ cell of the maternal grandfather. These observations demonstrate that de novo deletions of X-linked genes can occur in either male or female gametes
Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler

OpenAIRE

Howard, Andrew W.; Marcy, Geoffrey W.; Bryson, Stephen T.; Jenkins, Jon M.; Rowe, Jason F.; Batalha, Natalie M.; Borucki, William J.; Koch, David G.; Dunham, Edward W.; Gautier III, Thomas N.; Van Cleve, Jeffrey; Cochran, William D.; Latham, David W.; Lissauer, Jack J.; Torres, Guillermo

2011-01-01

We report the distribution of planets as a function of planet radius (R_p), orbital period (P), and stellar effective temperature (Teff) for P < 50 day orbits around GK stars. These results are based on the 1,235 planets (formally "planet candidates") from the Kepler mission that include a nearly complete set of detected planets as small as 2 Earth radii (Re). For each of the 156,000 target stars we assess the detectability of planets as a function of R_p and P. We also correct for the geomet...
Checking in on the Neighbors: Speckle Interferometry of Red Dwarf Stars

Science.gov (United States)

Mason, Brian; Hartkopf, William; Miles, Korie; Subasavage, John P.; Raghavan, Deepak; Henry, Todd

2018-01-01

High resolution optical speckle observations of M dwarf stars are reported which result in 113 resolved measurements of 80 systems and 256 other stars with no indications of duplicity. Nineteen of these had their first measures here, although all but two of those have later measures reported elsewhere. Included are six orbits, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.127+/-0.011 and 0.0961+/-0.0085 \\msun ~ for A and B, respectively. All of the orbit pairs have short periods of between five and thirty-eight years and hold the promise of accurate masses in the near future. For many other pairs we can establish their nature as physical or not depending on their relative motion. Of the 80 systems, 32 have orbits, 25 others are physical, 4 are optical and 19 are currently unknown.
Ultraviolet radiation from F and K stars and implications for planetary habitability

Science.gov (United States)

Kasting, J. F.; Whittet, D. C.; Sheldon, W. R.

1997-01-01

Now that extrasolar planets have been found, it is timely to ask whether some of them might be suitable for life. Climatic constraints on planetary habitability indicate that a reasonably wide habitable zone exists around main sequence stars with spectral types in the early-F to mid-K range. However, it has not been demonstrated that planets orbiting such stars would be habitable when biologically-damaging energetic radiation is also considered. The large amounts of UV radiation emitted by early-type stars have been suggested to pose a problem for evolving life in their vicinity. But one might also argue that the real problem lies with late-type stars, which emit proportionally less radiation at the short wavelengths (lambda < 200 nm) required to split O2 and initiate ozone formation. We show here that neither of these concerns is necessarily fatal to the evolution of advanced life: Earth-like planets orbiting F and K stars may well receive less harmful UV radiation at their surfaces than does the Earth itself.
Thermal design and analysis of high power star sensors

Directory of Open Access Journals (Sweden)

Fan Jiang

2015-09-01

Full Text Available The requirement for the temperature stability is very high in the star sensors as the high precision needs for the altitude information. Thermal design and analysis thus is important for the high power star sensors and their supporters. CCD, normally with Peltier thermoelectric cooler (PTC, is the most important sensor component in the star sensors, which is also the main heat source in the star sensors suite. The major objective for the thermal design in this paper is to design a radiator to optimize the heat diffusion for CCD and PTC. The structural configuration of star sensors, the heat sources and orbit parameters were firstly introduced in this paper. The influences of the geometrical parameters and coating material characteristics of radiators on the heat diffusion were investigated by heat flux analysis. Carbon–carbon composites were then chosen to improve the thermal conductivity for the sensor supporters by studying the heat transfer path. The design is validated by simulation analysis and experiments on orbit. The satellite data show that the temperatures of three star sensors are from 17.8 °C to 19.6 °C, while the simulation results are from 18.1 °C to 20.1 °C. The temperatures of radiator are from 16.1 °C to 16.8 °C and the corresponding simulation results are from 16.0 °C to 16.5 °C. The temperature variety of each star sensor is less than 2 °C, which satisfies the design objectives.

The dynamics of the multi-planet system orbiting Kepler-56

Energy Technology Data Exchange (ETDEWEB)

Li, Gongjie; Naoz, Smadar; Johnson, John Asher [Harvard Smithsonian Center for Astrophysics, Institute for Theory and Computation, 60 Garden Street, Cambridge, MA 02138 (United States); Valsecchi, Francesca; Rasio, Frederic A., E-mail: gli@cfa.harvard.edu, E-mail: snaoz@cfa.harvard.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, Evanston, IL 60208 (United States)

2014-10-20

Kepler-56 is a multi-planet system containing two coplanar inner planets that are in orbits misaligned with respect to the spin axis of the host star, and an outer planet. Various mechanisms have been proposed to explain the broad distribution of spin-orbit angles among exoplanets, and these theories fall under two broad categories. The first is based on dynamical interactions in a multi-body system, while the other assumes that disk migration is the driving mechanism in planetary configuration and that the star (or disk) is titled with respect to the planetary plane. Here we show that the large observed obliquity of Kepler 56 system is consistent with a dynamical origin. In addition, we use observations by Huber et al. to derive the obliquity's probability distribution function, thus improving the constrained lower limit. The outer planet may be the cause of the inner planets' large obliquities, and we give the probability distribution function of its inclination, which depends on the initial orbital configuration of the planetary system. We show that even in the presence of precise measurement of the true obliquity, one cannot distinguish the initial configurations. Finally we consider the fate of the system as the star continues to evolve beyond the main sequence, and we find that the obliquity of the system will not undergo major variations as the star climbs the red giant branch. We follow the evolution of the system and find that the innermost planet will be engulfed in ∼129 Myr. Furthermore we put an upper limit of ∼155 Myr for the engulfment of the second planet. This corresponds to ∼3% of the current age of the star.
Crystal Structure of Human Factor VIII: Implications for the Formation of the Factor IXa-Factor VIIIa Complex

Energy Technology Data Exchange (ETDEWEB)

Ngo, J.C.; Huang, M.; Roth, D.A.; Furie, B.C.; Furie, B. (Wyeth); (MBL)

2008-06-03

Factor VIII is a procofactor that plays a critical role in blood coagulation, and is missing or defective in hemophilia A. We determined the X-ray crystal structure of B domain-deleted human factor VIII. This protein is composed of five globular domains and contains one Ca{sup 2+} and two Cu{sup 2+} ions. The three homologous A domains form a triangular heterotrimer where the A1 and A3 domains serve as the base and interact with the C2 and C1 domains, respectively. The structurally homologous C1 and C2 domains reveal membrane binding features. Based on biochemical studies, a model of the factor IXa-factor VIIIa complex was constructed by in silico docking. Factor IXa wraps across the side of factor VIII, and an extended interface spans the factor VIII heavy and light chains. This model provides insight into the activation of factor VIII and the interaction of factor VIIIa with factor IXa on the membrane surface.
Crystal Structure of Human Factor VIII: Implications for the Formation of the Factor IXa-Factor VIIIa Complex

Energy Technology Data Exchange (ETDEWEB)

Chi Ki Ngo,J.; Huang, M.; Roth, D.; Furie, B.; Furie, B.

2008-01-01

Factor VIII is a procofactor that plays a critical role in blood coagulation, and is missing or defective in hemophilia A. We determined the X-ray crystal structure of B domain-deleted human factor VIII. This protein is composed of five globular domains and contains one Ca(2+) and two Cu(2+) ions. The three homologous A domains form a triangular heterotrimer where the A1 and A3 domains serve as the base and interact with the C2 and C1 domains, respectively. The structurally homologous C1 and C2 domains reveal membrane binding features. Based on biochemical studies, a model of the factor IXa-factor VIIIa complex was constructed by in silico docking. Factor IXa wraps across the side of factor VIII, and an extended interface spans the factor VIII heavy and light chains. This model provides insight into the activation of factor VIII and the interaction of factor VIIIa with factor IXa on the membrane surface.
DISCOVERY OF A LOW-MASS COMPANION TO THE SOLAR-TYPE STAR TYC 2534-698-1

International Nuclear Information System (INIS)

Kane, Stephen R.; Mahadevan, Suvrath; Sivarani, Thirupathi; Cochran, William D.; Street, Rachel A.; Henry, Gregory W.; Williamson, Michael H.

2009-01-01

Brown dwarfs and low-mass stellar companions are interesting objects to study since they occupy the mass region between deuterium and hydrogen burning. We report here the serendipitous discovery of a low-mass companion in an eccentric orbit around a solar-type main-sequence star. The stellar primary, TYC 2534-698-1, is a G2V star that was monitored both spectroscopically and photometrically over the course of several months. Radial velocity observations indicate a minimum mass of 0.037 M sun and an orbital period of ∼103 days for the companion. Photometry outside of the transit window shows the star to be stable to within ∼6 millimags. The semimajor axis of the orbit places the companion in the 'brown dwarf desert' and we discuss potential follow-up observations that could constrain the mass of the companion.
Henry VIII, McLeod syndrome and Jacquetta's curse.

Science.gov (United States)

Stride, P; Lopes Floro, K

2013-01-01

The mental decline of King Henry VIII from being a jovial, charismatic and athletic young man into an increasingly paranoid, brutal tyrant in later life, ever more concerned at his lack of one or more male heirs, has attracted many medical diagnostic theories. Previous hypotheses have included diabetes, syphilis and hypothyroidism, among others. However, these inadequately explain Henry's failure to produce a male heir, despite multiple pairings. The latest postulated diagnoses for Henry are the coexistence of both Kell blood group antigenicity (possibly inherited from Jacquetta Woodville, Henry's maternal great grandmother) causing related impaired fertility, and McLeod syndrome, causing psychotic changes. As the mutated McLeod protein of the syndrome significantly reduces the expression, effectively inactivating the Kell antigen, we critically review this theory, examining in detail the pathophysiology of these conditions and assessing the genealogy of Henry VIII and its effect in subsequent generations.
Evidence for the formation of sodium hassate(VIII)

International Nuclear Information System (INIS)

Zweidorf, A. von; Angert, R.; Bruechle, W.; Buerger, S.; Eberhardt, K.; Eichler, R.; Hummrich, H.; Jaeger, E.; Kling, H.O.; Kratz, J.V.; Kuczewski, B.; Langrock, G.; Mendel, M.; Rieth, U.; Schaedel, M.; Schausten, B.; Schimpf, E.; Thoerle, P.; Trautmann, N.; Tsukada, K.; Wiehl, N.; Wirth, G.

2004-01-01

Hassium, element 108, was produced in the fusion reaction between 26 Mg and 248 Cm. The hassium recoils were oxidized in-situ to a highly volatile oxide, presumably HsO 4 , and were transported in a mixture of He and O 2 to a deposition and detection system. The latter consisted of 16 silicon PIN-photodiodes facing a layer of NaOH, which served, in the presence of a certain partial pressure of water in the transport gas, as reactive surface for the deposition of the volatile tetroxides. Six correlated α-decay chains of Hs were detected in the first 5 detectors centred around detection position 3. In analogy to OsO 4 , which forms Na 2 [OsO 4 (OH) 2 ], an osmate(VIII), with aqueous NaOH, HsO 4 presumably was deposited as Na 2 [HsO 4 (OH) 2 ], a hassate(VIII). (orig.)
The spectrum and term system of S VIII

International Nuclear Information System (INIS)

Bengtsson, P.; Jupen, C.; Engstroem, L.; Redfors, A.; Westerlind, M.

1993-01-01

The spectrum of seven times ionized sulfur, S VIII, has been observed in the wavelength range 50-1200 A. Both beam-foil and laser-produced plasma light sources have been used. 71 new lines representing the transitions 2p 5 -2p 4 3d, 2p 4 3s-3p, 3p-3d, 3d-4f, 4f-5g and 5g-6h have been identified and 100 energy levels, of which 46 are new, are now accurately established. The spectral analysis is supported by isoelectronic comparisons along the F I-sequence and by parametric least-squares fits of Slater integrals to the observed levels. The ionization potential in S VIII is determined to 2 651 899 ± 60 cm -1 and estimated ionization energies are derived for the isoelectronic elements between F I and Ar X. (orig.)
Magnetic fields driven by tidal mixing in radiative stars

Science.gov (United States)

Vidal, Jérémie; Cébron, David; Schaeffer, Nathanaël; Hollerbach, Rainer

2018-04-01

Stellar magnetism plays an important role in stellar evolution theory. Approximatively 10 per cent of observed main sequence (MS) and pre-main-sequence (PMS) radiative stars exhibit surface magnetic fields above the detection limit, raising the question of their origin. These stars host outer radiative envelopes, which are stably stratified. Therefore, they are assumed to be motionless in standard models of stellar structure and evolution. We focus on rapidly rotating, radiative stars which may be prone to the tidal instability, due to an orbital companion. Using direct numerical simulations in a sphere, we study the interplay between a stable stratification and the tidal instability, and assess its dynamo capability. We show that the tidal instability is triggered regardless of the strength of the stratification (Brunt-Väisälä frequency). Furthermore, the tidal instability can lead to both mixing and self-induced magnetic fields in stably stratified layers (provided that the Brunt-Väisälä frequency does not exceed the stellar spin rate in the simulations too much). The application to stars suggests that the resulting magnetic fields could be observable at the stellar surfaces. Indeed, we expect magnetic field strengths up to several Gauss. Consequently, tidally driven dynamos should be considered as a (complementary) dynamo mechanism, possibly operating in radiative MS and PMS stars hosting orbital companions. In particular, tidally driven dynamos may explain the observed magnetism of tidally deformed and rapidly rotating Vega-like stars.
Purification and characterization of factor VIII 1,689-Cys: a nonfunctional cofactor occurring in a patient with severe hemophilia A.

Science.gov (United States)

O'Brien, D P; Tuddenham, E G

1989-06-01

We have purified the factor VIII from a CRM+ Hemophilia A plasma (90 U/dL VIII:Ag but 0 U/dL VIII:C) and analyzed the protein before and after thrombin activation by Western blotting with monoclonal antibodies (MoAbs). Normal or patient citrated plasma was ultracentrifuged, cryo-ethanol-precipitated and chromatographed on Sepharose 6B. The void volume fractions were reduced and subjected to ion exchange chromatography yielding material of specific activity approximately 1,000 U/mg protein (VIII:C or VIII:Ag). Factor VIII purified in this way from normal plasma is fully activatable by thrombin with proteolytic fragmentation as previously described by F. Rotblat et al (Biochemistry 24: 4294, 1985). Factor VIII 1,689-Cys has the normal distribution of factor VIII light and heavy chains prior to thrombin activation. After exposure to thrombin the heavy chain polypeptides were fully proteolysed but the light chain was totally resistant to cleavage. This is consistent with the demonstration in the patient's leucocyte DNA of a C to T transition in codon 1,689 converting Arg to Cys at the light chain thrombin cleavage site as previously described by J. Gitschier et al (Blood 72:1022, 1988). Uncleaved light chain of Factor VIII 1,689-Cys is not released from von Willebrand factor (vWF) by thrombin, but this is not the sole cause of the functional defect since the protein purified free of vWF has no coagulant activity. We conclude that the functional defect in factor VIII 1,689-Cys is a consequence of failure to release the acidic peptide from the light chain upon thrombin activation.
Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790

Science.gov (United States)

Hernán-Obispo, M.; Gálvez-Ortiz, M. C.; Anglada-Escudé, G.; Kane, S. R.; Barnes, J. R.; de Castro, E.; Cornide, M.

2010-03-01

Context. BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on the surface, and strong flare events, despite the moderate rotational velocity of the star. In addition, radial velocity variations with a semi-amplitude of up to 1 km s-1 were detected. Aims: We investigate the nature of these radial velocity variations, in order to determine whether they are due to stellar activity or the reflex motion of the star induced by a companion. Methods: We have analysed high-resolution echelle spectra by measuring stellar activity indicators and computing radial velocity (RV) and bisector velocity spans. Two-band photometry was also obtained to produce the light curve and determine the photometric period. Results: Based upon the analysis of the bisector velocity span, as well as spectroscopic indices of chromospheric indicators, Ca ii H & K, Hα, and taking the photometric analysis into account, we report that the best explanation for the RV variation is the presence of a substellar companion. The Keplerian fit of the RV data yields a solution for a close-in massive planet with an orbital period of 7.78 days. The presence of the close-in massive planet could also be an interpretation for the high level of stellar activity detected. Since the RV data are not part of a planet search programme, we can consider our results as a serendipitous evidence of a planetary companion. To date, this is the youngest main sequence star for which a planetary candidate has been reported. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC). Based on observations made with the Italian Telescopio Nazionale Galileo
BINARY NEUTRON STARS IN QUASI-EQUILIBRIUM

International Nuclear Information System (INIS)

Taniguchi, Keisuke; Shibata, Masaru

2010-01-01

Quasi-equilibrium sequences of binary neutron stars are constructed for a variety of equations of state in general relativity. Einstein's constraint equations in the Isenberg-Wilson-Mathews approximation are solved together with the relativistic equations of hydrostationary equilibrium under the assumption of irrotational flow. We focus on unequal-mass sequences as well as equal-mass sequences, and compare those results. We investigate the behavior of the binding energy and total angular momentum along a quasi-equilibrium sequence, the endpoint of sequences, and the orbital angular velocity as a function of time, changing the mass ratio, the total mass of the binary system, and the equation of state of a neutron star. It is found that the orbital angular velocity at the mass-shedding limit can be determined by an empirical formula derived from an analytic estimation. We also provide tables for 160 sequences, which will be useful as a guideline of numerical simulations for the inspiral and merger performed in the near future.
NICER Discovers the Ultracompact Orbit of the Accreting Millisecond Pulsar IGR J17062–6143

Science.gov (United States)

Strohmayer, T. E.; Arzoumanian, Z.; Bogdanov, S.; Bult, P. M.; Chakrabarty, D.; Enoto, T.; Gendreau, K. C.; Guillot, S.; Harding, A. K.; Ho, W. C. G.; Homan, J.; Jaisawal, G. K.; Keek, L.; Kerr, M.; Mahmoodifar, S.; Markwardt, C. B.; Ransom, S. M.; Ray, P. S.; Remillard, R.; Wolff, M. T.

2018-05-01

We present results of recent Neutron Star Interior Composition Explorer (NICER) observations of the accreting millisecond X-ray pulsar (AMXP) IGR J17062‑6143 that show that it resides in a circular, ultracompact binary with a 38-minute orbital period. NICER observed the source for ≈26 ks over a 5.3-day span in 2017 August, and again for 14 and 11 ks in 2017 October and November, respectively. A power spectral analysis of the August exposure confirms the previous detection of pulsations at 163.656 Hz in Rossi X-ray Timing Explorer (RXTE) data, and reveals phase modulation due to orbital motion of the neutron star. A coherent search for the orbital solution using the Z 2 method finds a best-fitting circular orbit with a period of 2278.21 s (37.97 minutes), a projected semimajor axis of 0.00390 lt-s, and a barycentric pulsar frequency of 163.6561105 Hz. This is currently the shortest known orbital period for an AMXP. The mass function is 9.12 × 10‑8 M ⊙, presently the smallest known for a stellar binary. The minimum donor mass ranges from ≈0.005 to 0.007 M ⊙ for a neutron star mass from 1.2 to 2 M ⊙. Assuming mass transfer is driven by gravitational radiation, we find donor mass and binary inclination bounds of 0.0175–0.0155 M ⊙ and 19° < i < 27.°5, where the lower and upper bounds correspond to 1.4 and 2 M ⊙ neutron stars, respectively. Folding the data accounting for the orbital modulation reveals a sinusoidal profile with fractional amplitude 2.04 ± 0.11% (0.3–3.2 keV).
BinCat: a Catalog of Nearby Binary Stars with Tools for Calculating Light-Leakage for Direct Imaging Missions

Science.gov (United States)

Holte, Elias Peter; Sirbu, Dan; Belikov, Ruslan

2018-01-01

Binary stars have been largely left out of direct imaging surveys for exoplanets, specifically for earth-sized planets in their star's habitable zone. Utilizing new direct imaging techniques brings us closer to being able to detect earth-like exoplanets around binary stars. In preparation for the upcoming WFIRST mission and other direct imaging-capable missions (HabEx, LUVIOR) it is important to understand the expected science yield resulting from the implementation of these imaging techniques. BinCat is a catalog of binary systems within 30 parsecs to be used as a target list for future direct imaging missions. There is a non-static component along with BinCat that allows researchers to predict the expected light-leakage between a binary component and its off-axis companion (a value critical to the aforementioned techniques) at any epoch. This is accomplished by using orbital elements from the Sixth Orbital Catalog to model the orbits of the binaries. The software was validated against the historical data used to generate the orbital parameters. When orbital information is unknown or the binaries are purely optical the proper motion of the pair taken from the Washington Double Star catalog is integrated in time to estimate expected light-leakage.
40 CFR Appendix Viii to Part 266 - Organic Compounds for Which Residues Must Be Analyzed

Science.gov (United States)

2010-07-01

... AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF SPECIFIC HAZARDOUS WASTES AND SPECIFIC TYPES OF HAZARDOUS WASTE MANAGEMENT FACILITIES Pt. 266, App. VIII Appendix VIII to Part 266... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Organic Compounds for Which Residues...
40 CFR Appendix Viii to Part 268 - LDR Effective Dates of Injected Prohibited Hazardous Wastes

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 26 2010-07-01 2010-07-01 false LDR Effective Dates of Injected Prohibited Hazardous Wastes VIII Appendix VIII to Part 268 Protection of Environment ENVIRONMENTAL PROTECTION... to Part 268—LDR Effective Dates of Injected Prohibited Hazardous Wastes National Capacity LDR...
Outward Migration of Giant Planets in Orbital Resonance

Science.gov (United States)

D'Angelo, G.; Marzari, F.

2013-05-01

A pair of giant planets interacting with a gaseous disk may be subject to convergent orbital migration and become locked into a mean motion resonance. If the orbits are close enough, the tidal gaps produced by the planets in the disk may overlap. This represents a necessary condition to activate the outward migration of the pair. However, a number of other conditions must also be realized in order for this mechanism to operate. We have studied how disk properties, such as turbulence viscosity, temperature, surface density gradient, mass, and age, may affect the outcome of the outward migration process. We have also investigated the implications on this mechanism of the planets' gas accretion. If the pair resembles Jupiter and Saturn, the 3:2 orbital resonance may drive them outward until they reach stalling radii for migration, which are within ~10 AU of the star for disks representative of the early proto-solar nebula. However, planet post-formation conditions in the disk indicate that such planets become typically locked in the 1:2 orbital resonance, which does not lead to outward migration. Planet growth via gas accretion tends to alter the planets' mass-ratio and/or the disk accretion rate toward the star, reducing or inhibiting outward migration. Support from NASA Outer Planets Research Program and NASA Origins of Solar Systems Program is gratefully acknowledged.
Temperate Earth-sized planets transiting a nearby ultracool dwarf star.

Science.gov (United States)

Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

2016-05-12

Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.
The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

Science.gov (United States)

Shields, Aomawa L; Meadows, Victoria S; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

2013-08-01

Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice
A Simple Method for Reproducing Orbital Plots for Illustration Using Microsoft Paint and Microsoft Excel

Science.gov (United States)

Niebuhr, Cole

2018-04-01

Papers published in the astronomical community, particularly in the field of double star research, often contain plots that display the positions of the component stars relative to each other on a Cartesian coordinate plane. Due to the complexities of plotting a three-dimensional orbit into a two-dimensional image, it is often difficult to include an accurate reproduction of the orbit for comparison purposes. Methods to circumvent this obstacle do exist; however, many of these protocols result in low-quality blurred images or require specific and often expensive software. Here, a method is reported using Microsoft Paint and Microsoft Excel to produce high-quality images with an accurate reproduction of a partial orbit.
Structural characterization of the novel aminoglycoside phosphotransferase AphVIII from Streptomyces rimosus with enzymatic activity modulated by phosphorylation

Energy Technology Data Exchange (ETDEWEB)

Boyko, Konstantin M., E-mail: kmb@inbi.ras.ru [Bach Institute of Biochemistry, Federal Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt. 33, Bld. 2, 119071, Moscow (Russian Federation); National Research Center “Kurchatov Institute”, Kurchatov Complex of NBICS-technologies, Akad. Kurchatova sqr., 1, Moscow, 123182 (Russian Federation); Gorbacheva, Marina A.; Korzhenevskiy, Dmitry A. [National Research Center “Kurchatov Institute”, Kurchatov Complex of NBICS-technologies, Akad. Kurchatova sqr., 1, Moscow, 123182 (Russian Federation); Alekseeva, Maria G.; Mavletova, Dilara A.; Zakharevich, Natalia V.; Elizarov, Sergey M.; Rudakova, Natalia N.; Danilenko, Valery N. [Vavilov Institute of General Genetics, Russian Academy of Sciences, Gubkina str. 3, Moscow, 119333 (Russian Federation); Popov, Vladimir O. [Bach Institute of Biochemistry, Federal Research Centre of Biotechnology of the Russian Academy of Sciences, Leninsky Prospekt. 33, Bld. 2, 119071, Moscow (Russian Federation); National Research Center “Kurchatov Institute”, Kurchatov Complex of NBICS-technologies, Akad. Kurchatova sqr., 1, Moscow, 123182 (Russian Federation)

2016-09-02

Aminoglycoside phosphotransferases represent a broad class of enzymes that promote bacterial resistance to aminoglycoside antibiotics via the phosphorylation of hydroxyl groups in the latter. Here we report the spatial structure of the 3′-aminoglycoside phosphotransferase of novel VIII class (AphVIII) solved by X-ray diffraction method with a resolution of 2.15 Å. Deep analysis of APHVIII structure and its comparison with known structures of aminoglycoside phosphotransferases of various types reveals that AphVIII has a typical two-domain fold and, however, possesses some unique characteristics that distinguish the enzyme from its known homologues. The most important difference is the presence of the activation loop with unique Ser146 residue. We demonstrate that in the apo-state of the enzyme the activation loop does not interact with other parts of the enzyme and seems to adopt catalytically competent state only after substrate binding. - Highlights: • 3D structure of the novel aminoglycoside phosphotransferase AphVIII was obtained. • AphVIII activation loop is clearly identified in the electron density. • AphVIII has some unique structural features in its substrate C-ring binding pocket.

Spectroscopic orbit for HDE 245770 A0535+26

International Nuclear Information System (INIS)

Hutchings, J.B.

1984-01-01

Optical spectroscopic data are examined using the X-ray intensity period of 111 days. Optical and X-ray pulse-timing orbit parameters agree well and indicate an eccentricity of approximately 0.3. Masses of the stars and periastron effects are discussed. 6 references
Hemodialysis in a patient with severe hemophilia A and factor VIII inhibitor.

Science.gov (United States)

Gopalakrishnan, Natarajan; Usha, Thiruvengadam; Thopalan, Balasubramaniyan; Dhanapriya, Jeyachandran; Dineshkumar, Thanigachalam; Thirumalvalavan, Kaliaperumal; Sakthirajan, Ramanathan

2016-10-01

Hemophilia A is a hereditary X-linked recessive disease caused by mutations in the gene encoding factor VIII (FVIII), occurring in 1 out of 10,000 persons. Life expectancy and quality of life have dramatically improved recently in patients with hemophilia. Chronic kidney disease and need for renal replacement therapy in these patients are rare. The development of inhibitors to FVIII is the most serious complication of hemophilia and makes treatment of bleeds very challenging. We describe here a 28-year-old male patient with severe hemophilia A with presence of factor VIII inhibitor, who had end stage renal disease. Central venous access device was inserted along with infusion of factor eight inhibitor bypass activity before and after the procedure. He is currently on thrice weekly hemodialysis and doing well for 6 months without bleeding episodes. To our knowledge, hemophilia A with factor VIII inhibitor managed with hemodialysis has not been reported so far. © 2016 International Society for Hemodialysis.
Spectrophotometric determination of hydrogen peroxide with osmium(VIII) and m-carboxyphenylfluorone.

Science.gov (United States)

Hoshino, Mitsuru; Kamino, Shinichiro; Doi, Mitsunobu; Takada, Shingo; Mitani, Shota; Yanagihara, Rika; Asano, Mamiko; Yamaguchi, Takako; Fujita, Yoshikazu

2014-01-03

Spectrophotometric determination of hydrogen peroxide was accomplished with osmium(VIII) and m-carboxyphenylfluorone (MCPF) in the presence of cetyltrimethylammonium chloride (CTAC). In the determination of hydrogen peroxide based on the fading of the color of osmium(VIII)-MCPF complex, Beer's law was obeyed in the range 20-406 ng mL(-1), with an effective molar absorption coefficient (at 580 nm) of 5.21×10(4) L mol(-1) cm(-1) and a relative standard deviation of 0.33% (n=6). Further, we performed the characterization of MCPF and obtained the crystal structure. Copyright © 2013 Elsevier B.V. All rights reserved.
Four new planets around giant stars and the mass-metallicity correlation of planet-hosting stars

Science.gov (United States)

Jones, M. I.; Jenkins, J. S.; Brahm, R.; Wittenmyer, R. A.; Olivares E., F.; Melo, C. H. F.; Rojo, P.; Jordán, A.; Drass, H.; Butler, R. P.; Wang, L.

2016-05-01

Context. Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets. In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. Aims: During the past six years we have conducted a radial velocity follow-up program of 166 giant stars to detect substellar companions and to characterize their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. Methods: We took multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we computed precision radial velocities and derived atmospheric and physical parameters. Additionally, velocities computed from UCLES spectra are presented here. By studying the periodic radial velocity signals, we detected the presence of several substellar companions. Results: We present four new planetary systems around the giant stars HIP 8541, HIP 74890, HIP 84056, and HIP 95124. Additionally, we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5-5.9% around stars with [Fe/H] ~ 0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆ ~ 1.0 and 2.1 M⊙, with a maximum of f = 13.0+10.1-4.2% at M⋆ = 2.1 M⊙. Conclusions: We conclude that giant planets are preferentially formed around metal-rich stars. In addition, we conclude that they are more efficiently formed around more massive stars, in the stellar mass range of ~1.0-2.1 M⊙. These observational results confirm previous findings for solar
First Kepler results on compact pulsators - V. Slowly pulsating subdwarf B stars in short-period binaries

DEFF Research Database (Denmark)

Kawaler, Stephen D.; Reed, Michael D.; Østensen, Roy H.

2010-01-01

of sdB stars with a close M-dwarf companion with orbital periods of less than half a day. Because the orbital period is so short, the stars should be in synchronous rotation, and if so, the rotation period should imprint itself on the multiplet structure of the pulsations. However, we do not find clear......The survey phase of the Kepler Mission includes a number of hot subdwarf B (sdB) stars to search for non-radial pulsations. We present our analysis of two sdB stars that are found to be g-mode pulsators of the V1093 Her class. These two stars also display the distinct irradiation effect typical...... evidence for such rotational splitting. Though the stars do show some frequency spacings that are consistent with synchronous rotation, they also display multiplets with splittings that are much smaller. Longer-duration time series photometry will be needed to determine if those small splittings...
Orbital Eccentricity and the Stability of Planets in the Alpha Centauri System

Science.gov (United States)

Lissauer, Jack

2016-01-01

Planets on initially circular orbits are typically more dynamically stable than planets initially having nonzero eccentricities. However, the presence of a major perturber that forces periodic oscillations of planetary eccentricity can alter this situation. We investigate the dependance of system lifetime on initial eccentricity for planets orbiting one star within the alpha Centauri system. Our results show that initial conditions chosen to minimize free eccentricity can substantially increase stability compared to planets on circular orbits.
Density wave induced star formation: The optical surface brightness of galaxies

International Nuclear Information System (INIS)

Bash, F.N.

1979-01-01

A model for the galactic orbits of molecular clouds has been devised. The molecular clouds are assumed to be launched from the two-armed spiral-shock wave, to orbit in the Galaxy like ballistic particles with gravitational perturbations due to the density-wave spiral-potential, and each cloud is assumed to produce a cluster of stars. Each cloud radiates detectable 12 C 16 O (J=0→1) spectral line radiation from birth for 40 million years. Stars are seen in the cloud about 25 million years after birth, and the star cluster is assumed to continue in ballistic orbit around the Galaxy.The model has been tested by comparing its predicted velocity-longitude diagram for CO against that observed for the Galaxy and by comparing the model's predicted distribution of light in the UBV photometric bands against observed surface photometry for Sb and SC galaxies. The interpolation of the initial velocities in the model was corrected, and the model was examined to see whether preshock or postshock initial velocities better fit the observations. The model gives very good general agreement and reproduces many of the features observed in the CO velocity-longitude diagram
A Be-type star with a black-hole companion.

Science.gov (United States)

Casares, J; Negueruela, I; Ribó, M; Ribas, I; Paredes, J M; Herrero, A; Simón-Díaz, S

2014-01-16

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the approximately 80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (ref. 5; also known as HD 215227), although that conclusion was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of MWC 656. This, together with an improved radial velocity curve of the Be star through fitting sharp Fe II profiles from the equatorial disk, and a refined Be classification (to that of a B1.5-B2 III star), indicates that a black hole of 3.8 to 6.9 solar masses orbits MWC 656, the candidate counterpart of the γ-ray source AGL J2241+4454 (refs 5, 6). The black hole is X-ray quiescent and fed by a radiatively inefficient accretion flow giving a luminosity less than 1.6 × 10(-7) times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect in conventional X-ray surveys.
RUNAWAY DWARF CARBON STARS AS CANDIDATE SUPERNOVA EJECTA

Energy Technology Data Exchange (ETDEWEB)

Plant, Kathryn A.; Margon, Bruce; Guhathakurta, Puragra; Cunningham, Emily C.; Toloba, Elisa [Department of Astronomy and Astrophysics and University of California Observatories, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Munn, Jeffrey A., E-mail: kaplant@ucsc.edu [US Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86005-8521 (United States)

2016-12-20

The dwarf carbon (dC) star SDSS J112801.67+004034.6 has an unusually high radial velocity, 531 ± 4 km s{sup −1}. We present proper motion and new spectroscopic observations which imply a large Galactic rest frame velocity, 425 ± 9 km s{sup −1}. Several other SDSS dC stars are also inferred to have very high galactocentric velocities, again each based on both high heliocentric radial velocity and also confidently detected proper motions. Extreme velocities and the presence of C {sub 2} bands in the spectra of dwarf stars are both rare. Passage near the Galactic center can accelerate stars to such extreme velocities, but the large orbital angular momentum of SDSS J1128 precludes this explanation. Ejection from a supernova in a binary system or disruption of a binary by other stars are possibilities, particularly as dC stars are thought to obtain their photospheric C {sub 2} via mass transfer from an evolved companion.
OBSERVATIONS OF BINARY STARS WITH THE DIFFERENTIAL SPECKLE SURVEY INSTRUMENT. IV. OBSERVATIONS OF KEPLER, CoRoT, AND HIPPARCOS STARS FROM THE GEMINI NORTH TELESCOPE

International Nuclear Information System (INIS)

Horch, Elliott P.; Howell, Steve B.; Everett, Mark E.; Ciardi, David R.

2012-01-01

We present the results of 71 speckle observations of binary and unresolved stars, most of which were observed with the DSSI speckle camera at the Gemini North Telescope in 2012 July. The main purpose of the run was to obtain diffraction-limited images of high-priority targets for the Kepler and CoRoT missions, but in addition, we observed a number of close binary stars where the resolution limit of Gemini was used to better determine orbital parameters and/or confirm results obtained at or below the diffraction limit of smaller telescopes. Five new binaries and one triple system were discovered, and first orbits are calculated for other two systems. Several systems are discussed in detail.
The secular tidal disruption of stars by low-mass Super Massive Black Holes secondaries in galactic nuclei

Science.gov (United States)

Fragione, Giacomo; Leigh, Nathan

2018-06-01

Stars passing too close to a super massive black hole (SMBH) can produce tidal disruption events (TDEs). Since the resulting stellar debris can produce an electromagnetic flare, TDEs are believed to probe the presence of single SMBHs in galactic nuclei, which otherwise remain dark. In this paper, we show how stars orbiting an IMBH secondary are perturbed by an SMBH primary. We find that the evolution of the stellar orbits are severely affected by the primary SMBH due to secular effects and stars orbiting with high inclinations with respect to the SMBH-IMBH orbital plane end their lives as TDEs due to Kozai-Lidov oscillations, hence illuminating the secondary SMBH/IMBH. Above a critical SMBH mass of ≈1.15 × 108 M⊙, no TDE can occur for typical stars in an old stellar population since the Schwarzschild radius exceeds the tidal disruption radius. Consequently, any TDEs due to such massive SMBHs will remain dark. It follows that no TDEs should be observed in galaxies more massive than ≈4.15 × 1010 M⊙, unless a lower-mass secondary SMBH or IMBH is also present. The secular mechanism for producing TDEs considered here therefore offers a useful probe of SMBH-SMBH/IMBH binarity in the most massive galaxies. We further show that the TDE rate can be ≈10-4 - 10-3 yr-1, and that most TDEs occur on ≈0.5 Myr. Finally, we show that stars may be ejected with velocities up to thousands of km s-1, which could contribute to the observed population of Galactic hypervelocity stars.
Star Tracker Performance Estimate with IMU

Science.gov (United States)

Aretskin-Hariton, Eliot D.; Swank, Aaron J.

2015-01-01

A software tool for estimating cross-boresight error of a star tracker combined with an inertial measurement unit (IMU) was developed to support trade studies for the Integrated Radio and Optical Communication project (iROC) at the National Aeronautics and Space Administration Glenn Research Center. Typical laser communication systems, such as the Lunar Laser Communication Demonstration (LLCD) and the Laser Communication Relay Demonstration (LCRD), use a beacon to locate ground stations. iROC is investigating the use of beaconless precision laser pointing to enable laser communication at Mars orbits and beyond. Precision attitude knowledge is essential to the iROC mission to enable high-speed steering of the optical link. The preliminary concept to achieve this precision attitude knowledge is to use star trackers combined with an IMU. The Star Tracker Accuracy (STAcc) software was developed to rapidly assess the capabilities of star tracker and IMU configurations. STAcc determines the overall cross-boresight error of a star tracker with an IMU given the characteristic parameters: quantum efficiency, aperture, apparent star magnitude, exposure time, field of view, photon spread, detector pixels, spacecraft slew rate, maximum stars used for quaternion estimation, and IMU angular random walk. This paper discusses the supporting theory used to construct STAcc, verification of the program and sample results.
Super massive black hole in galactic nuclei with tidal disruption of stars

International Nuclear Information System (INIS)

Zhong, Shiyan; Berczik, Peter; Spurzem, Rainer

2014-01-01

Tidal disruption of stars by super massive central black holes from dense star clusters is modeled by high-accuracy direct N-body simulation. The time evolution of the stellar tidal disruption rate, the effect of tidal disruption on the stellar density profile, and, for the first time, the detailed origin of tidally disrupted stars are carefully examined and compared with classic papers in the field. Up to 128k particles are used in simulation to model the star cluster around a super massive black hole, and we use the particle number and the tidal radius of the black hole as free parameters for a scaling analysis. The transition from full to empty loss-cone is analyzed in our data, and the tidal disruption rate scales with the particle number, N, in the expected way for both cases. For the first time in numerical simulations (under certain conditions) we can support the concept of a critical radius of Frank and Rees, which claims that most stars are tidally accreted on highly eccentric orbits originating from regions far outside the tidal radius. Due to the consumption of stars moving on radial orbits, a velocity anisotropy is found inside the cluster. Finally we estimate the real galactic center based on our simulation results and the scaling analysis.
Super Massive Black Hole in Galactic Nuclei with Tidal Disruption of Stars

Science.gov (United States)

Zhong, Shiyan; Berczik, Peter; Spurzem, Rainer

2014-09-01

Tidal disruption of stars by super massive central black holes from dense star clusters is modeled by high-accuracy direct N-body simulation. The time evolution of the stellar tidal disruption rate, the effect of tidal disruption on the stellar density profile, and, for the first time, the detailed origin of tidally disrupted stars are carefully examined and compared with classic papers in the field. Up to 128k particles are used in simulation to model the star cluster around a super massive black hole, and we use the particle number and the tidal radius of the black hole as free parameters for a scaling analysis. The transition from full to empty loss-cone is analyzed in our data, and the tidal disruption rate scales with the particle number, N, in the expected way for both cases. For the first time in numerical simulations (under certain conditions) we can support the concept of a critical radius of Frank & Rees, which claims that most stars are tidally accreted on highly eccentric orbits originating from regions far outside the tidal radius. Due to the consumption of stars moving on radial orbits, a velocity anisotropy is found inside the cluster. Finally we estimate the real galactic center based on our simulation results and the scaling analysis.
Activity-induced radial velocity variation of M dwarf stars

DEFF Research Database (Denmark)

Andersen, Jan Marie; Korhonen, Heidi Helena

2012-01-01

that can drown out a planetary signature. Cool, low-mass M dwarf stars can be highly active, which can make detection of potentially habitable planets around these stars difficult. We investigate radial velocity variations caused by different activity (spot) patterns on M dwarf stars in order to determine...... the limits of detectability for small planets orbiting active M dwarfs. We report on our progress toward the aim of answering the following questions: What types of spot patterns are realistic for M dwarf stars? What effect will spots have on M dwarf RV measurements? Can jitter from M dwarf spots mimic...... planetary signals? What is the ideal observing wavelength to reduce M dwarf jitter?...
Autonomous star tracker based on active pixel sensors (APS)

Science.gov (United States)

Schmidt, U.

2017-11-01

Star trackers are opto-electronic sensors used onboard of satellites for the autonomous inertial attitude determination. During the last years, star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads. The Jena-Optronik GmbH is active in the field of opto-electronic sensors like star trackers since the early 80-ties. Today, with the product family ASTRO5, ASTRO10 and ASTRO15, all marked segments like earth observation, scientific applications and geo-telecom are supplied to European and Overseas customers. A new generation of star trackers can be designed based on the APS detector technical features. The measurement performance of the current CCD based star trackers can be maintained, the star tracker functionality, reliability and robustness can be increased while the unit costs are saved.
Continuum orbital approximations in weak-coupling theories for inelastic electron scattering

International Nuclear Information System (INIS)

Peek, J.M.; Mann, J.B.

1977-01-01

Two approximations, motivated by heavy-particle scattering theory, are tested for weak-coupling electron-atom (ion) inelastic scattering theory. They consist of replacing the one-electron scattering orbitals by their Langer uniform approximations and the use of an average trajectory approximation which entirely avoids the necessity for generating continuum orbitals. Numerical tests for a dipole-allowed and a dipole-forbidden event, based on Coulomb-Born theory with exchange neglected, reveal the error trends. It is concluded that the uniform approximation gives a satisfactory prediction for traditional weak-coupling theories while the average approximation should be limited to collision energies exceeding at least twice the threshold energy. The accuracy for both approximations is higher for positive ions than for neutral targets. Partial-wave collision-strength data indicate that greater care should be exercised in using these approximations to predict quantities differential in the scattering angle. An application to the 2s 2 S-2p 2 P transition in Ne VIII is presented
Precision Attitude Determination System (PADS) system design and analysis: Single-axis gimbal star tracker

Science.gov (United States)

1974-01-01

The feasibility is evaluated of an evolutionary development for use of a single-axis gimbal star tracker from prior two-axis gimbal star tracker based system applications. Detailed evaluation of the star tracker gimbal encoder is considered. A brief system description is given including the aspects of tracker evolution and encoder evaluation. System analysis includes evaluation of star availability and mounting constraints for the geosynchronous orbit application, and a covariance simulation analysis to evaluate performance potential. Star availability and covariance analysis digital computer programs are included.
Factor VIII-associated antigen in human lymphatic endothelium.

Science.gov (United States)

Nagle, R B; Witte, M H; Martinez, A P; Witte, C L; Hendrix, M J; Way, D; Reed, K

1987-03-01

Lymphatic vascular endothelium both on tissue section and in culture exhibits positivity for Factor VIII-associated antigen although staining is generally less intense and more spotty than in comparable blood vascular endothelium. Lymphatic endothelium also exhibits Weibel-Palade bodies. Neither marker, therefore, reliably distinguishes blood vascular endothelium from lymphatic endothelium.
The nuclear spectroscopic telescope array (NuSTAR) high-energy X-ray mission

DEFF Research Database (Denmark)

Madsen, Kristin K.; Harrison, Fiona A.; Hongjun An

2014-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission was launched on 2012 June 13 and is the first focusing high-energy X-ray telescope in orbit operating above ~10 keV. NuSTAR flies two co-aligned Wolter-I conical approximation X-ray optics, coated with Pt/C and W/Si multilayers...

AN IMPROVED DISTANCE AND MASS ESTIMATE FOR SGR A* FROM A MULTISTAR ORBIT ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Boehle, A.; Ghez, A. M.; Meyer, L.; Yelda, S.; Albers, S.; Martinez, G. D.; Becklin, E. E.; Do, T.; Morris, M. R.; Sitarski, B.; Witzel, G. [UCLA, Department of Physics and Astronomy, Los Angeles, CA 90095 (United States); Schödel, R. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía S/N, E-18008 Granada (Spain); Lu, J. R. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Matthews, K., E-mail: aboehle@astro.ucla.edu [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, MC 301-17, Pasadena, CA 91125 (United States)

2016-10-10

We present new, more precise measurements of the mass and distance of our Galaxy’s central supermassive black hole, Sgr A*. These results stem from a new analysis that more than doubles the time baseline for astrometry of faint stars orbiting Sgr A*, combining 2 decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a star’s orbit from the deep adaptive optics data (2005–2013) to inform the search for the star in the speckle years (1995–2005). When this new analysis technique is combined with the first complete re-reduction of Keck Galactic Center speckle images using speckle holography, we are able to track the short-period star S0-38 ( K -band magnitude = 17, orbital period = 19 yr) through the speckle years. We use the kinematic measurements from speckle holography and adaptive optics to estimate the orbits of S0-38 and S0-2 and thereby improve our constraints of the mass ( M {sub bh}) and distance ( R {sub o} ) of Sgr A*: M {sub bh} = (4.02 ± 0.16 ± 0.04) × 10{sup 6} M {sub ⊙} and 7.86 ± 0.14 ± 0.04 kpc. The uncertainties in M {sub bh} and R {sub o} as determined by the combined orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5, respectively, compared to an orbital fit of S0-2 alone and a factor of ∼2.5 compared to previous results from stellar orbits. This analysis also limits the extended dark mass within 0.01 pc to less than 0.13 × 10{sup 6} M {sub ⊙} at 99.7% confidence, a factor of 3 lower compared to prior work.
Tidal disruption of stars in a supermassive black hole binary system: the influence of orbital properties on fallback and accretion rates

Science.gov (United States)

Vigneron, Quentin; Lodato, Giuseppe; Guidarelli, Alessio

2018-06-01

The disruption of a star by a supermassive black hole generates a sudden bright flare. Previous studies have focused on the disruption by single black holes, for which the fallback rate decays as ∝ t-5/3. In this paper, we generalize the study to the case of a supermassive black hole binary (SMBHB), using both analytical estimates and hydrodynamical simulations, looking for specific observable signatures. The range of binary separation for which it is possible to distinguish between the disruption created by a single or a binary black hole concerns typically separations of the order of a few milliparsecs for a primary of mass ˜106 M⊙. When the fallback rate is affected by the secondary, it undergoes two types interruptions, depending on the initial inclination θ of the orbit of the star relative to the plane of the SMBHB. For θ ≲ 70°, periodic sharp interruptions occur and the time of first interruption depends on the distance of the secondary black hole with the debris. If θ ≳ 70°, a first smooth interruption occurs, but not always followed by a further recovery of the fallback rate. This implies that most of the TDEs around a SMBHB will undergo periodic sharp interruptions of their light curve.
EVOLUTIONARY TRACKS OF THE CLIMATE OF EARTH-LIKE PLANETS AROUND DIFFERENT MASS STARS

Energy Technology Data Exchange (ETDEWEB)

Kadoya, S.; Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Faculty of Science Bldg. 1 #711, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan)

2016-07-10

The climatic evolution of the Earth depends strongly on the evolution of the insolation from the Sun and the amount of the greenhouse gasses, especially CO{sub 2} in the atmosphere. Here, we investigate the evolution of the climate of hypothetical Earths around stars whose masses are different from the solar mass with a luminosity evolution model of the stars, a mantle degassing model coupled with a parameterized convection model of the planetary interiors, and an energy balance climate model of the planetary surface. In the habitable zone (HZ), the climate of the planets is initially warm or hot, depending on the orbital semimajor axes. We found that, in the inner HZ, the climate of the planets becomes hotter with time owing to the increase in the luminosity of the central stars, while, in the outer HZ, it becomes colder and eventually globally ice-covered owing to the decrease in the CO{sub 2} degassing rate of the planets. The orbital condition for maintaining the warm climate similar to the present Earth becomes very limited, and more interestingly, the planet orbiting in the outer HZ becomes globally ice-covered after a certain critical age (∼3 Gyr for the hypothetical Earth with standard parameters), irrespective of the mass of the central star. This is because the critical age depends on the evolution of the planets and planetary factors, rather than on the stellar mass. The habitability of the Earth-like planet is shown to be limited with age even though it is orbiting within the HZ.
EVOLUTIONARY TRACKS OF THE CLIMATE OF EARTH-LIKE PLANETS AROUND DIFFERENT MASS STARS

International Nuclear Information System (INIS)

Kadoya, S.; Tajika, E.

2016-01-01

The climatic evolution of the Earth depends strongly on the evolution of the insolation from the Sun and the amount of the greenhouse gasses, especially CO_2 in the atmosphere. Here, we investigate the evolution of the climate of hypothetical Earths around stars whose masses are different from the solar mass with a luminosity evolution model of the stars, a mantle degassing model coupled with a parameterized convection model of the planetary interiors, and an energy balance climate model of the planetary surface. In the habitable zone (HZ), the climate of the planets is initially warm or hot, depending on the orbital semimajor axes. We found that, in the inner HZ, the climate of the planets becomes hotter with time owing to the increase in the luminosity of the central stars, while, in the outer HZ, it becomes colder and eventually globally ice-covered owing to the decrease in the CO_2 degassing rate of the planets. The orbital condition for maintaining the warm climate similar to the present Earth becomes very limited, and more interestingly, the planet orbiting in the outer HZ becomes globally ice-covered after a certain critical age (∼3 Gyr for the hypothetical Earth with standard parameters), irrespective of the mass of the central star. This is because the critical age depends on the evolution of the planets and planetary factors, rather than on the stellar mass. The habitability of the Earth-like planet is shown to be limited with age even though it is orbiting within the HZ.
Equilibrium states of nonsynchronous stars in detached binaries

International Nuclear Information System (INIS)

Lubow, S.H.

1979-01-01

The effects of nonsynchronous spin on equilibrium states for the radiative envelopes of detached members of close binaries are analyzed. With the adoption of the assumption that the nonsynchronous speeds, u, are much less than the relative orbital speed, Ωd, of the component stars, the full set of stellar structure equations, generalized to include the gas dynamical and heat transport effects of spin, are analyzed to linear order in u/Ωd. For these equilibria: (2) from this velocity field isobars and hence stellar shapes can be calculated for equilibrium states of slightly nonsynchronously rotating stars. On the orbit plane these surfaces coincide with the Roche equipotentials. (3) All sightly nonsynchronous equilibria are baroclinic. Isodensities and isotherms are inclined to isobars by an angle on the order of 0 0 .3 x (u/Ωd for a star in quasi-rigid rotation that nearly fills its Roche lobe). (4) The surface flux distribution departs from the usual gravity darkening law by an amount that scales with u/Ωd. Comparisons of this work are made with the results of previous investigations, and possibilities for future investigations are discussed
The nuclear spectroscopic telescope array (NuSTAR) high-energy X-ray mission

DEFF Research Database (Denmark)

Harrison, Fiona A.; Craig, William W.; Christensen, Finn Erland

2013-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 to 79 keV, extending the sensitivity of focusing far beyond the ~10 keV high-energy cutoff achieved by all previous X...
SUPERMASSIVE BLACK HOLES IN A STAR-FORMING GASEOUS CIRCUMNUCLEAR DISK

Energy Technology Data Exchange (ETDEWEB)

Del Valle, L.; Escala, A.; Molina, J. [Departamento de Astronomía, Universidad de Chile (Chile); Maureira-Fredes, C.; Amaro-Seoane, P. [Max Planck Institut fur Gravitationsphysik (Albert-Einstein-Institut), D-14476 Potsdam (Germany); Cuadra, J., E-mail: ldelvalleb@gmail.com [Instituto de Astrofísica, Pontificia Universidad Catolica de Chile (Chile)

2015-09-20

Using N-body/smoothed particle hydrodynamics simulations we study the evolution of the separation of a pair of supermassive black holes (SMBHs) embedded in a star-forming circumnuclear disk (CND). This type of disk is expected to be formed in the central kiloparsec of the remnant of gas-rich galaxy mergers. Our simulations indicate that orbital decay of the SMBHs occurs more quickly when the mean density of the CND is higher, due to increased dynamical friction. However, in simulations where the CND is fragmented in high-density gaseous clumps (clumpy CND), the orbits of the SMBHs are erratically perturbed by the gravitational interaction with these clumps, delaying, in some cases, the orbital decay of the SMBHs. The densities of these gaseous clumps in our simulations and in recent studies of clumpy CNDs are two orders of magnitude higher than the observed density of molecular clouds in isolated galaxies or ultraluminous infrared galaxies (ULIRGs), thus, we expect that SMBH orbits are perturbed less in real CNDs than in the simulated CNDs of this study and other recent studies. We also find that the migration timescale has a weak dependence on the star formation rate of the CND. Furthermore, the migration timescale of an SMBH pair in a star-forming clumpy CND is at most a factor of three longer than the migration timescale of a pair of SMBHs in a CND modeled with more simple gas physics. Therefore, we estimate that the migration timescale of the SMBHs in a clumpy CND is on the order of 10{sup 7} years.
A system of three transiting super-Earths in a cool dwarf star

Science.gov (United States)

Díez Alonso, E.; Suárez& Gómez, S. L.; González Hernández, J. I.; Suárez Mascareño, A.; González Gutiérrez, C.; Velasco, S.; Toledo-Padrón, B.; de Cos Juez, F. J.; Rebolo, R.

2018-05-01

We present the detection of three super-Earths transiting the cool star LP415-17, monitored by K2 mission in its 13th campaign. High-resolution spectra obtained with High Accuracy Radial velocity Planet Searcher-North/Telescopio Nazionale Galileo (HARPS-N/TNG) showed that the star is a mid-late K dwarf. Using spectral synthesis models, we infer its effective temperature, surface gravity, and metallicity, and subsequently determined from evolutionary models a stellar radius of 0.58 R⊙. The planets have radii of 1.8, 2.6, and 1.9 R⊕ and orbital periods of 6.34, 13.85, and 40.72 d. High-resolution images discard any significant contamination by an intervening star in the line of sight. The orbit of the furthest planet has radius of 0.18 au, close to the inner edge of the habitable zone. The system is suitable to improve our understanding of formation and dynamical evolution of super-Earth systems in the rocky-gaseous threshold, their atmospheres, internal structure, composition, and interactions with host stars.
Time Transfer Experiment by TCE on the ETS-VIII Satellite

National Research Council Canada - National Science Library

Nakagawa, Fumimaru; Takahashi, Yasuhiro; Amagai, Jun; Tabuchi, Ryo; Hama, Shin'ichi; Hosokawa, Mizuhiko

2007-01-01

.... At NICT, we developed Time Comparison Equipment (TCE) both onboard ETS-VIII and in the Earth station for precise time transfer between the atomic clocks on the satellite and a ground reference clock...
Binary stars observed with adaptive optics at the starfire optical range

Energy Technology Data Exchange (ETDEWEB)

Drummond, Jack D. [Air Force Research Laboratory, Directed Energy Directorate, RDSAM, 3550 Aberdeen Avenue SE, Kirtland AFB, NM 87117-5776 (United States)

2014-03-01

In reviewing observations taken of binary stars used as calibration objects for non-astronomical purposes with adaptive optics on the 3.5 m Starfire Optical Range telescope over the past 2 years, one-fifth of them were found to be off-orbit. In order to understand such a high number of discrepant position angles and separations, all previous observations in the Washington Double Star Catalog for these rogue binaries were obtained from the Naval Observatory. Adding our observations to these yields new orbits for all, resolving the discrepancies. We have detected both components of γ Gem for the first time, and we have shown that 7 Cam is an optical pair, not physically bound.
AN INCREASE IN THE MASS OF PLANETARY SYSTEMS AROUND LOWER-MASS STARS

International Nuclear Information System (INIS)

Mulders, Gijs D.; Pascucci, Ilaria; Apai, Dániel

2015-01-01

Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0–2.8 R ⨁ ) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8 R ⨁ ) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass–radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4 M ⨁ in F stars to 5 M ⨁ in G and K stars to 7 M ⨁ in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks—either through type-I migration or radial drift of dust grains—that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets
AN INCREASE IN THE MASS OF PLANETARY SYSTEMS AROUND LOWER-MASS STARS

Energy Technology Data Exchange (ETDEWEB)

Mulders, Gijs D.; Pascucci, Ilaria; Apai, Dániel, E-mail: mulders@lpl.arizona.edu [Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States)

2015-12-01

Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0–2.8 R{sub ⨁}) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8 R{sub ⨁}) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass–radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4 M{sub ⨁} in F stars to 5 M{sub ⨁} in G and K stars to 7 M{sub ⨁} in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks—either through type-I migration or radial drift of dust grains—that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets.
Chemical Compositions of Stars in the Globular Cluster NGC 3201: Tracers of Multi-Epoch Star Formation

Science.gov (United States)

Simmerer, Jennifer A.; Ivans, I. I.; Filler, D.

2012-01-01

The retrograde halo globular cluster NGC 3201 contains stars of substantially different iron abundance ([Fe/H]), a property that puts it at odds with the vast majority of the Galactic cluster system. Though its unusual orbit prompted speculation that NGC 3201 was the remnant of a captured object, much like the multi-metallicity globular cluster Omega Centauri, NGC 3201 is much less massive than Omega Centauri and all of the other halo globular clusters that have internal metallicity variations. We present the abundances of 21 elements in 24 red giant branch stars in NGC 3201 based on high-resolution (R 40,000), high signal-to-noise (S/N 70) spectra. We find that the detailed abundance pattern of NGC 3201 is unique amongst multi-metallicity halo clusters. Unlike M22, Omega Centauri, and NGC 1851, neither metal-poor nor metal-rich stars show any evidence of s-process enrichment (a product of the advanced evolution of low- and intermediate-mass stars). We find that while Na, O, and Al vary from star to star as is typical in globular clusters, there is no systematic difference between the abundance pattern in the metal-poor cluster stars and that of the metal-rich cluster stars. Furthermore, we find that the metallicity variations in NGC 3201 are independent of the well-known Na-O anticorrelation, which separates it from every other multi-metallicity cluster. In the context of a multi-episode star formation model, this implies that NGC 3201 began life with the [Fe/H] variations we measure now.
The first planet detected in the WTS: an inflated hot Jupiter in a 3.35 d orbit around a late F star

Science.gov (United States)

Cappetta, M.; Saglia, R. P.; Birkby, J. L.; Koppenhoefer, J.; Pinfield, D. J.; Hodgkin, S. T.; Cruz, P.; Kovács, G.; Sipőcz, B.; Barrado, D.; Nefs, B.; Pavlenko, Y. V.; Fossati, L.; del Burgo, C.; Martín, E. L.; Snellen, I.; Barnes, J.; Bayo, A.; Campbell, D. A.; Catalan, S.; Gálvez-Ortiz, M. C.; Goulding, N.; Haswell, C.; Ivanyuk, O.; Jones, H. R.; Kuznetsov, M.; Lodieu, N.; Marocco, F.; Mislis, D.; Murgas, F.; Napiwotzki, R.; Palle, E.; Pollacco, D.; Sarro Baro, L.; Solano, E.; Steele, P.; Stoev, H.; Tata, R.; Zendejas, J.

2012-12-01

We report the discovery of WTS-1b, the first extrasolar planet found by the WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom Infrared Telescope (UKIRT) in 2007 August. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ˜ 16 were constructed for ˜60 000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby-Eberly Telescope (HET) allowed us to estimate the spectroscopic parameters of the host star, a late-F main-sequence dwarf (V = 16.13) with possibly slightly subsolar metallicity, and to measure its radial velocity variations. The combined analysis of the light curves and spectroscopic data resulted in an orbital period of the substellar companion of 3.35 d, a planetary mass of 4.01 ± 0.35 MJ and a planetary radius of 1.49-0.18+0.16 RJ. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 MJ. The high irradiation from the host star ranks the planet in the pM class. Based on observations collected at the 3.8-m United Kingdom Infrared Telescope (Hawaii, USA), the Hobby-Eberly Telescope (Texas, USA), the 2.5-m Isaac Newton Telescope (La Palma, Spain), the William Herschel Telescope (La Palma, Spain), the German-Spanish Astronomical Centre (Calar Alto, Spain), the Kitt Peak National Observatory (Arizona, USA) and the Hertfordshire's Bayfordbury Observatory.
Updating the orbital ephemeris of the dipping source XB 1254-690 and the distance to the source

Science.gov (United States)

Gambino, Angelo F.; Iaria, Rosario; Di Salvo, Tiziana; Matranga, Marco; Burderi, Luciano; Pintore, Fabio; Riggio, Alessandro; Sanna, Andrea

2017-09-01

XB 1254-690 is a dipping low mass X-ray binary system hosting a neutron star and showing type I X-ray bursts. We aim at obtaining a more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply, for the first time, an orbital timing technique to XB 1254-690, using the arrival times of the dips present in the light curves that have been collected during 26 yr of X-ray pointed observations acquired from different space missions. We estimate the dip arrival times using a statistical method that weights the count-rate inside the dip with respect to the level of persistent emission outside the dip. We fit the obtained delays as a function of the orbital cycles both with a linear and a quadratic function. We infer the orbital ephemeris of XB 1254-690, improving the accuracy of the orbital period with respect to previous estimates. We infer a mass of M 2 = 0.42 ± 0.04 M ʘ for the donor star, in agreement with estimations already present in literature, assuming that the star is in thermal equilibrium while it transfers part of its mass via the inner Lagrangian point, and assuming a neutron star mass of 1.4 M ʘ. Using these assumptions, we also constrain the distance to the source, finding a value of 7.6 ± 0.8 kpc. Finally, we discuss the evolution of the system, suggesting that it is compatible with a conservative mass transfer driven by magnetic braking.
How does the Mass Transport in Disk Galaxy Models Influence the Character of Orbits?

Directory of Open Access Journals (Sweden)

Zotos Euaggelos E.

2014-12-01

Full Text Available We explore the regular or chaotic nature of orbits of stars moving in the meridional (R, z plane of an axially symmetric time-dependent disk galaxy model with a central, spherically symmetric nucleus. In particular, mass is linearly transported from the disk to the galactic nucleus, in order to mimic, in a way, the case of self-consistent interactions of an actual N-body simulation. We thus try to unveil the influence of this mass transportation on the different families of orbits of stars by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families, evolve as the galaxy develops a dense and massive nucleus in its core. The SALI method is applied to samples of orbits in order to distinguish safely between ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics is used for identifying the various families of regular orbits and also for recognizing the secondary resonances that bifurcate from them. Our computations strongly suggest that the amount of the observed chaos is substantially increased as the nucleus becomes more massive. Furthermore, extensive numerical calculations indicate that there are orbits which change their nature from regular to chaotic and vice versa and also orbits which maintain their orbital character during the galactic evolution. The present outcomes are compared to earlier related work.
VizieR Online Data Catalog: Double stars with wide separations in the AGK3 (Halbwachs+, 2016)

Science.gov (United States)

Halbwachs, J. L.; Mayor, M.; Udry, S.

2016-10-01

A large list of common proper motion stars selected from the third Astronomischen Gesellschaft Katalog (AGK3) was monitored with the CORAVEL (for COrrelation RAdial VELocities) spectrovelocimeter, in order to prepare a sample of physical binaries with very wide separations. In paper I,66 stars received special attention, since their radial velocities (RV) seemed to be variable. These stars were monitored over several years in order to derive the elements of their spectroscopic orbits. In addition, 10 of them received accurate RV measurements from the SOPHIE spectrograph of the T193 telescope at the Observatory of Haute-Provence. For deriving the orbital elements of double-lined spectroscopic binaries (SB2s), a new method was applied, which assumed that the RV of blended measurements are linear combinations of the RV of the components. 13 SB2 orbits were thus calculated. The orbital elements were eventually obtained for 52 spectroscopic binaries (SBs), two of them making a triple system. 40 SBs received their first orbit and the orbital elements were improved for 10 others. In addition, 11 SBs were discovered with very long periods for which the orbital parameters were not found. It appeared that HD 153252 has a close companion, which is a candidate brown dwarf with a minimum mass of 50 Jupiter masses. In paper II, 80 wide binaries (WBs) were detected, and 39 optical pairs were identified. Adding CPM stars with separations close enough to be almost certain they are physical, a "bias-controlled" sample of 116 wide binaries was obtained, and used to derive the distribution of separations from 100 to 30,000 au. The distribution obtained doesn't match the log-constant distribution, but is in agreement with the log-normal distribution. The spectroscopic binaries detected among the WB components were used to derive statistical informations about the multiple systems. The close binaries in WBs seem to be similar to those detected in other field stars. As for the WBs, they
Planets around the evolved stars 24 Boötis and γ Libra: A 30 d-period planet and a double giant-planet system in possible 7:3 MMR

Science.gov (United States)

Takarada, Takuya; Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Nagasawa, Makiko; Izumiura, Hideyuki; Kambe, Eiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru

2018-05-01

We report the detection of planets around two evolved giant stars from radial velocity measurements at Okayama Astrophysical observatory. 24 Boo (G3 IV) has a mass of 0.99 M_{⊙}, a radius of 10.64 R_{⊙}, and a metallicity of [Fe/H] = -0.77. The star hosts one planet with a minimum mass of 0.91 MJup and an orbital period of 30.35 d. The planet has one of the shortest orbital periods among those ever found around evolved stars using radial-velocity methods. The stellar radial velocities show additional periodicity with 150 d, which can probably be attributed to stellar activity. The star is one of the lowest-metallicity stars orbited by planets currently known. γ Lib (K0 III) is also a metal-poor giant with a mass of 1.47 M_{⊙}, a radius of 11.1 R_{⊙}, and [Fe/H] = -0.30. The star hosts two planets with minimum masses of 1.02 MJup and 4.58 MJup, and periods of 415 d and 964 d, respectively. The star has the second-lowest metallicity among the giant stars hosting more than two planets. Dynamical stability analysis for the γ Lib system sets the minimum orbital inclination angle to be about 70° and suggests that the planets are in 7:3 mean-motion resonance, though the current best-fitting orbits for the radial-velocity data are not totally regular.
RR Lyrae stars in and around NGC 6441: signatures of dissolving cluster stars

Science.gov (United States)

Kunder, Andrea

2018-06-01

Detailed elemental abundance patterns of metal-poor ([Fe/H]~ -1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of globular clusters. Here an attempt is made to identify such presumptive destroyed stars originating from the massive, inner Galaxy globular cluster NGC~6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of forty RRLs centered on the globular cluster NGC~6441. All of the 13 RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 +- 5~km/s and a star-to-star scatter of 11~km/s. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC~6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster's orbit. Therefore, either the tidal radius of NGC~6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC~6441 that are building up the old spheroidal bulge. Both the mean velocity of the cluster as well as the underlying field population is consistent with belonging to an old spheroidal bulge with low rotation and high velocity dispersion that formed before the bar.
Unravelling the role of the SW Sextantis stars in the evolution of cataclysmic variables

Science.gov (United States)

Torres, Manuel; Steeghs, Danny; Gaensicke, Boris; Marsh, Tom; Rodriguez-Gil, Pablo; Schmidtobreick, Linda; Long, Knox; Schreiber, Matthias

2007-08-01

SW Sextantis stars are a relatively large group of cataclysmic variables (CVs) whose properties contradict all predictions made by the current CV evolution theories. Very little is known about the properties of their accreting white dwarfs and their donor stars, as the stellar components are usually outshone by an extremely bright accretion flow. Consequently, a proper assesment of their evolutionary state is illusionary. We are monitoring the brightness of a number of SW Sex stars and request here Gemini/GMOS-N ToO time to obtain orbital phase-resolved spectroscopy if one of them enters a low state, since this is the only opportunity for studying the stellar components individually. These data will be used to accurately measure the mass ratio of the system which, combined with the orbital inclination derived from modelling of either the disc eclipses in the high state or the ellipsoidal modulation in the low state, will eventually provide the first detailed system parameters for any SW Sex star.

Light equation in eclipsing binary CV Boo: third body candidate in elliptical orbit

Science.gov (United States)

Bogomazov, A. I.; Kozyreva, V. S.; Satovskii, B. L.; Krushevska, V. N.; Kuznyetsova, Y. G.; Ehgamberdiev, S. A.; Karimov, R. G.; Khalikova, A. V.; Ibrahimov, M. A.; Irsmambetova, T. R.; Tutukov, A. V.

2016-12-01

A short period eclipsing binary star CV Boo is tested for the possible existence of additional bodies in the system with a help of the light equation method. We use data on the moments of minima from the literature as well as from our observations during 2014 May-July. A variation of the CV Boo's orbital period is found with a period of {≈}75 d. This variation can be explained by the influence of a third star with a mass of {≈}0.4 M_{⊙} in an eccentric orbit with e≈0.9. A possibility that the orbital period changes on long time scales is discussed. The suggested tertiary companion is near the chaotic zone around the central binary, so CV Boo represents an interesting example to test its dynamical evolution. A list of 14 minima moments of the binary obtained from our observations is presented.
The first symbiotic stars from the LAMOST survey

International Nuclear Information System (INIS)

Li, Jiao; Chen, Xue-Fei; Han, Zhan-Wen; Mikołajewska, Joanna; Luo, A-Li; Wu, Yue; Yang, Ming; Rebassa-Mansergas, Alberto; Hou, Yong-Hui; Wang, Yue-Fei; Zhang, Yong

2015-01-01

Symbiotic stars are interacting binary systems with the longest orbital periods. They are typically formed by a white dwarf and a red giant that are embedded in a nebula. These objects are natural astrophysical laboratories for studying the evolution of binaries. Current estimates of the population of symbiotic stars in the Milky Way vary from 3000 up to 400 000. However, a current census has found less than 300. The Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) survey can obtain hundreds of thousands of stellar spectra per year, providing a good opportunity to search for new symbiotic stars. We detect four such binaries among 4 147 802 spectra released by LAMOST, of which two are new identifications. The first is LAMOST J12280490–014825.7, considered to be an S-type halo symbiotic star. The second is LAMOST J202629.80+423652.0, a D-type symbiotic star. (paper)
BINARY CENTRAL STARS OF PLANETARY NEBULAE DISCOVERED THROUGH PHOTOMETRIC VARIABILITY. IV. THE CENTRAL STARS OF HaTr 4 AND Hf 2-2

Energy Technology Data Exchange (ETDEWEB)

Hillwig, Todd C.; Schaub, S. C. [Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383 (United States); Bond, Howard E. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Frew, David J. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Bodman, Eva H. L., E-mail: todd.hillwig@valpo.edu [Southeastern Association for Research in Astronomy (SARA) (United States)

2016-08-01

We explore the photometrically variable central stars of the planetary nebulae HaTr 4 and Hf 2-2. Both have been classified as close binary star systems previously based on their light curves alone. Here, we present additional arguments and data confirming the identification of both as close binaries with an irradiated cool companion to the hot central star. We include updated light curves, orbital periods, and preliminary binary modeling for both systems. We also identify for the first time the central star of HaTr 4 as an eclipsing binary. Neither system has been well studied in the past, but we utilize the small amount of existing data to limit possible binary parameters, including system inclination. These parameters are then compared to nebular parameters to further our knowledge of the relationship between binary central stars of planetary nebulae and nebular shaping and ejection.
The Substellar Companion ROXs12 B: Near-Infrared Spectrum, System Architecture, and Spin-Orbit Misalignment

Science.gov (United States)

Bowler, Brendan; Kraus, Adam L.; Bryan, Marta; Knutson, Heather; Brogi, Matteo; Rizzuto, Aaron; Mace, Gregory N.; Vanderburg, Andrew; Liu, Michael C.; Hillenbrand, Lynne; Cieza, Lucas

2018-01-01

ROXs 12 B is a substellar companion near the deuterium-burning limit orbiting a young star in Ophiuchus/Upper Scorpius. We present moderate-resolution near-infrared spectroscopy of this little-studied object, which shows clear evidence of low surface gravity and youth. Although ROXs 12 B does not possess obvious signs of a circumplanetary disk, we find that at least half of young (alignment in this system. The rotation axis of ROXs 12 A and the orbital axis of ROXs 12 B are likely misaligned, suggesting this companion formed more akin to fragmenting binary stars than planets in an equatorial disk.
NuSTAR results and future plans for magnetar and rotation‐powered pulsar observations

DEFF Research Database (Denmark)

An, H.; Kaspi, V.M.; Archibald, R.

2014-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing hard X‐ray mission in orbit and operates in the 3–79 keV range. NuSTAR's sensitivity is roughly two orders of magnitude better than previous missions in this energy band thanks to its superb angular resolution. Since its lau...
A mysterious dust clump in a disk around an evolved binary star system.

Science.gov (United States)

Jura, M; Turner, J

1998-09-10

The discovery of planets in orbit around the pulsar PSR1257+12 shows that planets may form around post-main-sequence stars. Other evolved stars, such as HD44179 (an evolved star which is part of the binary system that has expelled the gas and dust that make the Red Rectangle nebula), possess gravitationally bound orbiting dust disks. It is possible that planets might form from gravitational collapse in such disks. Here we report high-angular-resolution observations at millimetre and submillimetre wavelengths of the dusk disk associated with the Red Rectangle. We find a dust clump with an estimated mass near that of Jupiter in the outer region of the disk. The clump is larger than our Solar System, and far beyond where planet formation would normally be expected, so its nature is at present unclear.
Mechanistic aspects of Os(VIII) catalysed oxidation of loop diuretic ...

Indian Academy of Sciences (India)

furosemide by Ag(III) periodate complex in aqueous alkaline medium. SHWETA J .... Os(VIII) catalysed DPA oxidation, the order in [OH. −. ] ... Victoria-3170, Australia) connected to a rapid ..... follows. The furosemide, periodate and hydroxide ion.
Searching for stable orbits in the HD 10180 planetary system

Directory of Open Access Journals (Sweden)

Laskar J.

2011-02-01

Full Text Available A planetary system with at least seven planets has been found around the star HD 10180. However, the traditional Keplerian and n-body ﬁts to the data provide an orbital solution that becomes unstable very quickly, which may quest the reliability of the observations. Here we show that stable orbital conﬁgurations can be obtained if general relativity and long-term dissipation raised by tides on the innermost planet are taken into account.
Survival of a brown dwarf after engulfment by a red giant star.

Science.gov (United States)

Maxted, P F L; Napiwotzki, R; Dobbie, P D; Burleigh, M R

2006-08-03

Many sub-stellar companions (usually planets but also some brown dwarfs) orbit solar-type stars. These stars can engulf their sub-stellar companions when they become red giants. This interaction may explain several outstanding problems in astrophysics but it is unclear under what conditions a low mass companion will evaporate, survive the interaction unchanged or gain mass. Observational tests of models for this interaction have been hampered by a lack of positively identified remnants-that is, white dwarf stars with close, sub-stellar companions. The companion to the pre-white dwarf AA Doradus may be a brown dwarf, but the uncertain history of this star and the extreme luminosity difference between the components make it difficult to interpret the observations or to put strong constraints on the models. The magnetic white dwarf SDSS J121209.31 + 013627.7 may have a close brown dwarf companion but little is known about this binary at present. Here we report the discovery of a brown dwarf in a short period orbit around a white dwarf. The properties of both stars in this binary can be directly observed and show that the brown dwarf was engulfed by a red giant but that this had little effect on it.
3D spin-orbit angle of Kepler-25 and HAT-P-7

Directory of Open Access Journals (Sweden)

Benomar Othman

2015-01-01

Full Text Available The number of discovered exoplanets now exceeds 1500, mostly due to the Kepler space instrument observations. Many of these planet orbit in less than a week around their host stars. This implies that the inward migration of those planets is a basic ingredient of successful theories of planet formation and evolution. Several mechanisms have been proposed to explain the observed periods, which lead to different orbit eccentricity and obliquity distributions. Here we summarise and discuss the results of obliquities for two Kepler stars: HAT-P-7 and Kepler-25. These are interesting stellar systems as we could carry out a joint analysis using asteroseismology, transit lightcurve and the Rossiter-McLaughlin effect in order to measure the three dimensional obliquity.
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. V. A Massive Jupiter orbiting the very-low-metallicity giant star BD+03 2562 and a possible planet around HD 103485

Science.gov (United States)

Villaver, E.; Niedzielski, A.; Wolszczan, A.; Nowak, G.; Kowalik, K.; Adamów, M.; Maciejewski, G.; Deka-Szymankiewicz, B.; Maldonado, J.

2017-10-01

Context. Evolved stars with planets are crucial to understanding the dependency of the planet formation mechanism on the mass and metallicity of the parent star and to studying star-planet interactions. Aims: We present two evolved stars (HD 103485 and BD+03 2562) from the Tracking Advanced PlAnetary Systems (TAPAS) with HARPS-N project devoted to RV precision measurements of identified candidates within the PennState - Toruń Centre for Astronomy Planet Search. Methods: The paper is based on precise radial velocity (RV) measurements. For HD 103485 we collected 57 epochs over 3317 days with the Hobby-Eberly Telescope (HET) and its high-resolution spectrograph and 18 ultra-precise HARPS-N data over 919 days. For BD+03 2562 we collected 46 epochs of HET data over 3380 days and 19 epochs of HARPS-N data over 919 days. Results: We present the analysis of the data and the search for correlations between the RV signal and stellar activity, stellar rotation, and photometric variability. Based on the available data, we interpret the RV variations measured in both stars as Keplerian motion. Both stars have masses close to Solar (1.11 M⊙ HD 103485 and 1.14 M⊙ BD+03 2562), very low metallicities ([Fe/H] = - 0.50 and - 0.71 for HD 103485 and BD+03 2562), and both have Jupiter planetary mass companions (m2sini = 7 and 6.4 MJ for HD 103485 and BD+03 2562 resp.) in close to terrestrial orbits (1.4 au HD 103485 and 1.3 au BD+03 2562) with moderate eccentricities (e = 0.34 and 0.2 for HD 103485 and BD+03 2562). However, we cannot totally rule-out the possibility that the signal in the case of HD 103485 is due to rotational modulation of active regions. Conclusions: Based on the current data, we conclude that BD+03 2562 has a bona fide planetary companion while for HD 103485 we cannot totally exclude the possibility that the best explanation for the RV signal modulations is not the existence of a planet but stellar activity. If the interpretation remains that both stars have
DISCOVERY OF A LOW-MASS COMPANION TO A METAL-RICH F STAR WITH THE MARVELS PILOT PROJECT

International Nuclear Information System (INIS)

Fleming, Scott W.; Ge Jian; Mahadevan, Suvrath; Lee, Brian; Cuong Nguyen, Duy; Morehead, Robert C.; Wan Xiaoke; Zhao Bo; Liu Jian; Guo Pengcheng; Kane, Stephen R.; Eastman, Jason D.; Siverd, Robert J.; Scott Gaudi, B.; Niedzielski, Andrzej; Sivarani, Thirupathi; Stassun, Keivan G.; Gary, Bruce; Wolszczan, Alex; Barnes, Rory

2010-01-01

We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot project. The host star has an effective temperature T eff = 6135 ± 40 K, logg = 4.4 ± 0.1, and [Fe/H] = 0.32 ± 0.01, indicating a mass of M = 1.25 ± 0.09 M sun and R = 1.15 ± 0.15 R sun . The companion has an orbital period of 5.69449 ± 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M J , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of 'Hot Jupiters'. We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius ∼>0.8 R J at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer.
Low-mass Stars with Extreme Mid-Infrared Excesses: Potential Signatures of Planetary Collisions

Science.gov (United States)

Theissen, Christopher; West, Andrew

2018-01-01

I investigate the occurrence of extreme mid-infrared (MIR) excesses, a tracer of large amounts of dust orbiting stars, in low-mass stellar systems. Extreme MIR excesses, defined as an excess IR luminosity greater than 1% of the stellar luminosity (LIR/L* ≥ 0.01), have previously only been observed around a small number of solar-mass (M⊙) stars. The origin of this excess has been hypothesized to be massive amounts of orbiting dust, created by collisions between terrestrial planets or large planetesimals. Until recently, there was a dearth of low-mass (M* ≤ 0.6M⊙) stars exhibiting extreme MIR excesses, even though low-mass stars are ubiquitous (~70% of all stars), and known to host multiple terrestrial planets (≥ 3 planets per star).I combine the spectroscopic sample of low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 (70,841 stars) with MIR photometry from the Wide-field Infrared Survey Explorer (WISE), to locate stars exhibiting extreme MIR excesses. I find the occurrence frequency of low-mass field stars (stars with ages ≥ 1 Gyr) exhibiting extreme MIR excesses is much larger than that for higher-mass field stars (0.41 ± 0.03% versus 0.00067 ± 0.00033%, respectively).In addition, I build a larger sample of low-mass stars based on stellar colors and proper motions using SDSS, WISE, and the Two-Micron All-Sky Survey (8,735,004 stars). I also build a galactic model to simulate stellar counts and kinematics to estimate the number of stars missing from my sample. I perform a larger, more complete study of low-mass stars exhibiting extreme MIR excesses, and find a lower occurrence frequency (0.020 ± 0.001%) than found in the spectroscopic sample but that is still orders of magnitude larger than that for higher-mass stars. I find a slight trend for redder stars (lower-mass stars) to exhibit a higher occurrence frequency of extreme MIR excesses, as well as a lower frequency with increased stellar age. These samples probe important
Occurrence and core-envelope structure of 1-4x Earth-size planets around Sun-like stars

OpenAIRE

Marcy, Geoffrey W.; Weiss, Lauren M.; Petigura, Erik A.; Isaacson, Howard; Howard, Andrew W.; Buchhave, Lars A.

2014-01-01

Small planets, 1-4x the size of Earth, are extremely common around Sun-like stars, and surprisingly so, as they are missing in our solar system. Recent detections have yielded enough information about this class of exoplanets to begin characterizing their occurrence rates, orbits, masses, densities, and internal structures. The Kepler mission finds the smallest planets to be most common, as 26% of Sun-like stars have small, 1-2 R_e planets with orbital periods under 100 days, and 11% have 1-2...
Star formation history: Modeling of visual binaries

Science.gov (United States)

Gebrehiwot, Y. M.; Tessema, S. B.; Malkov, O. Yu.; Kovaleva, D. A.; Sytov, A. Yu.; Tutukov, A. V.

2018-05-01

Most stars form in binary or multiple systems. Their evolution is defined by masses of components, orbital separation and eccentricity. In order to understand star formation and evolutionary processes, it is vital to find distributions of physical parameters of binaries. We have carried out Monte Carlo simulations in which we simulate different pairing scenarios: random pairing, primary-constrained pairing, split-core pairing, and total and primary pairing in order to get distributions of binaries over physical parameters at birth. Next, for comparison with observations, we account for stellar evolution and selection effects. Brightness, radius, temperature, and other parameters of components are assigned or calculated according to approximate relations for stars in different evolutionary stages (main-sequence stars, red giants, white dwarfs, relativistic objects). Evolutionary stage is defined as a function of system age and component masses. We compare our results with the observed IMF, binarity rate, and binary mass-ratio distributions for field visual binaries to find initial distributions and pairing scenarios that produce observed distributions.
PERSEPSI SISWA KELAS VIII TENTANG KESEHATAN REPRODUKSI REMAJA DAN PENYAKIT MENULAR SEKSUAL

Directory of Open Access Journals (Sweden)

Omega Rianda Rustian

2015-06-01

This study is based on interviews conducted in one of the BK school teacher. This study aimed to determine the perception class VIII student perceptions on adolescent reproductive health and sexually transmitted diseases in SMP Islam Sultan Agung 1 Semarang. The method used in this research is descriptive quantitative survey methods. Population in this research is class VIII SMP Islam Sultan Agung 1 Semarang totaling 151 students with a sampling technique used is accidental to obtain a sample of 60. Data collection tools in the form of a psychological scale with data analysis techniques using descriptive analysis percentage. The average result of students' perceptions on adolescent reproductive health in the high category (74% and perceptions of students about sexually transmitted diseases in the very high category (76%. That class VIII SMP Islam Sultan Agung 1 Semarang already have an idea of the meaning of adolescent reproductive health is a state of good health both physically healthy, functioning, as well as reproductive performance in adolescent and the meaning of sexually transmitted diseases are caused by viruses, parasites, or function as a result of sexual intercourse.
THE LICK-CARNEGIE EXOPLANET SURVEY: A SATURN-MASS PLANET IN THE HABITABLE ZONE OF THE NEARBY M4V STAR HIP 57050

International Nuclear Information System (INIS)

Haghighipour, Nader; Vogt, Steven S.; Rivera, Eugenio J.; Laughlin, Greg; Meschiari, Stefano; Paul Butler, R.; Henry, Gregory W.

2010-01-01

Precision radial velocities (RV) from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of Msin i ∼ 0.3 M J , an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the RV variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary temperature of ∼230 K. The star has a metallicity of [Fe/H] = 0.32 ± 0.06 dex, of order twice solar and among the highest metallicity stars in the immediate solar neighborhood. This newly discovered planet provides further support that the well-known planet-metallicity correlation for F, G, and K stars also extends down into the M-dwarf regime. The a priori geometric probability for transits of this planet is only about 1%. However, the expected eclipse depth is ∼7%, considerably larger than that yet observed for any transiting planet. Though long on the odds, such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with Hubble Space Telescope. At the expected planetary effective temperature, the atmosphere may contain water clouds.
The Lick-Carnegie Exoplanet Survey: A Saturn-Mass Planet in the Habitable Zone of the Nearby M4V Star HIP 57050

Science.gov (United States)

Haghighipour, Nader; Vogt, Steven S.; Butler, R. Paul; Rivera, Eugenio J.; Laughlin, Greg; Meschiari, Stefano; Henry, Gregory W.

2010-05-01

Precision radial velocities (RV) from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of Msin i ~ 0.3 M J, an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the RV variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary temperature of ~230 K. The star has a metallicity of [Fe/H] = 0.32 ± 0.06 dex, of order twice solar and among the highest metallicity stars in the immediate solar neighborhood. This newly discovered planet provides further support that the well-known planet-metallicity correlation for F, G, and K stars also extends down into the M-dwarf regime. The a priori geometric probability for transits of this planet is only about 1%. However, the expected eclipse depth is ~7%, considerably larger than that yet observed for any transiting planet. Though long on the odds, such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with Hubble Space Telescope. At the expected planetary effective temperature, the atmosphere may contain water clouds.
NuSTAR calibration facility and multilayer reference database: Optic response model comparison to NuSTAR on-ground calibration data

DEFF Research Database (Denmark)

Brejnholt, Nicolai

. To couple the as-coated multilayer to the actual optics, ray tracing is carried out in a detailed geometric model of the optic, including in-situ measured figure error for the mounted substrates. The effective area as a function of energy estimated from ray tracing is compared to NuSTAR on......The Nuclear Spectroscopic Telescope ARray (NuSTAR) is a NASA Small Explorer mission carrying the first focusing hard X-ray telescope (5 − 80 keV ) to orbit. NuSTAR is slated for launch in 2012. Through a leap in sensitivity, the realization of focusing optics holds promise of heralding in a golden...... the optic response for both on- and off-axis NuSTAR observations, detailed knowledge of the as-coated multilayer is required. The purpose of this thesis is to establish a multilayer reference database. As an integral part of this effort, a hard X-ray calibration facility was designed and constructed. Each...
A SEARCH FOR ASTEROIDS, MOONS, AND RINGS ORBITING WHITE DWARFS

International Nuclear Information System (INIS)

Di Stefano, Rosanne; Howell, Steve B.; Kawaler, Steven D.

2010-01-01

Do white dwarfs host asteroid systems? Although several lines of argument suggest that white dwarfs may be orbited by large populations of asteroids, transits would provide the most direct evidence. We demonstrate that the Kepler mission has the capability to detect transits of white dwarfs by asteroids. Because white-dwarf asteroid systems, if they exist, are likely to contain many asteroids orbiting in a spatially extended distribution, discoveries of asteroid transits can be made by monitoring only a small number of white dwarfs, compatible with Kepler's primary mission, which is to monitor stars with potentially habitable planets. Possible future missions that survey 10 times as many stars with similar sensitivity and minute-cadence monitoring can establish the characteristics of asteroid systems around white dwarfs, such as the distribution of asteroid sizes and semimajor axes. Transits by planets would be more dramatic, but the probability that they will occur is lower. Ensembles of planetary moons and/or the presence of rings around planets can also produce transits detectable by Kepler. The presence of moons and rings can significantly increase the probability that Kepler will discover planets orbiting white dwarfs, even while monitoring only a small number of them.

HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2

Science.gov (United States)

Van Eylen, V.; Dai, F.; Mathur, S.; Gandolfi, D.; Albrecht, S.; Fridlund, M.; García, R. A.; Guenther, E.; Hjorth, M.; Justesen, A. B.; Livingston, J.; Lund, M. N.; Pérez Hernández, F.; Prieto-Arranz, J.; Regulo, C.; Bugnet, L.; Everett, M. E.; Hirano, T.; Nespral, D.; Nowak, G.; Palle, E.; Silva Aguirre, V.; Trifonov, T.; Winn, J. N.; Barragán, O.; Beck, P. G.; Chaplin, W. J.; Cochran, W. D.; Csizmadia, S.; Deeg, H.; Endl, M.; Heeren, P.; Grziwa, S.; Hatzes, A. P.; Hidalgo, D.; Korth, J.; Mathis, S.; Montañes Rodriguez, P.; Narita, N.; Patzold, M.; Persson, C. M.; Rodler, F.; Smith, A. M. S.

2018-05-01

We report the discovery and characterization of HD 89345b (K2-234b; EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved star. HD 89345 is a bright star (V = 9.3 mag) observed by the K2 mission with one-minute time sampling. It exhibits solar-like oscillations. We conducted asteroseismology to determine the parameters of the star, finding the mass and radius to be 1.12^{+0.04}_{-0.01} M_⊙ and 1.657^{+0.020}_{-0.004} R_⊙, respectively. The star appears to have recently left the main sequence, based on the inferred age, 9.4^{+0.4}_{-1.3} Gyr, and the non-detection of mixed modes. The star hosts a "warm Saturn" (P = 11.8 days, Rp = 6.86 ± 0.14 R⊕). Radial-velocity follow-up observations performed with the FIES, HARPS, and HARPS-N spectrographs show that the planet has a mass of 35.7 ± 3.3 M⊕. The data also show that the planet's orbit is eccentric (e ≈ 0.2). An investigation of the rotational splitting of the oscillation frequencies of the star yields no conclusive evidence on the stellar inclination angle. We further obtained Rossiter-McLaughlin observations, which result in a broad posterior of the stellar obliquity. The planet seems to conform to the same patterns that have been observed for other sub-Saturns regarding planet mass and multiplicity, orbital eccentricity, and stellar metallicity.
Globular Clusters: Absolute Proper Motions and Galactic Orbits

Science.gov (United States)

Chemel, A. A.; Glushkova, E. V.; Dambis, A. K.; Rastorguev, A. S.; Yalyalieva, L. N.; Klinichev, A. D.

2018-04-01

We cross-match objects from several different astronomical catalogs to determine the absolute proper motions of stars within the 30-arcmin radius fields of 115 Milky-Way globular clusters with the accuracy of 1-2 mas yr-1. The proper motions are based on positional data recovered from the USNO-B1, 2MASS, URAT1, ALLWISE, UCAC5, and Gaia DR1 surveys with up to ten positions spanning an epoch difference of up to about 65 years, and reduced to Gaia DR1 TGAS frame using UCAC5 as the reference catalog. Cluster members are photometrically identified by selecting horizontal- and red-giant branch stars on color-magnitude diagrams, and the mean absolute proper motions of the clusters with a typical formal error of about 0.4 mas yr-1 are computed by averaging the proper motions of selected members. The inferred absolute proper motions of clusters are combined with available radial-velocity data and heliocentric distance estimates to compute the cluster orbits in terms of the Galactic potential models based on Miyamoto and Nagai disk, Hernquist spheroid, and modified isothermal dark-matter halo (axisymmetric model without a bar) and the same model + rotating Ferre's bar (non-axisymmetric). Five distant clusters have higher-than-escape velocities, most likely due to large errors of computed transversal velocities, whereas the computed orbits of all other clusters remain bound to the Galaxy. Unlike previously published results, we find the bar to affect substantially the orbits of most of the clusters, even those at large Galactocentric distances, bringing appreciable chaotization, especially in the portions of the orbits close to the Galactic center, and stretching out the orbits of some of the thick-disk clusters.
Assessing magnetic torques and energy fluxes in close-in star-planet systems

OpenAIRE

Strugarek, A

2016-01-01

Planets in close-in orbit interact with the magnetized wind of their hosting star. This magnetic interaction was proposed to be a source for enhanced emissions in the chromosphere of the star, and to participate in setting the migration time-scale of the close-in planet. The efficiency of the magnetic interaction is know to depend on the magnetic properties of the host star, of the planet, and on the magnetic topology of the interaction. We use a global, three-dimensional numerical model of c...
THE NASA-UC ETA-EARTH PROGRAM. III. A SUPER-EARTH ORBITING HD 97658 AND A NEPTUNE-MASS PLANET ORBITING Gl 785

International Nuclear Information System (INIS)

Howard, Andrew W.; Marcy, Geoffrey W.; Isaacson, Howard; Johnson, John Asher; Fischer, Debra A.; Wright, Jason T.; Henry, Gregory W.; Valenti, Jeff A.; Anderson, Jay; Piskunov, Nikolai E.

2011-01-01

We report the discovery of planets orbiting two bright, nearby early K dwarf stars, HD 97658 and Gl 785. These planets were detected by Keplerian modeling of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey. HD 97658 b is a close-in super-Earth with minimum mass Msin i = 8.2 ± 1.2 M + , orbital period P = 9.494 ± 0.005 days, and an orbit that is consistent with circular. Gl 785 b is a Neptune-mass planet with Msin i = 21.6 ± 2.0 M + , P = 74.39 ± 0.12 days, and orbital eccentricity e = 0.30 ± 0.09. Photometric observations with the T12 0.8 m automatic photometric telescope at Fairborn Observatory show that HD 97658 is photometrically constant at the radial velocity period to 0.09 mmag, supporting the existence of the planet.
Factor VIII levels and the risk of pre-eclampsia, HELLP syndrome, pregnancy related hypertension and severe intrauterine growth retardation.

Science.gov (United States)

Witsenburg, C P J; Rosendaal, F R; Middeldorp, J M; Van der Meer, F J M; Scherjon, S A

2005-01-01

Recently, acquired as well as genetic prothrombotic factors are associated with thrombotic events. These factors have also been related to conditions of uteroplacental insufficiency such as pre-eclampsia, HELLP syndrome and severe intrauterine growth restriction (IUGR). The aim of this study was to determine whether elevated factor VIII levels are associated with uteroplacental insufficiency, in particular pre-eclampsia, HELLP syndrome or pregnancy-induced hypertension and intrauterine growth retardation. Plasma samples of 75 women with a history of pregnancy complicated by pre-eclampsia, HELLP syndrome, pregnancy induced hypertension or intrauterine growth restriction were tested for factor VIII:C (FVIII:C) levels at a minimum of 10 weeks post-partum. Laboratory results were compared to factor VIII:C levels found in a healthy control group of 272 women. Mean factor VIII:C levels were similar at 123 IU/dl in both the patient group and the controls. In a logistic regression model, after adjusting for age and blood group, no effect of factor VIII:C levels on the risk of pregnancy complications was observed, with the exception of IUGR with (OR 2.9, CI 1.0-8.7) or without hypertension (OR 2.0, CI 0.7-6.4). If the elevated level of factor VIII would be the sole factor responsible for the increased risk observed, one would expect to find an effect of blood group on risk as well (blood group being an important determinant of FVIII:C). While no such effect could be shown a causal relationship between elevated levels of factor VIII and conditions of uteroplacental insufficiency such as pre-eclampsia, HELLP syndrome, pregnancy-induced hypertension and IUGR is not very likely.
The Masses and Evolutionary State of the Stars in the Dwarf Nova SS Cygni

Science.gov (United States)

Bitner, Martin A.; Robinson, Edward L.; Behr, Bradford B.

2007-06-01

The dwarf nova SS Cygni is a close binary star consisting of a K star transferring mass to a white dwarf by way of an accretion disk. We have obtained new spectroscopic observations of SS Cyg. Fits of synthetic spectra for Roche lobe-filling stars to the absorption-line spectrum of the K star yield the amplitude of the K star's radial velocity curve and the mass ratio, KK=162.5+/-1.0 km s-1 and q=MK/MWD=0.685+/-0.015. The fits also show that the accretion disk and white dwarf contribute a fraction f=0.535+/-0.075 of the total flux at 5500 Å. Taking the weighted average of our results with previously published results obtained using similar techniques, we find =163.7+/-0.7 km s-1 and =0.683+/-0.012. The orbital light curve of SS Cyg shows an ellipsoidal variation diluted by light from the disk and white dwarf. From an analysis of the ellipsoidal variations, we limit the orbital inclination to the range 45degAustin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.
Effective Induction Heating around Strongly Magnetized Stars

Science.gov (United States)

Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.; Noack, L.; Lüftinger, T.; Zaitsev, V. V.; Lammer, H.

2018-05-01

Planets that are embedded in the changing magnetic fields of their host stars can experience significant induction heating in their interiors caused by the planet’s orbital motion. For induction heating to be substantial, the planetary orbit has to be inclined with respect to the stellar rotation and dipole axes. Using WX UMa, for which the rotation and magnetic axes are aligned, as an example, we show that for close-in planets on inclined orbits, induction heating can be stronger than the tidal heating occurring inside Jupiter’s satellite Io; namely, it can generate a surface heat flux exceeding 2 W m‑2. An internal heating source of such magnitude can lead to extreme volcanic activity on the planet’s surface, possibly also to internal local magma oceans, and to the formation of a plasma torus around the star aligned with the planetary orbit. A strongly volcanically active planet would eject into space mostly SO2, which would then dissociate into oxygen and sulphur atoms. Young planets would also eject CO2. Oxygen would therefore be the major component of the torus. If the O I column density of the torus exceeds ≈1012 cm‑2, the torus could be revealed by detecting absorption signatures at the position of the strong far-ultraviolet O I triplet at about 1304 Å. We estimate that this condition is satisfied if the O I atoms in the torus escape the system at a velocity smaller than 1–10 km s‑1. These estimates are valid also for a tidally heated planet.
AN APPARENT PRECESSING HELICAL OUTFLOW FROM A MASSIVE EVOLVED STAR: EVIDENCE FOR BINARY INTERACTION

Energy Technology Data Exchange (ETDEWEB)

Lau, R. M.; Hankins, M. J.; Herter, T. L. [Astronomy Department, Cornell University, Ithaca, NY 14853-6801 (United States); Morris, M. R. [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Mills, E. A. C. [National Radio Astronomy Observatory, P.O. Box O 1009, Lopezville Drive, Socorro, NM 87801 (United States); Ressler, M. E. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2016-02-20

Massive, evolved stars play a crucial role in the metal enrichment, dust budget, and energetics of the interstellar medium; however, the details of their evolution are uncertain because of their rarity and short lifetimes before exploding as supernovae. Discrepancies between theoretical predictions from single-star evolutionary models and observations of massive stars have evoked a shifting paradigm that implicates the importance of binary interaction. We present mid- to far-infrared observations from the Stratospheric Observatory for Infrared Astronomy of a conical “helix” of warm dust (∼180 K) that appears to extend from the Wolf–Rayet star WR102c. Our interpretation of the helix is a precessing, collimated outflow that emerged from WR102c during a previous evolutionary phase as a rapidly rotating luminous blue variable. We attribute the precession of WR102c to gravitational interactions with an unseen compact binary companion whose orbital period can be constrained to 800 days < P < 1400 days from the inferred precession period, τ{sub p} ∼ 1.4 × 10{sup 4} yr, and limits imposed on the stellar and orbital parameters of the system. Our results concur with the range of orbital periods (P ≲ 1500 days) where spin-up via mass exchange is expected to occur for massive binary systems.
Orbiting binary black hole evolutions with a multipatch high order finite-difference approach

International Nuclear Information System (INIS)

Pazos, Enrique; Tiglio, Manuel; Duez, Matthew D.; Kidder, Lawrence E.; Teukolsky, Saul A.

2009-01-01

We present numerical simulations of orbiting black holes for around 12 cycles, using a high order multipatch approach. Unlike some other approaches, the computational speed scales almost perfectly for thousands of processors. Multipatch methods are an alternative to adaptive mesh refinement, with benefits of simplicity and better scaling for improving the resolution in the wave zone. The results presented here pave the way for multipatch evolutions of black hole-neutron star and neutron star-neutron star binaries, where high resolution grids are needed to resolve details of the matter flow.
Testing General Relativity with Stellar Orbits around the Supermassive Black Hole in Our Galactic Center.

Science.gov (United States)

Hees, A; Do, T; Ghez, A M; Martinez, G D; Naoz, S; Becklin, E E; Boehle, A; Chappell, S; Chu, D; Dehghanfar, A; Kosmo, K; Lu, J R; Matthews, K; Morris, M R; Sakai, S; Schödel, R; Witzel, G

2017-05-26

We demonstrate that short-period stars orbiting around the supermassive black hole in our Galactic center can successfully be used to probe the gravitational theory in a strong regime. We use 19 years of observations of the two best measured short-period stars orbiting our Galactic center to constrain a hypothetical fifth force that arises in various scenarios motivated by the development of a unification theory or in some models of dark matter and dark energy. No deviation from general relativity is reported and the fifth force strength is restricted to an upper 95% confidence limit of |α|<0.016 at a length scale of λ=150 astronomical units. We also derive a 95% confidence upper limit on a linear drift of the argument of periastron of the short-period star S0-2 of |ω[over ˙]_{S0-2}|<1.6×10^{-3} rad/yr, which can be used to constrain various gravitational and astrophysical theories. This analysis provides the first fully self-consistent test of the gravitational theory using orbital dynamic in a strong gravitational regime, that of a supermassive black hole. A sensitivity analysis for future measurements is also presented.
Neutron stars as probes of extreme energy density matter

Indian Academy of Sciences (India)

2015-05-07

May 7, 2015 ... and the orbital period decay due to the emission of gravitational radiation. ˙P = −. 192π ... masses severely restrict the EoS of neutron star matter. Masses ..... (9) Is unstable burning of carbon (C) the real cause of superbursts?
Galactic Doppelgängers: The Chemical Similarity Among Field Stars and Among Stars with a Common Birth Origin

Science.gov (United States)

Ness, M.; Rix, H.-W.; Hogg, David W.; Casey, A. R.; Holtzman, J.; Fouesneau, M.; Zasowski, G.; Geisler, D.; Shetrone, M.; Minniti, D.; Frinchaboy, Peter M.; Roman-Lopes, Alexandre

2018-02-01

We explore to what extent stars within Galactic disk open clusters resemble each other in the high-dimensional space of their photospheric element abundances and contrast this with pairs of field stars. Our analysis is based on abundances for 20 elements, homogeneously derived from APOGEE spectra (with carefully quantified uncertainties of typically 0.03 dex). We consider 90 red giant stars in seven open clusters and find that most stars within a cluster have abundances in most elements that are indistinguishable (in a {χ }2-sense) from those of the other members, as expected for stellar birth siblings. An analogous analysis among pairs of > 1000 field stars shows that highly significant abundance differences in the 20 dimensional space can be established for the vast majority of these pairs, and that the APOGEE-based abundance measurements have high discriminating power. However, pairs of field stars whose abundances are indistinguishable even at 0.03 dex precision exist: ∼0.3% of all field star pairs and ∼1.0% of field star pairs at the same (solar) metallicity [Fe/H] = 0 ± 0.02. Most of these pairs are presumably not birth siblings from the same cluster, but rather doppelgängers. Our analysis implies that “chemical tagging” in the strict sense, identifying birth siblings for typical disk stars through their abundance similarity alone, will not work with such data. However, our approach shows that abundances have extremely valuable information for probabilistic chemo-orbital modeling, and combined with velocities, we have identified new cluster members from the field.
On the Post-Keplerian Corrections to the Orbital Periods of a Two-body System and Their Application to the Galactic Center

Energy Technology Data Exchange (ETDEWEB)

Iorio, Lorenzo [Ministero dell’Istruzione, dell’Università e della Ricerca (M.I.U.R.)-Istruzione (Italy); Zhang, Fupeng, E-mail: lorenzo.iorio@libero.it, E-mail: zhangfp7@mail.sysu.edu.cn [School of Physics and Astronomy, Sun Yat-Sen University, Guangzhou 510275 (China)

2017-04-10

We perform detailed numerical analyses of the orbital motion of a test particle around a spinning primary, with the aim of investigating the possibility of using the post-Keplerian (pK) corrections to the orbiter’s periods (draconitic, anomalistic, and sidereal) as a further opportunity to perform new tests of post-Newtonian gravity. As a specific scenario, the S-stars orbiting the massive black hole (MBH) supposedly lurking in Sgr A* at the center of the Galaxy are adopted. We first study the effects of the pK Schwarzchild, Lense–Thirring, and quadrupole moment accelerations experienced by a target star for various possible initial orbital configurations. It turns out that the results of the numerical simulations are consistent with the analytical ones in the small eccentricity approximation for which almost all the latter ones were derived. For highly elliptical orbits, the sizes of the three pK corrections considered turn out to increase remarkably. The periods of the observed S2 and S0-102 stars as functions of the MBH’s spin axis orientation are considered as well. The pK accelerations lead to corrections of the orbital periods of the order of 1–100 days (Schwarzschild), 0.1–10 hr (Lense–Thirring), and 1–10{sup 3} s (quadrupole) for a target star with a = 300–800 au and e ≈ 0.8, which could be measurable with future facilities.
Two Earth-sized planets orbiting Kepler-20.

Science.gov (United States)

Fressin, Francois; Torres, Guillermo; Rowe, Jason F; Charbonneau, David; Rogers, Leslie A; Ballard, Sarah; Batalha, Natalie M; Borucki, William J; Bryson, Stephen T; Buchhave, Lars A; Ciardi, David R; Désert, Jean-Michel; Dressing, Courtney D; Fabrycky, Daniel C; Ford, Eric B; Gautier, Thomas N; Henze, Christopher E; Holman, Matthew J; Howard, Andrew; Howell, Steve B; Jenkins, Jon M; Koch, David G; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Quinn, Samuel N; Ragozzine, Darin; Sasselov, Dimitar D; Seager, Sara; Barclay, Thomas; Mullally, Fergal; Seader, Shawn E; Still, Martin; Twicken, Joseph D; Thompson, Susan E; Uddin, Kamal

2011-12-20

Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R(⊕)), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R(⊕)) and the other smaller than the Earth (0.87R(⊕)), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.
Class VIII Medical Materiel Controls in the U.S. European Command

National Research Council Canada - National Science Library

1991-01-01

.... Class VIII medical materiel inventories are maintained as part of the U.S. war reserve stocks to ensure military readiness and to provide needed health care during wartime or contingencies. The U.S...
VLBA Changes Picture of Famous Star-Forming Region

Science.gov (United States)

2007-10-01

Using the supersharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), astronomers have made the most precise measurement ever of the distance to a famous star-forming region. The measurement -- to the heavily studied Orion Nebula -- changes scientists' understanding of the characteristics of the young stars in the region. Parallax Diagram Trigonometric Parallax method determines distance to star by measuring its slight shift in apparent position as seen from opposite ends of Earth's orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF Star Track Apparent track of star GMR A in the Orion Nebula Cluster, showing shift caused by Earth's orbital motion and star's movement in space. CREDIT: Sandstrom et al., NRAO/AUI/NSF Click on Images for Larger Files "This measurement is four times more precise than previous distance estimates. Because our measurement reduces the distance to this region, it tells us that the stars there are less bright than thought before, and changes the estimates of their ages," said Geoff Bower, an astronomer at the University of California at Berkeley. Bower, along with Karin Sandstrom, J.E.G. Peek, Alberto Bolatto and Richard Plambeck, all of Berkeley, published their findings in the October 10 edition of the Astrophysical Journal. The scientists determined the distance to a star called GMR A, one of a cluster of stars in the Orion Nebula, by measuring the slight shift in the star's apparent position in the sky caused by the Earth's motion around the Sun. Observing the star when the Earth is on opposite sides of its annual orbit allows astronomers to measure the angle of this small shift and thus provides a direct trigonometric calculation of its distance. "By using this technique, called parallax, we get a direct measurement that does not depend on various assumptions that are required to use less-direct methods," Bower said. "Only a telescope with the remarkable ability to see fine detail that is provided by the VLBA is
PALFA Discovers Neutron Stars on a Collision Course

Science.gov (United States)

Kohler, Susanna

2018-03-01

Got any plans in 46 million years? If not, you should keep an eye out for PSR J1946+2052 around that time this upcoming merger of two neutron stars promises to be an exciting show!Survey SuccessAverage profile for PSR J1946+2052 at 1.43 GHz from a 2 hr observation from the Arecibo Observatory. [Stovall et al. 2018]It seems like we just wrote about the dearth of known double-neutron-star systems, and about how new surveys are doing their best to find more of these compact binaries. Observing these systems improves our knowledge of how pairs of evolved stars behave before they eventually spiral in, merge, and emit gravitational waves that detectors like the Laser Interferometer Gravitational-wave Observatory might observe.Todays study, led by Kevin Stovall (National Radio Astronomy Observatory), goes to show that these surveys are doing a great job so far! Yet another double-neutron-star binary, PSR J1946+2052, has now been discovered as part of the Arecibo L-Band Feed Array pulsar (PALFA) survey. This one is especially unique due to the incredible speed with which these neutron stars orbit each other and their correspondingly (relatively!) short timescale for merger.An Extreme ExampleThe PALFA survey, conducted with the enormous 305-meter radio dish at Arecibo, has thus far resulted in the discovery of 180 pulsars including two double-neutron-star systems. The most recent discovery by Stovall and collaborators brings that number up to three, for a grand total of 16 binary-neutron-star systems (confirmed and unconfirmed) known to date.The 305-m Arecibo Radio Telescope, built into the landscape at Arecibo, Puerto Rico. [NOAO/AURA/NSF/H. Schweiker/WIYN]The newest binary in this collection, PSR J1946+2052, exhibits a pulsar with a 17-millisecond spin period thatwhips around its compact companion at a terrifying rate: the binary period is just 1.88 hours. Follow-up observations with the Jansky Very Large Array and other telescopes allowed the team to identify the binarys
Construction of a mouse model of factor VIII deficiency by gene targeting

Energy Technology Data Exchange (ETDEWEB)

Bi, L.; Lawler, A.; Gearhart, J. [Univ. of Pennsylvania School of Medicine, Philadelphia, PA (United States)] [and others

1994-09-01

To develop a small animal model of hemophilia A for gene therapy experiments, we set out to construct a mouse model for factor VIII deficiency by gene targeting. First, we screened a mouse liver cDNA library using a human FVIII cDNA probe. We cloned a 2.6 Kb partial mouse factor VIII cDNA which extends from 800 base pairs of the 3{prime} end of exon 14 to the 5{prime} end of exon 26. A mouse genomic library made from strain 129 was then screened to obtain genomic fragments covering the exons desired for homologous recombination. Two genomic clones were obtained, and one covering exon 15 through 22 was used for gene targeting. To make gene targeting constructs, a 5.8 Kb genomic DNA fragment covering exons 15 to 19 of the mouse FVIII gene was subcloned, and the neo expression cassette was inserted into exons 16 and 17 separately by different strategies. These two constructs were named MFVIIIC-16 and MFVIIIC-17. The constructs were linearized and transfected into strain 129 mouse ES cells by electroporation. Factor VIII gene-knockout ES cell lines were selected by G-418 and screened by genomic Southern blots. Eight exon 16 targeted cell lines and five exon 17 targeted cell lines were obtained. Three cell lines from each construct were injected into blastocysts and surgically transferred into foster mothers. Multiple chimeric mice with 70-90% hair color derived from the ES-cell genotype were seen with both constructs. Germ line transmission of the ES-cell genotype has been obtained for the MFVIIIC-16 construct, and multiple hemophilia A carrier females have been identified. Factor VIII-deficient males will be conceived soon.
FRIENDS OF HOT JUPITERS. II. NO CORRESPONDENCE BETWEEN HOT-JUPITER SPIN-ORBIT MISALIGNMENT AND THE INCIDENCE OF DIRECTLY IMAGED STELLAR COMPANIONS

Energy Technology Data Exchange (ETDEWEB)

Ngo, Henry; Knutson, Heather A.; Hinkley, Sasha; Batygin, Konstantin [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA (United States); Crepp, Justin R.; Bechter, Eric B. [Department of Physics, University of Notre Dame, Notre Dame, IN (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI (United States); Johnson, John A. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Morton, Timothy D. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA (United States); Muirhead, Philip S., E-mail: hngo@caltech.edu [Department of Astronomy, Boston University, Boston, MA (United States)

2015-02-20

Multi-star systems are common, yet little is known about a stellar companion's influence on the formation and evolution of planetary systems. For instance, stellar companions may have facilitated the inward migration of hot Jupiters toward to their present day positions. Many observed short-period gas giant planets also have orbits that are misaligned with respect to their star's spin axis, which has also been attributed to the presence of a massive outer companion on a non-coplanar orbit. We present the results of a multi-band direct imaging survey using Keck NIRC2 to measure the fraction of short-period gas giant planets found in multi-star systems. Over three years, we completed a survey of 50 targets ('Friends of Hot Jupiters') with 27 targets showing some signature of multi-body interaction (misaligned or eccentric orbits) and 23 targets in a control sample (well-aligned and circular orbits). We report the masses, projected separations, and confirmed common proper motion for the 19 stellar companions found around 17 stars. Correcting for survey incompleteness, we report companion fractions of 48% ± 9%, 47% ± 12%, and 51% ± 13% in our total, misaligned/eccentric, and control samples, respectively. This total stellar companion fraction is 2.8σ larger than the fraction of field stars with companions approximately 50-2000 AU. We observe no correlation between misaligned/eccentric hot Jupiter systems and the incidence of stellar companions. Combining this result with our previous radial velocity survey, we determine that 72% ± 16% of hot Jupiters are part of multi-planet and/or multi-star systems.
Star tracker operation in a high density proton field

Science.gov (United States)

Miklus, Kenneth J.; Kissh, Frank; Flynn, David J.

1993-01-01

Algorithms that reject transient signals due to proton effects on charge coupled device (CCD) sensors have been implemented in the HDOS ASTRA-l Star Trackers to be flown on the TOPEX mission scheduled for launch in July 1992. A unique technique for simulating a proton-rich environment to test trackers is described, as well as the test results obtained. Solar flares or an orbit that passes through the South Atlantic Anomaly can subject the vehicle to very high proton flux levels. There are three ways in which spurious proton generated signals can impact tracker performance: the many false signals can prevent or extend the time to acquire a star; a proton-generated signal can compromise the accuracy of the star's reported magnitude and position; and the tracked star can be lost, requiring reacquisition. Tests simulating a proton-rich environment were performed on two ASTRA-1 Star Trackers utilizing these new algorithms. There were no false acquisitions, no lost stars, and a significant reduction in reported position errors due to these improvements.

Gravitational waves from a spinning particle scattered by a relativistic star: Axial mode case

International Nuclear Information System (INIS)

Tominaga, Kazuhiro; Saijo, Motoyuki; Maeda, Kei-ichi

2001-01-01

We use a perturbation method to study gravitational waves from a spinning test particle scattered by a relativistic star. The present analysis is restricted to axial modes. By calculating the energy spectrum, the wave forms, and the total energy and angular momentum of gravitational waves, we analyze the dependence of the emitted gravitational waves on particle spin. For a normal neutron star, the energy spectrum has one broad peak whose characteristic frequency corresponds to the angular velocity at the turning point (a periastron). Since the turning point is determined by the orbital parameter, there exists a dependence of the gravitational wave on particle spin. We find that the total energy of l=2 gravitational waves gets larger as the spin increases in the antiparallel direction to the orbital angular momentum. For an ultracompact star, in addition to such an orbital contribution, we find the quasinormal modes excited by a scattered particle, whose excitation rate to gravitational waves depends on the particle spin. We also discuss the ratio of the total angular momentum to the total energy of gravitational waves and explain its spin dependence
Rotation of the Mass Donors in High-mass X-ray Binaries and Symbiotic Stars

Directory of Open Access Journals (Sweden)

K. Stoyanov

2015-02-01

Full Text Available Our aim is to investigate the tidal interaction in High-mass X-ray Binaries and Symbiotic stars in order to determine in which objects the rotation of the mass donors is synchronized or pseudosynchronized with the orbital motion of the compact companion. We find that the Be/X-ray binaries are not synchronized and the orbital periods of the systems are greater than the rotational periods of the mass donors. The giant and supergiant High-mass X-ray binaries and symbiotic stars are close to synchronization. We compare the rotation of mass donors in symbiotics with the projected rotational velocities of field giants and find that the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. We find that the projected rotational velocity of the red giant in symbiotic star MWC 560 is v sin i= 8.2±1.5 km.s−1, and estimate its rotational period to be Prot<>/sub = 144 - 306 days. Using the theoretical predictions of tidal interaction and pseudosynchronization, we estimate the orbital eccentricity e = 0.68 − 0.82.
THREE PLANETS ORBITING WOLF 1061

Energy Technology Data Exchange (ETDEWEB)

Wright, D. J.; Wittenmyer, R. A.; Tinney, C. G.; Bentley, J. S.; Zhao, Jinglin, E-mail: duncan.wright@unsw.edu.au [Department of Astronomy and Australian Centre for Astrobiology, School of Physics, University of New South Wales, NSW 2052 (Australia)

2016-02-01

We use archival HARPS spectra to detect three planets orbiting the M3 dwarf Wolf 1061 (GJ 628). We detect a 1.36 M{sub ⊕} minimum-mass planet with an orbital period P = 4.888 days (Wolf 1061b), a 4.25 M{sub ⊕} minimum-mass planet with orbital period P = 17.867 days (Wolf 1061c), and a likely 5.21 M{sub ⊕} minimum-mass planet with orbital period P = 67.274 days (Wolf 1061d). All of the planets are of sufficiently low mass that they may be rocky in nature. The 17.867 day planet falls within the habitable zone for Wolf 1061 and the 67.274 day planet falls just outside the outer boundary of the habitable zone. There are no signs of activity observed in the bisector spans, cross-correlation FWHMs, calcium H and K indices, NaD indices, or Hα indices near the planetary periods. We use custom methods to generate a cross-correlation template tailored to the star. The resulting velocities do not suffer the strong annual variation observed in the HARPS DRS velocities. This differential technique should deliver better exploitation of the archival HARPS data for the detection of planets at extremely low amplitudes.
Star Formation at the Galactic Center

Science.gov (United States)

Kohler, Susanna

2015-08-01

Could stars be forming in the inhospitable environment near Sagittarius A* in the heart of the Milky Way? A possible signature of low-mass star formation has recently been found just two light-years from the black hole at the center of our galaxy — a region that was previously thought to be too hostile for such activity. Searching for Signatures: Previous observations of the central few light-years of the Milky Way had focused on a population of about 200 massive, young and very bright stars in tight orbits around Sgr A*. These stars are only a few million years old and prompted scientists to wonder: have they somehow managed to form in situ, in spite of their close proximity to the black hole, or did they form further out and then migrate in? Motivated by this mystery, Farhad Yusef-Zadeh of Northwestern University and collaborators looked for evidence of even younger stars close to Sagittarius A*, which would demonstrate that star formation in the area is an ongoing process. Using the Very Large Array (VLA), the collaboration discovered several small sources in one arm of activity near Sgr A*. This 34-GHz image provides a close-up view of two protoplanetary disk candidates (labeled P26 and P8) located near Sgr A*. These objects are outlined on the right side by a bow shock caused by impacting stellar wind that streams from the young, hot stars closer to the Galactic center. The disks are thought to contain recently-formed, low-mass stars. (Credit: Yusef-Zadeh et al., 2015) Heated Disks: The team identified these sources as candidate photoevaporative protoplanetary disks, or “proplyds” — areas of dense, ionized gas and dust surrounding young, newly formed stars. The proplyd candidates are between 10,000 and 100,000 years old, and they lie along the edge of a large molecular cloud. It is likely that this cloud produced the disks by providing a reservoir of gas to feed the star-formation activity. The region surrounding these proplyds is blasted with harsh
Kepler Mission: A Wide-FOV Photometer Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-like stars

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Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Jenkins, Jon M.; Caldwell, Douglas;

2002-01-01

The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 m aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

RELATIONSHIP OF INTEREST, LEARNING MOTIVATION AND ATTITUDE WITH RESULTS LEARNING CLASS VIII SMP STATE 13 MAKASSAR

Directory of Open Access Journals (Sweden)

Putri Athirah Azis

2016-12-01

Full Text Available The study aims at examining (1 the correlation of learning interest towards learning result of grade students, (2 the correlation of learning motivation towards learning result of grade students, (3 the correlation of students attitude towards learning result, (4 the correlationof interest, learning motivation, and attitude collaboratively towards learning result. The study is an ex post facto. The population of the study was grade VIII at SMPN 13 Makassar. Samples were 105 students taken by employing random sampling technique. Data were collected through questionnaire and documentation. Data were analyzed using regression test. The result of study reveal that (1 there is significant correlation (p<0,01 of interest towards learning result of grade VIII students at SMPN 13 Makassar. Co-efficient correlation (r is 0,718 and its effectiveness contribution (R2 is 51,5%, (2 there is significant correlation (p<0,01 of motivation towards learning result of grade VIII students at SMPN 13 Makassar. Co-efficient correlation (r is 0,775 and its effectiveness contribution (R2 is 60,1%, (3 there is significant correlation (p<0,01 of attitude towards learning result of grade VIII students at SMPN 13 Makassar. Co-efficient correlation (r is 0,737 and its effectiveness contribution (R2 is 54,4%, (4 there is significant correlation (p<0,01 of interest, motivation and attitude collaboratively towards learning result of grade VIII students at SMPN 13 Makassar. Co-efficient correlation (r is 0,861 and its effectiveness contribution (R2 is 74,1%,
Stellar signatures of AGN-jet-triggered star formation

International Nuclear Information System (INIS)

Dugan, Zachary; Silk, Joseph; Bryan, Sarah; Gaibler, Volker; Haas, Marcel

2014-01-01

To investigate feedback between relativistic jets emanating from active galactic nuclei and the stellar population of the host galaxy, we analyze the long-term evolution of the orbits of the stars formed in the galaxy-scale simulations by Gaibler et al. of jets in massive, gas-rich galaxies at z ∼ 2-3. We find strong, jet-induced differences in the resulting stellar populations of galaxies that host relativistic jets and galaxies that do not, including correlations in stellar locations, velocities, and ages. Jets are found to generate distributions of increased radial and vertical velocities that persist long enough to effectively augment the stellar structure of the host. The jets cause the formation of bow shocks that move out through the disk, generating rings of star formation within the disk. The bow shock often accelerates pockets of gas in which stars form, yielding populations of stars with significant radial and vertical velocities, some of which have large enough velocities to escape the galaxy. These stellar population signatures can serve to identify past jet activity as well as jet-induced star formation.
The Lives of Stars: Insights from the TGAS–RAVE–LAMOST Data Set

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Vickers, John J.; Smith, Martin C.

2018-06-01

In this paper, we investigate how the chemical and kinematic properties of stars vary as a function of age. Using data from a variety of photometric, astrometric, and spectroscopic surveys, we calculate the ages, phase space information, and orbits for ∼125,000 stars covering a wide range of stellar parameters. We find indications that the inner regions of the disk reached high levels of enrichment early, while the outer regions were more substantially enriched in intermediate and recent epochs. We consider these enrichment histories through comparison of the ages of stars, their metallicities, and kinematic properties, such as their angular momentum in the solar neighborhood (which is a proxy for orbital radius). We calculate rates at which the velocity dispersions evolve, investigate the Oort constants for populations of different ages (finding a slightly negative ∂V C/∂R and ∂V R /∂R for all ages, which is most negative for the oldest stars), as well as examine the behavior of the deviation angle of the velocity vertex as a function of age (which we find to fall from ∼15° for the 2 Gyr old population to ∼6° at around 6.5 Gyr of age, after which it remains unchanged). We find evidence for stellar churning, and find that the churned stars have a slightly younger age distribution than the rest of the data.
Precision Orbit of δ Delphini and Prospects for Astrometric Detection of Exoplanets

Science.gov (United States)

Gardner, Tyler; Monnier, John D.; Fekel, Francis C.; Williamson, Mike; Duncan, Douglas K.; White, Timothy R.; Ireland, Michael; Adams, Fred C.; Barman, Travis; Baron, Fabien; ten Brummelaar, Theo; Che, Xiao; Huber, Daniel; Kraus, Stefan; Roettenbacher, Rachael M.; Schaefer, Gail; Sturmann, Judit; Sturmann, Laszlo; Swihart, Samuel J.; Zhao, Ming

2018-03-01

Combining visual and spectroscopic orbits of binary stars leads to a determination of the full 3D orbit, individual masses, and distance to the system. We present a full analysis of the evolved binary system δ Delphini using astrometric data from the MIRC and PAVO instruments on the CHARA long-baseline interferometer, 97 new spectra from the Fairborn Observatory, and 87 unpublished spectra from the Lick Observatory. We determine the full set of orbital elements for δ Del, along with masses of 1.78 ± 0.07 M ⊙ and 1.62 ± 0.07 M ⊙ for each component, and a distance of 63.61 ± 0.89 pc. These results are important in two contexts: for testing stellar evolution models and for defining the detection capabilities for future planet searches. We find that the evolutionary state of this system is puzzling, as our measured flux ratios, radii, and masses imply a ∼200 Myr age difference between the components, using standard stellar evolution models. Possible explanations for this age discrepancy include mass transfer scenarios with a now-ejected tertiary companion. For individual measurements taken over a span of two years, we achieve 2 M J on orbits >0.75 au around individual components of hot binary stars via differential astrometry.
THE TWO CENTRAL STARS OF NGC 1514: CAN THEY ACTUALLY BE RELATED?

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Méndez, Roberto H.; Kudritzki, Rolf-Peter [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Urbaneja, Miguel A., E-mail: mendez@ifa.hawaii.edu [Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstr. 25/8, A-6020 Innsbruck (Austria)

2016-10-01

The central star of the planetary nebula NGC 1514 is among the visually brightest central stars in the sky ( V = 9.5). It has long been known to show a composite spectrum, consisting of an A-type star and a much hotter star responsible for the ionization of the surrounding nebula. These two stars have always been assumed to form a binary system. High-resolution spectrograms obtained with Espadons at the Canada–France–Hawaii Telescope on Maunakea have allowed us to measure good radial velocities for both stars: they differ by 13 ± 2 km s{sup −1}. The stellar velocities were unchanged after 500 days. We have also estimated the metallicity of the cooler star. Combining these data with other information available in the literature, we conclude that, unless all the published nebular radial velocities are systematically wrong, the cooler star is just a chance alignment, and the two stars are not orbiting each other. The cooler star cannot have played any role in the formation of NGC 1514.
A search for radio emission from exoplanets around evolved stars

Science.gov (United States)

O'Gorman, E.; Coughlan, C. P.; Vlemmings, W.; Varenius, E.; Sirothia, S.; Ray, T. P.; Olofsson, H.

2018-04-01

The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not generate sufficiently strong magnetic fields to emit electron cyclotron maser emission at the low frequencies used in observations (typically ≥150 MHz). In comparison, the large mass-loss rates of evolved stars could enable exoplanets at larger orbital distances to emit detectable radio emission. Here, we first show that the large ionized mass-loss rates of certain evolved stars relative to the solar value could make them detectable with the LOw Frequency ARray (LOFAR) at 150 MHz (λ = 2 m), provided they have surface magnetic field strengths >50 G. We then report radio observations of three long period (>1 au) planets that orbit the evolved stars β Gem, ι Dra, and β UMi using LOFAR at 150 MHz. We do not detect radio emission from any system but place tight 3σ upper limits of 0.98, 0.87, and 0.57 mJy on the flux density at 150 MHz for β Gem, ι Dra, and β UMi, respectively. Despite our non-detections these stringent upper limits highlight the potential of LOFAR as a tool to search for exoplanetary radio emission at meter wavelengths.
Successful Pregnancy in a Patient with Combined Deficiency of Factor V and Factor VIII.

Science.gov (United States)

El Adib, Ahmed Ghassan; Majdi, Farah; Dilai, Mohamed Othmane; Asmouki, Hamid; Bassir, Ahlam; Harou, Karam; Soumani, Abderraouf; Younous, Said; Mahmal, Lahoucine

2014-01-01

Inherited combined factor V and factor VIII deficiency (F5F8D) is autosomal recessive transmission disorder. Epistaxis, postsurgical bleeding, and menorrhagia are the most common symptoms. The risk of miscarriage and placental abruption is consequent. We report a case of successful pregnancy in a patient with F5F8D. 20-year-old woman, born of consanguineous parents, third gestate, first parity, two miscarriages, admitted for child birth of a spontaneous pregnancy estimated at 38 weeks and was diagnosed with F5F8D. At admission, patient was hemodynamically stable, with good obstetric conditions. The biologic results showed low levels of PT (52%), factor V (7%), and factor VIII (5%), and the activated partial thromboplastin time was prolonged (68,6%). Parturient was admitted in intensive care unit, maternal and fetal monitoring was performed. Fresh frozen plasma (FFP) and factor VIII concentrates were perfused at the induction of labor. Analgesia used fentanyl titration. The delivery gave birth to a newborn male, with Apgar 10/10 and 3000 g. The puerperium was simple without any important bleeding. Laboratory tests for the newborn were acceptable. Little literature is available on this subject and there are no guidelines available concerning pregnancy; we chose to prescribe a combination of factor VIII concentrate and FFP in pre-, per- and postpartum. The same protocol was successfully used in a patient before dental extraction and prostatectomy. Vaginal delivery is possible, as our case. Management by multidisciplinary team is recommended.
A close insight to factor VIII inhibitor in the congenital hemophilia A.

Science.gov (United States)

Tabriznia-Tabrizi, Shamsoreza; Gholampour, Marzie; Mansouritorghabeh, Hassan

2016-09-01

Hemophilia A (HA) has an X-linked pattern of inheritance and is the most common of the hemorrhagic disorders. HA is caused by a decreased or deficiency of the functional clotting factor VIII (FVIII) and effects 1 in 5000-10,000 male births. The common treatment for hemophilia is replacement therapy by plasma-derived or recombinant FVIII. Approximately 20-30% of people with a severe type of HA develop an inhibitor and this phenomenon is the main challenge in the management of these patients. Genetic factors and environmental determinants contribute to inhibitor development. Here, the roles of various genetic and environmental factors such as the type of FVIII concentrate used, the number of exposure days, and peak treatment time will be discussed in detail. It seems this information is helpful for hematologists. A literature review was done in January 2016 on PubMed and Scopus using the following keywords:' h(a)emophilia A & factor VIII inhibitor', 'h(a)emophilia A & factor VIII alloantibody', 'h(a)emophilia A & inhibitor'. There was no time limitation; however, there was an English language limitation placed on the articles selected. Expert commentary: Influential genetic and environmental factors in developing inhibitors have been discussed. Most of the risk factors are related to previously untreated patients with hemophili.
CANDIDATE PLANETS IN THE HABITABLE ZONES OF KEPLER STARS

International Nuclear Information System (INIS)

Gaidos, Eric

2013-01-01

A key goal of the Kepler mission is the discovery of Earth-size transiting planets in ''habitable zones'' where stellar irradiance maintains a temperate climate on an Earth-like planet. Robust estimates of planet radius and irradiance require accurate stellar parameters, but most Kepler systems are faint, making spectroscopy difficult and prioritization of targets desirable. The parameters of 2035 host stars were estimated by Bayesian analysis and the probabilities p HZ that 2738 candidate or confirmed planets orbit in the habitable zone were calculated. Dartmouth Stellar Evolution Program models were compared to photometry from the Kepler Input Catalog, priors for stellar mass, age, metallicity and distance, and planet transit duration. The analysis yielded probability density functions for calculating confidence intervals of planet radius and stellar irradiance, as well as p HZ . Sixty-two planets have p HZ > 0.5 and a most probable stellar irradiance within habitable zone limits. Fourteen of these have radii less than twice the Earth; the objects most resembling Earth in terms of radius and irradiance are KOIs 2626.01 and 3010.01, which orbit late K/M-type dwarf stars. The fraction of Kepler dwarf stars with Earth-size planets in the habitable zone (η ⊕ ) is 0.46, with a 95% confidence interval of 0.31-0.64. Parallaxes from the Gaia mission will reduce uncertainties by more than a factor of five and permit definitive assignments of transiting planets to the habitable zones of Kepler stars.
Interrogation of duplicitous stars with an APT

Science.gov (United States)

Bopp, Bernard W.

1992-01-01

Preliminary results from intensive spectroscopic and APT monitoring of two interacting binary systems are presented. Both V644 Mon (Be + K:) and HD 37453 (F5 II + B) show complex, composite, and variable spectral. APT observations extending over three years show both stars to vary by 0.1-0.2 mag in V. The photometric variability of V644 Mon appears to be irregular, though there is some evidence for periodic behavior in the 50-60 day range. HD 37453 has an orbital period of 66.75 days; the best-fit photometric period is not quite half this value, indicating the star is an ellipsoidal variable.
SPECKLE IMAGING EXCLUDES LOW-MASS COMPANIONS ORBITING THE EXOPLANET HOST STAR TRAPPIST-1

International Nuclear Information System (INIS)

Howell, Steve B.; Scott, Nicholas J.; Everett, Mark E.; Horch, Elliott P.; Winters, Jennifer G.; Hirsch, Lea; Nusdeo, Dan

2016-01-01

We have obtained the highest-resolution images available of TRAPPIST-1 using the Gemini-South telescope and our speckle imaging camera. Observing at 692 and 883 nm, we reached the diffraction limit of the telescope providing a best resolution of 27 mas or, at the distance of TRAPPIST-1, a spatial resolution of 0.32 au. Our imaging of the star extends from 0.32 to 14.5 au. We show that to a high confidence level, we can exclude all possible stellar and brown dwarf companions, indicating that TRAPPIST-1 is a single star.
SPECKLE IMAGING EXCLUDES LOW-MASS COMPANIONS ORBITING THE EXOPLANET HOST STAR TRAPPIST-1

Energy Technology Data Exchange (ETDEWEB)

Howell, Steve B.; Scott, Nicholas J. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Everett, Mark E. [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Horch, Elliott P. [Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT, 06515 (United States); Winters, Jennifer G. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, 02138 (United States); Hirsch, Lea [Astronomy Department, University of California, Berkeley, 510 Campbell Hall, Berkeley, CA, 94720 (United States); Nusdeo, Dan [Department of Physics and Astronomy, Georgia State University, P.O. Box 5060, Atlanta, GA 30302 (United States)

2016-09-20

We have obtained the highest-resolution images available of TRAPPIST-1 using the Gemini-South telescope and our speckle imaging camera. Observing at 692 and 883 nm, we reached the diffraction limit of the telescope providing a best resolution of 27 mas or, at the distance of TRAPPIST-1, a spatial resolution of 0.32 au. Our imaging of the star extends from 0.32 to 14.5 au. We show that to a high confidence level, we can exclude all possible stellar and brown dwarf companions, indicating that TRAPPIST-1 is a single star.
Efficacy and safety of rVIII-SingleChain: results of a phase 1/3 multicenter clinical trial in severe hemophilia A

Science.gov (United States)

Mahlangu, Johnny; Kuliczkowski, Kazimierz; Karim, Faraizah Abdul; Stasyshyn, Oleksandra; Kosinova, Marina V.; Lepatan, Lynda Mae; Skotnicki, Aleksander; Boggio, Lisa N.; Klamroth, Robert; Oldenburg, Johannes; Hellmann, Andrzej; Santagostino, Elena; Baker, Ross I.; Fischer, Kathelijn; Gill, Joan C.; P’Ng, Stephanie; Chowdary, Pratima; Escobar, Miguel A.; Khayat, Claudia Djambas; Rusen, Luminita; Bensen-Kennedy, Debra; Blackman, Nicole; Limsakun, Tharin; Veldman, Alex; St. Ledger, Katie

2016-01-01

Recombinant VIII (rVIII)-SingleChain is a novel B-domain–truncated recombinant factor VIII (rFVIII), comprised of covalently bonded factor VIII (FVIII) heavy and light chains. It was designed to have a higher binding affinity for von Willebrand factor (VWF). This phase 1/3 study investigated the efficacy and safety of rVIII-SingleChain in the treatment of bleeding episodes, routine prophylaxis, and surgical prophylaxis. Participants were ≥12 years of age, with severe hemophilia A (endogenous FVIII <1%). The participants were allocated by the investigator to receive rVIII-SingleChain in either an on-demand or prophylaxis regimen. Of the 175 patients meeting study eligibility criteria, 173 were treated with rVIII-SingleChain, prophylactically (N = 146) or on-demand (N = 27). The total cumulative exposure was 14 306 exposure days (EDs), with 120 participants reaching ≥50 EDs and 52 participants having ≥100 EDs. Hemostatic efficacy was rated by the investigator as excellent or good in 93.8% of the 835 bleeds treated and assessed. Across all prophylaxis regimens, the median annualized spontaneous bleeding rate was 0.00 (Q1, Q3: 0.0, 2.4) and the median overall annualized bleeding rate (ABR) was 1.14 (Q1, Q3: 0.0, 4.2). Surgical hemostasis was rated as excellent/good in 100% of major surgeries by the investigator. No participant developed FVIII inhibitors. In conclusion, rVIII-SingleChain is a novel rFVIII molecule showing excellent hemostatic efficacy in surgery and in the control of bleeding events, low ABR in patients on prophylaxis, and a favorable safety profile in this large clinical study. This trial was registered at www.clinicaltrials.gov as #NCT01486927. PMID:27330001
Spectroscopic confirmation of the first symbiotic star in a globular cluster

Science.gov (United States)

Zurek, David

2013-10-01

We have recently discovered an 18-minute period in the ultraviolet of a star in the globular cluster NGC 1851. In the redder optical bands, this star is red and bright, while it shows a clear UV excess relative to other stars at similar positions in the HR diagram. The system is most likely a symbiotic binary, composed of a cool evolved star and a white dwarf, with an 18 minute spin period, accreting the cool star's wind. The binary would be the first such object ever found in a globular cluster, and only the third in the Galaxy where the white dwarf spin period is measured. The only viable alternatives are that the two components are a chance superposition - something with a nontrivial chance of happening in a globular cluster core. In such a case, the 18 minute period would most likely be the spin period of a magnetic white dwarf in an intermediate polar cataclysmic variable {this would be the first confirmed magnetic CV in a globular cluster}, or the orbital period of a double-degenerate AM CVn binary. Each of these three possibilities show unique {and very different} emission line spectra in the blue wavelength range. Two orbits of HST with STIS/G430L will produce a spectrum of sufficient signal-to-noise to distinguish between these 3 scenarios. The result will be an important constraint on N-body models of globular clusters.
Eclipsing binary stars with a δ Scuti component

Science.gov (United States)

Kahraman Aliçavuş, F.; Soydugan, E.; Smalley, B.; Kubát, J.

2017-09-01

Eclipsing binaries with a δ Sct component are powerful tools to derive the fundamental parameters and probe the internal structure of stars. In this study, spectral analysis of six primary δ Sct components in eclipsing binaries has been performed. Values of Teff, v sin I, and metallicity for the stars have been derived from medium-resolution spectroscopy. Additionally, a revised list of δ Sct stars in eclipsing binaries is presented. In this list, we have only given the δ Sct stars in eclipsing binaries to show the effects of the secondary components and tidal-locking on the pulsations of primary δ Sct components. The stellar pulsation, atmospheric and fundamental parameters (e.g. mass, radius) of 92 δ Sct stars in eclipsing binaries have been gathered. Comparison of the properties of single and eclipsing binary member δ Sct stars has been made. We find that single δ Sct stars pulsate in longer periods and with higher amplitudes than the primary δ Sct components in eclipsing binaries. The v sin I of δ Sct components is found to be significantly lower than that of single δ Sct stars. Relationships between the pulsation periods, amplitudes and stellar parameters in our list have been examined. Significant correlations between the pulsation periods and the orbital periods, Teff, log g, radius, mass ratio, v sin I and the filling factor have been found.

Modeling Multi-wavelength Stellar Astrometry. III. Determination of the Absolute Masses of Exoplanets and Their Host Stars

Science.gov (United States)

Coughlin, J. L.; López-Morales, Mercedes

2012-05-01

Astrometric measurements of stellar systems are becoming significantly more precise and common, with many ground- and space-based instruments and missions approaching 1 μas precision. We examine the multi-wavelength astrometric orbits of exoplanetary systems via both analytical formulae and numerical modeling. Exoplanets have a combination of reflected and thermally emitted light that causes the photocenter of the system to shift increasingly farther away from the host star with increasing wavelength. We find that, if observed at long enough wavelengths, the planet can dominate the astrometric motion of the system, and thus it is possible to directly measure the orbits of both the planet and star, and thus directly determine the physical masses of the star and planet, using multi-wavelength astrometry. In general, this technique works best for, though is certainly not limited to, systems that have large, high-mass stars and large, low-mass planets, which is a unique parameter space not covered by other exoplanet characterization techniques. Exoplanets that happen to transit their host star present unique cases where the physical radii of the planet and star can be directly determined via astrometry alone. Planetary albedos and day-night contrast ratios may also be probed via this technique due to the unique signature they impart on the observed astrometric orbits. We develop a tool to examine the prospects for near-term detection of this effect, and give examples of some exoplanets that appear to be good targets for detection in the K to N infrared observing bands, if the required precision can be achieved.
MODELING MULTI-WAVELENGTH STELLAR ASTROMETRY. III. DETERMINATION OF THE ABSOLUTE MASSES OF EXOPLANETS AND THEIR HOST STARS

International Nuclear Information System (INIS)

Coughlin, J. L.; López-Morales, Mercedes

2012-01-01

Astrometric measurements of stellar systems are becoming significantly more precise and common, with many ground- and space-based instruments and missions approaching 1 μas precision. We examine the multi-wavelength astrometric orbits of exoplanetary systems via both analytical formulae and numerical modeling. Exoplanets have a combination of reflected and thermally emitted light that causes the photocenter of the system to shift increasingly farther away from the host star with increasing wavelength. We find that, if observed at long enough wavelengths, the planet can dominate the astrometric motion of the system, and thus it is possible to directly measure the orbits of both the planet and star, and thus directly determine the physical masses of the star and planet, using multi-wavelength astrometry. In general, this technique works best for, though is certainly not limited to, systems that have large, high-mass stars and large, low-mass planets, which is a unique parameter space not covered by other exoplanet characterization techniques. Exoplanets that happen to transit their host star present unique cases where the physical radii of the planet and star can be directly determined via astrometry alone. Planetary albedos and day-night contrast ratios may also be probed via this technique due to the unique signature they impart on the observed astrometric orbits. We develop a tool to examine the prospects for near-term detection of this effect, and give examples of some exoplanets that appear to be good targets for detection in the K to N infrared observing bands, if the required precision can be achieved.
Evolution of the solar system in the presence of a solar companion star

International Nuclear Information System (INIS)

Hut, P.

1986-01-01

A review is presented of the dynamical implications of a companion star in a wide orbit around the sun, with a semimajor axis of about half a parsec. The motivation behind the hypothesis of a solar companion star is reviewed briefly along with alternative hypotheses, and the general problem of solar system dynamics with a solar companion star is discussed. Four principal questions are posed and answered concerning the consistency of the solar companion theory in providing the required modulation in comet arrival times: (1) What is the expected lifetime of a solar companion? (2) How stable is the orbital period? (3) Does a single perihelion passage of a solar companion perturb enough comets? (4) Do repeated perihelion passages of a solar companion perturb too many comets? Some applications outside the solar system involving wide binaries, interstellar clouds, and dark matter in the Galactic disk are discussed, and the viability of the solar companion theory is critically assessed
Speckle Interferometry of Red Dwarf Stars

Science.gov (United States)

Mason, Brian D.; Hartkopf, William I.; Miles, Korie N.; Subasavage, John P.; Raghavan, Deepak; Henry, Todd J.

2018-05-01

We report high-resolution optical speckle observations of 336 M dwarfs, which results in 113 measurements of the relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the systems. We also present the earliest measurements of relative position for 17 others. We include orbits for six of the systems, two revised and four reported for the first time. For one of the systems with a new orbit, G 161-7, we determine masses of 0.156 ± 0.011 and 0.1175+/- 0.0079 {{ \\mathcal M }}ȯ for the A and B components, respectively. All six of these new calculated orbits have short periods (between five and 38 years) and hold the promise of deriving accurate masses in the near future. For many other pairs we can establish their nature as physical or chance alignment, depending on their relative motion. Of the 80 systems, 32 have calculated orbits, 25 others are physical pairs, four are optical pairs, and 19 are currently unknown.
The nature of the companion star in Circinus X-1

Science.gov (United States)

Johnston, Helen M.; Soria, Roberto; Gibson, Joel

2016-02-01

We present optical spectra and images of the X-ray binary Circinus X-1. The optical light curve of Cir X-1 is strongly variable, changing in brightness by 1.2 mag in the space of four days. The shape of the light curve is consistent with that seen in the 1980s, when the X-ray and radio counterparts of the source were at least ten times as bright as they are currently. We detect strong, variable H α emission lines, consisting of multiple components which vary with orbital phase. We estimate the extinction to the source from the strength of the diffuse interstellar bands and the Balmer decrement; the two methods give AV = 7.6 ± 0.6 mag and AV > 9.1 mag, respectively. The optical light curve can be modelled as arising from irradiation of the companion star by the central X-ray source, where a low-temperature star fills its Roche lobe in an orbit of moderate eccentricity (e ˜ 0.4). We suggest that the companion star is overluminous and underdense, due to the impact of the supernova which occurred less than 5000 yr ago.
Star clouds of Magellan

International Nuclear Information System (INIS)

Tucker, W.

1981-01-01

The Magellanic Clouds are two irregular galaxies belonging to the local group which the Milky Way belongs to. By studying the Clouds, astronomers hope to gain insight into the origin and composition of the Milky Way. The overall structure and dynamics of the Clouds are clearest when studied in radio region of the spectrum. One benefit of directly observing stellar luminosities in the Clouds has been the discovery of the period-luminosity relation. Also, the Clouds are a splendid laboratory for studying stellar evolution. It is believed that both Clouds may be in the very early stage in the development of a regular, symmetric galaxy. This raises a paradox because some of the stars in the star clusters of the Clouds are as old as the oldest stars in our galaxy. An explanation for this is given. The low velocity of the Clouds with respect to the center of the Milky Way shows they must be bound to it by gravity. Theories are given on how the Magellanic Clouds became associated with the galaxy. According to current ideas the Clouds orbits will decay and they will spiral into the Galaxy
Is life most likely around Sun-like stars?

Science.gov (United States)

Lingam, Manasvi; Loeb, Abraham

2018-05-01

We consider the habitability of Earth-analogs around stars of different masses, which is regulated by the stellar lifetime, stellar wind-induced atmospheric erosion, and biologically active ultraviolet (UV) irradiance. By estimating the timescales associated with each of these processes, we show that they collectively impose limits on the habitability of Earth-analogs. We conclude that planets orbiting most M-dwarfs are not likely to host life, and that the highest probability of complex biospheres is for planets around K- and G-type stars. Our analysis suggests that the current existence of life near the Sun is slightly unusual, but not significantly anomalous.
Hypervelocity star candidates in Gaia DR1/TGAS

Science.gov (United States)

Marchetti, T.; Rossi, E. M.; Kordopatis, G.; Brown, A. G. A.; Rimoldi, A.; Starkenburg, E.; Youakim, K.; Ashley, R.

2018-04-01

Hypervelocity stars (HVSs) are characterized by a total velocity in excess of the Galactic escape speed, and with trajectories consistent with coming from the Galactic Centre. We apply a novel data mining routine, an artificial neural network, to discover HVSs in the TGAS subset of the first data release of the Gaia satellite, using only the astrometry of the stars. We find 80 stars with a predicted probability >90% of being HVSs, and we retrieved radial velocities for 47 of those. We discover 14 objects with a total velocity in the Galactic rest frame >400 km s-1, and 5 of these have a probability >50% of being unbound from the Milky Way. Tracing back orbits in different Galactic potentials, we discover 1 HVS candidate, 5 bound HVS candidates, and 5 runaway star candidates with remarkably high velocities, between 400 and 780 km s-1. We wait for future Gaia releases to confirm the goodness of our sample and to increase the number of HVS candidates.
The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

Science.gov (United States)

Brown, Warren R.; Kilic, Mukremin; Gianninas, A.

2017-04-01

We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ˜1 dex error for sdA stars, likely explained by metal line blanketing below 9000 K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ≃1.2 M ⊙ main sequence stars with ≃0.8 M ⊙ companions. While WDs must exist at sdA temperatures, only ˜1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A-F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.
The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

International Nuclear Information System (INIS)

Brown, Warren R.; Kilic, Mukremin; Gianninas, A.

2017-01-01

We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ∼1 dex error for sdA stars, likely explained by metal line blanketing below 9000 K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ≃1.2 M ⊙ main sequence stars with ≃0.8 M ⊙ companions. While WDs must exist at sdA temperatures, only ∼1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A–F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.
The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

Energy Technology Data Exchange (ETDEWEB)

Brown, Warren R. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Kilic, Mukremin; Gianninas, A., E-mail: wbrown@cfa.harvard.edu, E-mail: kilic@ou.edu, E-mail: alexg@nhn.ou.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK, 73019 (United States)

2017-04-10

We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution spectroscopy. However, colors and proper motions indicate that sdA stars are cooler and more luminous, and thus larger in radius, than published ELM WDs. We demonstrate that surface gravities derived from pure hydrogen models suffer a systematic ∼1 dex error for sdA stars, likely explained by metal line blanketing below 9000 K. A detailed study of five eclipsing binaries with radial velocity orbital solutions and infrared excess establishes that these sdA stars are metal-poor ≃1.2 M {sub ⊙} main sequence stars with ≃0.8 M {sub ⊙} companions. While WDs must exist at sdA temperatures, only ∼1% of a magnitude-limited sdA sample should be ELM WDs. We conclude that the majority of sdA stars are metal-poor A–F type stars in the halo, and that recently discovered pulsating ELM WD-like stars with no obvious radial velocity variations may be SX Phe variables, not pulsating WDs.
Is the Young Star RZ Piscium Consuming Its Own (Planetary) Offspring?

Science.gov (United States)

Punzi, K. M.; Kastner, J. H.; Melis, C.; Zuckerman, B.; Pilachowski, C.; Gingerich, L.; Knapp, T.

2018-01-01

The erratically variable star RZ Piscium (RZ Psc) displays extreme optical dropout events and strikingly large excess infrared emission. To ascertain the evolutionary status of this intriguing star, we obtained observations of RZ Psc with the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton), as well as high-resolution optical spectroscopy with the Hamilton Echelle on the Lick Shane 3 m telescope and with HIRES on the Keck I 10 m telescope. The optical spectroscopy data demonstrate that RZ Psc is a pre-main sequence star with an effective temperature of 5600 ± 75 K and log g of 4.35 ± 0.10. The ratio of X-ray to bolometric luminosity, {log}{L}X/{L}{bol}, lies in the range ‑3.7 to ‑3.2, consistent with ratios typical of young, solar-mass stars, thereby providing strong support for the young star status of RZ Psc. The Li absorption line strength of RZ Psc suggests an age in the range 30–50 Myr, which in turn implies that RZ Psc lies at a distance of ∼170 pc. Adopting this estimated distance, we find the Galactic space velocity of RZ Psc to be similar to the space velocities of stars in young moving groups near the Sun. Optical spectral features indicative of activity and/or circumstellar material are present in our spectra over multiple epochs, which provide evidence for the presence of a significant mass of circumstellar gas associated with RZ Psc. We suggest that the destruction of one or more massive orbiting bodies has recently occurred within 1 au of the star, and we are viewing the aftermath of such an event along the plane of the orbiting debris.
Stability criteria for wide binary stars harboring Oort Clouds

Science.gov (United States)

Calandra, M. F.; Correa-Otto, J. A.; Gil-Hutton, R. A.

2018-03-01

Context. In recent years, several numerical studies have been done in the field of the stability limit. Although, many of them included the analysis of asteroids or planets, is not possible to find in the literature any work on how the presence of a binary star could affect other possible configurations in a three-body problem. In order to develop this subject we consider other structures like Oort Clouds in wide binary systems. Regarding the existence of Oort Clouds in extrasolar systems there are recent works that do not reject its possible existence. Aim. The aim of this work is to obtain the stability limit for Oort Cloud objects considering different masses of the secondary star and zero and non-zero inclinations of the particles. We improve our numerical treatment getting a mathematical fit that allows us to find the limit and compare our results with other previous works in the field. Methods: We use a symplectic integrator to integrate binary systems where the primary star is m1 = 1 M⊙ and the secondary, m2, takes 0.25 M⊙ and 0.66 M⊙ in two sets of simulations S1 and S2. The orbital parameters of the secondary star were varied in order to study different scenarios. We also used two different integration times (one shorter than the other) and included the presence of 1000 to 10 000 massless particles in circular orbits to form the Oort Cloud. The particles were disposed in four different inclination planes to investigate how the presence of the binary companion could affect the stability limit. Results: Using the Maximum Eccentricity Method, emax, together with the critical semimajor axis acrit we found that the emax criteria could reduce the integration times to find the limit. For those cases where the particles were in inclined orbits we found that there are particle groups that survive the integration time with a high eccentricity. These particle groups are found for our two sets of simulations, meaning that they are independent of the secondary
A STRANGE STAR SCENARIO FOR THE FORMATION OF ECCENTRIC MILLISECOND PULSAR/HELIUM WHITE DWARF BINARIES

Energy Technology Data Exchange (ETDEWEB)

Jiang, Long; Li, Xiang-Dong [Department of Astronomy, Nanjing University, Nanjing 210046 (China); Dey, Jishnu; Dey, Mira, E-mail: lixd@nju.edu.cn [Department of Physics, Presidency University, 86/1, College Street, Kolkata 700 073 (India)

2015-07-01

According to the recycling scenario, millisecond pulsars (MSPs) have evolved from low-mass X-ray binaries (LMXBs). Their orbits are expected to be circular due to tidal interactions during binary evolution, as observed in most binary MSPs. There are some peculiar systems that do not fit this picture. Three recent examples are the PSRs J2234+06, J1946+3417, and J1950+2414, all of which are MSPs in eccentric orbits but with mass functions compatible with expected He white dwarf (WD) companions. It has been suggested these MSPs may have formed from delayed accretion-induced collapse of massive WDs, or the eccentricity may be induced by dynamical interaction between the binary and a circumbinary disk. Assuming that the core density of accreting neutron stars (NSs) in LMXBs may reach the density of quark deconfinement, which can lead to phase transition from NSs to strange quark stars, we show that the resultant MSPs are likely to have an eccentric orbit, due to the sudden loss of the gravitational mass of the NS during the transition. The eccentricities can be reproduced with a reasonable estimate of the mass loss. This scenario might also account for the formation of the youngest known X-ray binary Cir X–1, which also possesses a low-field compact star in an eccentric orbit.
THE CHANDRA VARIABLE GUIDE STAR CATALOG

International Nuclear Information System (INIS)

Nichols, Joy S.; Lauer, Jennifer L.; Morgan, Douglas L.; Sundheim, Beth A.; Henden, Arne A.; Huenemoerder, David P.; Martin, Eric

2010-01-01

Variable stars have been identified among the optical-wavelength light curves of guide stars used for pointing control of the Chandra X-ray Observatory. We present a catalog of these variable stars along with their light curves and ancillary data. Variability was detected to a lower limit of 0.02 mag amplitude in the 4000-10000 A range using the photometrically stable Aspect Camera on board the Chandra spacecraft. The Chandra Variable Guide Star Catalog (VGUIDE) contains 827 stars, of which 586 are classified as definitely variable and 241 are identified as possibly variable. Of the 586 definite variable stars, we believe 319 are new variable star identifications. Types of variables in the catalog include eclipsing binaries, pulsating stars, and rotating stars. The variability was detected during the course of normal verification of each Chandra pointing and results from analysis of over 75,000 guide star light curves from the Chandra mission. The VGUIDE catalog represents data from only about 9 years of the Chandra mission. Future releases of VGUIDE will include newly identified variable guide stars as the mission proceeds. An important advantage of the use of space data to identify and analyze variable stars is the relatively long observations that are available. The Chandra orbit allows for observations up to 2 days in length. Also, guide stars were often used multiple times for Chandra observations, so many of the stars in the VGUIDE catalog have multiple light curves available from various times in the mission. The catalog is presented as both online data associated with this paper and as a public Web interface. Light curves with data at the instrumental time resolution of about 2 s, overplotted with the data binned at 1 ks, can be viewed on the public Web interface and downloaded for further analysis. VGUIDE is a unique project using data collected during the mission that would otherwise be ignored. The stars available for use as Chandra guide stars are
Supernova remnant S 147 and its associated neutron star(s)

Science.gov (United States)

Gvaramadze, V. V.

2006-07-01

The supernova remnant S 147 harbors the pulsar PSR J 0538+2817 whose characteristic age is more than an order of magnitude greater than the kinematic age of the system (inferred from the angular offset of the pulsar from the geometric center of the supernova remnant and the pulsar proper motion). To reconcile this discrepancy we propose that PSR J 0538+2817 could be the stellar remnant of the first supernova explosion in a massive binary system and therefore could be as old as its characteristic age. Our proposal implies that S 147 is the diffuse remnant of the second supernova explosion (that disrupted the binary system) and that a much younger second neutron star (not necessarily manifesting itself as a radio pulsar) should be associated with S 147. We use the existing observational data on the system to suggest that the progenitor of the supernova that formed S 147 was a Wolf-Rayet star (so that the supernova explosion occurred within a wind bubble surrounded by a massive shell) and to constrain the parameters of the binary system. We also restrict the magnitude and direction of the kick velocity received by the young neutron star at birth and find that the kick vector should not strongly deviate from the orbital plane of the binary system.
MAGNETIC GRAIN TRAPPING AND THE HOT EXCESSES AROUND EARLY-TYPE STARS

Energy Technology Data Exchange (ETDEWEB)

Rieke, G. H.; Gáspár, András; Ballering, N. P., E-mail: grieke@as.arizona.edu, E-mail: agaspar@as.arizona.edu, E-mail: ballerin@email.arizona.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

2016-01-10

A significant fraction of main sequence stars observed interferometrically in the near-infrared have slightly extended components that have been attributed to very hot dust. To match the spectrum appears to require the presence of large numbers of very small (<200 nm in radius) dust grains. However, particularly for the hotter stars, it has been unclear how such grains can be retained close to the star against radiation pressure force. We find that the expected weak stellar magnetic fields are sufficient to trap nm-sized dust grains in epicyclic orbits for a few weeks or longer, sufficient to account for the hot excess emission. Our models provide a natural explanation for the requirement that the hot excess dust grains be smaller than 200 nm. They also suggest that magnetic trapping is more effective for rapidly rotating stars, consistent with the average vsini measurements of stars with hot excesses being larger (at ∼2σ) than those for stars without such excesses.
Identification and period investigation of pulsation variable star UY Camelopardalis, an RR Lyrae star in binary system

Science.gov (United States)

Li, Lin-Jia; Qian, Sheng-Bang; Voloshina, Irina; Metlov, Vladimir G.; Zhu, Li-Ying; Liao, Wen-Ping

2018-06-01

We present photometric measurements of the short period variable star UY Cam, which has been classified as a δ Scuti or c-type RR Lyrae (RRc) variable in different catalogs. Based on the analyses on Fourier coefficients and (NUV - V)0, we find that UY Cam is probably an RRc star. We obtain 58 new times of light maximum for UY Cam based on several sky surveys and our observations. Combining these with the times of light maximum in literature, a total of 154 times of light maximum are used to analyze the O - C diagram of UY Cam. The results show that the O - C pattern can be described by a downward parabolic component with a rate of -6.86 ± 0.47 × 10-11 d d-1, and a cyclic variation with a period of 65.7 ± 2.4 yr. We suppose these components are caused by the stellar evolution and the light travel time effect (LiTE) of a companion in elliptical orbit, respectively. By calculation, the minimum mass of the potential companion is about 0.17 M⊙, and its mass should be less than or equal to the pulsation primary star when the inclination i > 22.5°D. Therefore, the companion should be a low-mass star, like a late-type main-sequence star or a white dwarf. Due to the unique property of UY Cam, we suggest that more observations and studies on UY Cam and other RRc stars are needed to check the nature of these stars, including the pulsations and binarities.
VELOCITY VARIATIONS IN THE PHOENIX–HERMUS STAR STREAM

Energy Technology Data Exchange (ETDEWEB)

Carlberg, R. G. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Grillmair, C. J., E-mail: carlberg@astro.utoronto.ca, E-mail: carl@ipac.caltech.edu [Spitzer Science Center, 1200 E. California Blvd., Pasadena, CA 91125 (United States)

2016-10-20

Measurements of velocity and density perturbations along stellar streams in the Milky Way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. An interesting case to consider is the proposed Phoenix–Hermus star stream, which is long, thin, and on a nearly circular orbit, making it a particular good target to study for velocity variations along its length. In the presence of dark matter sub-halos, the stream velocities are significantly perturbed in a manner that is readily understood with the impulse approximation. A set of simulations shows that only sub-halos above a few 10{sup 7} M {sub ⊙} lead to reasonably long-lived observationally detectable velocity variations of amplitude of order 1 km s{sup −1}, with an average of about one visible hit per (two-armed) stream over a 3 Gyr interval. An implication is that globular clusters themselves will not have a visible impact on the stream. Radial velocities have the benefit of being completely insensitive to distance errors. Distance errors scatter individual star velocities perpendicular and tangential to the mean orbit, but their mean values remain unbiased. Calculations like these help build the quantitative case to acquire large, fairly deep, precision velocity samples of stream stars.
The statistical study of Chorus waves using the Double star TC1 data

Science.gov (United States)

Yearby, K.; Aryan, H.; Balikhin, M. A.; Krasnoselskikh, V.; Agapitov, O. V.

2013-12-01

The Double star satellite was launched on 29 December 2003 into an equatorial elliptical orbit with a perigee of 570km and an apogee of 78970km and an inclination of 28.5°. The satellite operated until 14 October 2007. The Double star TC1 data provides extensive coverage of the inner magnetosphere regions in the range of L shells >1.1L*, and a wide range of latitudes. This study presents a detailed statistical study of the Chorus waves during 4 years of the Double star operation.

Role of VI/II ratio on the growth of ZnO nanostructures using chemical bath deposition

Energy Technology Data Exchange (ETDEWEB)

Urgessa, Z.N., E-mail: zelalem.urgessa@nmmu.ac.za [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Oluwafemi, O.S. [Department of Chemistry and Chemical Technology, Walter Sisulu University, Mthatha Campus, Private Bag XI, 5117 (South Africa); Botha, J.R. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

2012-05-15

In this paper the growth process and morphological evolution of ZnO nanostructures were investigated in a series of experiments using chemical bath deposition. The experimental results indicate that the morphological evolution depends on the reaction conditions, particularly on OH{sup -} to Zn{sup 2+} ratio (which directly affects the pH). For low VI/II ratios, quasi-spherical nanoparticles of an average diameter 30 nm are obtained, whereas for larger VI/II ratios, nanorods with an average diameter less than 100 nm are produced, which indicates that by systematically controlling the VI/II ratio, it is possible to produce different shapes and sizes of ZnO nanostructures. A possible mechanism for the nanostructural change of the as-synthesized ZnO from particle to rod was elucidated based on the relative densities of H{sup +} and OH{sup -} in the solution.
Role of VI/II ratio on the growth of ZnO nanostructures using chemical bath deposition

International Nuclear Information System (INIS)

Urgessa, Z.N.; Oluwafemi, O.S.; Botha, J.R.

2012-01-01

In this paper the growth process and morphological evolution of ZnO nanostructures were investigated in a series of experiments using chemical bath deposition. The experimental results indicate that the morphological evolution depends on the reaction conditions, particularly on OH − to Zn 2+ ratio (which directly affects the pH). For low VI/II ratios, quasi-spherical nanoparticles of an average diameter 30 nm are obtained, whereas for larger VI/II ratios, nanorods with an average diameter less than 100 nm are produced, which indicates that by systematically controlling the VI/II ratio, it is possible to produce different shapes and sizes of ZnO nanostructures. A possible mechanism for the nanostructural change of the as-synthesized ZnO from particle to rod was elucidated based on the relative densities of H + and OH − in the solution.
PENGEMBANGAN KARAKTER KEDISIPLINAN DAN KEMAMPUAN PEMECAHAN MASALAH MELALUI MODEL LAPS-HEURISTIK MATERI LINGKARAN KELAS-VIII

Directory of Open Access Journals (Sweden)

Sri Wahyuni

2015-08-01

Full Text Available Tujuan penelitian ini adalah untuk mengetahui (1 apakah pembelajaran dengan model pembelajaran LAPS-Heuristik pada materi lingkaran kelas-VIII dapat mengembangkan karakter kedisiplinan peserta didik, (2 apakah pembelajaran dengan model pembelajaran LAPS-Heuristik pada materi lingkaran kelas-VIII dapat meningkatkan kemampuan pemecahan masalah peserta didik, (3 apakah kemampuan pemecahan masalah matematika peserta didik yang diajar dengan model pembelajaran LAPS-Heuristik pada materi lingkaran kelas-VIII dapat mencapai kriteria ketuntasan minimal yang ditentukan. Desain penelitian ini adalah kualitatif deskriptif, artinya menggambarkan atau mendeskripsikan kejadian-kejadian yang menjadi pusat perhatian secara kualitatif dan berdasar data kualitatif. Penentuan sumber data dalam penelitian ini menggunakan teknik purposive sampling, yaitu dipilih dengan pertimbangan dan tujuan tertentu. Data diperoleh dengan observasi, wawancara, dan tes yang kemudian dianalisis menggunakan analisis kualitatif dan analisis gain untuk mengukur peningkatan. Analisis kualitatif menunjukkan karakter kedisiplinan dan kemampuan pemecahan masalah peserta didik meningkat, serta kemampuan pemecahan masalah peserta didik mencapai KKM melalui model pembelajaran LAPS-Heuristik.
Einstein@Home DISCOVERY OF A PALFA MILLISECOND PULSAR IN AN ECCENTRIC BINARY ORBIT

Energy Technology Data Exchange (ETDEWEB)

Knispel, B.; Allen, B. [Leibniz Universität, Hannover, D-30167 Hannover (Germany); Lyne, A. G.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Freire, P. C. C.; Lazarus, P. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H. [Max-Planck-Institut für Gravitationsphysik, Callinstr. 38, D-30167 Hannover (Germany); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Brazier, A.; Chatterjee, S.; Cordes, J. M. [Department of Astronomy and Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States); Cardoso, F. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Deneva, J. S. [National Research Council, resident at the Naval Research Laboratory, Washington, DC 20375 (United States); Ferdman, R. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Hessels, J. W. T., E-mail: benjamin.knispel@aei.mpg.de [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); and others

2015-06-10

We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M{sub ⊙} and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.
Photometric and polarimetric variability and mass-loss rate of the massive binary Wolf-Rayet star HDE 311884 (WN6 + 05: V)

International Nuclear Information System (INIS)

Moffat, A.F.J.; Drissen, L.; Robert, C.; Lamontagne, R.; Coziol, R.

1990-01-01

Photometric and polarimetric monitoring of the Wolf-Rayet (W-R) + O-type binary system HDE 311884 = WR 47 over many orbital cycles shows the clear effects of phase-dependent electron scattering of O-star light as the orbiting O companion shines through varying column density of W-R stellar wind material. In contrast to this wind-type eclipse, the stars themselves do not quite eclipse. Both photometry and polarimetry give a consistent estimate of the mass-loss rate of the W-R component: at about 0.00003 solar mass/yr. The orbital inclination, i = 70 deg, along with the previously published velocity orbit, yields high masses: M(WN6) = 48 solar masses and M(O5:V) = 57 solar masses. 33 refs
SPIN–ORBIT ALIGNMENT FOR THREE TRANSITING HOT JUPITERS: WASP-103b, WASP-87b, and WASP-66b

Energy Technology Data Exchange (ETDEWEB)

Addison, B. C.; Tinney, C. G.; Wright, D. J. [Exoplanetary Science Group, School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Bayliss, D., E-mail: baddison2005@gmail.com [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)

2016-05-20

We have measured the sky-projected spin–orbit alignments for three transiting hot Jupiters, WASP-103b, WASP-87b, and WASP-66b, using spectroscopic measurements of the Rossiter–McLaughlin effect, with the CYCLOPS2 optical fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky-projected spin–orbit angles of λ = 3° ± 33°, λ = −8° ± 11°, and λ = −4° ± 22° for WASP-103b, WASP-87b, and WASP-66b, respectively, suggest that these three planets are likely on nearly aligned orbits with respect to their host star’s spin axis. WASP-103 is a particularly interesting system as its orbital distance is only 20% larger than its host star’s Roche radius and the planet likely experiences strong tidal effects. WASP-87 and WASP-66 are hot ( T {sub eff} = 6450 ± 120 K and T {sub eff} = 6600 ± 150 K, respectively) mid-F stars, making them similar to the majority of stars hosting planets on high-obliquity orbits. Moderate spin–orbit misalignments for WASP-103b and WASP-66b are consistent with our data, but polar and retrograde orbits are not favored for these systems.
SPIN–ORBIT ALIGNMENT FOR THREE TRANSITING HOT JUPITERS: WASP-103b, WASP-87b, and WASP-66b

International Nuclear Information System (INIS)

Addison, B. C.; Tinney, C. G.; Wright, D. J.; Bayliss, D.

2016-01-01

We have measured the sky-projected spin–orbit alignments for three transiting hot Jupiters, WASP-103b, WASP-87b, and WASP-66b, using spectroscopic measurements of the Rossiter–McLaughlin effect, with the CYCLOPS2 optical fiber bundle system feeding the UCLES spectrograph on the Anglo-Australian Telescope. The resulting sky-projected spin–orbit angles of λ = 3° ± 33°, λ = −8° ± 11°, and λ = −4° ± 22° for WASP-103b, WASP-87b, and WASP-66b, respectively, suggest that these three planets are likely on nearly aligned orbits with respect to their host star’s spin axis. WASP-103 is a particularly interesting system as its orbital distance is only 20% larger than its host star’s Roche radius and the planet likely experiences strong tidal effects. WASP-87 and WASP-66 are hot ( T eff = 6450 ± 120 K and T eff = 6600 ± 150 K, respectively) mid-F stars, making them similar to the majority of stars hosting planets on high-obliquity orbits. Moderate spin–orbit misalignments for WASP-103b and WASP-66b are consistent with our data, but polar and retrograde orbits are not favored for these systems.
Kepler Mission: a Discovery-Class Mission Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-Like Stars

Science.gov (United States)

Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Caldwell, Douglas; Kondo, Yoji;

2002-01-01

The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 in aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. Extending the mission to six years doubles the expected number of Earth-size planets in the HZ. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current Doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

Chromosome VIII disomy influences the nonsense suppression efficiency and transition metal tolerance of the yeast Saccharomyces cerevisiae.

Science.gov (United States)

Zadorsky, S P; Sopova, Y V; Andreichuk, D Y; Startsev, V A; Medvedeva, V P; Inge-Vechtomov, S G

2015-06-01

The SUP35 gene of the yeast Saccharomyces cerevisiae encodes the translation termination factor eRF3. Mutations in this gene lead to the suppression of nonsense mutations and a number of other pleiotropic phenotypes, one of which is impaired chromosome segregation during cell division. Similar effects result from replacing the S. cerevisiae SUP35 gene with its orthologues. A number of genetic and epigenetic changes that occur in the sup35 background result in partial compensation for this suppressor effect. In this study we showed that in S. cerevisiae strains in which the SUP35 orthologue from the yeast Pichia methanolica replaces the S. cerevisiae SUP35 gene, chromosome VIII disomy results in decreased efficiency of nonsense suppression. This antisuppressor effect is not associated with decreased stop codon read-through. We identified SBP1, a gene that localizes to chromosome VIII, as a dosage-dependent antisuppressor that strongly contributes to the overall antisuppressor effect of chromosome VIII disomy. Disomy of chromosome VIII also leads to a change in the yeast strains' tolerance of a number of transition metal salts. Copyright © 2015 John Wiley & Sons, Ltd.
Small Orbital Stereo Tracking Camera Technology Development

Science.gov (United States)

Gagliano, L.; Bryan, T.; MacLeod, T.

On-Orbit Small Debris Tracking and Characterization is a technical gap in the current National Space Situational Awareness necessary to safeguard orbital assets and crew. This poses a major risk of MOD damage to ISS and Exploration vehicles. In 2015 this technology was added to NASAs Office of Chief Technologist roadmap. For missions flying in or assembled in or staging from LEO, the physical threat to vehicle and crew is needed in order to properly design the proper level of MOD impact shielding and proper mission design restrictions. Need to verify debris flux and size population versus ground RADAR tracking. Use of ISS for In-Situ Orbital Debris Tracking development provides attitude, power, data and orbital access without a dedicated spacecraft or restricted operations on-board a host vehicle as a secondary payload. Sensor Applicable to in-situ measuring orbital debris in flux and population in other orbits or on other vehicles. Could enhance safety on and around ISS. Some technologies extensible to monitoring of extraterrestrial debris as well To help accomplish this, new technologies must be developed quickly. The Small Orbital Stereo Tracking Camera is one such up and coming technology. It consists of flying a pair of intensified megapixel telephoto cameras to evaluate Orbital Debris (OD) monitoring in proximity of International Space Station. It will demonstrate on-orbit optical tracking (in situ) of various sized objects versus ground RADAR tracking and small OD models. The cameras are based on Flight Proven Advanced Video Guidance Sensor pixel to spot algorithms (Orbital Express) and military targeting cameras. And by using twin cameras we can provide Stereo images for ranging & mission redundancy. When pointed into the orbital velocity vector (RAM), objects approaching or near the stereo camera set can be differentiated from the stars moving upward in background.
Evolution Models of Helium White Dwarf–Main-sequence Star Merger Remnants

International Nuclear Information System (INIS)

Zhang, Xianfei; Bi, Shaolan; Hall, Philip D.; Jeffery, C. Simon

2017-01-01

It is predicted that orbital decay by gravitational-wave radiation and tidal interaction will cause some close binary stars to merge within a Hubble time. The merger of a helium-core white dwarf with a main-sequence (MS) star can produce a red giant branch star that has a low-mass hydrogen envelope when helium is ignited and thus become a hot subdwarf. Because detailed calculations have not been made, we compute post-merger models with a stellar evolution code. We find the evolutionary paths available to merger remnants and find the pre-merger conditions that lead to the formation of hot subdwarfs. We find that some such mergers result in the formation of stars with intermediate helium-rich surfaces. These stars later develop helium-poor surfaces owing to diffusion. Combining our results with a model population and comparing to observed stars, we find that some observed intermediate helium-rich hot subdwarfs can be explained as the remnants of the mergers of helium-core white dwarfs with low-mass MS stars.
Evolution Models of Helium White Dwarf–Main-sequence Star Merger Remnants

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xianfei; Bi, Shaolan [Department of Astronomy, Beijing Normal University, Beijing, 100875 (China); Hall, Philip D.; Jeffery, C. Simon, E-mail: zxf@bnu.edu.cn [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom)

2017-02-01

It is predicted that orbital decay by gravitational-wave radiation and tidal interaction will cause some close binary stars to merge within a Hubble time. The merger of a helium-core white dwarf with a main-sequence (MS) star can produce a red giant branch star that has a low-mass hydrogen envelope when helium is ignited and thus become a hot subdwarf. Because detailed calculations have not been made, we compute post-merger models with a stellar evolution code. We find the evolutionary paths available to merger remnants and find the pre-merger conditions that lead to the formation of hot subdwarfs. We find that some such mergers result in the formation of stars with intermediate helium-rich surfaces. These stars later develop helium-poor surfaces owing to diffusion. Combining our results with a model population and comparing to observed stars, we find that some observed intermediate helium-rich hot subdwarfs can be explained as the remnants of the mergers of helium-core white dwarfs with low-mass MS stars.
Progress toward inducing immunologic tolerance to factor VIII

OpenAIRE

Scott, David W.; Pratt, Kathleen P.; Miao, Carol H.

2013-01-01

A major problem in treating hemophilia A patients with therapeutic factor VIII (FVIII) is that 20% to 30% of these patients produce neutralizing anti-FVIII antibodies. These antibodies block (inhibit) the procoagulant function of FVIII and thus are termed “inhibitors.” The currently accepted clinical method to attempt to eliminate inhibitors is immune tolerance induction (ITI) via a protocol requiring intensive FVIII treatment until inhibitor titers drop. Although often successful, ITI is ext...
The Demographics and Properties of Wide-Orbit, Planetary-Mass Companions from PSF Fitting of Spitzer/IRAC Images

Science.gov (United States)

Martinez, Raquel; Kraus, Adam L.

2017-06-01

Over the past decade, a growing population of planetary-mass companions ( 100 AU) from their host stars, challenging existing models of both star and planet formation. It is unclear whether these systems represent the low-mass extreme of stellar binary formation or the high-mass and wide-orbit extreme of planet formation theories, as various proposed formation pathways inadequately explain the physical and orbital aspects of these systems. Even so, determining which scenario best reproduces the observed characteristics of the PMCs will come once a statistically robust sample of directly-imaged PMCs are found and studied.We are developing an automated pipeline to search for wide-orbit PMCs to young stars in Spitzer/IRAC images. A Markov Chain Monte Carlo (MCMC) algorithm is the backbone of our novel point spread function (PSF) subtraction routine that efficiently creates and subtracts χ2-minimizing instrumental PSFs, simultaneously measuring astrometry and infrared photometry of these systems across the four IRAC channels (3.6 μm, 4.5 μm, 5.8 μm, and 8 μm). In this work, we present the results of a Spitzer/IRAC archival imaging study of 11 young, low-mass (0.044-0.88 M⊙ K3.5-M7.5) stars known to have faint, low-mass companions in 3 nearby star-forming regions (Chameleon, Taurus, and Upper Scorpius). We characterize the systems found to have low-mass companions with non-zero [I1] - [I4] colors, potentially signifying the presence of a circum(sub?)stellar disk. Plans for future pipeline improvements and paths forward will also be discussed. Once this computational foundation is optimized, the stage is set to quickly scour the nearby star-forming regions already imaged by Spitzer, identify potential candidates for further characterization with ground- or space-based telescopes, and increase the number of widely-separated PMCs known.
An adaptive optics multiplicity census of young stars in Upper Scorpius

Energy Technology Data Exchange (ETDEWEB)

Lafrenière, David [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, QC H3C 3J7 (Canada); Jayawardhana, Ray; Van Kerkwijk, Marten H. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Brandeker, Alexis [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Janson, Markus, E-mail: david@astro.umontreal.ca [Astrophysics Research Center, Queen' s University Belfast, BT7 1NN Belfast (United Kingdom)

2014-04-10

We present the results of a multiplicity survey of 91 stars spanning masses of ∼0.2-10 M {sub ☉} in the Upper Scorpius star-forming region, based on adaptive optics imaging with the Gemini North telescope. Our observations identified 29 binaries, 5 triples, and no higher order multiples. The corresponding raw multiplicity frequency is 0.37 ± 0.05. In the regime where our observations are complete—companion separations of 0.''1-5'' (∼15-800 AU) with magnitude limits ranging from K < 9.3 at 0.''1 to K < 15.8 at 5''—the multiplicity frequency is 0.27{sub −0.04}{sup +0.05}. For similar separations, the multiplicity frequency in Upper Scorpius is comparable to that in other dispersed star-forming regions, but is a factor of two to three higher than in denser star-forming regions or in the field. Our sample displays a constant multiplicity frequency as a function of stellar mass. Among our sample of binaries, we find that both wider (>100 AU) and higher-mass systems tend to have companions with lower companion-to-primary mass ratios. Three of the companions identified in our survey are unambiguously substellar and have estimated masses below 0.04 M {sub ☉} (two of them are new discoveries from this survey—1RXS J160929.1–210524b and HIP 78530B—although we have reported them separately in earlier papers). These three companions have projected orbital separations of 300-900 AU. Based on a statistical analysis factoring in sensitivity limits, we calculate an occurrence rate of 5-40 M {sub Jup} companions of ∼4.0% for orbital separations of 250-1000 AU, compared to <1.8% at smaller separations, suggesting that such companions are more frequent on wider orbits.
VLBA Scientists Study Birth of Sunlike Stars

Science.gov (United States)

1999-06-01

Three teams of scientists have used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope to learn tantalizing new details about how Sun-like stars are formed. Young stars, still growing by drawing in nearby gas, also spew some of that material back into their surroundings, like impatient infants that eat too quickly. The VLBA observations are giving astronomers new insights on both processes -- the accretion of material by the new stars and the outflows of material from them. "For the first time, we're actually seeing what happens right down next to the star in these young systems," said Mark Claussen, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. Claussen and other researchers announced their findings at the American Astronomical Society's meeting in Chicago. Material attracted by a young star's gravitational pull forms a flat, orbiting disk, called an accretion disk, in which the material circles closer and closer to the star until finally drawn into it. At the same time, material is ejected in "jets" speeding from the poles of the accretion disk. "The VLBA is showing us the first images of the region close to the star where the material in these jets is accelerated and formed into the `beams' of the jet," Claussen said. "We don't understand the details of these processes well," Claussen said. "These VLBA research projects are beginning to help unravel the mysteries of how stars like the Sun form." The teams are observing clumps of water vapor that naturally amplify radio emissions to see details smaller than the orbit of Mercury in young stellar systems as well as track gas motions. The clumps of gas are called masers, and amplify radio emission in much the same way that a laser amplifies light emission. "These images are just fantastic," said Al Wootten of NRAO in Charlottesville, VA. The maser clumps or "spots," emitting radio waves at a specific wavelength, can be tracked as they move over time. In addition
Dust discs around low-mass main-sequence stars

International Nuclear Information System (INIS)

Wolstencroft, R.D.; Walker, H.J.

1988-01-01

Current understanding of the formation of circumstellar discs as a natural accompaniment to the process of low-mass star formation is briefly reviewed. Models of the thermal emission from the dust discs around the prototype stars α Lyr, α PsA, β Pic and ε Eri are discussed, which indicate that the central regions of three of these discs are almost devoid of dust within radii ranging between 17 and 26 AU, with the temperature of the hottest dust lying between about 115 and 210 K. One possible explanation of the dust-free zones is the presence of a planet at the inner boundary of each cloud that sweeps up grains crossing its orbit. The colour, diameter and thickness of the optical image of β Pic, obtained by coronagraphic techniques, have provided further information on the size, radial distribution of number density and orbital inclination of the grains. The difference in surface brightness on the two sides of the disc is puzzling, but might be explained if the grains are elongated and aligned by the combined effects of a stellar wind and a magnetic field of spiral configuration. Finally, we discuss the orbital evolution and lifetimes of particles in these discs, which are governed primarily by radiation pressure, Poynting-Robertson drag and grain-grain collisions. (author)
RECENT STAR FORMATION IN THE LEADING ARM OF THE MAGELLANIC STREAM

Energy Technology Data Exchange (ETDEWEB)

Casetti-Dinescu, Dana I. [Department of Physics, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515 (United States); Bidin, Christian Moni [Instituto de Astronomía, Universidad Católica del Norte, Avenue Angamos 0610, Antofagasta (Chile); Girard, Terrence M.; Van Altena, William F. [Astronomy Department, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Méndez, Réne A. [Departmento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Vieira, Katherine [Centro de Investigaciones de Astronomía, Apartado Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of); Korchagin, Vladimir I., E-mail: casettid1@southernct.edu, E-mail: dana.casetti@yale.edu, E-mail: terry.girard@yale.edu, E-mail: william.vanaltena@yale.edu, E-mail: chr.moni.bidin@gmail.com, E-mail: ramendez.uchile@gmail.com, E-mail: kvieira@cida.ve, E-mail: vkorchagin@sfedu.ru [Institute of Physics, Southern Federal University, Stachki Street 124, 344090, Rostov-on-Don (Russian Federation)

2014-04-01

Strongly interacting galaxies undergo a short-lived but dramatic phase of evolution characterized by enhanced star formation, tidal tails, bridges, and other morphological peculiarities. The nearest example of a pair of interacting galaxies is the Magellanic Clouds, whose dynamical interaction produced the gaseous features known as the Magellanic Stream trailing the pair's orbit about the Galaxy, the bridge between the Clouds, and the leading arm (LA), a wide and irregular feature leading the orbit. Young, newly formed stars in the bridge are known to exist, giving witness to the recent interaction between the Clouds. However, the interaction of the Clouds with the Milky Way (MW) is less well understood. In particular, the LA must have a tidal origin; however, no purely gravitational model is able to reproduce its morphology and kinematics. A hydrodynamical interaction with the gaseous hot halo and disk of the Galaxy is plausible as suggested by some models and supporting neutral hydrogen (H I) observations. Here we show for the first time that young, recently formed stars exist in the LA, indicating that the interaction between the Clouds and our Galaxy is strong enough to trigger star formation in certain regions of the LA—regions in the outskirts of the MW disk (R ∼ 18 kpc), far away from the Clouds and the bridge.
RECENT STAR FORMATION IN THE LEADING ARM OF THE MAGELLANIC STREAM

International Nuclear Information System (INIS)

Casetti-Dinescu, Dana I.; Bidin, Christian Moni; Girard, Terrence M.; Van Altena, William F.; Méndez, Réne A.; Vieira, Katherine; Korchagin, Vladimir I.

2014-01-01

Strongly interacting galaxies undergo a short-lived but dramatic phase of evolution characterized by enhanced star formation, tidal tails, bridges, and other morphological peculiarities. The nearest example of a pair of interacting galaxies is the Magellanic Clouds, whose dynamical interaction produced the gaseous features known as the Magellanic Stream trailing the pair's orbit about the Galaxy, the bridge between the Clouds, and the leading arm (LA), a wide and irregular feature leading the orbit. Young, newly formed stars in the bridge are known to exist, giving witness to the recent interaction between the Clouds. However, the interaction of the Clouds with the Milky Way (MW) is less well understood. In particular, the LA must have a tidal origin; however, no purely gravitational model is able to reproduce its morphology and kinematics. A hydrodynamical interaction with the gaseous hot halo and disk of the Galaxy is plausible as suggested by some models and supporting neutral hydrogen (H I) observations. Here we show for the first time that young, recently formed stars exist in the LA, indicating that the interaction between the Clouds and our Galaxy is strong enough to trigger star formation in certain regions of the LA—regions in the outskirts of the MW disk (R ∼ 18 kpc), far away from the Clouds and the bridge
Lines profile variations and binarity in Wolf-Rayet stars

International Nuclear Information System (INIS)

Bisiacchi, G.F.; Firmani, C.; Lara, E. de

1982-01-01

Recently, HD50896, a WN5 star, for a long time considered as isolated, has been demonstrated to be a binary. This star shows very small displacement of the lines due to orbital motion and no evidence of the secondary spectrum. Is HD50896 a rare system in which the profile variations are peculiarly strong and easy to be detected, or are there many of these undetected binaries for which the analysis of the profile variation may be a powerful method to determine the periodicity. With this problem in mind the authors have observed a sample of 17 WR stars during a week to analyze both profile and radial velocity variations. This sample includes all the WR stars with Msub(v) 0 0 except for five stars that are binaries with determined period. All the spectra have been taken with a dispersion of 1.1 A channel -1 using a SIT television camera and a low dispersion spectrograph attached to the 2-meter telescope of the Observatorio Astronomico Nacional in San Pedro Martir, Baja California (Mexico). (Auth.)

CONSTRAINTS ON THE NEUTRON STAR AND INNER ACCRETION FLOW IN SERPENS X-1 USING NuSTAR

Energy Technology Data Exchange (ETDEWEB)

Miller, J. M. [Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1046 (United States); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, The University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Fuerst, F.; Grefenstette, B. W.; Tendulkar, S.; Harrison, F. A.; Rana, V. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bachetti, M.; Barret, D. [Universite de Toulouse, UPS-OMP, Toulouse (France); Boggs, S. E.; Craig, W. W.; Tomsick, J. A. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Chakrabarty, D. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Christensen, F. E. [Danish Technical University, Lyngby (Denmark); Hailey, C. J.; Paerels, F. [Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Natalucci, L. [Istituto di Astrofisica e Planetologia Spaziali (INAF), Via Fosso del Cavaliere 100, Roma I-00133 (Italy); Stern, D. K. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Zhang, W. W., E-mail: jonmm@umich.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-12-10

We report on an observation of the neutron star low-mass X-ray binary Serpens X-1, made with NuSTAR. The extraordinary sensitivity afforded by NuSTAR facilitated the detection of a clear, robust, relativistic Fe K emission line from the inner disk. A relativistic profile is required over a single Gaussian line from any charge state of Fe at the 5σ level of confidence, and any two Gaussians of equal width at the same confidence. The Compton back-scattering ''hump'' peaking in the 10-20 keV band is detected for the first time in a neutron star X-ray binary. Fits with relativistically blurred disk reflection models suggest that the disk likely extends close to the innermost stable circular orbit (ISCO) or stellar surface. The best-fit blurred reflection models constrain the gravitational redshift from the stellar surface to be z {sub NS} ≥ 0.16. The data are broadly compatible with the disk extending to the ISCO; in that case, z {sub NS} ≥ 0.22 and R {sub NS} ≤ 12.6 km (assuming M {sub NS} = 1.4 M {sub ☉} and a = 0, where a = cJ/GM {sup 2}). If the star is as large or larger than its ISCO, or if the effective reflecting disk leaks across the ISCO to the surface, the redshift constraints become measurements. We discuss our results in the context of efforts to measure fundamental properties of neutron stars, and models for accretion onto compact objects.
Fluid-phase immunoradiometric assay for the detection of qualitative abnormalities of factor VIII/von Willebrand factor in variants of von Willebrand's disease

International Nuclear Information System (INIS)

Girma, J.P.; Ardaillou, N.; Meyer, D.; Lavergne, J.M.; Larrieu, M.J.

1979-01-01

Antigenic reactivity of F.VIII/WF in variants of von Willebrand's disease (vWd) was studied with both fluid-phase and solid-phase immunoradiometric assays. Two different (rabbit and goat) 125 I-labeled specific antibodies against purified F.VIII/WF were used in both their divalent (lgG) and their monovalent (Fab fragment) forms. Dose-response curves obtained by reacting a constant amount of antibody with serial dilutions of plasmas from normal or homozygous vWd demonstrated the specificity of the test. The accuracy was significantly higher with 125 I-Fab fragments of goat anti-F.VIII/WF antiserum than intact goat lgG or rabbit lgG or Fab fragments. The significant decrease of the slope of the dose-response curves obtained with plasma from variants of vWd has been interpreted as due to the presence of abnormal F.VIII/WF molecules with decreased antigenic reactivity. A similar anomaly was found in cryosupernatant prepared from normal plasma, paralleling similarities demonstrated between variants of vWd and cryosupernatant. Results of experiments performed by reacting constant plasma dilutions from control or variants of vWd and varying concentrations of anti-F.VIII/WF Fab fragments (rabbit or goat) confirmed the decreased antigenic reactivity of variant F.VIII/WF
On the illumination of neutron star accretion discs

Science.gov (United States)

Wilkins, D. R.

2018-03-01

The illumination of the accretion disc in a neutron star X-ray binary by X-rays emitted from (or close to) the neutron star surface is explored through general relativistic ray tracing simulations. The applicability of the canonical suite of relativistically broadened emission line models (developed for black holes) to discs around neutron stars is evaluated. These models were found to describe well emission lines from neutron star accretion discs unless the neutron star radius is larger than the innermost stable orbit of the accretion disc at 6 rg or the disc is viewed at high inclination, above 60° where shadowing of the back side of the disc becomes important. Theoretical emissivity profiles were computed for accretion discs illuminated by hotspots on the neutron star surfaces, bands of emission and emission by the entirety of the hot, spherical star surface and in all cases, the emissivity profile of the accretion disc was found to be well represented by a single power law falling off slightly steeper than r-3. Steepening of the emissivity index was found where the emission is close to the disc plane and the disc can appear truncated when illuminated by a hotspot at high latitude. The emissivity profile of the accretion disc in Serpens X-1 was measured and found to be consistent with a single unbroken power law with index q=3.5_{-0.4}^{+0.3}, suggestive of illumination by the boundary layer between the disc and neutron star surface.
Dynamical and photometric models of star formation in tidal tails

International Nuclear Information System (INIS)

Wallin, J.F.

1990-01-01

An investigation into the causes of star formation in tidal tails has been conducted using a restricted three-body dynamical model in conjunction with a broadband photometric evolutionary code. Test particles are initially placed in circular orbits around a softened point mass and then perturbed by a companion passing in a parabotic orbit. During the passage, the density evolution of the galaxy is examined both in regions within the disk and in selected comoving regions in the tidal features. Even without the inclusion of self-gravity and hydrodynamics, regions of compression form inside the disk, along the tidal tail, and in the tidal bridge causing local density increases of up to 500 percent. By assuming that the density changes relate to the star-formation rate via a Schmidt (1959) law, limits on the density changes needed to make detectable changes in the colors are calculated. A spiral galaxy population is synthesized and the effects of modest changes in the star-formation rate are explored using a broadband photometric evolutionary code. Density changes similar to those found in the dynamical models will cause detectable changes in the colors of a stellar population. From these models, it is determined that the blue colors and knotty features observed in the tidal features of some galaxies result from increased rates of star formation induced by tidally produced density increases. Limitations of this model are discussed along with photometric evolutionary models based on the density evolution in the tails. 52 refs
Glioneuronal Heterotopia Presenting As a Cerebellopontine angle Tumor of the cranial Nerve VIII, Case Report.

Science.gov (United States)

Peris-Celda, M; Giannini, C; Diehn, F E; Eckel, L J; Neff, B A; Van Gompel, J J

2018-04-03

Vestibular schwannomas and meningiomas account for the great majority of lesions arising in the cerebellopontine angle (CPA). In this report, we present a case of glioneuronal heterotopia, also known as glioneuronal hamartoma, arising from the VIII cranial nerve, which is an extremely uncommon lesion. Important radiologic and surgical aspects are reviewed, which may help in early recognition and intraoperative decision making when these lesions are encountered. A healthy 29-year-old female presented with intermittent right facial numbness. Magnetic resonance imaging (MRI) showed an incidental minimally enhancing cerebellopontine angle lesion on the right VII-VIII cranial nerve complex. The patient declined serial observation and opted for operative intervention for resection. Intraoperatively, the lesion resembled neural tissue and was continuous with the VIII cranial nerve. Pathological analysis demonstrated mature glioneuronal tissue consistent with hamartomatous brain tissue. The patient maintained normal hearing and facial nerve function after surgery. Radiologic, surgical and pathological characteristics are described. Ectopic glioneuronal tissue of the VIII cranial nerve is a rare non-neoplastic lesion, and should be considered in the differential diagnosis of unusual appearing intracanalicular and cerebellopontine angle lesions. The congenital and benign nature of this entity makes observation a valid option for these cases, although they are so infrequent that they are often presumptively managed as vestibular schwannomas. Attempts to radically resect these lesions may result in higher rates of hearing loss or facial palsy due to their continuity with the cranial nerves. Copyright © 2018 Elsevier Inc. All rights reserved.
Characterization of a thrombin cleavage site mutation (Arg 1689 to Cys) in the factor VIII gene of two unrelated patients with cross-reacting material-positive hemophilia A.

Science.gov (United States)

Arai, M; Higuchi, M; Antonarakis, S E; Kazazian, H H; Phillips, J A; Janco, R L; Hoyer, L W

1990-01-15

The molecular defect responsible for moderate and severe hemophilia A has been identified for two unrelated patients with the CRM-positive form of this disorder (factor VIII activity of 0.02 and 0.05 U/mL with factor VIII antigen of 0.87 and 2.20 U/mL). In both cases, the immunopurified dysfunctional factor VIII protein is abnormal, in that the 80 Kd light chain is not cleaved by thrombin at arginine-1689. The basis for this failure was identified by polymerase chain reaction amplification of exon 14 of the variant factor VIII genes and direct sequencing of the amplified products. In both cases, a single base substitution (C to T) was identified that produces an arginine to cysteine substitution at amino acid residue 1689. These data identify the molecular defects of the two identical factor VIII variant proteins. The dysfunctional factor VIII has been designated "Factor VIII-East Hartford," the residence of the patient in whom the defect was first identified.
RETIRED A STARS AND THEIR COMPANIONS. VII. 18 NEW JOVIAN PLANETS

International Nuclear Information System (INIS)

Johnson, John Asher; Clanton, Christian; Crepp, Justin R.; Howard, Andrew W.; Marcy, Geoffrey W.; Bowler, Brendan P.; Isaacson, Howard; Henry, Gregory W.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Wright, Jason T.

2011-01-01

We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 ≤ M * /M ☉ ≤ 1.95, radii 2.5 ≤ R * /R ☉ ≤ 8.7, and metallicities –0.46 ≤ [Fe/H] ≤+0.30. The planets have minimum masses 0.9 M Jup ≤ M P sin i ∼ Jup and semimajor axes a ≥ 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5 M ☉ and provide valuable additional information about the properties of planets around stars more massive than the Sun.
Lacerations to Zones VIII and IX: It Is Not Just a Tendon Injury

Directory of Open Access Journals (Sweden)

Charla R. Fischer

2011-01-01

Full Text Available Extensor tendon injuries are widely believed to be straightforward problems that are relatively simple to manage. However, these injuries can be complex and demand a thorough understanding of anatomy to achieve the best functional outcomes. When lacerations occur in the forearm as in Zones VIII and IX injury, the repair of the extensor tendon and muscle, and posterior interosseous nerve (PIN is often challenging. A review of the literature shows little guidance and attention for these injuries. We present four patients with injuries to Zones VIII and IX as well as a review of surgical technique, postoperative rehabilitation, and pearls that may be of benefit to those managing these injuries.
The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Near the Habitable Zone of a Wide Range of Stars

Science.gov (United States)

Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.

1997-01-01

The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change. in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours. From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg. field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.
The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Neat the Habitable Zone of a Wide Range of Stars

Science.gov (United States)

Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.; Young, Richard E. (Technical Monitor)

1997-01-01

The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours, From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.
PENGARUH KEMANDIRIAN BELAJAR DAN PENGGUNAAN UANG SAKU TERHADAP PRESTASI BELAJAR KOMPETENSI DASAR EKONOMI KELAS VII DAN VIII

OpenAIRE

Apri Dwi Astuti

2012-01-01

Kemandirian belajar membantu siswa untuk bertanggung jawab dan menumbuhkan kesadaran belajar. Penggunaan uang saku menumbuhkan jiwa mandiri, jujur dan komitmen. Adapun hasil observasi awal menunjukkan masih ada siswa kels VII dan VIII SMP Semesta untuk kompetensi dasar ekonomi dibawah KKM. Tujuan penelitian ini untuk mengetahui pengaruh kemandirian belajar dn penggunaan uang saku terhadap prestasi belajar kompetensi dasar ekonomi kelas VII dan VIII SMP Semesta. Populasi penelitian ini adalah ...
The Gemini NICI planet-finding campaign: the orbit of the young exoplanet β Pictoris b

Energy Technology Data Exchange (ETDEWEB)

Nielsen, Eric L.; Liu, Michael C.; Chun, Mark; Ftaclas, Christ [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Wahhaj, Zahed [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago (Chile); Biller, Beth A. [Institute for Astronomy, The University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Hayward, Thomas L. [Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena (Chile); Males, Jared R.; Close, Laird M.; Morzinski, Katie M.; Skemer, Andrew J.; Hinz, Philip M. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kuchner, Marc J. [Goddard Space Flight Center, Code 667, Greenbelt, MD 20771 (United States); Rodigas, Timothy J. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States); Toomey, Douglas W. [Mauna Kea Infrared, LLC, 21 Pookela Street, Hilo, HI 96720 (United States)

2014-10-20

We present new astrometry for the young (12-21 Myr) exoplanet β Pictoris b taken with the Gemini/NICI and Magellan/MagAO instruments between 2009 and 2012. The high dynamic range of our observations allows us to measure the relative position of β Pic b with respect to its primary star with greater accuracy than previous observations. Based on a Markov Chain Monte Carlo analysis, we find the planet has an orbital semi-major axis of 9.1{sub −0.5}{sup +5.3} AU and orbital eccentricity <0.15 at 68% confidence (with 95% confidence intervals of 8.2-48 AU and 0.00-0.82 for semi-major axis and eccentricity, respectively, due to a long narrow degenerate tail between the two). We find that the planet has reached its maximum projected elongation, enabling higher precision determination of the orbital parameters than previously possible, and that the planet's projected separation is currently decreasing. With unsaturated data of the entire β Pic system (primary star, planet, and disk) obtained thanks to NICI's semi-transparent focal plane mask, we are able to tightly constrain the relative orientation of the circumstellar components. We find the orbital plane of the planet lies between the inner and outer disks: the position angle (P.A.) of nodes for the planet's orbit (211.8 ± 0.°3) is 7.4σ greater than the P.A. of the spine of the outer disk and 3.2σ less than the warped inner disk P.A., indicating the disk is not collisionally relaxed. Finally, for the first time we are able to dynamically constrain the mass of the primary star β Pic to 1.76{sub −0.17}{sup +0.18} M {sub ☉}.
EXPLORING HALO SUBSTRUCTURE WITH GIANT STARS: SUBSTRUCTURE IN THE LOCAL HALO AS SEEN IN THE GRID GIANT STAR SURVEY INCLUDING EXTENDED TIDAL DEBRIS FROM ωCENTAURI

International Nuclear Information System (INIS)

Majewski, Steven R.; Nidever, David L.; Damke, Guillermo J.; Patterson, Richard J.; García Pérez, Ana E.; Smith, Verne V.; Kunkel, William E.; Bizyaev, Dmitry

2012-01-01

We present the latitude-normalized radial velocity (v b ) distribution of 3318 subsolar metallicity, V ∼ b sequences. One sequence in the fourth Galactic quadrant lies within the l-v b space expected to contain tidal debris from the 'star cluster' ωCentauri. Not only does ωCen lie precisely in this l-v b sequence, but the positions and v b of member stars match those of N-body simulations of tidally disrupting dwarf galaxies on orbits ending with ωCen's current position and space motion. But the ultimate proof that we have very likely found extended parts of the ωCen tidal stream comes from echelle spectroscopy of a subsample of the stars that reveals a very particular chemical abundance signature known to occur only in ωCen. The newly discovered ωCen debris accounts for almost all fourth Galactic quadrant retrograde stars in the southern GGSS, which suggests ωCen is a dominant contributor of retrograde giant stars in the inner Galaxy.
Mass Modelling of Dwarf Spheroidal Galaxies: the Effect of Unbound Stars From Tidal Tails And the Milky Way

Energy Technology Data Exchange (ETDEWEB)

Klimentowski, Jaroslaw; Lokas, Ewa L.; /Warsaw, Copernicus Astron. Ctr.; Kazantzidis, Stelios; /KIPAC, Menlo Park; Prada, Francisco; /IAA, Granada; Mayer, Lucio; /Zurich,; Mamon, Gary A.; /Paris, Inst. Astrophys. /Meudon Observ.

2006-11-14

We study the origin and properties of the population of unbound stars in the kinematic samples of dwarf spheroidal galaxies. For this purpose we have run a high resolution N- body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. In agreement with the tidal stirring scenario of Mayer et al., the dwarf is placed on a highly eccentric orbit, its initial stellar component is in the form of an exponential disk and it has a NFW-like dark matter halo. After 10 Gyrs of evolution the dwarf produces a spheroidal stellar component and is strongly tidally stripped so that mass follows light and the stars are on almost isotropic orbits. From this final state, we create mock kinematic data sets for 200 stars by observing the dwarf in different directions.We find that when the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails.We also study another source of possible contamination by adding stars from the Milky Way. We demonstrate that most of the unbound stars can be removed by the method of interloper rejection proposed by den Hartog & Katgert and recently tested on simulated dark matter haloes. We model the cleaned up kinematic samples using solutions of the Jeans equation with constant mass-to-light ratio and velocity anisotropy parameter. We show that even for such strongly stripped dwarf the Jeans analysis, when applied to cleaned samples, allows us to reproduce the mass and mass-to-light ratio of the dwarf with accuracy typically better than 25 percent and almost exactly in the case when the line of sight is perpendicular to the tidal tails. The analysis was applied to the new data for the Fornax dSph galaxy for which we find a mass-to-light ratio of 11 solar units and isotropic orbits. We demonstrate that most of the contamination in the kinematic sample of Fornax probably originates from the Milky Way.
Role of orbital dynamics and cloud-cloud collisions in the formation of giant molecular clouds in global spiral structures

International Nuclear Information System (INIS)

Roberts, W.W. Jr.; Stewart, G.R.

1987-01-01

The role of orbit crowding and cloud-cloud collisions in the formation of GMCs and their organization in global spiral structure is investigated. Both N-body simulations of the cloud system and a detailed analysis of individual particle orbits are used to develop a conceptual understanding of how individual clouds participate in the collective density response. Detailed comparisons are made between a representative cloud-particle simulation in which the cloud particles collide inelastically with one another and give birth to and subsequently interact with young star associations and stripped down simulations in which the cloud particles are allowed to follow ballistic orbits in the absence of cloud-cloud collisions or any star formation processes. Orbit crowding is then related to the behavior of individual particle trajectories in the galactic potential field. The conceptual picture of how GMCs are formed in the clumpy ISMs of spiral galaxies is formulated, and the results are compared in detail with those published by other authors. 68 references
Estudo citofotométrico da expressão do marcador tumoral Fator VIII e fatores prognósticos no adenocarcinoma gástrico Cytophotometric study of the expression of the tumoral marker Factor VIII and prognostic factors in gastrci adenocarcinoma

Directory of Open Access Journals (Sweden)

Mary Tossa Nakamura

2007-12-01

Full Text Available RACIONAL: No câncer gástrico, a incidência, o diagnóstico e as opções terapêuticas apresentaram melhorias nas últimas décadas, porém o prognóstico permanece reservado, especialmente devido à maioria dos pacientes procurarem recurso médico com tumores avançados, metastáticos ou cirurgicamente irressecáveis já no diagnóstico. Biologia molecular é área de conhecimento recente com grandes questionamentos a serem respondidos e a atualidade dos fatos científicos mostra que o caminho deverá ser através da identificação de marcadores tumorais. Os grandes avanços na área da informática aprimoraram a análise da imagem celular através da citofotometria de imagem que possibilita através da imunoistoquímica estudar a proliferação celular e a angiogênese que participa em diversos processos tumorais, sendo pesquisadas por vários marcadores. Atualmente estudos são realizados para demonstrar o valor prognóstico de suas expressões, contudo, no adenocarcinoma gástrico resultados têm sido divergentes e estudos escassos. OBJETIVOS: Identificar e quantificar citofotometricamente a expressão dos marcadores da angiogênese através do fator VIII no adenocarcinoma e comparar suas expressões com fa classificação de Bormann, profundidade de invasão tumoral, grau de diferenciação, envolvimento nodal, padrão histológico e idade. MÉTODOS: Foram estudados 21 pacientes com adenocarcinoma gástrico, identificados de 1998 a 2006. Para a detecção do Fator VIII foi realizada imunoistoquímica, com anticorpo policlonal para Fator VIII. Foi realizada análise citofotométrica informatizada pelo sistema SAMBA 4000. RESULTADOS: Dos 21 pacientes 61,90% eram do sexo masculino e 38,10% do feminino, com idade mediana de 65 anos e apenas um não marcou para o Fator VIII (95,24% de marcação. As médias dos índices de marcagem para o Fator VIII foram de 61,14% (desvio-padrão de 15,06, variando de 29,16 a 73,91. Tumores com classifica
Orbital evolution of colliding star and pulsar winds in 2D and 3D: effects of dimensionality, EoS, resolution, and grid size

Science.gov (United States)

Bosch-Ramon, V.; Barkov, M. V.; Perucho, M.

2015-05-01

Context. The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary system suffers periodic and random variations of orbital and non-linear dynamical origins. The characterization of the evolution of the wind interaction region is necessary for understanding the rich phenomenology of these sources. Aims: For the first time, we simulate in 3 dimensions the interaction of isotropic stellar and relativistic pulsar winds along one full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size, and of different state equations: a γ̂-constant ideal gas, and an ideal gas with γ̂ dependent on temperature. Methods: We used the code PLUTO to carry out relativistic hydrodynamical simulations in 2 and 3 dimensions of the interaction between a slow dense wind and a mildly relativistic wind with Lorentz factor 2, along one full orbit in a region up to ~100 times the binary size. The different 2-dimensional simulations were carried out with equal and larger grid resolution and size, and one was done with a more realistic equation of state than in 3 dimensions. Results: The simulations in 3 dimensions confirm previous results in 2 dimensions, showing: a strong shock induced by Coriolis forces that terminates the pulsar wind also in the opposite direction to the star; strong bending of the shocked-wind structure against the pulsar motion; and the generation of turbulence. The shocked flows are also subject to a faster development of instabilities in 3 dimensions, which enhances shocks, two-wind mixing, and large-scale disruption of the shocked structure. In 2 dimensions, higher resolution simulations confirm lower resolution results, simulations with larger grid sizes strengthen the case for the loss of the general coherence of the shocked structure, and simulations with two different equations of state yield very similar results. In addition to the Kelvin-Helmholtz instability, discussed in
The Nuclear Spectroscopic Telescope Array (NuSTAR) High-Energy X-ray Mission

Science.gov (United States)

Harrison, Fiona A.; Craig, Willliam W.; Christensen, Finn E.; Hailey, Charles J.; Zhang, William W.; Boggs, Steven E.; Stern, Daniel; Cook, W. Rick; Forster, Karl; Giommi, Paolo;

2013-01-01

High-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 to 79 keV, extending the sensitivity of focusing far beyond the 10 keV high-energy cutoff achieved by all previous X-ray satellites. The inherently low background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than 100-fold improvement in sensitivity over the collimated or coded mask instruments that have operated in this bandpass. Using its unprecedented combination of sensitivity and spatial and spectral resolution, NuSTAR will pursue five primary scientific objectives: (1) probe obscured active galactic nucleus (AGN) activity out to thepeak epoch of galaxy assembly in the universe (at z 2) by surveying selected regions of the sky; (2) study the population of hard X-ray-emitting compact objects in the Galaxy by mapping the central regions of the Milky Way; (3) study the non-thermal radiation in young supernova remnants, both the hard X-ray continuum and the emission from the radioactive element 44Ti; (4) observe blazars contemporaneously with ground-based radio, optical, and TeV telescopes, as well as with Fermi and Swift, to constrain the structure of AGN jets; and (5) observe line and continuum emission from core-collapse supernovae in the Local Group, and from nearby Type Ia events, to constrain explosion models. During its baseline two-year mission, NuSTAR will also undertake a broad program of targeted observations. The observatory consists of two co-aligned grazing-incidence X-ray telescopes pointed at celestial targets by a three-axis stabilized spacecraft. Deployed into a 600 km, near-circular, 6 inclination orbit, the observatory has now completed commissioning, and is performing consistent with pre-launch expectations. NuSTAR is now executing its primary science mission, and with an expected orbit lifetime of 10 yr, we anticipate proposing a guest investigator program, to begin in late 2014.

Factor VIII and von Willebrand factor co-delivery by endothelial cells

NARCIS (Netherlands)

Bouwens, E.A.M.|info:eu-repo/dai/nl/314061894

2011-01-01

A defect in coagulation factor VIII (FVIII) results in the inherited bleeding disorder hemophilia A. Current treatment of hemophilia A is hampered by the need of frequent administration of costly FVIII products. Therefore gene therapy is an attractive alternative for protein replacement to treat
Historical intensity VIII earthquakes along the Rhone valley (Valais, Switzerland): primary and secondary effects

Energy Technology Data Exchange (ETDEWEB)

Fritsche, S.; Faeh, D.; Schwarz-Zanetti, G.

2012-06-15

In recent years the upper Rhone Valley has been one of the most intensively investigated regions by the Swiss Seismological Service. The high seismicity in the region encourages research in the seismological field and one main focus has been historical seismology. This report presents the state of the art of our historical investigations by giving an overview of the effects of four damaging earthquakes with intensity larger than VII, for which a fairly large number of documents could be found and analyzed. The overview includes the events of 1584 (Aigle, epicentral intensity VIII), 1755 (Brig, epicentral intensity VIII), 1855 (Visp, epicentral intensity VIII), and 1946 (Sierre, epicentral intensity VIII for the main shock and intensity VII for the largest aftershock). The paper focuses mainly on primary and secondary effects in the epicentral region, providing the key data and a general characterization of the event. Generally, primary effects such as the reaction of the population and impact on buildings took more focus in the past. Thus building damage is more frequently described in historic documents. However, we also found a number of sources describing secondary effects such as landslides, snow avalanches, and liquefaction. Since the sources may be useful, we include citations of these documents. The 1584 Aigle event, for example, produced exceptional movements in the Lake of Geneva, which can be explained by an expanded sub aquatic slide with resultant tsunami and seiche. The strongest of the aftershocks of the 1584 event triggered a destructive landslide covering the villages Corbeyrier and Yvorne, Vaud. All macroseismic data on the discussed events are accessible through the web page of the Swiss Seismological Service (http://www.seismo.ethz.ch). (authors)

MAGNETIC FLUX EXPULSION IN STAR FORMATION

International Nuclear Information System (INIS)

Zhao Bo; Li Zhiyun; Nakamura, Fumitaka; Krasnopolsky, Ruben; Shang, Hsien

2011-01-01

Stars form in dense cores of magnetized molecular clouds. If the magnetic flux threading the cores is dragged into the stars, the stellar field would be orders of magnitude stronger than observed. This well-known 'magnetic flux problem' demands that most of the core magnetic flux be decoupled from the matter that enters the star. We carry out the first exploration of what happens to the decoupled magnetic flux in three dimensions, using a magnetohydrodynamic (MHD) version of the ENZO adaptive mesh refinement code. The field-matter decoupling is achieved through a sink particle treatment, which is needed to follow the protostellar accretion phase of star formation. We find that the accumulation of the decoupled flux near the accreting protostar leads to a magnetic pressure buildup. The high pressure is released anisotropically along the path of least resistance. It drives a low-density expanding region in which the decoupled magnetic flux is expelled. This decoupling-enabled magnetic structure has never been seen before in three-dimensional MHD simulations of star formation. It generates a strong asymmetry in the protostellar accretion flow, potentially giving a kick to the star. In the presence of an initial core rotation, the structure presents an obstacle to the formation of a rotationally supported disk, in addition to magnetic braking, by acting as a rigid magnetic wall that prevents the rotating gas from completing a full orbit around the central object. We conclude that the decoupled magnetic flux from the stellar matter can strongly affect the protostellar collapse dynamics.
PERIODIC VARIABILITY OF LOW-MASS STARS IN SLOAN DIGITAL SKY SURVEY STRIPE 82

International Nuclear Information System (INIS)

Becker, A. C.; Hawley, S. L.; Ivezic, Z.; Kowalski, A. F.; Sesar, B.; Bochanski, J. J.; West, A. A.

2011-01-01

We present a catalog of periodic stellar variability in the 'Stripe 82' region of the Sloan Digital Sky Survey. After aggregating and re-calibrating catalog-level data from the survey, we ran a period-finding algorithm (Supersmoother) on all point-source light curves. We used color selection to identify systems that are likely to contain low-mass stars, in particular M dwarfs and white dwarfs. In total, we found 207 candidates, the vast majority of which appear to be in eclipsing binary systems. The catalog described in this paper includes 42 candidate M dwarf/white dwarf pairs, four white dwarf pairs, 59 systems whose colors indicate they are composed of two M dwarfs and whose light-curve shapes suggest they are in detached eclipsing binaries, and 28 M dwarf systems whose light-curve shapes suggest they are in contact binaries. We find no detached systems with periods longer than 3 days, thus the majority of our sources are likely to have experienced orbital spin-up and enhanced magnetic activity. Indeed, 26 of 27 M dwarf systems that we have spectra for show signs of chromospheric magnetic activity, far higher than the 24% seen in field stars of the same spectral type. We also find binaries composed of stars that bracket the expected boundary between partially and fully convective interiors, which will allow the measurement of the stellar mass-radius relationship across this transition. The majority of our contact systems have short orbital periods, with small variance (0.02 days) in the sample near the observed cutoff of 0.22 days. The accumulation of these stars at short orbital period suggests that the process of angular momentum loss, leading to period evolution, becomes less efficient at short periods. These short-period systems are in a novel regime for studying the effects of orbital spin-up and enhanced magnetic activity, which are thought to be the source of discrepancies between mass-radius predictions and measurements of these properties in eclipsing
DISCOVERY OF THE COLDEST IMAGED COMPANION OF A SUN-LIKE STAR

International Nuclear Information System (INIS)

Thalmann, C.; Carson, J.; Goto, M.; Feldt, M.; Henning, T.; Klahr, H.; Mordasini, C.; Janson, M.; McElwain, M.; Egner, S.; Hayano, Y.; Suzuki, R.; Hashimoto, J.; Kandori, R.; Kudo, T.; Kusakabe, N.; Morino, J.-I.; Suto, H.; Tamura, M.; Hodapp, K. W.

2009-01-01

We present the discovery of a brown dwarf or possible planet at a projected separation of 1.''9 = 29 AU around the star GJ 758, placing it between the separations at which substellar companions are expected to form by core accretion (∼5 AU) or direct gravitational collapse (typically ∼>100 AU). The object was detected by direct imaging of its thermal glow with Subaru/HiCIAO. At 10-40 times the mass of Jupiter and a temperature of 550-640 K, GJ 758 B constitutes one of the few known T-type companions, and the coldest ever to be imaged in thermal light around a Sun-like star. Its orbit is likely eccentric and of a size comparable to Pluto's orbit, possibly as a result of gravitational scattering or outward migration. A candidate second companion is detected at 1.''2 at one epoch.
On the Possibility of Habitable Trojan Planets in Binary Star Systems.

Science.gov (United States)

Schwarz, Richard; Funk, Barbara; Bazsó, Ákos

2015-12-01

Approximately 60% of all stars in the solar neighbourhood (up to 80% in our Milky Way) are members of binary or multiple star systems. This fact led to the speculations that many more planets may exist in binary systems than are currently known. To estimate the habitability of exoplanetary systems, we have to define the so-called habitable zone (HZ). The HZ is defined as a region around a star where a planet would receive enough radiation to maintain liquid water on its surface and to be able to build a stable atmosphere. We search for new dynamical configurations-where planets may stay in stable orbits-to increase the probability to find a planet like the Earth.
The difficult births of sunlike stars

International Nuclear Information System (INIS)

Stahler, S.; Comins, N.

1988-01-01

Over 4.5 billion years ago a small region deep inside an enormous cloud of interstellar gas and dust, located in an outer spiral arm of the Milky Way, gradually contracted until it became gravitationally unstable. When the density in this region of the cloud became great enough to allow gravity to overcome all other forces acting on it, the region collapsed. Materials swirled inward, condensed, heated up, radiated energy, and eventually settled down to form the Sun and our solar system. What properties did that original unstable region have when it began to shrink? Astronomers know it rotated, because its angular momentum manifests itself today mostly in the orbital motions of the planets. But that alone cannot help us answer even the most fundamental questions we have about how stars like the Sun form. To find out more, astronomers are studying similar collapsing regions of interstellar gas and dust in the Milky Way known as cold cores, which are even now in the process of becoming solar-type stars. Astronomers want to answer three specific questions: What qualities do these cold cores have that allow stars like the Sun to form from them? What exactly happens during the collapse process? And how do newly formed stars evolve?
Effects of Mg/Ga and V/III source ratios on hole concentration of N-polar (000\\bar{1}) p-type GaN grown by metalorganic vapor phase epitaxy

Science.gov (United States)

Nonoda, Ryohei; Shojiki, Kanako; Tanikawa, Tomoyuki; Kuboya, Shigeyuki; Katayama, Ryuji; Matsuoka, Takashi

2016-05-01

The effects of growth conditions such as Mg/Ga and V/III ratios on the properties of N-polar (000\\bar{1}) p-type GaN grown by metalorganic vapor phase epitaxy were studied. Photoluminescence spectra from Mg-doped GaN depended on Mg/Ga and V/III ratios. For the lightly doped samples, the band-to-acceptor emission was observed at 3.3 eV and its relative intensity decreased with increasing V/III ratio. For the heavily doped samples, the donor-acceptor pair emission was observed at 2.8 eV and its peak intensity monotonically decreased with V/III ratio. The hole concentration was maximum for the Mg/Ga ratio. This is the same tendency as in group-III polar (0001) growth. The V/III ratio also reduced the hole concentration. The higher V/III ratio reduced the concentration of residual donors such as oxygen by substituting nitrogen atoms. The surface became rougher with increasing V/III ratio and the hillock density increased.
Spin–Orbit Alignment of Exoplanet Systems: Ensemble Analysis Using Asteroseismology

DEFF Research Database (Denmark)

Campante, T. L.; Lund, M. N.; Kuszlewicz, James S.

2016-01-01

seems to be well aligned with the stellar spin axis ( ##IMG## [http://ej.iop.org/images/0004-637X/819/1/85/apj522683ieqn2.gif] $psi =12rc. 6_-11.0^+6.7$ ). While the latter result is in apparent contradiction with a statement made previously in the literature that the multi-transiting system Kepler-25...... observed with NASA’s Kepler satellite. Our results for i s are consistent with alignment at the 2 σ level for all stars in the sample, meaning that the system surrounding the red-giant star Kepler-56 remains as the only unambiguous misaligned multiple-planet system detected to date. The availability...... of a measurement of the projected spin–orbit angle λ for two of the systems allows us to estimate ψ . We find that the orbit of the hot Jupiter HAT-P-7b is likely to be retrograde ( ##IMG## [http://ej.iop.org/images/0004-637X/819/1/85/apj522683ieqn1.gif] $psi =116rc. 4_-14.7^+30.2$ ), whereas that of Kepler-25c...
Topological magnon bands in ferromagnetic star lattice

International Nuclear Information System (INIS)

Owerre, S A

2017-01-01

The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1–3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii–Moriya (DM) spin–orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases. (paper)
Topological magnon bands in ferromagnetic star lattice.

Science.gov (United States)

Owerre, S A

2017-05-10

The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1-3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii-Moriya (DM) spin-orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases.
On the rates of type Ia supernovae originating from white dwarf collisions in quadruple star systems

Science.gov (United States)

Hamers, Adrian S.

2018-04-01

We consider the evolution of stellar hierarchical quadruple systems in the 2+2 (two binaries orbiting each other's barycentre) and 3+1 (triple orbited by a fourth star) configurations. In our simulations, we take into account the effects of secular dynamical evolution, stellar evolution, tidal evolution and encounters with passing stars. We focus on type Ia supernovae (SNe Ia) driven by collisions of carbon-oxygen (CO) white dwarfs (WDs). Such collisions can arise from several channels: (1) collisions due to extremely high eccentricities induced by secular evolution, (2) collisions following a dynamical instability of the system, and (3) collisions driven by semisecular evolution. The systems considered here have initially wide inner orbits, with initial semilatus recti larger than 12 {au}, implying no interaction if the orbits were isolated. However, taking into account dynamical evolution, we find that ≈0.4 (≈0.6) of 2+2 (3+1) systems interact. In particular, Roche Lobe overflow can be triggered possibly in highly eccentric orbits, dynamical instability can ensue due to mass-loss-driven orbital expansion or secular evolution, or a semisecular regime can be entered. We compute the delay-time distributions (DTDs) of collision-induced SNe Ia, and find that they are flatter compared to the observed DTD. Moreover, our combined SNe Ia rates are (3.7± 0.7) × 10^{-6} M_⊙^{-1} and (1.3± 0.2) × 10^{-6} M_⊙^{-1} for 2+2 and 3+1 systems, respectively, three orders of magnitude lower compared to the observed rate, of order 10^{-3} M_⊙^{-1}. The low rates can be ascribed to interactions before the stars evolve to CO WDs. However, our results are lower limits given that we considered a subset of quadruple systems.
Idiopathic factor VIII inhibitor autoantibody in a man presented after accident.

NARCIS (Netherlands)

Mansouritorghabeh, H.; Lak, M.; Heerde, W.L. van

2009-01-01

Acquired hemophilia A is a rare but severe autoimmune bleeding disorder caused by autoantibodies against factor VIII activity and is a potentially life-threatening hemorrhagic disorder. The incidence of acquired hemophilia A has been estimated as 1.48 cases per million per year. The overall rate of
The Drifting Star

Science.gov (United States)

2008-04-01

By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its
EG Andromedae: A New Orbit and Additional Evidence for a Photoionized Wind

Science.gov (United States)

Kenyon, Scott J.; Garcia, Michael R.

2016-07-01

We analyze a roughly 20 yr set of spectroscopic observations for the symbiotic binary EG And. Radial velocities derived from echelle spectra are best fit with a circular orbit having an orbital period of P = 483.3 ± 1.6 days and semi-amplitude K = 7.34 ± 0.07 km s-1. Combined with previous data, these observations rule out an elliptical orbit at the 10σ level. Equivalent widths of H I Balmer emission lines and various absorption features vary in phase with the orbital period. Relative to the radius of the red giant primary, the apparent size of the H II region is consistent with a model where a hot secondary star with effective temperature T h ≈ 75,000 K ionizes the wind from the red giant.
LONG-LIVED CHAOTIC ORBITAL EVOLUTION OF EXOPLANETS IN MEAN MOTION RESONANCES WITH MUTUAL INCLINATIONS

Energy Technology Data Exchange (ETDEWEB)

Barnes, Rory; Deitrick, Russell; Quinn, Thomas R. [Astronomy Department, University of Washington, Box 951580, Seattle, WA 98195 (United States); Greenberg, Richard [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 86716 (United States); Raymond, Sean N., E-mail: rory@astro.washington.edu [NASA Astrobiology Institute-Virtual Planetary Laboratory Lead Team (United States)

2015-03-10

We present N-body simulations of resonant planets with inclined orbits that show chaotically evolving eccentricities and inclinations that can persist for at least 10 Gyr. A wide range of behavior is possible, from fast, low amplitude variations to systems in which eccentricities reach 0.9999 and inclinations 179.°9. While the orbital elements evolve chaotically, at least one resonant argument always librates. We show that the HD 73526, HD 45364, and HD 60532 systems may be in chaotically evolving resonances. Chaotic evolution is apparent in the 2:1, 3:1, and 3:2 resonances, and for planetary masses from lunar- to Jupiter-mass. In some cases, orbital disruption occurs after several gigayears, implying the mechanism is not rigorously stable, just long-lived relative to the main sequence lifetimes of solar-type stars. Planet-planet scattering appears to yield planets in inclined resonances that evolve chaotically in about 0.5% of cases. These results suggest that (1) approximate methods for identifying unstable orbital architectures may have limited applicability, (2) the observed close-in exoplanets may be produced during epochs of high eccentricit induced by inclined resonances, (3) those exoplanets' orbital planes may be misaligned with the host star's spin axis, (4) systems with resonances may be systematically younger than those without, (5) the distribution of period ratios of adjacent planets detected via transit may be skewed due to inclined resonances, and (6) potentially habitable planets may have dramatically different climatic evolution than Earth. The Gaia spacecraft is capable of discovering giant planets in these types of orbits.
LONG-LIVED CHAOTIC ORBITAL EVOLUTION OF EXOPLANETS IN MEAN MOTION RESONANCES WITH MUTUAL INCLINATIONS

International Nuclear Information System (INIS)

Barnes, Rory; Deitrick, Russell; Quinn, Thomas R.; Greenberg, Richard; Raymond, Sean N.

2015-01-01

We present N-body simulations of resonant planets with inclined orbits that show chaotically evolving eccentricities and inclinations that can persist for at least 10 Gyr. A wide range of behavior is possible, from fast, low amplitude variations to systems in which eccentricities reach 0.9999 and inclinations 179.°9. While the orbital elements evolve chaotically, at least one resonant argument always librates. We show that the HD 73526, HD 45364, and HD 60532 systems may be in chaotically evolving resonances. Chaotic evolution is apparent in the 2:1, 3:1, and 3:2 resonances, and for planetary masses from lunar- to Jupiter-mass. In some cases, orbital disruption occurs after several gigayears, implying the mechanism is not rigorously stable, just long-lived relative to the main sequence lifetimes of solar-type stars. Planet-planet scattering appears to yield planets in inclined resonances that evolve chaotically in about 0.5% of cases. These results suggest that (1) approximate methods for identifying unstable orbital architectures may have limited applicability, (2) the observed close-in exoplanets may be produced during epochs of high eccentricit induced by inclined resonances, (3) those exoplanets' orbital planes may be misaligned with the host star's spin axis, (4) systems with resonances may be systematically younger than those without, (5) the distribution of period ratios of adjacent planets detected via transit may be skewed due to inclined resonances, and (6) potentially habitable planets may have dramatically different climatic evolution than Earth. The Gaia spacecraft is capable of discovering giant planets in these types of orbits
The Discovery of λ Bootis Stars: The Southern Survey I

Energy Technology Data Exchange (ETDEWEB)

Gray, R. O.; Riggs, Q. S.; Newsome, I. M. [Department of Physics and Astronomy, Appalachian State University, Boone, NC 26808 (United States); Koen, C. [Department of Statistics, University of the Western Cape, Private Bag X17, Bellville, 7535 Cape Town (South Africa); Murphy, S. J. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Corbally, C. J. [Vatican Observatory Research Group, Steward Observatory, Tucson, AZ, 85721-0065 (United States); Cheng, K.-P. [California State University, Fullerton, Fullerton, CA (United States); Neff, J. E. [National Science Foundation, Arlington, VA (United States)

2017-07-01

The λ Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that λ Boo stars have higher frequencies of “bright” debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR 8799, a λ Boo star with a resolved debris disk, suggests that the λ Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 λ Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of λ Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 λ Boo stars and have confirmed 12 others. As a step toward determining the proportion of λ Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22 μ m. On this basis, we cannot conclude that λ Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many λ Boo debris disks are cool and do not radiate strongly at 22 μ m.
The Discovery of λ Bootis Stars: The Southern Survey I

International Nuclear Information System (INIS)

Gray, R. O.; Riggs, Q. S.; Newsome, I. M.; Koen, C.; Murphy, S. J.; Corbally, C. J.; Cheng, K.-P.; Neff, J. E.

2017-01-01

The λ Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that λ Boo stars have higher frequencies of “bright” debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR 8799, a λ Boo star with a resolved debris disk, suggests that the λ Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 λ Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of λ Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 λ Boo stars and have confirmed 12 others. As a step toward determining the proportion of λ Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22 μ m. On this basis, we cannot conclude that λ Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many λ Boo debris disks are cool and do not radiate strongly at 22 μ m.
The Discovery of λ Bootis Stars: The Southern Survey I

Science.gov (United States)

Gray, R. O.; Riggs, Q. S.; Koen, C.; Murphy, S. J.; Newsome, I. M.; Corbally, C. J.; Cheng, K.-P.; Neff, J. E.

2017-07-01

The λ Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that λ Boo stars have higher frequencies of “bright” debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR 8799, a λ Boo star with a resolved debris disk, suggests that the λ Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 λ Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of λ Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 λ Boo stars and have confirmed 12 others. As a step toward determining the proportion of λ Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22 μm. On this basis, we cannot conclude that λ Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many λ Boo debris disks are cool and do not radiate strongly at 22 μm.
REFINED NEUTRON STAR MASS DETERMINATIONS FOR SIX ECLIPSING X-RAY PULSAR BINARIES

International Nuclear Information System (INIS)

Rawls, Meredith L.; Orosz, Jerome A.; McClintock, Jeffrey E.; Torres, Manuel A. P.; Bailyn, Charles D.; Buxton, Michelle M.

2011-01-01

We present an improved method for determining the mass of neutron stars in eclipsing X-ray pulsar binaries and apply the method to six systems, namely, Vela X-1, 4U 1538-52, SMC X-1, LMC X-4, Cen X-3, and Her X-1. In previous studies to determine neutron star mass, the X-ray eclipse duration has been approximated analytically by assuming that the companion star is spherical with an effective Roche lobe radius. We use a numerical code based on Roche geometry with various optimizers to analyze the published data for these systems, which we supplement with new spectroscopic and photometric data for 4U 1538-52. This allows us to model the eclipse duration more accurately and thus calculate an improved value for the neutron star mass. The derived neutron star mass also depends on the assumed Roche lobe filling factor β of the companion star, where β = 1 indicates a completely filled Roche lobe. In previous work a range of β between 0.9 and 1.0 was usually adopted. We use optical ellipsoidal light-curve data to constrain β. We find neutron star masses of 1.77 ± 0.08 M sun for Vela X-1, 0.87 ± 0.07 M sun for 4U 1538-52 (eccentric orbit), 1.00 ± 0.10 M sun for 4U 1538-52 (circular orbit), 1.04 ± 0.09 M sun for SMC X-1, 1.29 ± 0.05 M sun for LMC X-4, 1.49 ± 0.08 M sun for Cen X-3, and 1.07 ± 0.36 M sun for Her X-1. We discuss the limits of the approximations that were used to derive the earlier mass determinations, and we comment on the implications our new masses have for observationally refining the upper and lower bounds of the neutron star mass distribution.
One-electron spectrum of Xe VIII

International Nuclear Information System (INIS)

Roberts, J.R.; Knystautas, E.J.; Sugar, J.

1979-01-01

The spectrum of Xe VIII has been observed in a theta-pinch discharge. New line identifications were made that determine the energies of the 6s, 7s, 6p, and 5f terms relative to the 5s 2 S ground state and confirm the previously known 5p and 5d terms. An independent system of levels derived from the observed 4f-ng (n = 5,6) transitions was found. Its position relative to the ground state is obtained from a predicted value for the 5g effective quantum number n*. From the ns series (n=5--7) a value for the ionization enegy of 105.91 +- 0.05 eV was derived

Stars Form Surprisingly Close to Milky Way's Black Hole

Science.gov (United States)

2005-10-01

The supermassive black hole at the center of the Milky Way has surprisingly helped spawn a new generation of stars, according to observations from NASA's Chandra X-ray Observatory. This novel mode of star formation may solve several mysteries about the supermassive black holes that reside at the centers of nearly all galaxies. "Massive black holes are usually known for violence and destruction," said Sergei Nayakshin of the University of Leicester, United Kingdom, and coauthor of a paper on this research in an upcoming issue of the Monthly Notices of the Royal Astronomical Society. "So it's remarkable that this black hole helped create new stars, not just destroy them." Black holes have earned their fearsome reputation because any material -- including stars -- that falls within the so-called event horizon is never seen again. However, these new results indicate that the immense disks of gas known to orbit many black holes at a "safe" distance from the event horizon can help nurture the formation of new stars. Animation of Stars Forming Around Black Hole Animation of Stars Forming Around Black Hole This conclusion came from new clues that could only be revealed in X-rays. Until the latest Chandra results, astronomers have disagreed about the origin of a mysterious group of massive stars discovered by infrared astronomers to be orbiting less than a light year from the Milky Way's central black hole, a.k.a. Sagittarius A*, or Sgr A*. At such close distances to Sgr A*, the standard model for star formation predicts that gas clouds from which stars form should have been ripped apart by tidal forces from the black hole. Two models to explain this puzzle have been proposed. In the disk model, the gravity of a dense disk of gas around Sgr A* offsets the tidal forces and allows stars to form; in the migration model, the stars formed in a star cluster far away from the black hole and migrated in to form the ring of massive stars. The migration scenario predicts about a
Innocent Bystanders: Orbital Dynamics of Exomoons During Planet–Planet Scattering

Science.gov (United States)

Hong, Yu-Cian; Raymond, Sean N.; Nicholson, Philip D.; Lunine, Jonathan I.

2018-01-01

Planet–planet scattering is the leading mechanism to explain the broad eccentricity distribution of observed giant exoplanets. Here we study the orbital stability of primordial giant planet moons in this scenario. We use N-body simulations including realistic oblateness and evolving spin evolution for the giant planets. We find that the vast majority (∼80%–90% across all our simulations) of orbital parameter space for moons is destabilized. There is a strong radial dependence, as moons past ∼ 0.1 {R}{Hill} are systematically removed. Closer-in moons on Galilean-moon-like orbits (<0.04 R Hill) have a good (∼20%–40%) chance of survival. Destabilized moons may undergo a collision with the star or a planet, be ejected from the system, be captured by another planet, be ejected but still orbiting its free-floating host planet, or survive on heliocentric orbits as “planets.” The survival rate of moons increases with the host planet mass but is independent of the planet’s final (post-scattering) orbits. Based on our simulations, we predict the existence of an abundant galactic population of free-floating (former) moons.
Probing dark matter with star clusters: a dark matter core in the ultra-faint dwarf Eridanus II

Science.gov (United States)

Contenta, Filippo; Balbinot, Eduardo; Petts, James A.; Read, Justin I.; Gieles, Mark; Collins, Michelle L. M.; Peñarrubia, Jorge; Delorme, Maxime; Gualandris, Alessia

2018-05-01

We present a new technique to probe the central dark matter (DM) density profile of galaxies that harnesses both the survival and observed properties of star clusters. As a first application, we apply our method to the `ultra-faint' dwarf Eridanus II (Eri II) that has a lone star cluster ˜45 pc from its centre. Using a grid of collisional N-body simulations, incorporating the effects of stellar evolution, external tides and dynamical friction, we show that a DM core for Eri II naturally reproduces the size and the projected position of its star cluster. By contrast, a dense cusped galaxy requires the cluster to lie implausibly far from the centre of Eri II (>1 kpc), with a high inclination orbit that must be observed at a particular orbital phase. Our results, therefore, favour a DM core. This implies that either a cold DM cusp was `heated up' at the centre of Eri II by bursty star formation or we are seeing an evidence for physics beyond cold DM.
A STATISTICAL RECONSTRUCTION OF THE PLANET POPULATION AROUND KEPLER SOLAR-TYPE STARS

International Nuclear Information System (INIS)

Silburt, Ari; Wu, Yanqin; Gaidos, Eric

2015-01-01

Using the cumulative catalog of planets detected by the NASA Kepler mission, we reconstruct the intrinsic occurrence of Earth- to Neptune-size (1-4 R ⊕ ) planets and their distributions with radius and orbital period. We analyze 76,711 solar-type (0.8 < R * /R ☉ < 1.2) stars with 430 planets on 20-200 day orbits, excluding close-in planets that may have been affected by the proximity to the host star. Our analysis considers errors in planet radii and includes an ''iterative simulation'' technique that does not bin the data. We find a radius distribution that peaks at 2-2.8 Earth radii, with lower numbers of smaller and larger planets. These planets are uniformly distributed with logarithmic period, and the mean number of such planets per star is 0.46 ± 0.03. The occurrence is ∼0.66 if planets interior to 20 days are included. We estimate the occurrence of Earth-size planets in the ''habitable zone'' (defined as 1-2 R ⊕ , 0.99-1.7 AU for solar-twin stars) as 6.4 −1.1 +3.4 %. Our results largely agree with those of Petigura et al., although we find a higher occurrence of 2.8-4 Earth-radii planets. The reasons for this excess are the inclusion of errors in planet radius, updated Huber et al. stellar parameters, and also the exclusion of planets that may have been affected by proximity to the host star
O-C analysis of the pulsating subdwarf B star PG 1219 + 534

Science.gov (United States)

Otani, Tomomi; Stone-Martinez, Alexander; Oswalt, Terry D.; Morello, Claudia; Moss, Adam; Singh, Dana; Sampson, Kenneth; DeAbreu, Caila; Khan, Aliyah; Seepersad, Austin; Shaikh, Mehvesh; Wilson, Linda

2017-01-01

PG 1219 + 534 (KY Uma) is a subdwarf B pulsating star with multiple periodicities between 120 - 175 s. So far, the most promising theory for the origin of subdwarf B (sdB) stars is that they result from binary mass transfer near the Helium Flash stage of evolution. The observations of PG 1219 +534 reported here are part of our program to constrain this evolutional theory by searching for companions and determining orbital separations around sdB pulsators using the Observed-minus-Calculated (O-C) method. A star’s position in space will wobble due to the gravitational forces of any companion or planet. If the star emits a periodic signal like pulsations, its orbital motion around the system’s center of mass causes periodic changes in the light pulse arrival times. PG 1219 + 534 was monitored for 90 hours during 2010-1 and 2016 using the 0.9m SARA-KP telescope at Kitt Peak National Observatory (KPNO), Arizona, and the 0.8 m Ortega telescope at Florida Institute of Technology in Melbourne. In this poster we present our time-series photometry and O-C analysis of this data.
Investigating the Relativistic Motion of the Stars Near the Supermassive Black Hole in the Galactic Center

Energy Technology Data Exchange (ETDEWEB)

Parsa, M.; Eckart, A.; Shahzamanian, B.; Zajaček, M.; Straubmeier, C. [I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany); Karas, V. [Astronomical Institute, Academy of Science, Boční II 1401, CZ-14131 Prague (Czech Republic); Zensus, J. A., E-mail: parsa@ph1.uni-koeln.de [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)

2017-08-10

The S-star cluster in the Galactic center allows us to study the physics close to a supermassive black hole, including distinctive dynamical tests of general relativity. Our best estimates for the mass of and the distance to Sgr A* using the three stars with the shortest period (S2, S38, and S55/S0-102) and Newtonian models are M {sub BH} = (4.15 ± 0.13 ± 0.57) × 10{sup 6} M {sub ⊙} and R {sub 0} = 8.19 ± 0.11 ± 0.34 kpc. Additionally, we aim at a new and practical method to investigate the relativistic orbits of stars in the gravitational field near Sgr A*. We use a first-order post-Newtonian approximation to calculate the stellar orbits with a broad range of periapse distance r {sub p} . We present a method that employs the changes in orbital elements derived from elliptical fits to different sections of the orbit. These changes are correlated with the relativistic parameter defined as ϒ ≡ r {sub s} / r {sub p} (with r {sub s} being the Schwarzschild radius) and can be used to derive ϒ from observational data. For S2 we find a value of ϒ = 0.00088 ± 0.00080, which is consistent, within the uncertainty, with the expected value of ϒ = 0.00065 derived from M {sub BH} and the orbit of S2. We argue that the derived quantity is unlikely to be dominated by perturbing influences such as noise on the derived stellar positions, field rotation, and drifts in black hole mass.
A Binary Nature of the Marginal CP Star Sigma Sculptoris

Science.gov (United States)

Janík, Jan; Krtička, Jiří; Mikulášek, Zdeněk; Zverko, Juraj; Pintado, Olga; Paunzen, Ernst; Prvák, Milan; Skalický, Jan; Zejda, Miloslav; Adam, Christian

2018-05-01

The A2 V star σ Scl was suspected of being a low-amplitude rotating variable of the Ap-type star by several authors. Aiming to decide whether the star is a variable chemically peculiar (CP) star, we searched for the photometric and spectroscopic variability, and determined chemical abundances of σ Scl. The possible variability was tested using several types of periodograms applied to the photometry from Long-Term Photometry of Variables project (LTPV) and Hipparcos. Sixty spectrograms of high signal-to-noise (S/N) were obtained and used for chemical analysis of the stellar atmosphere and for looking for spectral variability that is symptomatic for the CP stars. We did not find any signs of the light variability or prominent chemical peculiarity, that is specific for the CP stars. The only exception is the abundance of scandium, which is significantly lower than the solar one and yttrium and barium, which are strongly overabundant. As a by-product of the analysis, and with the addition of 29 further spectra, we found that σ Scl is a single-lined spectroscopic binary with orbital period of 46.877(8) d. We argue that σ Scl is not an Ap star, but rather a marginal Am star in SB1 system. The spectral energy distribution of the binary reveals infrared excess due to circumstellar material.
THE BINARITY OF MILKY WAY F,G,K STARS AS A FUNCTION OF EFFECTIVE TEMPERATURE AND METALLICITY

Energy Technology Data Exchange (ETDEWEB)

Gao, Shuang; Liu, Chao; Zhang, Xiaobin; Justham, Stephen; Deng, Licai; Yang, Ming [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2014-06-20

We estimate the fraction of F,G,K stars with close binary companions by analysing multi-epoch stellar spectra from the Sloan Digital Sky Survey (SDSS) and LAMOST for radial velocity variations. We employ a Bayesian method to infer the maximum likelihood of the fraction of binary stars with orbital periods of 1000 days or shorter, assuming a simple model distribution for a binary population with circular orbits. The overall inferred fraction of stars with such a close binary companion is 43.0% ± 2.0% for a sample of F,G,K stars from SDSS SEGUE, and 30% ± 8.0% in a similar sample from LAMOST. The apparent close binary fraction decreases with the stellar effective temperature. We divide the SEGUE and LEGUE data into three subsamples with different metallicity ([Fe/H] < –1.1; –1.1 < [Fe/H] < –0.6; –0.6 < [Fe/H]), for which the inferred close binary fractions are 56 ± 5.0%, 56.0 ± 3%, and 30 ± 5.7%. The metal-rich stars from our sample are therefore substantially less likely to possess a close binary companion than otherwise similar stars drawn from metal-poor populations. The different ages and formation environments of the Milky Way's thin disk, thick disk, and halo may contribute to explaining these observations. Alternatively, metallicity may have a significant effect on the formation and/or evolution of binary stars.
46 CFR 54.01-2 - Adoption of division 1 of section VIII of the ASME Boiler and Pressure Vessel Code.

Science.gov (United States)

2010-10-01

... Boiler and Pressure Vessel Code. 54.01-2 Section 54.01-2 Shipping COAST GUARD, DEPARTMENT OF HOMELAND... division 1 of section VIII of the ASME Boiler and Pressure Vessel Code. (a) Pressure vessels shall be designed, constructed, and inspected in accordance with section VIII of the ASME Boiler and Pressure Vessel...
Influence of Problem Based Learning on Critical Thinking Skills and Competence Class VIII SMPN 1 Gunuang Omeh, 2016/2017

Science.gov (United States)

Aswan, D. M.; Lufri, L.; Sumarmin, R.

2018-04-01

This research intends to determine the effect of Problem Based Learning models on students' critical thinking skills and competences. This study was a quasi-experimental research. The population of the study was the students of class VIII SMPN 1 Subdistrict Gunuang Omeh. Random sample selection is done by randomizing the class. Sample class that was chosen VIII3 as an experimental class given that treatment study based on problems and class VIII1 as control class that treatment usually given study. Instrument that used to consist of critical thinking test, cognitive tests, observation sheet of affective and psychomotor. Independent t-test and Mann Whitney U test was used for the analysis. Results showed that there was significant difference (sig competences.
AN M DWARF COMPANION TO AN F-TYPE STAR IN A YOUNG MAIN-SEQUENCE BINARY

Energy Technology Data Exchange (ETDEWEB)

Eigmüller, Ph.; Csizmadia, Sz.; Erikson, A.; Fridlund, M.; Pasternacki, Th.; Rauer, H. [Institute of Planetary Research, German Aerospace Center Rutherfordstr. 2, D-12489 Berlin (Germany); Eislöffel, J.; Lehmann, H.; Hartmann, M.; Hatzes, A. [Thüringer Landessternwarte Tautenburg Sternwarte 5, D-07778 Tautenburg (Germany); Tkachenko, A. [Instituut voor Sterrenkunde, KU Leuven Celestijnenlaan 200D, 3001 Leuven (Belgium); Voss, H., E-mail: philipp.eigmueller@dlr.de [Universitat de Barcelona, Department of Astronomy and Meteorology Martí i Franquès, 1, E-08028 Barcelona (Spain)

2016-03-15

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung–Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 ± 0.073) M{sub ⊙} and a radius of (1.474 ± 0.040) R{sub ⊙}. The companion is an M dwarf with a mass of (0.188 ± 0.014) M{sub ⊙} and a radius of (0.234 ± 0.009) R{sub ⊙}. The orbital period is (1.35121 ± 0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin–orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass–radius relation of both components are in agreement with this finding.
A high false positive rate for Kepler planetary candidates of giant stars using asterodensity profiling

International Nuclear Information System (INIS)

Sliski, David H.; Kipping, David M.

2014-01-01

Asterodensity profiling (AP) is a relatively new technique for studying transit light curves. By comparing the mean stellar density derived from the transit light curve to that found through an independent method, AP provides information on several useful properties such as orbital eccentricity and blended light. We present an AP survey of 41 Kepler Objects of Interest (KOIs), with a single transiting candidate, for which the target star's mean stellar density has been measured using asteroseismology. The ensemble distribution of the AP measurements for the 31 dwarf stars in our sample shows excellent agreement with the spread expected if the KOIs were genuine and have realistic eccentricities. In contrast, the same test for the 10 giants in our sample reveals significant incompatibility at >4σ confidence. While extreme eccentricities could be invoked, this hypothesis requires four of the KOIs to contact their host star at periastron passage, including the recently claimed confirmation of Kepler-91b. After carefully examining several hypotheses, we conclude that the most plausible explanation is that the transiting objects orbit a different star to that measured with asteroseismology—cases we define as false-positives. Based on the AP distribution, we estimate a false-positive rate (FPR) for Kepler's giant stars with a single transiting object of FPR ≅ 70% ± 30%.
Orbital parameters of the multiple system EM Boo

Science.gov (United States)

Özkardeş, B.; Bakış, H.; Bakış, V.

2018-02-01

EM Boo is a relatively bright (V = 8.98 mag.) and short orbital period (P⁓2.45 days) binary star member of the multiple system WDS J14485+2445AB. There is neither photometric nor spectroscopic study of the system in the literature. In this work, we obtained spectroscopic orbital parameters of the system from new high resolution spectroscopic observations made with échelle spectrograph attached to UBT60 telescope of Akdeniz University. The spectroscopic solution yielded the values K1 = 100.7±2.6 km/s, K2 = 120.1±2.6 km/s and Vγ = -14.6±3.1 km/s, and thus the mass ratio of the system q = 0.838±0.064.
Isolating integrals of the motion for stellar orbits in a rotating galactic bar

International Nuclear Information System (INIS)

Vandervoort, P.O.

1979-01-01

The study of the equilibrium of a rotating galactic bar requires an enumeration of the isolating integrals of the motion of a star in the prevailing gravitational field. In general, Jacobi's integral is the only exact isolating integral known. This paper describes a search for an additional isolating integral for orbits confined to a plane perpendicular to the axis of the bar's rotation. It is shown that, in general, the equations of motion admit an additional integral exactly which is a nonhomogeneous quadratic form in the momenta of the star only if (1) the gravitational potential is axisymmetric, (2) the gravitational potential is harmonic, or (3) the bar does not rotate and the gravitational potential is separable in elliptic coordinates. A formal integral of the motion is constructed for orbits in a slightly anharmonic potential. Numerical solutions of the equations of motion for orbits in a slightly anharmonic potential behave as if there were indeed an additional isolating integral, and that behavior is represented very well in terms of the formal integral. If the rotation of the bar is rapid and/or the nonaxisymmetry of the bar is weak, then the additional integral restricts the motion of a star in much the same way that the angular momentum restricts motion in an axisymmetric potential. Conversely, if the rotation of the bar is slow and/or the nonaxisymmetry of the bar is strong, then the additional integral restricts the motion in much the same way that the difference of the separable energies would if the motion were separable in Cartesian coordinates
A radio-pulsing white dwarf binary star.

Science.gov (United States)

Marsh, T R; Gänsicke, B T; Hümmerich, S; Hambsch, F-J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

2016-09-15

White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10 7 -year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.
The TERMS Project: Improved Orbital Parameters and Photometry of HD168443 and the Photometry Pipeline

Science.gov (United States)

Pilyavsky, Genady; Mahadevan, S.; Kane, S. R.; Howard, A. W.; Ciardi, D. R.; de Pree, C.; Dragomir, D.; Fischer, D.; Henry, G. W.; Jensen, E. L. N.; Laughlin, G.; Marlowe, H.; Rabus, M.; von Braun, K.; Wright, J. T.; Wang, X.

2012-01-01

The discovery of transiting planets around bright stars holds the potential to greatly enhance our understanding of planetary atmospheres. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) project focuses on updating the ephemerides of known exoplanets, put tighter constraints on the orbital parameters and shrink the large errors on the predicted transit windows, enabling photometric monitoring to search for a transit signature. Here, we present the revised orbital parameters and the photometric coverage during a predicted transit window of HD168443b, a massive planet orbiting the bright star HD 168443 (V = 6.92) with a period of 58.11 days. The high eccentricity of the planetary orbit (e = 0.53) significantly enhances the a-priori transit probability (3.7%) from what is expected for a circular orbit (2.5%). The transit ephemeris was updated using refined orbital parameters from additional Keck-HIRES radial velocities. The photometry obtained at the 1 m telescope in Cerro Tololo Inter-American Observatory (CTIO) and the T8 0.8 m Automated Photometric Telescope (APT) at Fairborn Observatory achieved the necessary millimag precision. The expected change in flux (0.5%) for HD168443 was not observed during the predicted transit window, thus allowing us to rule out the transit and put tighter constrains on the orbital inclination of HD168443b. Additionally, we present the software used to analyze the CTIO data. Developed by the TERMS team, this IDL based package is a fast, precise, and easy to use program which has eliminated the need for external software and command line prompts by utilizing the functionality of a graphical user interface (GUI).
TWO STARS TWO WAYS: CONFIRMING A MICROLENSING BINARY LENS SOLUTION WITH A SPECTROSCOPIC MEASUREMENT OF THE ORBIT

Energy Technology Data Exchange (ETDEWEB)

Yee, Jennifer C.; Johnson, John Asher; Eastman, Jason; Vanderburg, Andrew [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Skowron, Jan [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Gould, Andrew [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Pineda, J. Sebastian [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Howard, Andrew, E-mail: jyee@cfa.harvard.edu, E-mail: jjohnson@cfa.harvard.edu, E-mail: jason.eastman@cfa.harvard.edu, E-mail: avanderburg@cfa.harvard.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822-1839 (United States)

2016-04-20

Light curves of microlensing events involving stellar binaries and planetary systems can provide information about the orbital elements of the system due to orbital modulations of the caustic structure. Accurately measuring the orbit in either the stellar or planetary case requires detailed modeling of subtle deviations in the light curve. At the same time, the natural, Cartesian parameterization of a microlensing binary is partially degenerate with the microlens parallax. Hence, it is desirable to perform independent tests of the predictions of microlens orbit models using radial velocity (RV) time series of the lens binary system. To this end, we present 3.5 years of RV monitoring of the binary lens system OGLE-2009-BLG-020 L, for which Skowron et al. constrained all internal parameters of the 200–700 day orbit. Our RV measurements reveal an orbit that is consistent with the predictions of the microlens light curve analysis, thereby providing the first confirmation of orbital elements inferred from microlensing events.
One or more bound planets per Milky Way star from microlensing observations.

Science.gov (United States)

Cassan, A; Kubas, D; Beaulieu, J-P; Dominik, M; Horne, K; Greenhill, J; Wambsganss, J; Menzies, J; Williams, A; Jørgensen, U G; Udalski, A; Bennett, D P; Albrow, M D; Batista, V; Brillant, S; Caldwell, J A R; Cole, A; Coutures, Ch; Cook, K H; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Hill, K; Kains, N; Kane, S; Marquette, J-B; Martin, R; Pollard, K R; Sahu, K C; Vinter, C; Warren, D; Watson, B; Zub, M; Sumi, T; Szymański, M K; Kubiak, M; Poleski, R; Soszynski, I; Ulaczyk, K; Pietrzyński, G; Wyrzykowski, L

2012-01-11

Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10 AU (Sun-Earth distance) from their stars. We find that 17(+6)(-9)% of stars host Jupiter-mass planets (0.3-10 M(J), where M(J) = 318 M(⊕) and M(⊕) is Earth's mass). Cool Neptunes (10-30 M(⊕)) and super-Earths (5-10 M(⊕)) are even more common: their respective abundances per star are 52(+22)(-29)% and 62(+35)(-37)%. We conclude that stars are orbited by planets as a rule, rather than the exception.
Safety, efficacy and pharmacokinetics of rVIII-SingleChain in children with severe hemophilia A: results of a multicenter clinical trial.

Science.gov (United States)

Stasyshyn, O; Djambas Khayat, C; Iosava, G; Ong, J; Abdul Karim, F; Fischer, K; Veldman, A; Blackman, N; St Ledger, K; Pabinger, I

2017-04-01

Essentials rVIII-SingleChain is a novel recombinant factor VIII with covalently bonded heavy and light chains. Efficacy, safety and pharmacokinetics were studied in pediatric patients with severe hemophilia A. Across all prophylaxis regimens, the median annualized spontaneous bleeding rate was 0.00. rVIII-SingleChain showed excellent hemostatic efficacy and a favorable safety profile. Background rVIII-SingleChain is a novel B-domain truncated recombinant factor VIII (rFVIII) comprised of covalently bonded FVIII heavy and light chains, demonstrating a high binding affinity to von Willebrand factor. Objectives This phase III study investigated the safety, efficacy and pharmacokinetics of rVIII-SingleChain in previously treated pediatric patients hemophilia A. Patients/Methods Patients could be assigned to prophylaxis or on-demand therapy by the investigator. For patients assigned to prophylaxis, the treatment regimen and dose were based on the bleeding phenotype. For patients receiving on-demand therapy, dosing was guided by World Federation of Hemophilia recommendations. The primary endpoint was treatment success, defined as a rating of 'excellent' or 'good' on the investigator's clinical assessment of hemostatic efficacy for all treated bleeding events. Results The study enrolled 84 patients (0 to 50 EDs. In the 347 bleeds treated and evaluated by the investigator, hemostatic efficacy was rated as excellent or good in 96.3%. The median annualized spontaneous bleeding rate was 0.00 (Q1, Q3: 0.00, 2.20), and the median annualized bleeding rate was 3.69 (Q1, Q3: 0.00, 7.20) across all prophylaxis regimens. No participant developed an inhibitor. Conclusions rVIII-SingleChain is a novel rFVIII molecule showing excellent hemostatic efficacy and a favorable safety profile in a clinical study in children hemophilia A. © 2017 The Authors. Journal of Thrombosis and Haemostasis published by Wiley Periodicals, Inc. on behalf of International Society on Thrombosis and
OBSERVATIONS OF BINARY STARS WITH THE DIFFERENTIAL SPECKLE SURVEY INSTRUMENT. V. TOWARD AN EMPIRICAL METAL-POOR MASS–LUMINOSITY RELATION

International Nuclear Information System (INIS)

Horch, Elliott P.; Van Altena, William F.; Demarque, Pierre; Howell, Steve B.; Everett, Mark E.; Ciardi, David R.; Teske, Johanna K.; Henry, Todd J.; Winters, Jennifer G.

2015-01-01

In an effort to better understand the details of the stellar structure and evolution of metal-poor stars, the Gemini North telescope was used on two occasions to take speckle imaging data of a sample of known spectroscopic binary stars and other nearby stars in order to search for and resolve close companions. The observations were obtained using the Differential Speckle Survey Instrument, which takes data in two filters simultaneously. The results presented here are of 90 observations of 23 systems in which one or more companions was detected, and six stars where no companion was detected to the limit of the camera capabilities at Gemini. In the case of the binary and multiple stars, these results are then further analyzed to make first orbit determinations in five cases, and orbit refinements in four other cases. The mass information is derived, and since the systems span a range in metallicity, a study is presented that compares our results with the expected trend in total mass as derived from the most recent Yale isochrones as a function of metal abundance. These data suggest that metal-poor main-sequence stars are less massive at a given color than their solar-metallicity analogues in a manner consistent with that predicted from the theory

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