WorldWideScience

Sample records for hot evolved stars

  1. X-ray Emission from Hot Bubbles in nebulae around Evolved Stars

    Science.gov (United States)

    Toalá Sánz, Jesús Alberto

    This thesis presents an observational and numerical study on the X-ray emission related to the formation and evolution from hot bubbles in nebulae around evolved stars. The observational part of this study consists mainly in observations obtained from the X-ray satellites X-ray Multi Mirror Mission (XMM-Newton) and Chandra X-ray Observatory (CXO). We have made use of optical, infrared, and ultraviolet observations that have complemented our results and analysis. These observations have allowed us to study the Wolf-Rayet (WR) nebulae S 308 and NGC 6888 and that around the WR star WR 16. We have also studied the planetary nebulae (PNe) NGC 6543 and Abell 78 (A 78). The X-ray telescopes, XMM-Newton and CXO, have allowed us to study the distribution and physical characteristics of the hot and diffuse gas in the WR nebulae S 308 and NGC 6888 with exquisite detail. Even though the CXO observations do not map entirely NGC 6888, we are able to estimate global parameters of the X-ray emission making use of ROSAT observations. Previous observations performed with were hampered by Suzaku, ROSAT, and ASCA were hampered by a large number of point sources in the line of sight of the nebulae. S 308 was observed with XMM-Newton with four pointings. We have made use of the most up-to-date tools for the analysis of soft and diffuse X-ray emission (the ESAS tasks). We found that in both nebulae the hot gas has a plasma temperature of 1-1.5×10^6 K and it is delineated by the [O III] emission and not the Hα as stated in previous studies. A notable difference between these two WR nebulae is that S 308 has a limb-brightened morphology in the distribution of its hot gas, while NGC 6888 displays three maxima. We have studied the WR nebula around WR 16 with archived XMM-Newton observations. Even though it was expected that diffuse X-ray emission should be detected from a spherical, non-disrupted WR nebula, by comparison with S 308 and NGC 6888, we are not able to detect such emission

  2. KELT-12b: A $P \\sim 5$ Day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star

    CERN Document Server

    Stevens, Daniel J; Gaudi, B Scott; Beatty, Thomas G; Siverd, Robert J; Bieryla, Allyson; Fulton, Benjamin J; Crepp, Justin R; Gonzales, Erica J; Coker, Carl T; Penev, Kaloyan; Stassun, Keivan G; Jensen, Eric L N; Howard, Andrew W; Latham, David W; Rodriguez, Joseph E; Zambelli, Roberto; Bozza, Valerio; Reed, Phillip A; Gregorio, Joao; Buchhave, Lars A; Pepper, Joshua; Berlind, Perry; Novati, Sebastiano Calchi; Calkins, Michael L; D'Ago, Giuseppe; Eastman, Jason D; Colón, Knicole D; DePoy, D L; Esquerdo, Gilbert A; Gould, Andrew; Kielkopf, John F; Labadie-Bartz, Jonathan; Lund, Michael B; Manner, Mark; Marshall, Jennifer L; McLeod, Kim K; Oberst, Thomas E; Penny, Matthew T; Pogge, Richard W; Scarpetta, Gaetano; Trueblood, Mark; Trueblood, Patricia

    2016-01-01

    We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting a mildly evolved host star. We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the $V = 10.64$ host, TYC 2619-1057-1, has $T_{\\rm eff} = 6278 \\pm 51$ K, $\\log{g_\\star} = 3.89^{+0.054}_{-0.051}$, and [Fe/H] = $0.19^{+0.083}_{-0.085}$, with an inferred mass $M_{\\star} = 1.59^{+0.071}_{-0.091} M_\\odot$ and radius $R_\\star = 2.37 \\pm 0.18 R_\\odot$. The planetary companion has $M_{\\rm P} = 0.95 \\pm 0.14 M_{\\rm J}$, $R_{\\rm P} = 1.79^{+0.18}_{-0.17} R_{\\rm J}$, $\\log{g_{\\rm P}} = 2.87^{+0.097}_{-0.098}$, and density $\\rho_{\\rm P} = 0.21^{+0.075}_{-0.054}$ g cm$^{-3}$, making it one of the most inflated giant planets known. The time of inferior conjunction in ${\\rm BJ...

  3. Pulsations as a mass-loss trigger in evolved hot stars

    CERN Document Server

    Kraus, Michaela; Haucke, Maximiliano; Cidale, Lydia; Venero, Roberto; Fernandes, Marcelo Borges; Tomic, Sanja; Cure, Michel

    2013-01-01

    During the post-main sequence evolution massive stars pass through several short-lived phases, in which they experience enhanced mass loss in the form of clumped winds and mass ejection events of unclear origin. The discovery that stars populating the blue, luminous part of the Hertzsprung-Russell diagram can pulsate hence suggests that stellar pulsations might influence or trigger enhanced mass loss and eruptions. We present recent results for two objects in different phases: a B[e] star at the end of the main sequence and a B-type supergiant.

  4. Hot Subluminous Stars

    Science.gov (United States)

    Heber, U.

    2016-08-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters ω Cen and NGC 2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US 708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HW Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HW

  5. Hot subluminous stars

    CERN Document Server

    Heber, Ulrich

    2016-01-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich vs. He-poor hot subdwarf stars of the globular clusters omega Cen and NGC~2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope phase of evolution.They provide a clean-cut laboratory to study this important but yet purely understood phase of stellar evolution. Substellar companions to sdB stars have also been found. For HW~Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the pulsator V391 ...

  6. Really Hot Stars

    Science.gov (United States)

    2003-04-01

    galaxy, another has been found in the nearby galaxy IC 1613, and five others are situated in the Magellanic Clouds. Astronomers have also detected the presence of HeII ions in a number of remote galaxies undergoing a phase of intense star formation ("starburst galaxies") and in the vicinity of ultraluminous X-ray sources in very distant galaxies. What is going on in those remote objects in the early Universe? Do we see the action of young and very hot stars or is something unknown going on? What can the existence of those hot nebulae in young galaxies tell about the evolution of our own Milky Way? Searching for the energy source We would like to know, but those distant nebulae are unfortunately too faint to be studied in any reasonable detail, even by means of the largest available telescopes. The only way forward is therefore to look closer at the nearest ones in the hope that they will provide clues about the processes leading to the observed high excitation and thus help to better understand their cousins in those distant galaxies. There appears to be three possible answers to the basic question about the nature of the energetic sources that heat these strange emission nebulae: * very fast particles: if there is in the area a fast-moving gas (more than 100 km/s), the shock created by the impact of this material is able to heat the ambient interstellar medium sufficiently to produce a HeII nebula. * ultraviolet emission from massive stars: according to the most recent model calculations, even the most massive O-type stars do not emit enough ultraviolet light to ionize a sufficient number of helium atoms in the surrounding nebula to produce a detectable HeII nebula. However, some of the hottest stars of the so-called Wolf-Rayet (W-R) type (that are the evolved descendants of O-stars) may produce enough high energy emission to completely ionize the helium atoms in their surroundings. * intense X-ray emission: close binary stars in which one component is a "compact

  7. Transiting planets from WASP-South, Euler, and TRAPPIST. WASP-68 b, WASP-73 b, and WASP-88 b, three hot Jupiters transiting evolved solar-type stars

    Science.gov (United States)

    Delrez, L.; Van Grootel, V.; Anderson, D. R.; Collier-Cameron, A.; Doyle, A. P.; Fumel, A.; Gillon, M.; Hellier, C.; Jehin, E.; Lendl, M.; Neveu-VanMalle, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Smith, A. M. S.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.; West, R. G.

    2014-03-01

    Using the WASP transit survey, we report the discovery of three new hot Jupiters, WASP-68 b, WASP-73 b and WASP-88 b. The planet WASP-68 bhas a mass of 0.95 ± 0.03 MJup, a radius of 1.24-0.06+0.10 RJup, and orbits a V = 10.7 G0-type star (1.24 ± 0.03 M⊙ 1.69-0.06+0.11 R⊙, Teff = 5911 ± 60 K) with a period of 5.084298 ± 0.000015 days. Its size is typical of hot Jupiters with similar masses. The planet WASP-73 bis significantly more massive (1.88-0.06+0.07 MJup) and slightly larger (1.16-0.08+0.12 RJup) than Jupiter. It orbits a V = 10.5 F9-type star (1.34-0.04+0.05 M⊙, 2.07-0.08+0.19 R⊙, Teff = 6036 ± 120 K) every 4.08722 ± 0.00022 days. Despite its high irradiation (~2.3 × 109 erg s-1 cm-2), WASP-73 b has a high mean density (1.20-0.30+0.26 ρJup) that suggests an enrichment of the planet in heavy elements. The planet WASP-88 bis a 0.56 ± 0.08 MJuphot Jupiter orbiting a V = 11.4 F6-type star (1.45 ± 0.05 M⊙, 2.08-0.06+0.12 R⊙, Teff = 6431 ± 130 K) with a period of 4.954000 ± 0.000019 days. With a radius of 1.70-0.07+0.13 RJup, it joins the handful of planets with super-inflated radii. The ranges of ages we determine through stellar evolution modeling are 4.5-7.0 Gyr for WASP-68, 2.8-5.7 Gyr for WASP-73 and 1.8-4.3 Gyr for WASP-88. The star WASP-73 appears to be significantly evolved, close to or already in the subgiant phase. The stars WASP-68 and WASP-88 are less evolved, although in an advanced stage of core H-burning. Tables 1-3 are available in electronic form at http://www.aanda.orgThe photometric time-series used in this work are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A143

  8. Quantitative spectroscopy of hot stars

    Science.gov (United States)

    Kudritzki, R. P.; Hummer, D. G.

    1990-01-01

    A review on the quantitative spectroscopy (QS) of hot stars is presented, with particular attention given to the study of photospheres, optically thin winds, unified model atmospheres, and stars with optically thick winds. It is concluded that the results presented here demonstrate the reliability of Qs as a unique source of accurate values of the global parameters (effective temperature, surface gravity, and elemental abundances) of hot stars.

  9. Swift, UVOT and Hot Stars

    CERN Document Server

    Siegel, Michael H; Hagen, Lea M Z; Hoversten, Erik A

    2015-01-01

    We present the results of our ongoing investigation into the properties of hot stars and young stellar populations using the Swift/UVOT telescope. We present UVOT photometry of open and globular clusters and show that UVOT is capable of characterizing a variety of rare hot stars, including Post-Asymptotic Giant Branch and Extreme Horizontal Branch Stars. We also present very early reults of our survey of stellar populations in the Small Magellanic Cloud. We find that the SMC has experienced recent bouts of star formation but constraining the exact star formation history will depend on finding an effective model of the reddening within the SMC.

  10. Hot-Jupiter Breakfasts Realign Stars

    Science.gov (United States)

    Kohler, Susanna

    2015-08-01

    Two researchers at the University of Chicago have recently developed a new theory to explain an apparent dichotomy in the orbits of planets around cool vs. hot stars. Their model proposes that the spins of cool stars are affected when they ingest hot Jupiters (HJs) early in their stellar lifetimes. A Puzzling Dichotomy: In exoplanet studies, there is a puzzling difference observed between planet orbits around cool and hot (those with Teff ≥ 6250 K) stars: the orbital planes of planets around cool stars are primarily aligned with the host star's spin, whereas the orbital planes of planets around hot stars seem to be randomly distributed. Previous attempts to explain this dichotomy have focused on tidal interactions between the host star and the planets observed in the system. Now Titos Matsakos and Arieh Königl have taken these models a step further — by including in their calculations not only the effects of observed planets, but also those of HJs that may have been swallowed by the star long before we observed the systems. Modeling Meals: Plots of the distribution of the obliquity λ for hot Jupiters around cool hosts (upper plot) and hot hosts (lower plot). The dashed line shows the initial distribution, the bins show the model prediction for the final distribution after the systems evolve, and the black dots show the current observational data. [Matsakos & Königl, 2015]" class="size-thumbnail wp-image-223" height="386" src="http://aasnova.org/wp-content/uploads/2015/08/fig22-260x386.png" width="260" /> Plots of the distribution of the obliquity λ for hot Jupiters around cool hosts (upper plot) and hot hosts (lower plot). The dashed line shows the initial distribution, the bins show the model prediction for the final distribution after the systems evolve, and the black dots show the current observational data. [Matsakos & Königl, 2015] The authors' model assumes that as HJs are formed and migrate inward through the protoplanetary disk, they stall out near

  11. Transiting planets from WASP-South, Euler and TRAPPIST: WASP-68 b, WASP-73 b and WASP-88 b, three hot Jupiters transiting evolved solar-type stars

    CERN Document Server

    Delrez, L; Anderson, D R; Collier-Cameron, A; Doyle, A P; Fumel, A; Gillon, M; Hellier, C; Jehin, E; Lendl, M; Neveu-VanMalle, M; Maxted, P F L; Pepe, F; Pollacco, D; Queloz, D; Ségransan, D; Smalley, B; Smith, A M S; Southworth, J; Triaud, A H M J; Udry, S; West, R G

    2013-01-01

    We report the discovery by the WASP transit survey of three new hot Jupiters, WASP-68 b, WASP-73 b and WASP-88 b. WASP-68 b has a mass of 0.95+-0.03 M_Jup, a radius of 1.24-0.06+0.10 R_Jup, and orbits a V=10.7 G0-type star (1.24+-0.03 M_sun, 1.69-0.06+0.11 R_sun, T_eff=5911+-60 K) with a period of 5.084298+-0.000015 days. Its size is typical of hot Jupiters with similar masses. WASP-73 b is significantly more massive (1.88-0.06+0.07 M_Jup) and slightly larger (1.16-0.08+0.12 R_Jup) than Jupiter. It orbits a V=10.5 F9-type star (1.34-0.04+0.05 M_sun, 2.07-0.08+0.19 R_sun, T_eff=6036+-120 K) every 4.08722+-0.00022 days. Despite its high irradiation (2.3 10^9 erg s^-1 cm^-2), WASP-73 b has a high mean density (1.20-0.30+0.26 \\rho_Jup) that suggests an enrichment of the planet in heavy elements. WASP-88 b is a 0.56+-0.08 M_Jup planet orbiting a V=11.4 F6-type star (1.45+-0.05 M_sun, 2.08-0.06+0.12 R_sun, T_eff=6431+-130 K) with a period of 4.954000+-0.000019 days. With a radius of 1.70-0.07+0.13 R_Jup, it joins t...

  12. Hot Jupiters and cool stars

    Energy Technology Data Exchange (ETDEWEB)

    Villaver, Eva; Mustill, Alexander J. [Department of Theoretical Physics, Universidad Autónoma de Madrid, Módulo 8, 28049 Madrid (Spain); Livio, Mario [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Siess, Lionel, E-mail: eva.villaver@uam.es [Institut d' Astronomie et d' Astrophysique, Université Libre de Bruxelles, B-1050 Bruxelles (Belgium)

    2014-10-10

    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 {sub ☉}), 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.

  13. SALT Spectroscopy of Evolved Massive Stars

    Science.gov (United States)

    Kniazev, A. Y.; Gvaramadze, V. V.; Berdnikov, L. N.

    2017-06-01

    Long-slit spectroscopy with the Southern African Large Telescope (SALT) of central stars of mid-infrared nebulae detected with the Spitzer Space Telescope and Wide-Field Infrared Survey Explorer (WISE) led to the discovery of numerous candidate luminous blue variables (cLBVs) and other rare evolved massive stars. With the recent advent of the SALT fiber-fed high-resolution echelle spectrograph (HRS), a new perspective for the study of these interesting objects is appeared. Using the HRS we obtained spectra of a dozen newly identified massive stars. Some results on the recently identified cLBV Hen 3-729 are presented.

  14. SALT spectroscopy of evolved massive stars

    CERN Document Server

    Kniazev, A Y; Berdnikov, L N

    2016-01-01

    Long-slit spectroscopy with the Southern African Large Telescope (SALT) of central stars of mid-infrared nebulae detected with the Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) led to the discovery of numerous candidate luminous blue variables (cLBVs) and other rare evolved massive stars. With the recent advent of the SALT fibre-fed high-resolution echelle spectrograph (HRS), a new perspective for the study of these interesting objects is appeared. Using the HRS we obtained spectra of a dozen newly identified massive stars. Some results on the recently identified cLBV Hen 3-729 are presented.

  15. Mass Loss and Variability in Evolved Stars

    OpenAIRE

    Marengo, Massimo

    2014-01-01

    Mass loss and variability are two linked, fundamental properties of evolved stars. In this paper I review our current understanding of these processes, with a particular focus on how observations and models are used to constrain reliable mass loss prescriptions for stellar evolution and population synthesis models.

  16. Mass Loss and Variability in Evolved Stars

    OpenAIRE

    Marengo, Massimo

    2014-01-01

    Mass loss and variability are two linked, fundamental properties of evolved stars. In this paper I review our current understanding of these processes, with a particular focus on how observations and models are used to constrain reliable mass loss prescriptions for stellar evolution and population synthesis models.

  17. Hot moons and cool stars

    Directory of Open Access Journals (Sweden)

    Heller René

    2013-04-01

    Full Text Available The exquisite photometric precision of the Kepler space telescope now puts the detection of extrasolar moons at the horizon. Here, we firstly review observational and analytical techniques that have recently been proposed to find exomoons. Secondly, we discuss the prospects of characterizing potentially habitable extrasolar satellites. With moons being much more numerous than planets in the solar system and with most exoplanets found in the stellar habitable zone being gas giants, habitable moons could be as abundant as habitable planets. However, satellites orbiting planets in the habitable zones of cool stars will encounter strong tidal heating and likely appear as hot moons.

  18. Circumstellar Molecular Spectra towards Evolved Stars

    CERN Document Server

    Bakker, E J

    1997-01-01

    In this paper we discuss the relevance of, and possible scientific gains which can be acquired from studying circumstellar molecular spectra toward evolved stars. Where can we expect circumstellar molecular spectra, why would we want to study these spectra, which molecules might be present, and what can we learn from these studies? We present an overview of reported detections, and discuss some of the results.

  19. Monitoring evolved stars for binarity with the HERMES spectrograph

    CERN Document Server

    Gorlova, N; Vos, J; Ostensen, R H; Jorissen, A; Van Eck, S; Ikonnikova, N

    2014-01-01

    Binarity is often invoked to explain peculiarities that can not be explained by the standard theory of stellar evolution. Detecting orbital motion via the Doppler effect is the best method to test binarity when direct imaging is not possible. However, when the orbital period exceeds the duration of a typical observing run, monitoring often becomes problematic. Placing a high-throughput spectrograph on a small semi- robotic telescope allowed us to carry out a radial-velocity survey of various types of peculiar evolved stars. In this review we highlight some findings after the first four years of observations. Thus, we detect eccentric binaries among hot subdwarfs, barium, S stars, and post- AGB stars with disks, which are not predicted by the standard binary interaction theory. In disk objects, in addition, we find signs of the on- going mass transfer to the companion, and an intriguing line splitting, which we attribute to the scattered light of the primary.

  20. Hot subdwarf stars and their connection to thermonuclear supernovae

    CERN Document Server

    Geier, S; Ziegerer, E; Heber, U; Nemeth, P; Irrgang, A

    2016-01-01

    Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very thin hydrogen envelopes, which can be formed by common envelope ejection. Close sdB binaries with massive white dwarf (WD) companions are potential progenitors of thermonuclear supernovae type Ia (SN Ia). We discovered such a progenitor candidate as well as a candidate for a surviving companion star, which escapes from the Galaxy. More candidates for both types of objects have been found by crossmatching known sdB stars with proper motion and light curve catalogues. The Gaia mission will provide accurate astrometry and light curves of all the stars in our hot subdwarf sample and will allow us to compile a much larger all-sky catalogue of those stars. In this way we expect to find hundreds of progenitor binaries and ejected companions.

  1. Hot Stars Old-Fashioned or Trendy?

    CERN Document Server

    Pauldrach, A W A

    2002-01-01

    Spectroscopic analyses with the intention of the interpretation of the UV-spectra of the brightest stars as individuals - supernovae - or as components of star-forming regions - massive O stars - provide a powerful tool with great astrophysical potential for the determination of extragalactic distances and of the chemical composition of star-forming galaxies even at high redshifts. The perspectives of already initiated work with the new generation of tools for quantitative UV-spectroscopy of Hot Stars that have been developed during the last two decades are presented and the status of the continuing effort to construct corresponding models for Hot Star atmospheres is reviewed. Because the physics of the atmospheres of Hot Stars are strongly affected by velocity expansion dominating the spectra at all wavelength ranges, hydrodynamic model atmospheres for O-type stars and explosion models for Supernovae of Type Ia are necessary as basis for the synthesis and analysis of the spectra. It is shown that stellar par...

  2. NLTE wind models of hot subdwarf stars

    CERN Document Server

    Krticka, Jiri; 10.1007/s10509-010-0385-z

    2010-01-01

    We calculate NLTE models of stellar winds of hot compact stars (central stars of planetary nebulae and subdwarf stars). The studied range of subdwarf parameters is selected to cover a large part of these stars. The models predict the wind hydrodynamical structure and provide mass-loss rates for different abundances. Our models show that CNO elements are important drivers of subdwarf winds, especially for low-luminosity stars. We study the effect of X-rays and instabilities on these winds. Due to the line-driven wind instability, a significant part of the wind could be very hot.

  3. Evolved star water maser cloud size determined by star size

    CERN Document Server

    Richards, A M S; Gray, M D; Lekht, E E; Mendoza-Torres, J E; Murakawa, K; Rudnitskij, G; Yates, J A

    2012-01-01

    Cool, evolved stars undergo copious mass loss but the details of how the matter is returned to the ISM are still under debate. We investigated the structure and evolution of the wind at 5 to 50 stellar radii from Asymptotic Giant Branch and Red Supergiant stars. 22-GHz water masers around seven evolved stars were imaged using MERLIN, at sub-AU resolution. Each source was observed at between 2 and 7 epochs (several stellar periods). We compared our results with long-term Pushchino single dish monitoring. The 22-GHz emission is located in ~spherical, thick, unevenly filled shells. The outflow velocity doubles between the inner and outer shell limits. Water maser clumps could be matched at successive epochs separated by <2 years for AGB stars, or at least 5 years for RSG. This is much shorter than the decades taken for the wind to cross the maser shell, and comparison with spectral monitoring shows that some features fade and reappear. In 5 sources, most of the matched features brighten or dim in concert from...

  4. Combining seismology and spectropolarimetry of hot stars

    CERN Document Server

    Neiner, Coralie; Mathis, Stéphane; Degroote, Pieter

    2014-01-01

    Asteroseismology and spectropolarimetry have allowed us to progress significantly in our understanding of the physics of hot stars over the last decade. It is now possible to combine these two techniques to learn even more information about hot stars and constrain their models. While only a few magnetic pulsating hot stars are known as of today and have been studied with both seismology and spectropolarimetry, new opportunities - in particular Kepler2 and BRITE - are emerging and will allow us to rapidly obtain new combined results.

  5. Dust in Interstellar Clouds, Evolved Stars and Supernovae

    CERN Document Server

    Hartquist, T W; Falle, S A E G; Caselli, P; Ashmore, I

    2008-01-01

    Outflows of pre-main-sequence stars drive shocks into molecular material within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared, millimeter and submillimeter lines of many species including. Dust grains are important charge carriers and play a large role in coupling the magnetic field and flow of neutral gas. Some effects of the dust on the dynamics of oblique shocks began to emerge in the 1990s. However, detailed models of these shocks are required for the calculation of the grain sputtering contribution to gas phase abundances of species producing observed emissions. We are developing such models. Some of the molecular species introduced into the gas phase by sputtering in shocks or by thermally driven desorption in hot cores form on grain surfaces. Recently laboratory studies have begun to contribute to the understanding of surface reactions and thermally driven desorption important for the chemistry of star forming clouds. Dusty plasmas are prevalent in many evolved stars just as well ...

  6. The evolved pulsating CEMP star HD112869

    CERN Document Server

    Začs, L; Grankina, A; Deveikis, V; Kaminskyi, B; Pavlenko, Y; Musaev, F

    2015-01-01

    Radial velocity measurements, $BVR_C$ photometry, and high-resolution spectroscopy in the wavelength region from blue to near infrared are employed in order to clarify the evolutionary status of the carbon-enhanced metal-poor star HD112869 with unique ratio of carbon isotopes in the atmosphere. An LTE abundance analysis was carried out using the method of spectral synthesis and new self consistent 1D atmospheric models. The radial velocity monitoring confirmed semiregular variations with a peak-to-peak amplitude of about 10 km $s^{-1}$ and a dominating period of about 115 days. The light, color and radial velocity variations are typical of the evolved pulsating stars. The atmosphere of HD112869 appears to be less metal-poor than reported before, [Fe/H] = -2.3 $\\pm$0.2 dex. Carbon to oxygen and carbon isotope ratios are found to be extremely high, C/O $\\simeq$ 12.6 and $^{12}C/^{13}C \\gtrsim$ 1500, respectively. The s-process elements yttrium and barium are not enhanced, but neodymium appears to be overabundan...

  7. Evolved Stars: Interferometer Baby Food or Staple Diet?

    Science.gov (United States)

    Tuthill, Peter

    With their extreme red and infrared luminosities and large apparent diameters, evolved stars have nurtured generations of interferometers (beginning with Michelson's work on Betelgeuse) with unique science programs at attainable resolutions. Furthermore, the inflated photosphere and circumstellar material associated with dying stars presents complex targets with asymmetric structure on many scales encoding a wealth of poorly-understood astrophysics. A brief review the major past milestones and future prospects for interferometry's contribution to studies of circumstellar matter in evolved stars is presented.

  8. Angular Momentum Transport via Internal Gravity Waves in Evolving Stars

    CERN Document Server

    Fuller, Jim; Cantiello, Matteo; Brown, Ben

    2014-01-01

    Recent asteroseismic advances have allowed for direct measurements of the internal rotation rates of many sub-giant and red giant stars. Unlike the nearly rigidly rotating Sun, these evolved stars contain radiative cores that spin faster than their overlying convective envelopes, but slower than they would in the absence of internal angular momentum transport. We investigate the role of internal gravity waves in angular momentum transport in evolving low mass stars. In agreement with previous results, we find that convectively excited gravity waves can prevent the development of strong differential rotation in the radiative cores of Sun-like stars. As stars evolve into sub-giants, however, low frequency gravity waves become strongly attenuated and cannot propagate below the hydrogen burning shell, allowing the spin of the core to decouple from the convective envelope. This decoupling occurs at the base of the sub-giant branch when stars have surface temperatures of roughly 5500 K. However, gravity waves can s...

  9. Cold Dust in Three Massive Evolved Stars in the LMC

    CERN Document Server

    Boyer, M L; van Loon, J Th; Srinivasan, S; Clayton, G C; Kemper, F; Smith, L J; Matsuura, M; Woods, Paul M; Marengo, M; Meixner, M; Engelbracht, C; Gordon, K D; Hony, S; Indebetouw, R; Misselt, K; Okumura, K; Panuzzo, P; Riebel, D; Roman-Duval, J; Sauvage, M; Sloan, G C

    2010-01-01

    Massive evolved stars can produce large amounts of dust, and far-infrared (IR) data are essential for determining the contribution of cold dust to the total dust mass. Using Herschel, we search for cold dust in three very dusty massive evolved stars in the Large Magellanic Cloud: R71 is a Luminous Blue Variable, HD36402 is a Wolf-Rayet triple system, and IRAS05280-6910 is a red supergiant. We model the spectral energy distributions using radiative transfer codes and find that these three stars have mass-loss rates up to 10^-3 solar masses/year, suggesting that high-mass stars are important contributors to the life-cycle of dust. We found far-IR excesses in two objects, but these excesses appear to be associated with ISM and star-forming regions. Cold dust (T < 100 K) may thus not be an important contributor to the dust masses of evolved stars.

  10. Why do hot subdwarf stars pulsate?

    CERN Document Server

    Geier, S

    2015-01-01

    Hot subdwarf B stars (sdBs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. Several different kinds of pulsators are found among those stars. The mechanism that drives those pulsations is well known and the theoretically predicted instability regions for both the short-period p-mode and the long-period g-mode pulsators match the observed distributions fairly well. However, it remains unclear why only a fraction of the sdB stars pulsate, while stars with otherwise very similar parameters do not show pulsations. From an observers perspective I review possible candidates for the missing parameter that makes sdB stars pulsate or not.

  11. Protodiscs around Hot Magnetic Rotator Stars

    CERN Document Server

    Maheswaran, M

    2008-01-01

    We develop equations and obtain solutions for the structure and evolution of a protodisc region that is initially formed with no radial motion and super-Keplerian rotation speed when wind material from a hot rotating star is channelled towards its equatorial plane by a dipole-type magnetic field. Its temperature is around $10^7$K because of shock heating and the inflow of wind material causes its equatorial density to increase with time. The centrifugal force and thermal pressure increase relative to the magnetic force and material escapes at its outer edge. The protodisc region of a uniformly rotating star has almost uniform rotation and will shrink radially unless some instability intervenes. In a star with angular velocity increasing along its surface towards the equator, the angular velocity of the protodisc region decreases radially outwards and magnetorotational instability (MRI) can occur within a few hours or days. Viscosity resulting from MRI will readjust the angular velocity distribution of the pro...

  12. Magnetic spots on hot massive stars

    CERN Document Server

    Cantiello, Matteo

    2011-01-01

    Hot luminous stars show a variety of phenomena in their photospheres and winds which still lack clear physical explanation. Among these phenomena are photospheric turbulence, line profile variability (LPV), non-thermal emission, non-radial pulsations, discrete absorption components (DACs) and wind clumping. Cantiello et al. (2009) argued that a convection zone close to the stellar surface could be responsible for some of these phenomena. This convective zone is caused by a peak in the opacity associated with iron-group elements and is referred to as the "iron convection zone" (FeCZ). Assuming dynamo action producing magnetic fields at equipartition in the FeCZ, we investigate the occurrence of subsurface magnetism in OB stars. Then we study the surface emergence of these magnetic fields and discuss possible observational signatures of magnetic spots. Simple estimates are made using the subsurface properties of massive stars, as calculated in 1D stellar evolution models. We find that magnetic fields of suffici...

  13. A Binary Orbit for the Massive, Evolved Star HDE 326823, a WR+O System Progenitor

    CERN Document Server

    Richardson, Noel D; Williams, Stephen 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 d 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.

  14. On the dissolution of evolving star clusters

    CERN Document Server

    Zwart, S F P; Makino, J; McMillan, S; Zwart, Simon F. Portegies; Hut, Piet; Makino, Junichiro; Millan, Stephen Mc

    1998-01-01

    Using direct N-body simulations which include both the evolution of single stars and the tidal field of the parent galaxy, we study the dynamical evolution of globular clusters and rich open clusters. We compare our results with other N-body simulations and Fokker-Planck calculations. Our simulations, performed on the GRAPE-4, employ up to 32,768 stars. The results are not in agreement with Fokker-Planck models, in the sense that the lifetimes of stellar systems derived using the latter are an order of magnitude smaller than those obtained in our simulations. For our standard run, Fokker-Planck calculations obtained a lifetime of 0.28 Gyr, while our equivalent N-body calculations find about 4 Gyr. The principal reason for the discrepancy is that a basic assumption of the Fokker-Plank approach is not valid for typical cluster parameters. The stellar evolution timescale is comparable to the dynamical timescale, and therefore the assumption of dynamical equilibrium leads to an overestimate of the dynamical effec...

  15. ON THE NATURE OF RAPIDLY ROTATING SINGLE EVOLVED STARS

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva, R. Rodrigues; Canto Martins, B. L.; De Medeiros, J. R., E-mail: renan@dfte.ufrn.br [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Campus Universitário, Natal RN (Brazil)

    2015-03-01

    We present an analysis of the nature of the rapidly rotating, apparently single giant based on rotational and radial velocity measurements carried out by the CORAVEL spectrometers. From the analyzed sample, composed of 2010 spectroscopic, apparently single, evolved stars of luminosity classes IV, III, II, and Ib with spectral types G and K, we classified 30 stars that presented unusual, moderate to rapid rotation. This work reports, for the first time, the presence of these abnormal rotators among subgiant, bright giant, and Ib supergiant stars. To date, this class of stars was reported only among giant stars of luminosity class III. Most of these abnormal rotators present an IRAS infrared excess, which, in principle, can be related to dust around these stars.

  16. Evolving spherical boson stars on a 3D Cartesian grid

    Science.gov (United States)

    Guzmán, F. Siddhartha

    2004-08-01

    A code to evolve boson stars in 3D is presented as the starting point for the evolution of scalar field systems with arbitrary symmetries. It was possible to reproduce the known results related to perturbations discovered with 1D numerical codes in the past, which include evolution of stable and unstable equilibrium configurations. In addition, the apparent and event horizons masses of a collapsing boson star are shown for the first time. The present code is expected to be useful at evolving possible sources of gravitational waves related to scalar field objects and to handle toy models of systems perturbed with scalar fields in 3D.

  17. Evolving spherical boson stars on a 3D cartesian grid

    CERN Document Server

    Guzman, F S

    2004-01-01

    A code to evolve boson stars in 3D is presented as the starting point for the evolution of scalar field systems with arbitrary symmetries. It was possible to reproduce the known results related to perturbations discovered with 1D numerical codes in the past, which include evolution of stable and unstable equilibrium configurations. In addition, the apparent and event horizons masses of a collapsing boson star are shown for the first time. The present code is expected to be useful at evolving possible sources of gravitational waves related to scalar field objects and to handle toy models of systems perturbed with scalar fields in 3D.

  18. Advanced Spectral Library II: Hot Stars

    Science.gov (United States)

    Ayres, Thomas

    2013-10-01

    Stars are the bright matter of the Universe. Without them, it would be a dull and dreary place indeed: no light, no heavy elements, no planets, no life. It also is safe to say that stellar spectroscopy is a cornerstone of astrophysics, providing much of what we know concerning temperatures and masses of stars, their compositions, planets, and the dynamics and evolution of the galaxies they inhabit. This is especially true for the satellite ultraviolet, owing to the rich collection of atomic and ionic transitions found there. Unfortunately, the archive of Space Telescope Imaging Spectrograph rarely achieves the high S/N of the best ground-based spectra, and relatively few objects have the full wavelength coverage for which the powerful, highly multiplexed, second generation Hubble instrument was designed. Our aim is to collect STIS UV echelle spectra - comparable in S/N and resolution to the best ground-based material - for a diverse sample of representative stars, to build an Advanced Spectral Library; a foundation for astrophysical exploration: stellar, interstellar, and beyond. Our first effort, in Cycle 18, involved cool stars. Now we turn attention to the hot side of the H-R diagram.Our Treasury program will provide detailed stellar "atlases," based on advanced processing of the STIS echellegrams. Members of our broad collaboration will analyze these data for specific purposes, such as dynamics of O-star mass-loss; detection of rare species in sharp-lined B stars; and properties and kinematics of local interstellar clouds; but public release {based on the "ASTRAL-I" model} will enable many other investigations by a much wider community, for decades to come.

  19. ENERGY STAR Certified Commercial Hot Food Holding Cabinet

    Data.gov (United States)

    U.S. Environmental Protection Agency — Certified models meet all ENERGY STAR requirements as listed in the Version 2.0 ENERGY STAR Program Requirements for Commercial Hot Food Holding Cabinets that are...

  20. Atmospheric Heating and Wind Acceleration in Cool Evolved Stars

    CERN Document Server

    Airapetian, Vladimir S

    2014-01-01

    A chromosphere is a universal attribute of stars of spectral type later than ~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This chapter provides a review of the observational requirements and theoretical approaches for modeling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma...

  1. A sensitive search for methanol line emission toward evolved stars

    CERN Document Server

    Gomez, J F; Suarez, O; Rizzo, J R; de Gregorio-Monsalvo, I

    2014-01-01

    We present a sensitive search for methanol line emission in evolved stars at 1 cm, aiming to detect, for the first time, methanol masers in this type of objects. Our sample comprised post-AGB stars and young planetary nebulae (PNe), whose mass-loss processes and circumstellar structures resemble those of young stellar objects (YSOs), where methanol masers are detected. Class I masers were searched for in 73 objects, whereas Class II ones were searched in 16. No detection was obtained. The non-detection of Class I methanol masers indicated that methanol production in dust grains and/or the enhancement of its gas-phase abundance in the shocked regions of evolved objects are not as efficient as in YSOs. We suggest that relatively more evolved PNe might have a better probability of harboring Class II masers.

  2. Nearby Hot Stars May Change Our View of Distant Sources

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    As if it werent enough that quasars distant and bright nuclei of galaxies twinkle of their own accord due to internal processes, nature also provides another complication: these distant radio sources can also appear to twinkle because of intervening material between them and us. A new study has identified a possible source for the material getting in the way.Unexplained VariabilityA Spitzer infrared view of the Helix nebula, which contains ionized streamers of gas extending radially outward from the central star. [NASA/JPL-Caltech/Univ. of Ariz.]Distant quasars occasionally display extreme scintillation, twinkling with variability timescales shorter than a day. This intra-day variability is much greater than we can account for with standard models of the interstellar medium lying between the quasar and us. So what could cause this extreme scattering instead?The first clue to this mystery came from the discovery of strong variability in the radio source PKS 1322110. In setting up follow-up observations of this object, Mark Walker (Manly Astrophysics, Australia) and collaborators noticed that, in the plane of the sky, PKS 1322110 lies very near the bright star Spica. Could this be coincidence, or might this bright foreground star have something to do with the extreme scattering observed?Diagram explaining the source of the intra-day radio source variability as intervening filaments surrounding a hot star. [M. Walker/CSIRO/Manly Astrophysics]Swarms of ClumpsWalker and collaborators put forward a hypothesis: perhaps the ultraviolet photons of nearby hot stars ionize plasma around them, which in turn causes the extreme scattering of the distant background sources.As a model, the authors consider the Helix Nebula, in which a hot, evolved star is surrounded by cool globules of molecular hydrogen gas. The radiation from the star hits these molecular clumps, dragging them into long radial streamers and ionizing their outer skins.Though the molecular clumps in the Helix

  3. An HI 21-cm line survey of evolved stars

    CERN Document Server

    Gerard, E; Libert, Y

    2011-01-01

    The HI line at 21 cm is a tracer of circumstellar matter around AGB stars, and especially of the matter located at large distances (0.1-1 pc) from the central stars. It can give unique information on the kinematics and on the physical conditions in the outer parts of circumstellar shells and in the regions where stellar matter is injected into the interstellar medium. However this tracer has not been much used up to now, due to the difficulty of separating the genuine circumstellar emission from the interstellar one. With the Nancay Radiotelescope we are carrying out a survey of the HI emission in a large sample of evolved stars. We report on recent progresses of this long term programme, with emphasis on S-type stars.

  4. UIT Detection of Hot Stars in the Globular Cluster NGC362

    CERN Document Server

    Dorman, B; O'Connell, R W; Landsman, W B; Rood, R T; Bohlin, R C; Neff, S G; Roberts, M S; Smith, A M; Stecher, T P; Dorman, Ben; Shah, Ronak Y.; Connell, Robert W. O'; Landsman, Wayne B.; Rood, Robert T.; Bohlin, Ralph C.; Neff, Susan G.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

    1997-01-01

    We used the Ultraviolet Imaging Telescope during the March 1995 Astro-2 mission to obtain a deep far-UV image of the globular cluster NGC 362, which was formerly thought to have an almost entirely red horizontal branch (HB). 84 hot (T_eff > 8500 K) stars were detected within a radius of 8'.25 of the cluster center. Of these, 43 have FUV magnitudes consistent with HB stars in NGC 362, and at least 34 are cluster members. The number of cluster members is made uncertain by background contamination from blue stars in the Small Magellanic Cloud (SMC). There are six candidate supra-HB stars which have probably evolved from the HB. We discuss the implications of these results for the production of hot blue stars in stellar populations.

  5. Mid-Infrared interferometry of dust around massive evolved stars

    CERN Document Server

    Rajagopal, Jayadev; Wallace, D; Danchi, W C; Chesneau, O; López, B; Monnier, J D; Ireland, M; Tuthill, P G

    2007-01-01

    We report long-baseline interferometric measurements of circumstellar dust around massive evolved stars with the MIDI instrument on the Very Large Telescope Interferometer and provide spectrally dispersed visibilities in the 8-13 micron wavelength band. We also present diffraction-limited observations at 10.7 micron on the Keck Telescope with baselines up to 8.7 m which explore larger scale structure. We have resolved the dust shells around the late type WC stars WR 106 and WR 95, and the enigmatic NaSt1 (formerly WR 122), suspected to have recently evolved from a Luminous Blue Variable (LBV) stage. For AG Car, the protoypical LBV in our sample, we marginally resolve structure close to the star, distinct from the well-studied detached nebula. The dust shells around the two WC stars show fairly constant size in the 8-13 micron MIDI band, with gaussian half-widths of ~ 25 to 40 mas. The compact dust we detect around NaSt1 and AG Car favors recent or ongoing dust formation. Using the measured visibilities, we bu...

  6. HOT GAS LINES IN T TAURI STARS

    Energy Technology Data Exchange (ETDEWEB)

    Ardila, David R. [NASA Herschel Science Center, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States); Herczeg, Gregory J. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Gregory, Scott G.; Hillenbrand, Lynne A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Ingleby, Laura; Bergin, Edwin; Bethell, Thomas; Calvet, Nuria [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); France, Kevin; Brown, Alexander [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Edwards, Suzan [Department of Astronomy, Smith College, Northampton, MA 01063 (United States); Johns-Krull, Christopher [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Linsky, Jeffrey L. [JILA, University of Colorado and NIST, 440 UCB Boulder, CO 80309-0440 (United States); Yang, Hao [Institute for Astrophysics, Central China Normal University, Wuhan 430079 (China); Valenti, Jeff A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Abgrall, Herve [LUTH and UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, Place J. Janssen, F-92195 Meudon (France); Alexander, Richard D. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Brown, Joanna M.; Espaillat, Catherine [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138 (United States); Hussain, Gaitee, E-mail: ardila@ipac.caltech.edu [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); and others

    2013-07-01

    For Classical T Tauri Stars (CTTSs), the resonance doublets of N V, Si IV, and C IV, as well as the He II 1640 A line, trace hot gas flows and act as diagnostics of the accretion process. In this paper we assemble a large high-resolution, high-sensitivity data set of these lines in CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars: 1 Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C IV, Si IV, and N V lines in CTTSs all have similar shapes. We decompose the C IV and He II lines into broad and narrow Gaussian components (BC and NC). The most common (50%) C IV line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. For CTTSs, a strong BC is the result of the accretion process. The contribution fraction of the NC to the C IV line flux in CTTSs increases with accretion rate, from {approx}20% to up to {approx}80%. The velocity centroids of the BCs and NCs are such that V{sub BC} {approx}> 4 V{sub NC}, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He II CTTSs lines are generally symmetric and narrow, with FWHM and redshifts comparable to those of WTTSs. They are less redshifted than the CTTSs C IV lines, by {approx}10 km s{sup -1}. The amount of flux in the BC of the He II line is small compared to that of the C IV line, and we show that this is consistent with models of the pre-shock column emission. Overall, the observations are consistent with the presence of multiple accretion columns with different densities or with accretion models that predict a slow-moving, low-density region in the periphery of the accretion column. For HN Tau A and RW Aur A, most of the C IV line is blueshifted suggesting that the C IV emission is produced by shocks within outflow jets. In our sample, the Herbig Ae star DX Cha is the only object for which we find a

  7. Single neutron star systems evolving with fallback discs

    Science.gov (United States)

    Ertan, Unal; Caliskan, Sirin; Alpar, Mehmet Ali; Benli, Onur; Trümper, Joachim E.

    2016-07-01

    We have investigated the long-term evolution of the young neutron star systems, namely anomalous X-ray pulsars (AXPs), soft gamma repeaters (SGRs), dim isolated neutron stars (XDINs), and the so-called "high-B radio pulsars" in the frame of the fallback disk disc model. We have shown that the X-ray luminosities and the rotational properties of individual sources in these different populations can be achieved by neutron stars evolving with fallback disks and with conventional dipole magnetic fields of young neutron stars. Presence of small-scale magnetar fields in the higher multi-poles which are likely to be responsible for soft gamma bursts observed from these systems is compatible with the fallback disk model, since the rotational evolution of the star is governed by the interaction between the large-scale dipole field and the disc. The results of our model is self-consistent in that (1) the X-ray luminosity, period and period derivative of individual sources are produced simultaneously, and (2) these results are obtained with very similar set of main disk parameters for all these systems with rather different properties. Our results indicate that all known AXPs, except two sources, are in the accretion phase at present. The 6 XDINs with confirmed period and period derivatives reached their long periods in the accretion epochs in the past. At present, XDINs are evolving in the propeller phase without accretion, but they are still slowing down under effect of the disk torques. For the "high-B radio pulsars", the source properties are obtained in the phases when accretion is not allowed, which is consistent with the radio pulsar property of these sources.

  8. Bipolar outflows from the most luminous evolved stars, especially the unique case of eta CAR

    Science.gov (United States)

    Davidson, K.

    1996-05-01

    If recent experience is a valid guide, very massive evolved stars typically show outward signs of axial (non-spherical) symmetry; some cases are dramatic. Large-scale bipolar structure has lately been identified around most well-studied Luminous Blue Variables (LBVs), while their country cousins the B[e] stars (not the same as Be stars) have long been thought to have equatorial disks. Radiation pressure makes these stars fundamentally different from ordinary massive stars, helping in more than one way to encourage axial and equatorial structures. Two general questions have thus arisen: (1) Is bipolar structure practically universal among very massive evolved stars? (2) Does the crucial LBV instability occur in an essentially equatorial or axial way, to the extent that spherical theories are misleading? The special case of eta Carinae provides insights largely because its structure is so obvious and well-defined. Its polar lobes are dramatic enough by themselves, but the large-scale equatorial debris are even more wonderfully suggestive. HST spectroscopy and imaging are giving information about the equatorial structure over a wide range of size scales. Additional questions particularly inspired by eta Car are (3) How seriously are mass-loss estimates modified by this type of structure? The latitudinal distribution of ejected mass is not yet known, but it is clear that any analysis of the spectrum assuming spherical symmetry would be invalid, for this or any star with similar structure. (4) Did this prominent equatorial structure result from a much smaller wind-compressed disk, or is it the result of preferentially equatorial ejection in the LBV eruption? (5) How can we tell the difference between the effects of stellar rotation and of a close companion, for such a luminous star? (Radiation pressure prevents mass exchange in a very massive close binary, so the two cases look almost alike.) Finally, we must eventually compare the axially symmetric structures of hot

  9. Stellar wind models of subluminous hot stars

    CERN Document Server

    Krticka, J; Krtickova, I

    2016-01-01

    Mass-loss rate is one of the most important stellar parameters. We aim to provide mass-loss rates as a function of subdwarf parameters and to apply the formula for individual subdwarfs, to predict the wind terminal velocities, to estimate the influence of the magnetic field and X-ray ionization on the stellar wind, and to study the interaction of subdwarf wind with mass loss from Be and cool companions. We used our kinetic equilibrium (NLTE) wind models with the radiative force determined from the radiative transfer equation in the comoving frame (CMF) to predict the wind structure of subluminous hot stars. Our models solve stationary hydrodynamical equations, that is the equation of continuity, equation of motion, and energy equation and predict basic wind parameters. We predicted the wind mass-loss rate as a function of stellar parameters, namely the stellar luminosity, effective temperature, and metallicity. The derived wind parameters (mass-loss rates and terminal velocities) agree with the values derived...

  10. The Gaia satellite: a tool for Emission Line Stars and Hot Stars

    CERN Document Server

    Martayan, Christophe; Blomme, Ronny; Jonckheere, Anthony; Borges, Marcelo; De Batz, Bertrand; Leroy, Bernard; Sordo, Rosanna; Bouret, Jean-Claude; Martins, Fabrice; Zorec, Jean; Neiner, Coralie; Nazé, Yael; Alecian, Evelyne; Floquet, Michele; Hubert, Anne-Marie; Briot, Danielle; Miroshnichenko, Anatholy; Kolka, Indrek; Stee, Philippe; Lanz, Thierry; Meynet, Georges

    2008-01-01

    The Gaia satellite will be launched at the end of 2011. It will observe at least 1 billion stars, and among them several million emission line stars and hot stars. Gaia will provide parallaxes for each star and spectra for stars till V magnitude equal to 17. After a general description of Gaia, we present the codes and methods, which are currently developed by our team. They will provide automatically the astrophysical parameters and spectral classification for the hot and emission line stars in the Milky Way and other close Local Group galaxies such as the Magellanic Clouds.

  11. Massive main-sequence stars evolving at the Eddington limit

    Science.gov (United States)

    Sanyal, D.; Grassitelli, L.; Langer, N.; Bestenlehner, J. M.

    2015-08-01

    Context. Massive stars play a vital role in the Universe, however, their evolution even on the main-sequence is not yet well understood. Aims: Because of the steep mass-luminosity relation, massive main-sequence stars become extremely luminous. This brings their envelopes very close to the Eddington limit. We analyse stellar evolutionary models in which the Eddington limit is reached and exceeded, explore the rich diversity of physical phenomena that take place in their envelopes, and investigate their observational consequences. Methods: We use published grids of detailed stellar models, computed with a state-of-the-art, one-dimensional hydrodynamic stellar evolution code using LMC composition, to investigate the envelope properties of core hydrogen burning massive stars. Results: We find that the Eddington limit is almost never reached at the stellar surface, even for stars up to 500 M⊙. When we define an appropriate Eddington limit locally in the stellar envelope, we can show that most stars more massive than ~40 M⊙ actually exceed this limit, in particular, in the partial ionisation zones of iron, helium, or hydrogen. While most models adjust their structure such that the local Eddington limit is exceeded at most by a few per cent, our most extreme models do so by a factor of more than seven. We find that the local violation of the Eddington limit has severe consequences for the envelope structure, as it leads to envelope inflation, convection, density inversions, and, possibly to, pulsations. We find that all models with luminosities higher than 4 × 105L⊙, i.e. stars above ~40 M⊙ show inflation, with a radius increase of up to a factor of about 40. We find that the hot edge of the S Dor variability region coincides with a line beyond which our models are inflated by more than a factor of two, indicating a possible connection between S Dor variability and inflation. Furthermore, our coolest models show highly inflated envelopes with masses of up to

  12. Rayleigh scattering in the atmospheres of hot stars

    Science.gov (United States)

    Fišák, J.; Krtička, J.; Munzar, D.; Kubát, J.

    2016-05-01

    Context. Rayleigh scattering is a result of an interaction of photons with bound electrons. Rayleigh scattering is mostly neglected in calculations of hot star model atmospheres because most of the hydrogen atoms are ionized and the heavier elements have a lower abundance than hydrogen. In atmospheres of some chemically peculiar stars, helium overabundant regions containing singly ionized helium are present and Rayleigh scattering can be a significant opacity source. Aims: We evaluate the contribution of Rayleigh scattering by neutral hydrogen and singly ionized helium in the atmospheres of hot stars with solar composition and in the atmospheres of helium overabundant stars. Methods: We computed several series of model atmospheres using the TLUSTY code and emergent fluxes using the SYNSPEC code. These models describe atmospheres of main sequence B-type stars with different helium abundance. We used an existing grid of models for atmospheres with solar chemical composition and we calculated an additional grid for helium-rich stars with N(He)/N(H) = 10. Results: Rayleigh scattering by neutral hydrogen can be neglected in atmospheres of hot stars, while Rayleigh scattering by singly ionized helium can be a non-negligible opacity source in some hot stars, especially in helium-rich stars.

  13. Dynamical Interactions Make Hot Jupiters in Open Star Clusters

    CERN Document Server

    Shara, Michael M; Mardling, Rosemary A

    2014-01-01

    Explaining the origin and evolution of exoplanetary "hot Jupiters" remains a significant challenge. One possible mechanism for their production is planet-planet interactions, which produces hot Jupiters from planets born far from their host stars but near their dynamical stability limits. In the much more likely case of planets born far from their dynamical stability limits, can hot Jupiters can be formed in star clusters? Our N-body simulations of planetary systems inside star clusters answer this question in the affirmative, and show that hot Jupiter formation is not a rare event. We detail three case studies of the dynamics-induced births of hot Jupiters on highly eccentric orbits that can only occur inside star clusters. The hot Jupiters' orbits bear remarkable similarities to those of some of the most extreme exoplanets known: HAT-P-32 b, HAT-P-2 b, HD 80606 b and GJ 876 d. If stellar perturbations formed these hot Jupiters then our simulations predict that these very hot, inner planets are sometimes acc...

  14. The magnetic field of the evolved star W43A

    Science.gov (United States)

    Amiri, N.; Vlemmings, W.; van Langevelde, H. J.

    2010-01-01

    Context. The majority of the observed planetary nebulae exhibit elliptical or bipolar structures. Recent observations have shown that asymmetries already start during the last stages of the AGB phase. Theoretical modeling has indicated that magnetically collimated jets may be responsible for the formation of the non-spherical planetary nebulae. Direct measurement of the magnetic field of evolved stars is possible using polarization observations of different maser species occurring in the circumstellar envelopes around these stars. Aims: The aim of this project is to measure the Zeeman splitting caused by the magnetic field in the OH and H2O maser regions occurring in the circumstellar envelope and bipolar outflow of the evolved star W43A. We compare the magnetic field obtained in the OH maser region with the one measured in the H2O maser jet. Methods: We used the UK Multi-Element Radio Linked Interferometer Network (MERLIN) to observe the polarization of the OH masers in the circumstellar envelope of W43A. Likewise, we used the Green Bank Telescope (GBT) observations to measure the magnetic field strength obtained previously in the H2O maser jet. Results: We report a measured magnetic field of approximately 100 μ G in the OH maser region of the circumstellar envelope around W43A. The GBT observations reveal a magnetic field strength B_|| of ~30 mG changing sign across the H2O masers at the tip of the red-shifted lobe of the bipolar outflow. We also find that the OH maser shell shows no sign of non-spherical expansion and that it probably has an expansion velocity that is typical for the shells of regular OH/IR stars. Conclusions: The GBT observations confirm that the magnetic field collimates the H2O maser jet, while the OH maser observations show that a strong large-scale magnetic field is present in the envelope surrounding the W43A central star. The magnetic field in the OH maser envelope is consistent with the one extrapolated from the H2O measurements

  15. Rayleigh scattering in the atmospheres of hot stars

    CERN Document Server

    Fišák, Jakub; Munzar, Dominik; Kubát, Jiří

    2016-01-01

    Rayleigh scattering is a result of an interaction of photons with bound electrons. Rayleigh scattering is mostly neglected in calculations of hot star model atmospheres because most of the hydrogen atoms are ionized and the heavier elements have a lower abundance than hydrogen. In atmospheres of some chemically peculiar stars, helium overabundant regions containing singly ionized helium are present and Rayleigh scattering can be a significant opacity source. We evaluate the contribution of Rayleigh scattering by neutral hydrogen and singly ionized helium in the atmospheres of hot stars with solar composition and in the atmospheres of helium overabundant stars. We computed several series of model atmospheres using the TLUSTY code and emergent fluxes using the SYNSPEC code. These models describe atmospheres of main sequence B-type stars with different helium abundance. We used an existing grid of models for atmospheres with solar chemical composition and we calculated an additional grid for helium-rich stars wi...

  16. Evolved stars at high angular resolution: present and future

    CERN Document Server

    Paladini, C

    2016-01-01

    The late evolutionary stages of stellar evolution are a key ingredient for our understanding in many fields of astrophysics, including stellar evolution and the enrichment of the interstellar medium (ISM) via stellar yields. Already the first interferometric campaigns identified evolved stars as the primary targets because of their extended and partially optically thin atmospheres, and the brightness in the infrared. Interferometric studies spanning different wavelength ranges, from visual to mid-infrared, have greatly increased our knowledge of the complex atmospheres of these objects where different dynamic processes are at play. In less than two decades this technique went from measuring simple diameters to produce the first images of stellar surfaces. By scanning the extended atmospheres we constrained theoretical models, learnt about molecular stratification, dust formation, and stellar winds, and there is still a lot to be done. In this contribution I will review the recent results that optical/infrared...

  17. Hot Stars: Old-Fashioned or Trendy? (With 24 Figures)

    Science.gov (United States)

    Pauldrach, A. W. A.

    Spectroscopic analyses with the intention of the interpretation of the UV-spectra of the brightest stars as individuals - supernovae - or as components of star-forming regions - massive O stars - provide a powerful tool with great astrophysical potential for the determination of extragalactic distances and of the chemical composition of star-forming galaxies even at high redshifts. The perspectives of already initiated work with the new generation of tools for quantitative UV-spectroscopy of Hot Stars that have been developed during the last two decades are presented and the status of the continuing effort to construct corresponding models for Hot Star atmospheres is reviewed. Because the physics of the atmospheres of Hot Stars are strongly affected by velocity expansion dominating the spectra at all wavelength ranges, hydrodynamic model atmospheres for O-type stars and explosion models for Supernovae of Type Ia are necessary as basis for the synthesis and analysis of the spectra. It is shown that stellar parameters, abundances and stellar wind properties can be determined by the methods of spectral diagnostics already developed. Additionally, it will be demonstrated that models and synthetic spectra of Type Ia Supernovae of required quality are already available that make it possible to tackle the question of whether Supernovae Ia are standard candles in a cosmological sense and the SN-luminosity distances thus indicate accelerated expansion of the universe.

  18. An interferometric view of hot star disks

    CERN Document Server

    Faes, Daniel Moser

    2015-01-01

    Optical long baseline interferometry was recently established as a technique capable of resolving stars and their circumstellar environments at the milliarcsecond (mas) resolution level. This high-resolution opens an entire new window to the study of astrophysical systems, providing information inaccessible by other techniques. Astrophysical disks are observed in a wide variety of systems, from galaxies up to planetary rings, commonly sharing similar physical processes. Two particular disk like systems are studied in the thesis: (i) B He-rich stars that exhibits magnetic fields in order of kG and that trap their winds in structures called magnetospheres; and (ii) Be stars, fast rotating stars that create circumstellar viscous disks. This study uses the interferometric technique to investigate both the photosphere proper and the circumstellar environment of these stars. The objective is to combine interferometry with other observational techniques (such as spectroscopy and polarimetry) to perform a complete an...

  19. HR8844: A new hot Am star ?

    CERN Document Server

    Monier, R; Royer, F

    2016-01-01

    Using one archival high dispersion high quality spectrum of HR8844 (A0V) obtained with the echelle spectrograph SOPHIE at Observatoire de Haute Provence, we show that this star is not a superficially normal A0V star as hitherto thought. The model atmosphere and spectrum synthesis modeling of the spectrum of HR8844 reveals large departures of its abundances from the solar composition. We report here on our first determinations of the elemental abundances of 41 elements in the atmosphere of HR8844. Most of the light elements are underabundant whereas the very heavy elements are overabundant in HR8844.This interesting new chemically peculiar star could be a hybrid object between the HgMn stars and the Am stars.

  20. The hot Gamma-Doradus and Maia stars

    CERN Document Server

    Balona, L A; Joshi, Yogesh C; Joshi, S; Sharma, K; Semenko, E; Pandey, G; Chakradhari, N K; Mkrtichian, David; Hema, B P; Nemec, J M

    2016-01-01

    The hot $\\gamma$~Doradus stars have multiple low frequencies characteristic of $\\gamma$~Dor or SPB variables, but are located between the red edge of the SPB and the blue edge of the $\\gamma$~Dor instability strips where all low-frequency modes are stable in current models of these stars. Though $\\delta$~Sct stars also have low frequencies, there is no sign of high frequencies in hot $\\gamma$~Dor stars. We obtained spectra to refine the locations of some of these stars in the H-R diagram and conclude that these are, indeed, anomalous pulsating stars. The Maia variables have multiple high frequencies characteristic of $\\beta$~Cep and $\\delta$~Sct stars, but lie between the red edge of the $\\beta$~Cep and the blue edge of the $\\delta$~Sct instability strips. We compile a list of all Maia candidates and obtain spectra of two of these stars. Again, it seems likely that these are anomalous pulsating stars which are currently not understood.

  1. Weighing stars: the identification of an Evolved Blue Straggler Star in the globular cluster 47 Tucanae

    CERN Document Server

    Ferraro, F R; Mucciarelli, A; Lanzoni, B; Dalessandro, E; Pallanca, C; Massari, D

    2015-01-01

    Globular clusters are known to host peculiar objects, named Blue Straggler Stars (BSSs), significantly heavier than the normal stellar population. While these stars can be easily identified during their core hydrogen-burning phase, they are photometrically indistinguishable from their low-mass sisters in advanced stages of the subsequent evolution. A clear-cut identification of these objects would require the direct measurement of the stellar mass. We used the detailed comparison between chemical abundances derived from neutral and from ionized spectral lines as a powerful stellar "weighing device" to measure stellar mass and to identify an evolved BSS in 47 Tucanae. In particular, high-resolution spectra of three bright stars located slightly above the level of the "canonical" horizontal branch sequence in the color-magnitude diagram of 47 Tucanae, have been obtained with UVES spectrograph. The measurements of iron and titanium abundances performed separately from neutral and ionized lines reveal that two ta...

  2. The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project

    CERN Document Server

    Geier, S; Heber, U; Schaffenroth, V; Barlow, B N; stensen, R H O; O'Toole, S J; Ziegerer, E; Heuser, C; Maxted, P F L; Gänsicke, B T; Marsh, T R; Napiwotzki, R; Brünner, P; Schindewolf, M; Niederhofer, F

    2015-01-01

    The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions like massive white dwarfs, neutron stars or black holes. Here we provide classifications, atmospheric parameters and a complete radial velocity (RV) catalogue containing 1914 single measurements for an sample of 177 hot subluminous stars discovered based on SDSS DR7. 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions {of hydrogen-rich hot subdwarfs} in our sample to be smaller than $\\sim1.3\\%$, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding $\\sim8\\,{\\rm d}$. We detect a mismatch between the $\\Delta RV_{\\rm max}$-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with ...

  3. Hot subluminous stars: Highlights from the MUCHFUSS and Kepler missions

    Directory of Open Access Journals (Sweden)

    Geier S.

    2013-03-01

    Full Text Available Research into hot subdwarf stars is progressing rapidly. We present recent important discoveries. First we review the knowledge about magnetic fields in hot subdwarfs and highlight the first detection of a highly-magnetic, helium-rich sdO star. We briefly summarize recent discoveries based on Kepler light curves and finally introduce the closest known sdB+WD binary discovered by the MUCHFUSS project and discuss its relevance as a progenitor of a double-detonation type Ia supernova.

  4. The origin of magnetic fields in hot stars

    CERN Document Server

    Neiner, C; Alecian, E; Emeriau, C; Grunhut, J; BinaMIcS, the

    2015-01-01

    Observations of stable mainly dipolar magnetic fields at the surface of ~7% of single hot stars indicate that these fields are of fossil origin, i.e. they descend from the seed field in the molecular clouds from which the stars were formed. Recent results confort this theory. First, theoretical work and numerical simulations confirm that the properties of the observed fields correspond to those expected from fossil fields. They also showed that rapid rotation does not modify the surfacic dipolar magnetic configurations, but hinders the stability of fossil fields. This explains the lack of correlation between the magnetic field properties and stellar properties in massive stars. It may also explain the lack of detections of magnetic fields in Be stars, which rotate close to their break-up velocity. In addition, observations by the BinaMIcS collaboration of hot stars in binary systems show that the fraction of those hosting detectable magnetic fields is much smaller than for single hot stars. This could be rela...

  5. Summary of the Conference "The Physics of Evolved Stars"

    Science.gov (United States)

    De Marco, O.

    2015-12-01

    Olivier Chesneau was an astronomer of many talents. His expertise was on optical and infrared interferometry. Olivier*s tool of choice, the Very Large Telescope Interferometer (VLTI), allowed him to see solutions to open questions in stellar astrophysics. These visions led to collaborations with experts in each of the fields where VLTI observations could be useful. As a result Olivier was a man in the middle of a phenomenal network of astronomers, collaborators and friends. I am fortunate to have been one of them. In this contribution I summarise the conference "Physics of Evolved Stars", held in Nice in June 2015 in memory of Olivier. The conference neatly showcased the science that Olivier had been involved with during his life and laid out the advancements that were made thanks in great part to him and to the collaborations he started. Without doubt his bubbly, happy personality, child-like in a way, made him the perfect connector bringing the technique, the questions and the experts in diverse fields together. Dear to all who worked with him, he was truly the little prince of Astronomy. We shall miss him every day.

  6. Echelle long-slit optical spectroscopy of evolved stars

    CERN Document Server

    Contreras, C Sanchez; de Paz, A Gil; Goodrich, R

    2008-01-01

    We present echelle long-slit optical spectra of a sample of objects evolving off the AGB, most of them in the pre-planetary nebula (pPN) phase, obtained with the ESI and MIKE spectrographs at Keck-II and Magellan-I, respectively. The total wavelength range covered with ESI (MIKE) is ~3900 to 10900 A (~3600 to 7200A). In this paper, we focus our analysis mainly on the Halpha profiles. Prominent Halpha emission is detected in half of the objects, most of which show broad Halpha wings (up to ~4000 km/s). In the majority of the Halpha-emission sources, fast, post-AGB winds are revealed by P-Cygni profiles. In ~37% of the objects Halpha is observed in absorption. In almost all cases, the absorption profile is partially filled with emission, leading to complex, structured profiles that are interpreted as an indication of incipient post-AGB mass-loss. All sources in which Halpha is seen mainly in absorption have F-G type central stars, whereas sources with intense Halpha emission span a larger range of spectral type...

  7. Detection of carbonates in dust shells around evolved stars.

    Science.gov (United States)

    Kemper, F; Jäger, C; Waters, L B F M; Henning, Th; Molster, F J; Barlow, M J; Lim, T; de Koter, A

    2002-01-17

    Carbonates on large Solar System bodies like Earth and Mars (the latter represented by the meteorite ALH84001) form through the weathering of silicates in a watery (CO3)2- solution. The presence of carbonates in interplanetary dust particles and asteroids (again, represented by meteorites) is not completely understood, but has been attributed to aqueous alteration on a large parent body, which was subsequently shattered into smaller pieces. Despite efforts, the presence of carbonates outside the Solar System has hitherto not been established. Here we report the discovery of the carbonates calcite and dolomite in the dust shells of evolved stars, where the conditions are too primitive for the formation of large parent bodies with liquid water. These carbonates, therefore, are not formed by aqueous alteration, but perhaps through processes on the surfaces of dust or ice grains or gas phase condensation. The presence of carbonates which did not form by aqueous alteration suggests that some of the carbonates found in Solar System bodies no longer provide direct evidence that liquid water was present on large parent bodies early in the history of the Solar System.

  8. All known hot RCB stars are fading fast over the last century

    Science.gov (United States)

    Schaefer, Bradley E.

    2016-08-01

    The R Coronae Borealis (RCB) stars are cool supergiants that display irregular and deep dips in their light curves, caused by dust formation. There are four known hot RCB stars (DY Cen, MV Sgr, V348 Sgr, and HV 2671), with surface temperatures of 15 000-25 000 K, and prior work has suggested that three of these have secular fading in brightness. I have tested this result by measuring century-long light curves in the Johnson B band with modern comparison star magnitudes, and I have extended this by measuring many magnitudes over a wide time range as well as for the fourth hot RCB star. In all four cases, the B band magnitude of the maximum light is now fast fading. The fading rates (in units of magnitudes per century) are 2.5 for DY Cen after 1960, 1.3 for MV Sgr, 1.3 for V348 Sgr, and 0.7 for HV 2671. This secular fading is caused by the expected evolution of the star across the top of the Hertzsprung-Russell (HR) diagram at constant luminosity, as the temperature rises and the bolometric correction changes. For DY Cen, the brightness at maximum light is rising from 1906 to 1932, and this is caused by the temperature increase from near 5800 to 7500 K. Before 1934, DY Cen had frequent dust dips, while after 1934 there are zero dust dips, so there is some apparent connection between the rising temperature and the formation of the dust. Thus, we have watched DY Cen evolve from an ordinary RCB star up to a hot RCB star and now appearing as an extreme helium star, all in under one century.

  9. Hot Gas Lines in T Tauri Stars

    CERN Document Server

    Ardila, David R; Gregory, Scott G; Ingleby, Laura; France, Kevin; Brown, Alexander; Edwards, Suzan; Johns-Krull, Christopher; Linsky, Jeffrey L; Yang, Hao; Valenti, Jeff A; Abgrall, Hervé; Alexander, Richard D; Bergin, Edwin; Bethell, Thomas; Brown, Joanna M; Calvet, Nuria; Espaillat, Catherine; Hillenbrand, Lynne A; Hussain, Gaitee; Roueff, Evelyne; Schindhelm, Eric R; Walter, Frederick M

    2013-01-01

    For Classical T Tauri Stars (CTTSs), the resonance lines of N V, Si IV, and C IV, as well as the He II 1640 A line, act as diagnostics of the accretion process. Here we assemble a large high-resolution dataset of these lines in CTTSs and Weak T Tauri Stars (WTTSs). We present data for 35 stars: one Herbig Ae star, 28 CTTSs, and 6 WTTSs. We decompose the C IV and He II lines into broad and narrow Gaussian components (BC & NC). The most common (50 %) C IV line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. The velocity centroids of the BCs and NCs are such that V_BC > 4 * V_NC, consistent with the predictions of the accretion shock model, in at most 12 out of 22 CTTSs. We do not find evidence of the post-shock becoming buried in the stellar photosphere due to the pressure of the accretion flow. The He II CTTSs lines are generally symmetric and narrow, less redshifted than the CTTSs C IV lines, by ~10 km/sec. The flux in the BC of the He II line is small compared to that of t...

  10. On the origin of microturbulence in hot stars

    NARCIS (Netherlands)

    M. Cantiello; N. Langer; I. Brott; A. de Koter; S.N. Shore; J.S. Vink; A. Voegler; S.C. Yoon

    2008-01-01

    We present results from the first extensive study of convection zones in the envelopes of hot massive stars, which are caused by opacity peaks associated with iron and helium ionization. These convective regions can be located very close to the stellar surface. The region in the Hertzsprung-Russel d

  11. Rule or exception? Planetary nebulae around hot subdwarf stars

    CERN Document Server

    Aller, A; Ulla, A; Oreiro, R; Manteiga, M; Pérez, E; Rodríguez-López, C; 10.1017/S174392131201647X

    2012-01-01

    In this work, we present the first results of an ongoing survey to search for planetary nebulae (PNe) around hot subdwarf stars (sdOs). Deep images and intermediate-resolution long-slit spectra of RWT 152, the only confirmed PN+sdO system in the northern hemisphere, as well as preliminary results for other sdO+PN candidate are presented.

  12. Dust Production and Mass Loss in Cool Evolved Stars

    Science.gov (United States)

    Boyer, M. L.

    2013-01-01

    Following the red giant branch phase and the subsequent core He-burning phase, the low- to intermediate-mass stars (0.8star. I will briefly review the current status of models that include AGB mass loss and relate them to recent observations of AGB stars from the Surveying the Agents of Galaxy Evolution (SAGE) Spitzer surveys of the Small and Large Magellanic Clouds, including measures of the total dust input to the interstellar medium from AGB stars.

  13. An infrared diagnostic for magnetism in hot stars

    CERN Document Server

    Oksala, M E; Kraus, M; Fernandes, M Borges; Neiner, C; Condori, C A H; Campagnolo, J C N; Souza, T B

    2015-01-01

    Magnetospheric observational proxies are used for indirect detection of magnetic fields in hot stars in the X-ray, UV, optical, and radio wavelength ranges. To determine the viability of infrared (IR) hydrogen recombination lines as a magnetic diagnostic for these stars, we have obtained low-resolution (R~1200), near-IR spectra of the known magnetic B2V stars HR 5907 and HR 7355, taken with the Ohio State Infrared Imager/Spectrometer (OSIRIS) attached to the 4.1m Southern Astrophysical Research (SOAR) Telescope. Both stars show definite variable emission features in IR hydrogen lines of the Brackett series, with similar properties as those found in optical spectra, including the derived location of the detected magnetospheric plasma. These features also have the added advantage of a lowered contribution of stellar flux at these wavelengths, making circumstellar material more easily detectable. IR diagnostics will be useful for the future study of magnetic hot stars, to detect and analyze lower-density environ...

  14. Detection of 610-MHz radio emission from hot magnetic stars

    Science.gov (United States)

    Chandra, P.; Wade, G. A.; Sundqvist, J. O.; Oberoi, D.; Grunhut, J. H.; ud-Doula, A.; Petit, V.; Cohen, D. H.; Oksala, M. E.; David-Uraz, A.

    2015-09-01

    We have carried out a study of radio emission from a small sample of magnetic O- and B-type stars using the Giant Metrewave Radio Telescope, with the goal of investigating their magnetospheres at low frequencies. These are the lowest frequency radio measurements ever obtained of hot magnetic stars. The observations were taken at random rotational phases in the 1390 and the 610 MHz bands. Out of the eight stars, we detect five B-type stars in both the 1390 and the 610 MHz bands. The three O-type stars were observed only in the 1390 MHz band, and no detections were obtained. We explain this result as a consequence of free-free absorption by the free-flowing stellar wind exterior to the confined magnetosphere. We also study the variability of individual stars. One star - HD 133880 - exhibits remarkably strong and rapid variability of its low-frequency flux density. We discuss the possibility of this emission being coherent emission as reported for CU Vir by Trigilio et al.

  15. A Transiting Hot Jupiter Orbiting a Metal-Rich Star

    CERN Document Server

    Dunham, Edward W; Koch, David G; Batalha, Natalie M; Buchhave, Lars A; Brown, Timothy M; Caldwell, Douglas A; Cochran, William D; Endl, Michael; Fischer, Debra; Furesz, Gabor; Gautier, Thomas N; Geary, John C; Gilliland, Ronald L; Gould, Alan; Howell, Steve B; Jenkins, Jon M; Kjeldsen, Hans; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Meibom, Soren; Monet, David G; Rowe, Jason F; Sasselov, Dimitar D

    2010-01-01

    We announce the discovery of Kepler-6b, a transiting hot Jupiter orbiting a star with unusually high metallicity, [Fe/H] = +0.34 +/- 0.04. The planet's mass is about 2/3 that of Jupiter, Mp = 0.67 Mj, and the radius is thirty percent larger than that of Jupiter, Rp = 1.32 Rj, resulting in a density of 0.35 g/cc, a fairly typical value for such a planet. The orbital period is P = 3.235 days. The host star is both more massive than the Sun, Mstar = 1.21 Msun, and larger than the Sun, Rstar = 1.39 Rsun.

  16. Update on the KELT Transit Survey: Hot Planets around Hot, Bright Stars

    Science.gov (United States)

    Gaudi, B. Scott; KELT Collaboration

    2017-01-01

    The KELT Transit Survey consists of a pair of small-aperture, wide-angle automated telescope located at Winer Observatory in Sonoita, Arizona and the South African Astronomical Observatory (SAAO) in Sutherland, South Africa. Together, they are surveying roughly 60% of the sky for transiting planets. By virtue of their small apertures (42 mm) and large fields-of-view (26 degrees x 26 degrees), KELT is most sensitive to hot Jupiters transiting relatively bright (V~8-11), and thus relatively hot stars. Roughly half of the dwarf stars targeted by KELT are hotter than 6250K; such stars pose novel challenges, but also provide unique opportunities. I will provide an update on the most recent companions discovered by KELT, focusing in detail on a few particularly interesting systems. KELT is a joint collaboration between the Ohio State University, Vanderbilt University, and Lehigh University. This work was partially supported by NSF CAREER grant AST-1056524.

  17. Interferometric Studies of Hot Stars at Sydney University

    CERN Document Server

    Robertson, J G; Ireland, M J; Tuthill, P G; Tango, W J; Jacob, A P; North, J R; Brummelaar, T A ten

    2009-01-01

    The University of Sydney has a long history in optical stellar interferometry. The first project, in the 1960s, was the Narrabri Stellar Intensity Interferometer, which measured the angular diameters of 32 hot stars and established the temperature scale for spectral classes O - F. That instrument was followed by the Sydney University Stellar Interferometer (SUSI), which is now undergoing a third-generation upgrade, to use the multi-wavelength PAVO beam combiner. SUSI operates at visible rather than IR wavelengths and has baselines up to 160 m, so it is well suited to the study of hot stars. A number of studies have been carried out, and more are planned when commissioning of the PAVO system is complete. Conversion of the system to allow remote operation will allow larger scientific projects to be undertaken.

  18. Hot Neutron Stars with Hadron-Quark Crossover

    Science.gov (United States)

    Masuda, Kota; Hatsuda, Tetsuo; Takatsuka, Tatsuyuki

    2016-12-01

    The effects of the hadron-quark crossover on the bulk properties of cold and hot neutron stars (NSs) are studied. We suggested a new phenomenological equation of state (EOS), which interpolates the two phases at around 3 times the nuclear matter density (ρ0), and found that the cold NSs with the gravitational mass larger than 2M⊙ can be sustained. This is in sharp contrast to the case of the first-order hadron-quark transition where the quark matter inevitably leads to soft EOS. The interpolated EOS is also generalized to the supernova matter at finite temperature to describe the hot NSs at birth. The hadron-quark crossover is found to decrease the central temperature of the hot NSs under isentropic condition due to the color degrees of freedom.

  19. External Shaping of Circumstellar Envelopes of Evolved Stars

    Science.gov (United States)

    Cox, N. L. J.

    2015-08-01

    The circumstellar envelopes of asymptotic giant branch (AGB) stars and red supergiants (RSGs) are complex chemical and physical environments, and the specifics of their mass-loss history are important for both stellar and galactic evolution. One key aspect in this is to understand how the circumstellar medium of these stars can be shaped and affected by both internal and external mechanisms. These influences can skew our view on the (dust) chemistry and mass-loss history of these stars, and hence their role in the chemical enrichment of galaxies. This contribution focuses on the external mechanism related to the interaction between the slow dusty stellar wind and the local ambient medium. I will discuss what recent observations and hydrodynamical simulations have revealed and how these can help us learn more about AGB stars and RSGs, as well as the interstellar medium (ISM).

  20. CKVul: evolving nebula and three curious background stars

    CERN Document Server

    Hajduk, M; Zijlstra, A A

    2013-01-01

    We analyse the remnants of CK Vul (Nova Vul 1670) using optical imaging and spectroscopy. The imaging, obtained between 1991 and 2010, spans 5.6% of the life-time of the nebula. The flux of the nebula decreased during the last 2 decades. The central source still maintains the ionization of the innermost part of the nebula, but recombination proceeds in more distant parts of the nebula. Surprisingly, we discovered two stars located within 10 arcsec of the expansion centre of the radio emission that are characterized by pronounced long term variations and one star with high proper motion. The high proper motion star is a foreground object, and the two variable stars are background objects. The photometric variations of two variables are induced by a dusty cloud ejected by CK Vul and passing through the line of sight to those stars. The cloud leaves strong lithium absorption in the spectra of the stars. We discuss the nature of the object in terms of recent observations.

  1. Observational Constraints on Models of Rapidly Evolving Luminous Stars

    Science.gov (United States)

    Rosenfield, Philip; Dalcanton, Julianne; Bressan, Alessandro; Girardi, Leo; Marigo, Paola; Angst Team

    2015-01-01

    Resolved stellar populations in galaxies are excellent laboratories for testing our understanding of galaxy formation, integrated colors and luminosities, supernova progenitor masses, and energy input from stellar feedback. However, the usefulness of resolved stellar populations rests on the ability to accurately model the evolution of the underlying stars. Part of my thesis work is focused on two uncertain phases of stellar evolution; the luminous core helium burning (HeB) phase and the thermally pulsating AGB (TP-AGB) phase. Dwarf galaxies, imaged as part of the ACS Nearby Galaxy Survey Treasury and its HST/NIR follow-up campaign, provide ideal testing grounds for new models because the galaxies span ~2 dex in metallicity, many have significant HeB populations (i.e, the HeB sequence is populated with stars with masses from ~2-15 Msun), and many contain large numbers of TP-AGB stars. I will present how I used ANGST to constrain low metallicity stellar evolution models with the Padova-Trieste Stellar Evolution Code (PARSEC; the recently updated Padova Stellar Evolution Library) and COLIBRI (a new tool for modeling TP-AGB stars). Specifically, I will show how increasing the strength of core overshooting with increasing mass in HeB stars improves data and model agreement. I will also present constraints to the mass loss prescriptions of low mass, low metallicity TP-AGB stars.

  2. An infrared diagnostic for magnetism in hot stars

    Science.gov (United States)

    Oksala, M. E.; Grunhut, J. H.; Kraus, M.; Borges Fernandes, M.; Neiner, C.; Condori, C. A. H.; Campagnolo, J. C. N.; Souza, T. B.

    2015-06-01

    Magnetospheric observational proxies are used for indirect detection of magnetic fields in hot stars in the X-ray, UV, optical, and radio wavelength ranges. To determine the viability of infrared (IR) hydrogen recombination lines as a magnetic diagnostic for these stars, we have obtained low-resolution (R~ 1200), near-IR spectra of the known magnetic B2V stars HR 5907 and HR 7355, taken with the Ohio State Infrared Imager/Spectrometer (OSIRIS) attached to the 4.1 m Southern Astrophysical Research (SOAR) Telescope. Both stars show definite variable emission features in IR hydrogen lines of the Brackett series, with similar properties as those found in optical spectra, including the derived location of the detected magnetospheric plasma. These features also have the added advantage of a lowered contribution of stellar flux at these wavelengths, making circumstellar material more easily detectable. IR diagnostics will be useful for the future study of magnetic hot stars, to detect and analyze lower-density environments, and to detect magnetic candidates in areas obscured from UV and optical observations, increasing the number of known magnetic stars to determine basic formation properties and investigate the origin of their magnetic fields. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  3. ASTEROSEISMOLOGY OF EVOLVED STARS WITH KEPLER: A NEW WAY TO CONSTRAIN STELLAR INTERIORS USING MODE INERTIAS

    Energy Technology Data Exchange (ETDEWEB)

    Benomar, O.; Bedding, T. R.; Stello, D. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Belkacem, K. [LESIA, Observatoire de Paris, CNRS UMR 8109, Université Paris Diderot, 5 place J. Janssen, F-92195 Meudon (France); Di Mauro, M. P. [INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Ventura, R. [INAF-Astrophyscial Observatory of Catania, Via S. Sofia 78, I-95123 Catania (Italy); Mosser, B.; Goupil, M. J.; Samadi, R. [Department of Astronomy, The University of Tokyo, Tokyo 113-0033 (Japan); Garcia, R. A. [Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France)

    2014-02-01

    The asteroseismology of evolved solar-like stars is experiencing growing interest due to the wealth of observational data from space-borne instruments such as the CoRoT and Kepler spacecraft. In particular, the recent detection of mixed modes, which probe both the innermost and uppermost layers of stars, paves the way for inferring the internal structure of stars along their evolution through the subgiant and red giant phases. Mixed modes can also place stringent constraints on the physics of such stars and on their global properties (mass, age, etc.). Here, using two Kepler stars (KIC 4351319 and KIC 6442183), we demonstrate that measurements of mixed mode characteristics allow us to estimate the mode inertias, providing a new and additional diagnostics on the mode trapping and subsequently on the internal structure of evolved stars. We however stress that the accuracy may be sensitive to non-adiabatic effects.

  4. An oxygen-rich dust disk surrounding an evolved star in the Red Rectangle

    NARCIS (Netherlands)

    Waters, LBFM; Waelkens, C; van Winckel, H; Molster, FJ; Tielens, AGGM; van Loon, JT; Morris, PW; Cami, J; Bouwman, J; de Koter, A; de Jong, T; de Graauw, T

    1998-01-01

    The Red Rectangle(1) is the prototype of a class of carbon-rich reflection nebulae surrounding low-mass stars in the final stages of evolution. The central star of this nebula has ejected most of its layers (during the red-giant phase), which now form the surrounding cloud, and is rapidly evolving t

  5. Low-excitation atomic gas around evolved stars I. ISO observations of C-rich nebulae

    NARCIS (Netherlands)

    Fong, D; Meixner, M; Castro-Carrizo, A; Bujarrabal, [No Value; Latter, WB; Tielens, AGGM; Kelly, DM; Sutton, EC

    2001-01-01

    We present ISO LWS and SWS spectra of far-infrared (FIR) atomic fine structure lines in 12 carbon-rich evolved stars including asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNe) and planetary nebulae (PNe). The spectra include grating and Fabry-Perot measurements of the line emissio

  6. Low-excitation atomic gas around evolved stars II. ISO observations of O-rich nebulae

    NARCIS (Netherlands)

    Castro-Carrizo, A; Bujarrabal, [No Value; Fong, D; Meixner, M; Tielens, AGGM; Latter, WB; Barlow, MJ

    2001-01-01

    We have observed atomic fine-structure lines in the far-infrared (FIR) from 12 oxygen-rich evolved stars. The sample is composed of mostly proto-planetary nebulae (PPNe) and some planetary nebulae (PNe) and asymptotic giant branch (AGB) stars. ISO LWS and SWS observations of [O I]. [C II], [N II], [

  7. Massive main sequence stars evolving at the Eddington limit

    CERN Document Server

    Sanyal, Debashis; Langer, Norbert; Bestenlehner, Joachim M

    2015-01-01

    The evolution of massive stars even on the main sequence is not yet well understood. Due to the steep mass-luminosity relation, massive main sequence stars become very luminous. This brings their envelopes very close to the Eddington limit. We are analysing stellar evolutionary models in which the Eddington limit is reached and exceeded, and explore the rich diversity of physical phenomena which take place in their envelopes, and investigate their observational consequences. We use the grids of detailed stellar models by Brott et al. (2011) and Koehler et al. (2015), to investigate the envelope properties of core hydrogen burning massive stars. We find that at the stellar surface, the Eddington limit is almost never reached, even for stars up to 500 Msun. When an appropriate Eddington limit is defined locally in the stellar envelope, most stars more massive than 40 Msun actually exceed this limit, in particular in the partial ionization zones of iron, helium or hydrogen. While most models adjust their structu...

  8. Self-Similar Hot Accretion Flow onto a Neutron Star

    CERN Document Server

    Medvedev, M V

    2001-01-01

    We present analytical and numerical solutions which describe a hot, viscous, two-temperature accretion flow onto a neutron star or any other compact star with a surface. We assume Coulomb coupling between the protons and electrons, and free-free cooling from the electrons. Outside a thin boundary layer, where the accretion flow meets the star, we show that there is an extended settling region which is well-described by two self-similar solutions: (1) a two-temperature solution which is valid in an inner zone $r\\le10^{2.5}$ ($r$ is in Schwarzchild units), and (2) a one-temperature solution at larger radii. In both zones, $\\rho\\propto r^{-2}, \\Omega\\propto r^{-3/2}, v\\propto r^0,\\ T_p\\propto r^{-1}$; in the two-temperature zone, $T_e\\propto r^{-1/2}$. The luminosity of the settling zone arises from the rotational energy of the star as the star is braked by viscosity; hence the luminosity is independent of $\\dot M$. The settling solution is convectively and viscously stable and is unlikely to have strong winds o...

  9. Hot Radiative Accretion onto a Spinning Neutron Star

    CERN Document Server

    Medvedev, M V

    2004-01-01

    (Abridged) A new type of self-similar hot viscous radiative accretion flow onto a rapidly spinning neutron star has recently been discovered. This ``hot brake'' flow forms in the two-temperature zone (close to a central object), but at a sufficiently low accretion rate and a high spin it may extend in the radial direction beyond ~300 Schwarzchild radii into a one-temperature zone. When the spin of the star is small enough, the flow transforms smoothly to an advection-dominated accretion flow. All gas parameters (density, angular velocity, temperature, luminosity, angular momentum flux) except for the radial velocity are independent of the mass accretion rate. The radiative efficiency may be arbitrarily large as M-dot -> 0. The gas angular momentum is transported outward under most conditions, hence the central star is nearly always spun-down. The flow is convectively stable. We also find that themal conduction in the flow is strong enough to make the flow thermally stable. The very fact that the density, temp...

  10. WM-basic: Modeling atmospheres of hot stars

    Science.gov (United States)

    Pauldrach, A. W. A.

    2012-04-01

    WM-basic is an easy-to-use interface to a program package which models the atmospheres of Hot Stars (and also SN and GN). The release comprises all programs required to calculate model atmospheres which especially yield ionizing fluxes and synthetic spectra. WM-basic is a native 32-bit application, conforming to the Multiple Documents Interface (MDI) standards for Windows XP/2000/NT/9x. All components of the program package have been compiled with Digital Visual Fortran V6.6(Pro) and Microsoft Visual C++.

  11. Hot stars observed by XMM-Newton. I. The catalog and the properties of OB stars

    Science.gov (United States)

    Nazé, Y.

    2009-11-01

    Aims: Following the advent of increasingly sensitive X-ray observatories, deep observations of early-type stars became possible. However, the results for only a few objects or clusters have until now been reported and there has been no large survey comparable to that based upon the ROSAT All-Sky Survey (RASS). Methods: A limited survey of X-ray sources, consisting of all public XMM-Newton observations (2XMMi) and slew survey data (XMMSL1), is now available. The X-ray counterparts to hot, massive stars have been searched for in these catalogs. Results: About 300 OB stars were detected with XMM-Newton. Half of them were bright enough for a spectral analysis to be possible, and we make available the detailed spectral properties that were derived. The X-ray spectra of O stars are represented well by low (FNRS. Visiting astronomer, UNAM-Morelos (Mexico).

  12. Seismic indices -- a deep look inside evolved stars

    CERN Document Server

    Mosser, Benoit

    2015-01-01

    Independent of stellar modelling, global seismic parameters of red giants provide unique information on the individual stellar properties as well as on stellar evolution. They allow us to measure key stellar parameters, such as the stellar mass and radius, or to derive the distance of field stars. Furthermore, oscillations with a mixed character directly probe the physical conditions in the stellar core. Here, we explain how very precise seismic indices are obtained, and how they can be used for monitoring stellar evolution and performing Galactic archeology.

  13. Cannibals in the thick disk: the young $\\alpha-$rich stars as evolved blue stragglers

    CERN Document Server

    Jofre, P; Izzard, R G; Van Eck, S; Hawkins, K; Jorissen, A; Gilmore, G; Paladini, C

    2016-01-01

    Spectro-seismic measurements of red giant stars enabled the recent discovery of giant stars in the thick disk that are more massive than 1.4 M_sun (Martig et al 2015, Chiappini et al 2015). While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 of the "young" stars of Martig et al (2015) and 13 "old" stars with similar stellar parameters but with masses below 1 M_sun and found that some stars are in binary systems, contrary to what has been claimed before. Furthermore, with a population synthesis of only low-mass stars but including binary evolution and mass transfer, we can reproduce the masses and the [C/N] ratios of the 26 stars. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study th...

  14. Cannibals in the thick disk: the young α-rich stars as evolved blue stragglers

    Science.gov (United States)

    Jofré, P.; Jorissen, A.; Van Eck, S.; Izzard, R. G.; Masseron, T.; Hawkins, K.; Gilmore, G.; Paladini, C.; Escorza, A.; Blanco-Cuaresma, S.; Manick, R.

    2016-10-01

    Spectro-seismic measurements of red giants enabled the recent discovery of stars in the thick disk that are more massive than 1.4 M⊙. While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 "young" stars and 13 "old" stars with similar stellar parameters but with masses below 1.2 M⊙ and found that more of the young starsappear to be in binary systems with respect to the old stars.Furthermore, we show that the young stars do not follow the expected trend of [C/H] ratios versus mass for individual stars. However, with a population synthesis of low-mass stars including binary evolution and mass transfer, we can reproduce the observed [C/N] ratios versus mass. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study the evolution of field blue stragglers after they have left the main-sequence.

  15. Early type stars at high galactic latitudes II. Four evolved B-type stars of unusual chemical composition

    CERN Document Server

    Ramspeck, M; Edelmann, H

    2001-01-01

    We present the result of differential spectral analyses of a further four apparently normal B-type stars. Abundance anomalies (e.g. He, C, N enrichment), slow rotation and/or high gravities suggest that the programme stars are evolved low-mass B-type stars. In order to trace their evolutionary status several scenarios are discussed. Post-AGB evolution can be ruled out. PG 0229+064 and PG 1400+389 could be horizontal branch (HB) stars, while HD 76431 and SB 939 have already evolved away from the extreme HB (EHB). The low helium abundance of HD 76431 is consistent with post-EHB evolution. The enrichment in helium, carbon and nitrogen of the remaining stars can be explained either by deep mixing of nuclearly processed material to the surface or by diffusion processes modified by magnetic fields and/or stellar winds. A kinematic study of their galactic orbits indicates that the stars belong to an old disk population.

  16. Smashing the Guitar: An Evolving Neutron Star Bow Shock

    CERN Document Server

    Chatterjee, S

    2003-01-01

    The Guitar nebula is a spectacular example of an H-alpha bow shock nebula produced by the interaction of a neutron star with its environment. The radio pulsar B2224+65 is traveling at ~800--1600 km/s (for a distance of 1--2 kpc), placing it on the high-velocity tail of the pulsar velocity distribution. Here we report time evolution in the shape of the Guitar nebula, the first such observations for a bow shock nebula, as seen in H-alpha imaging with the Hubble Space Telescope. The morphology of the nebula provides no evidence for anisotropy in the pulsar wind, nor for fluctuations in the pulsar wind luminosity. The nebula shows morphological changes over two epochs spaced by seven years that imply the existence of significant gradients and inhomogeneities in the ambient interstellar medium. These observations offer astrophysically unique, in situ probes of length scales between 5E-4 pc and 0.012 pc. Model fitting suggests that the nebula axis -- and thus the three-dimensional velocity vector -- lies within 20 ...

  17. KELT-2Ab: A Hot Jupiter Transiting the Bright (V=8.77) Primary Star of a Binary System

    CERN Document Server

    Beatty, Thomas G; Siverd, Robert J; Eastman, Jason D; Bieryla, Allyson; Latham, David W; Buchhave, Lars A; Jensen, Eric L N; Manner, Mark; Stassun, Keivan G; Gaudi, B Scott; Berlind, Perry; Calkins, Michael L; Collins, Karen; DePoy, Darren L; Esquerdo, Gilbert A; Fulton, Benjamin J; Fűrész, Gábor; Geary, John C; Gould, Andrew; Hebb, Leslie; Kielkopf, John F; Marshall, Jennifer L; Pogge, Richard; Stanek, K Z; Stefanik, Robert P; Street, Rachel; Szentgyorgyi, Andrew H; Trueblood, Mark; Trueblood, Patricia; Stutz, Amelia M

    2012-01-01

    We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V=8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived "blue-hook" stage of evolution, with $\\teff=6151\\pm50{\\rm K}$, $\\log{g_*}=4.030_{-0.028}^{+0.013}$ and $\\feh=-0.018\\pm0.069$. The inferred stellar mass is $M_*=1.308_{-0.025}^{+0.028}$\\msun\\ and the star has a relatively large radius of $R_*=1.828_{-0.034}^{+0.070}$\\rsun. The planet is a typical hot Jupiter with period $4.113791\\pm0.00001$ days and a mass of $M_P=1.522\\pm0.078$\\mj\\ and radius of $R_P=1.286_{-0.047}^{+0.065}$\\rj. This is mildly inflated as compared to models of irradiated giant planets at the $\\sim$4 Gyr age of the system. KELT-2A is the third brightest star with a transiting planet identified by ground-based transit surveys, and the ninth brightest star overall with a transiting planet. KELT-2Ab's mass and radius are unique among the subset of planets with $V<9$ host stars, and therefore incre...

  18. Models of the circumstellar medium of evolving, massive runaway stars moving through the Galactic plane

    CERN Document Server

    Meyer, D M -A; Langer, N; Gvaramadze, V V; Mignone, A; Izzard, R G; Kaper, L

    2014-01-01

    At least 5 per cent of the massive stars are moving supersonically through the interstellar medium (ISM) and are expected to produce a stellar wind bow shock. We explore how the mass loss and space velocity of massive runaway stars affect the morphology of their bow shocks. We run two-dimensional axisymmetric hydrodynamical simulations following the evolution of the circumstellar medium of these stars in the Galactic plane from the main sequence to the red supergiant phase. We find that thermal conduction is an important process governing the shape, size and structure of the bow shocks around hot stars, and that they have an optical luminosity mainly produced by forbidden lines, e.g. [OIII]. The Ha emission of the bow shocks around hot stars originates from near their contact discontinuity. The H$\\alpha$ emission of bow shocks around cool stars originates from their forward shock, and is too faint to be observed for the bow shocks that we simulate. The emission of optically-thin radiation mainly comes from th...

  19. Crystalline silicate dust around evolved stars - II. The crystalline silicate complexes

    NARCIS (Netherlands)

    Molster, F. J.; Waters, L. B. F. M.; Tielens, A. G. G. M.

    This is the second paper in a series of three in which we present an exhaustive inventory of the solid state emission bands observed in a sample of 17 oxygen-rich dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared

  20. Evolved stars and the origin of abundance trends in planet hosts

    CERN Document Server

    Maldonado, J

    2016-01-01

    Tentative evidence that the properties of evolved stars with planets may be different from what we know for MS hosts has been recently reported. We aim to test whether evolved stars with planets show any chemical peculiarity that could be related to the planet formation process. We determine in a consistent way the metallicity and individual abundances of a large sample of evolved (subgiants and red giants) and MS stars with and without known planetary companions. No differences in the vs. condensation temperature (Tc) slopes are found between the samples of planet and non-planet hosts when all elements are considered. However, if the analysis is restricted to only refractory elements, differences in the Tc-slopes between stars with and without known planets are found. This result is found to be dependent on the stellar evolutionary stage, as it holds for MS and subgiant stars, while there seem to be no difference between planet and non-planet hosts among the sample of giants. A search for correlations betwe...

  1. Lithium abundances and extra mixing processes in evolved stars of M67

    CERN Document Server

    Martins, B L Canto; Palacios, A; de Laverny, P; Richard, O; Melo, C H F; Nascimento, J D do; De Medeiros, J R; 10.1051/0004-6361/201015015

    2011-01-01

    Aims. We present a spectroscopic analysis of a sample of evolved stars in M67 (turn-off, subgiant and giant stars) in order to bring observational constraints to evolutionary models taking into account non-standard transport processes. Methods. We determined the stellar parameters (Teff, log g, [Fe/H]), microturbulent and rotational velocities and, Lithium abundances (ALi) for 27 evolved stars of M67 with the spectral synthesis method based on MARCS model atmospheres. We also computed non-standard stellar evolution models, taking into account atomic diffusion and rotation-induced transport of angular momentum and chemicals that were compared with this set of homogeneous data. Results. The lithium abundances that we derive for the 27 stars in our sample follow a clear evolutionary pattern ranging from the turn-off to the Red Giant Branch. Our abundance determination confirms the well known decrease of lithium content for evolved stars. For the first time, we provide a consistent interpretation of both the surf...

  2. Magnetic grain trapping and the hot excesses around early-type stars

    CERN Document Server

    Rieke, George H; Ballering, Nicholas P

    2015-01-01

    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 about 2 sigma) than those for stars without such excesses.

  3. 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.

  4. 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.

  5. An Apparent Precessing Helical Outflow from a Massive Evolved Star: Evidence for Binary Interaction

    CERN Document Server

    Lau, Ryan M; Herter, Terry L; Morris, Mark R; Mills, Elisabeth A C; Ressler, Michael E

    2015-01-01

    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 (SOFIA) of a conical ``helix'' of warm dust ($\\sim180$ 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\\,\\mathrm{d}

  6. Rapidly Evolving and Luminous Transients Driven by Newly Born Neutron Stars

    CERN Document Server

    Yu, Yun-Wei; Dai, Zi-Gao

    2015-01-01

    We provide a general analysis on the properties of emitting material of some rapidly evolving and luminous transients discovered recently with the Pan-STARRS1 Medium Deep Survey. It is found that these transients are probably produced by a low-mass non-relativistic outflow that is continuously powered by a newly born, rapidly spinning, and highly magnetized neutron star. Such a system could originate from an accretion-induced collapse of a white dwarf or a merger of a neutron star-neutron star binary. Therefore, observations to these transients would be helpful for constraining white dwarf and neutron star physics and/or for searching and identifying gravitational wave signals from the mergers.

  7. Evolved stars in the Local Group galaxies. I. AGB evolution and dust production in IC 1613

    CERN Document Server

    Dell'Agli, F; Boyer, M L; Garcia-Hernandez, D A

    2016-01-01

    We used models of thermally-pulsing asymptotic giant branch (AGB) stars, that also describe the dust-formation process in the wind, to interpret the combination of near- and mid-infrared photometric data of the dwarf galaxy IC 1613. This is the first time that this approach is extended to an environment different from the Milky Way and the Magellanic Clouds (MCs). Our analysis, based on synthetic population techniques, shows a nice agreement between the observations and the expected distribution of stars in the colour-magnitude diagrams obtained with JHK and Spitzer bands. This allows a characterization of the individual stars in the AGB sample in terms of mass, chemical composition, and formation epoch of the progenitors. We identify the stars exhibiting the largest degree of obscuration as carbon stars evolving through the final AGB phases, descending from 1-1.25Msun objects of metallicity Z=0.001 and from 1.5-2.5Msun stars with Z=0.002. Oxygen-rich stars constitute the majority of the sample (65%), mainly ...

  8. Mining the HST Treasury: The ASTRAL Reference Spectra for Evolved M Stars

    Science.gov (United States)

    Carpenter, K. G.; Ayres, T.; Harper, G.; Kober, G.; Wahlgren, G. M.

    2012-01-01

    The "Advanced Spectral Library (ASTRAL) Project: Cool Stars" (PI = T. Ayres) is an HST Cycle 18 Treasury Program designed to collect a definitive set of representative, high-resolution (R greater than 100,000) and high signal/noise (S/N greater than 100) UV spectra of eight F-M evolved cool stars. These extremely high-quality STIS UV echelle spectra are available from the HST archive and through the University of Colorado (http://casa.colorado.edu/ayres/ASTRAL/) portal and will enable investigations of a broad range of problems -- stellar, interstellar. and beyond -- for many years. In this current paper, we concentrate on producing a roadrnap to the very rich spectra of the two evolved M stars in the sample, the M3.4 giant Gamma Crucis (GaCrux) and the M2Iab supergiant Alpha Orionis (Betelgeuse) and illustrate the huge increase in coverage and quality that these spectra provide over that previously available from IUE and earlier HST observations. These roadmaps will facilitate the study of the spectra, outer atmospheres, and winds of not only these stars. but also numerous other cool, low-gravity stars and make a very interesting comparison to the already-available atlases of the K2III giant Arcturus.

  9. Herschel/PACS observations of the 69 $\\mu m$ band of crystalline olivine around evolved stars

    CERN Document Server

    Blommaert, J A D L; Waters, L B F M; Waelkens, C; Min, M; Van Winckel, H; Molster, F; Decin, L; Groenewegen, M A T; Barlow, M; García-Lario, P; Kerschbaum, F; Posch, Th; Royer, P; Ueta, T; Vandenbussche, B; Van de Steene, G; van Hoof, P

    2014-01-01

    We present 48 Herschel/PACS spectra of evolved stars in the wavelength range of 67-72 $\\mu$m. This wavelength range covers the 69 $\\mu$m band of crystalline olivine ($\\text{Mg}_{2-2x}\\text{Fe}_{(2x)}\\text{SiO}_{4}$). The width and wavelength position of this band are sensitive to the temperature and composition of the crystalline olivine. Our sample covers a wide range of objects: from high mass-loss rate AGB stars (OH/IR stars, $\\dot M \\ge 10^{-5}$ M$_\\odot$/yr), through post-AGB stars with and without circumbinary disks, to planetary nebulae and even a few massive evolved stars. The goal of this study is to exploit the spectral properties of the 69 $\\mu$m band to determine the composition and temperature of the crystalline olivine. Since the objects cover a range of evolutionary phases, we study the physical and chemical properties in this range of physical environments. We fit the 69 $\\mu$m band and use its width and position to probe the composition and temperature of the crystalline olivine. For 27 sourc...

  10. XMM-Newton Detection of Hot Gas in Two Evolved Elliptical Planetary Nebulae: the Eskimo Nebula and the Ghost of Jupiter

    Science.gov (United States)

    Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.; Meixner, M.

    2004-12-01

    Planetary nebulae (PNe) consist of the stellar material ejected by low- and intermediate-mass stars (1-8 M⊙) at the end of the asymptotic giant branch phase (AGB). As such a star evolves off the AGB phase, the copious mass-loss strips off the stellar envelope and exposes the hot stellar core that ionizes the nebular material. The central stars of PNe present fast stellar winds with terminal velocities 1000-4000 km s-1, while fast collimated outflows with velocities up to 1000 km s-1 are also observed in PNe. The interactions of the fast stellar wind and/or collimated outflows with nebular material can give rise to diffuse X-ray emission from PNe. Diffuse X-ray emission has been detected only in young PNe previously. To investigate the evolution of hot gas in PN interiors, we obtained XMM-Newton observations of NGC 2392 (the Eskimo Nebula) and NGC 3242 (the Ghost of Jupiter), two evolved elliptical PNe. Diffuse X-ray emission is detected in both nebulae. In both cases, the hot gas is confined within the innermost shell, the X-ray spectrum can be described by a thin plasma emission model with temperature ˜2×106 K, and the X-ray luminosity is ˜1×1031 ergs s-1. Furthermore, the X-ray spectrum of NGC 3242 shows evidence of enhanced nitrogen abundance, while the X-ray morphology of NGC 2392 hints a possible association with its fast collimated outflows.

  11. The carrier of the "30" mu m emission feature in evolved stars - A simple model using magnesium sulfide

    NARCIS (Netherlands)

    Hony, S; Waters, LBFM; Tielens, AGGM

    2002-01-01

    We present 2-45 mum spectra of a large sample of carbon-rich evolved stars in order to study the "30" mum feature. We find the "30" mum feature in a wide range of sources: low mass loss carbon stars, extreme carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles from the sourc

  12. Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements

    Science.gov (United States)

    Hirano, Teruyuki; Sato, Bun'ei; Masuda, Kento; Benomar, Othman Michel; Takeda, Yoichi; Omiya, Masashi; Harakawa, Hiroki

    2016-10-01

    Tidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

  13. Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314

    CERN Document Server

    Sato, Bun'ei; Liu, Yujuan; Harakawa, Hiroki; Izumiura, Hideyuki; Kambe, Eiji; Toyota, Eri; Murata, Daisuke; Lee, Byeong-Cheol; Masuda, Seiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru; Zhao, Gang; Han, Inwoo

    2010-01-01

    We report the detections of two substellar companions orbiting around evolved intermediate-mass stars from precise Doppler measurements at Subaru Telescope and Okayama Astrophysical Observatory. HD 145457 is a K0 giant with a mass of 1.9 M_sun and has a planet of minimum mass m_2sini=2.9 M_J orbiting with period of P=176 d and eccentricity of e=0.11. HD 180314 is also a K0 giant with 2.6 M_sun and hosts a substellar companion of m_2sin i=22 M_J, which falls in brown-dwarf mass regime, in an orbit with P=396 d and e=0.26. HD 145457 b is one of the innermost planets and HD 180314 b is the seventh candidate of brown-dwarf-mass companion found around intermediate-mass evolved stars.

  14. Self-Similar Hot Accretion Flow onto a Neutron Star

    CERN Document Server

    Medvedev, M V; Medvedev, Mikhail V.; Narayan, Ramesh

    2000-01-01

    We consider hot, two-temperature, viscous accretion onto a rotating, unmagnetized neutron star. We assume Coulomb coupling betweenthe protons and electrons, and free-free cooling from the electrons. We show that the accretion flow has an extended settling region which can be described by means of two analytical self-similar solutions: a two-temperature solution which is valid in an inner zone, $r10^{2.5}$. In both zones the density varies as $\\rho\\propto r^{-2}$ and the angular velocity as $\\Omega\\propto r^{-3/2}$. We solve the flow equations numerically and confirm that the analytical solutions are accurate. The self-similar settling solution differs from the advection-dominated accretion flow discussed in the context of black hole accretion. The settling flow radiates the energy dissipated by viscosity; so it is not advection-dominated. Except for the radial velocity, all other gas properties - density, angular velocity, temperature, luminosity, angular momentum flux - are independent of the mass accretion ...

  15. Evolved Stars in the Core of the Massive Globular Cluster NGC 2419

    CERN Document Server

    Sandquist, Eric L

    2008-01-01

    We present an analysis of optical and ultraviolet Hubble Space Telescope photometry for evolved stars in the core of the distant massive globular cluster NGC 2419. We characterize the horizontal branch (HB) population in detail including corrections for incompleteness on the long blue tail. We present a method for removing (to first order) lifetime effects from the distribution of HB stars to facilitate more accurate measurements of helium abundance for clusters with blue HBs and to clarify the distribution of stars reaching the zero-age HB. The population ratio R = N_HB / N_RGB implies there may be slight helium enrichment among the EHB stars in the cluster, but that it is likely to be small (dY < 0.05). An examination of the upper main sequence does not reveal any sign of multiple populations. Through comparisons of optical CMDs, we present evidence that the EHB clump in NGC 2419 contains the end of the canonical horizontal branch, and that the boundary between the normal HB stars and blue hook stars sho...

  16. EVOLVE

    CERN Document Server

    Deutz, André; Schütze, Oliver; Legrand, Pierrick; Tantar, Emilia; Tantar, Alexandru-Adrian

    2017-01-01

    This book comprises nine selected works on numerical and computational methods for solving multiobjective optimization, game theory, and machine learning problems. It provides extended versions of selected papers from various fields of science such as computer science, mathematics and engineering that were presented at EVOLVE 2013 held in July 2013 at Leiden University in the Netherlands. The internationally peer-reviewed papers include original work on important topics in both theory and applications, such as the role of diversity in optimization, statistical approaches to combinatorial optimization, computational game theory, and cell mapping techniques for numerical landscape exploration. Applications focus on aspects including robustness, handling multiple objectives, and complex search spaces in engineering design and computational biology.

  17. Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars

    CERN Document Server

    Geier, S

    2012-01-01

    Context: Hot subdwarf B stars (sdBs) are considered to be core helium-burning stars with very thin hydrogen envelopes situated on or near the extreme horizontal branch (EHB). The formation of sdBs is still unclear as well as the chemical composition of their atmospheres. The observed helium depletion is attributed to atmospheric diffusion. Metal abundances have been determined for about a dozen sdBs only resulting in puzzling patterns with enrichment of heavy metals and depletion of lighter ones. Aims: In this paper we present a detailed metal abundance analysis of 106 sdBs. Methods: From high resolution spectra we measured elemental abundances of up to 24 different ions per star. A semi-automatic analysis pipeline was developed to calculate and fit LTE models to a standard set of spectral lines. Results: A general trend of enrichment was found with increasing temperature for most of the heavier elements. The lighter elements like carbon, oxygen and nitrogen are depleted and less affected by temperature. Alth...

  18. On the silicate crystallinities of oxygen-rich evolved stars and their mass-loss rates

    Science.gov (United States)

    Liu, Jiaming; Jiang, B. W.; Li, Aigen; Gao, Jian

    2017-04-01

    For decades ever since the early detection in the 1990s of the emission spectral features of crystalline silicates in oxygen-rich evolved stars, there is a long-standing debate on whether the crystallinity of the silicate dust correlates with the stellar mass-loss rate. To investigate the relation between the silicate crystallinities and the mass-loss rates of evolved stars, we carry out a detailed analysis of 28 nearby oxygen-rich stars. We derive the mass-loss rates of these sources by modelling their spectral energy distributions from the optical to the far-infrared. Unlike previous studies in which the silicate crystallinity was often measured in terms of the crystalline-to-amorphous silicate mass ratio, we characterize the silicate crystallinities of these sources with the flux ratios of the emission features of crystalline silicates to that of amorphous silicates. This does not require the knowledge of the silicate dust temperatures, which are the major source of uncertainties in estimating the crystalline-to-amorphous silicate mass ratio. With a Pearson correlation coefficient of ∼-0.24, we find that the silicate crystallinities and the mass-loss rates of these sources are not correlated. This supports the earlier findings that the dust shells of low mass-loss rate stars can contain a significant fraction of crystalline silicates without showing the characteristic features in their emission spectra.

  19. Spitzer SAGE survey of the Large Magellanic Cloud II : Evolved Stars and Infrared Color Magnitude Diagrams

    CERN Document Server

    Blum, R D; Olsen, K A; Frogel, J A; Werner, M; Meixner, M; Markwick-Kemper, F; Indebetouw, R; Whitney, B; Meade, M; Babler, B; Churchwell, E B; Gordon, K; Engelbracht, C W; Misselt, K; Vijh, U; Leitherer, C; Volk, K; Points, S; Reach, W; Hora, J L; Bernard, J P; Boulanger, F; Bracker, S; Cohen, M; Fukui, Y; Gallagher, J; Gorjian, V; Harris, J; Kelly, D; Kawamura, A; Latter, W B; Madden, S; Mizuno, A; Mizuno, N; Nota, A; Oey, M S; Onishi, T; Paladini, R; Panagia, N; Perez-Gonzalez, P; Shibai, H; Sato, S; Smith, L; Staveley-Smith, L; Tielens, A G G M; Ueta, T; Van Dyk, S D; Zaritsky, D

    2006-01-01

    Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying the Agents of a Galaxy's Evolution) survey of the Large Magellanic Cloud (LMC). IRAC and MIPS 24 um epoch one data are presented. These data represent the deepest, widest mid-infrared CMDs of their kind ever produced in the LMC. Combined with the 2MASS survey, the diagrams are used to delineate the evolved stellar populations in the Large Magellanic Cloud as well as Galactic foreground and extragalactic background populations. Some 32000 evolved stars brighter than the tip of the red giant branch are identified. Of these, approximately 17500 are classified as oxygen-rich, 7000 carbon-rich, and another 1200 as ``extreme'' asymptotic giant branch (AGB) stars. Brighter members of the latter group have been called ``obscured'' AGB stars in the literature owing to their dusty circumstellar envelopes. A large number (1200) of luminous oxygen--rich AGB stars/M supergiants are also identified. Finally, there is strong evidence from the 24 u...

  20. Are analogues of hot subdwarf stars responsible for the UVX phenomenon in galaxy nuclei?

    CERN Document Server

    Dorman, B; Rood, R T; Ben Dorman

    1994-01-01

    We present the case that populations of sdB/sdOB/sdO-type stars may be a common constituent of galactic stellar populations, responsible for the UV upturn ("UVX") observed in the spectra of spiral bulges and normal galaxy nuclei. Extreme Horizontal Branch stars with $\\log g > 5$ and $\\log \\teff > 20,000K$ have emerged in the last few years as the most likely candidate for the origin of the UVX. The magnitude of this far-UV flux in some systems (e.g. NGC~1399, NGC~4649) indicates that galactic nuclear regions must contain larger numbers of these subdwarfs than does the solar neighbourhood. This paper summarizes the results of a quantitative study of the UV radiation from evolved stellar populations. We have computed a large grid of stellar models in advanced stages of evolution, as well as a set of isochrones for ages 2-20 Gyr, for a wide range in composition. We use these calculations to derive synthetic UV colour indices for stellar populations with hot components.

  1. Effect of rotational mixing and metallicity on the hot star wind mass-loss rates

    CERN Document Server

    Krticka, Jiri

    2014-01-01

    Hot star wind mass-loss rates depend on the abundance of individual elements. This dependence is usually accounted for assuming scaled solar chemical composition. However, this approach may not be justified in evolved rotating stars. The rotational mixing brings CNO-processed material to the stellar surface, increasing the abundance of nitrogen at the expense of carbon and oxygen, which potentially influences the mass-loss rates. We study the influence of the modified chemical composition resulting from the rotational mixing on the wind parameters, particularly the wind mass-loss rates. We use our NLTE wind code to predict the wind structure and compare the calculated wind mass-loss rate for the case of scaled solar chemical composition and the composition affected by the CNO cycle. We show that for a higher mass-fraction of heavier elements $Z/Z_\\odot\\gtrsim0.1$ the change of chemical composition from the scaled solar to the CNO-processed scaled solar composition does not significantly affect the wind mass-l...

  2. Oscillations of red dwarfs in evolved low-mass binaries with neutron stars

    Science.gov (United States)

    Sarna, Marek J.; Lee, Umin; Muslimov, Alexander G.

    1994-01-01

    We investigate a novel aspect of a problem related to the properties of low-mass binaries (LMBs) with millisecond pulsars: the pulsations of the red dwarf (donor) companion of the neutron star (NS). The illumination of the donor star by the pulsar's high-energy nonthermal radiation and relativistic wind may substantially affect its structure. We present a quantitative analysis of the oscillation spectrum of a red dwarf which has evolved in an LMB and has undergone the stage of evaporation. We calculate the p- and g-modes for red dwarfs with masses in the interval (0.2-0.6) stellar mass. For comparison, similar calculations are presented for zero age main-sequence (ZAMS) stars of the same masses. For less massive donor stars (approximately 0.2 stellar mass) the oscillation spectrum becomes quantitatively different from that of their ZAMS counterparts. The differnce is due to the fact that a ZAMS star of 0.2 stellar mass is fully convective, while the donor star in an LMB is expected to be far from thermal equilibrium and not fully convective. As a result, in contrast to a low-mass ZAMS star, a red dwarf of the same mass in an LMB allows the existence of g-modes. We also consider tidally forced g-modes, and perform a linear analysis of these oscillations for different degrees of nonsynchronism between the orbital and spin rotation of the red dwarf component. We demonstrate the existence of a series of reasonances for the low-order g-modes which may occur in LMBs at a late stage of their evolution. We discuss the possibility that these oscillations may trigger Roche lobe overflow and sudden mass loss by the donor star. Further implications of this effect for gamma- and X-ray burst phenomena are outlined.

  3. On the X-ray Emission from Massive Star Clusters and their Evolving Superbubbles

    CERN Document Server

    Silich, S; Zeferino, G A A; Silich, Sergiy; Tenorio-Tagle, Guillermo; Zeferino, Gabriel Alejandro Anorve

    2005-01-01

    The X-ray emission properties from the hot thermalized plasma that results from the collisions of individual stellar winds and supernovae ejecta within rich and compact star clusters are discussed. We propose a simple analytical way of estimating the X-ray emission generated by super star clusters and derive an expression that indicates how this X-ray emission depends on the main cluster parameters. Our model predicts that the X-ray luminosity from the star cluster region is highly dependent on the star cluster wind terminal speed, a quantity related to the temperature of the thermalized ejecta.We have also compared the X-ray luminosity from the SSC plasma with the luminosity of the interstellar bubbles generated from the mechanical interaction of the high velocity star cluster winds with the ISM.We found that the hard (2.0 keV - 8.0 keV) X-ray emission is usually dominated by the hotter SSC plasma whereas the soft (0.3 keV - 2.0 keV) component is dominated by the bubble plasma. This implies that compact and ...

  4. Polarization measurements of hot dust stars and the local interstellar medium

    CERN Document Server

    Marshall, J P; Bott, K; Ertel, S; Kennedy, G M; Wyatt, M C; del Burgo, C; Absil, O; Bailey, J; Kedziora-Chudczer, L

    2016-01-01

    Debris discs are typically revealed through excess emission at infrared wavelengths. Most discs exhibit excess at mid- and far-infrared wavelengths, analogous to the solar system's Asteroid and Edgeworth-Kuiper belts. Recently, stars with strong (1 per cent) excess at near-infrared wavelengths were identified through interferometric measurements. Using the HIgh Precision Polarimetric Instrument (HIPPI), we examined a sub-sample of these hot dust stars (and appropriate controls) at parts-per-million sensitivity in SDSS g' (green) and r' (red) filters for evidence of scattered light. No detection of strongly polarized emission from the hot dust stars is seen. We therefore rule out scattered light from a normal debris disk as the origin of this emission. A wavelength dependent contribution from multiple dust components for hot dust stars is inferred from the dispersion (difference in polarization angle in red and green) of southern stars. Contributions of 17 ppm (green) and 30 ppm (red) are calculated, with stri...

  5. Infrared Tracers of Mass-Loss Histories and Wind-ISM Interactions in Hot Star Nebulae

    CERN Document Server

    Morris, P

    2008-01-01

    Infrared observations of hot massive stars and their environments provide a detailed picture of mass loss histories, dust formation, and dynamical interactions with the local stellar medium that can be unique to the thermal regime. We have acquired new infrared spectroscopy and imaging with the sensitive instruments onboard the Spitzer Space Telescope in guaranteed and open time programs comprised of some of the best known examples of hot stars with circumstellar nebulae, supplementing with unpublished Infrared Space Observatory spectroscopy. Here we present highlights of our work on the environment around the extreme P Cygni-type star HDE316285, revealing collisionally excited H2 for the first time in a hot star nebula, and providing some defining characteristics of the star's evolution and interactions with the ISM at unprecented detail in the infrared.

  6. The Circumstellar Environment of Evolved Stars as Revealed by Studies of Circumstellar Water Masers

    Science.gov (United States)

    Marvel, K.

    1997-11-01

    This dissertation presents the results of a multi-epoch very long baseline interferometric (VLBI) study of water masers located in the extended atmospheres of seven evolved stars. The research was performed using the Very Long Baseline Array and Very Large Array of the National Radio Astronomy Observatory. Water masers are found to exist in the atmospheres of evolved, oxygen-rich stars where a population inversion of the rotational transition at 22 GHz can be maintained by collisional pumping. The masers are identified as individual pockets or filaments of gas, which have good velocity coherence and may be imaged using radio interferometry. Stellar winds are initiated in these sources by dust formation and acceleration of the gas through momentum coupling. The typical wind speeds in the region of the water masers are 10 to 20 \\kms. The water masers in several evolved stars (VY CMa, VX Sgr, S Per, U Her, IK Tau, RX Boo and NML Cyg) have been observed at three epochs and exhibit proper motions consistent with the assumed source distances and the measured outflow velocity in the water maser region. Estimates of the distance to the sources using statistical approximation are in agreement with the currently accepted distances to the stars. The following stars had reliable distances determined using proper motion data: S Per (2.3 +/- 0.5 kpc), VY CMa (1.4 +/- 0.2 kpc), VX Sgr (1.4 +/- 0.3 kpc). An upper limit for the distance of NML Cyg was obtained ( 3.5 kpc). The remaining stars had too few maser detections (RX BOO, IK Tau) or were not strong enough at all epochs (U Her) to self-calibrate using the VLBA. A detailed kinematic model was used to describe the flow motions of the gas in the maser region. The regions are found to be complex and not well modeled by uniform radial outflow, radial outflow with rotation, or radial outflow with acceleration. The reasons for this are explored and include the probable presence of anisotropic velocity fields induced through non

  7. Formation of neutral disk-like zone around the active hot stars in symbiotic binaries

    CERN Document Server

    Carikova, Zuzana

    2011-01-01

    In this contribution we present the ionization structure in the enhanced wind from the hot star in symbiotic binaries during active phases. Rotation of the hot star leads to the compression of the outflowing material towards its equatorial plane. As a result a neutral disk-like zone around the active hot star near the orbital plane is created. We modelled the compression of the wind using the wind compression model. Further, we calculated the neutral disk-like zone in the enhanced wind from the hot star using the equation of the photoionization equilibrium. The presence of such neutral disk-like zones was also suggested on the basis of the modelling the spectral energy distribution of symbiotic binaries. We confront the calculated ionization structures in the enhanced wind from the hot star with the observations. We found that the calculated column density of the neutral hydrogen atoms in the neutral disk-like zone and the emission measure of the ionized part of the wind from the hot star are in a good agreem...

  8. Envelope loss of RGB/AGB stars and the formation of hot subdwarfs

    Directory of Open Access Journals (Sweden)

    Chen X.

    2013-03-01

    Full Text Available Low mass stars may lose their envelopes in the first giant branch (RGB or the asymptotic giant branch (AGB via envelope ejection (i.e. superwind. The envelope loss of AGB stars leads to the formation of carbon-oxygen (CO white dwarfs (WDs, while the envelope loss of AGB stars may lead to the formation of helium WDs. We mainly focus here on where a RGB/AGB star loses its envelope during its evolution and we show the inital - final mass relation. We also propose a possible channel for the formation of single hot subdwarf stars, in which an old metal-rich RGB star with positive envelope binding energy may lose its envelope and the naked helium core gets ignited to become a hot subdwarf. We also review the well-established Han et al. scenario for the formation of hot subdwarf stars, in which binary interactions lead to the formation of both single and binary hot subdwarfs. By detailed binary evolution calculations, we show that PG 1018-047, a hot subdwarf binary with a main sequence companion and a very long orbital period of 756  d, is explained naturally from the stable RLOF channel in the Han et al. scenario.

  9. Ongoing and co-evolving star formation in zCOSMOS galaxies hosting Active Galactic Nuclei

    CERN Document Server

    Silverman, J D; Maier, C; Lilly, S; Mainieri, V; Brusa, M; Cappelluti, N; Hasinger, G; Zamorani, G; Scodeggio, M; Bolzonella, M; Contini, T; Carollo, C M; Jahnke, K; Kneib, J -P; Le Fèvre, O; Merloni, A; Bardelli, S; Bongiorno, A; Brunner, H; Caputi, K; Civano, F; Comastri, A; Coppa, G; Cucciati, O; De la Torre, S; de Ravel, L; Elvis, M; Finoguenov, A; Fiore, F; Franzetti, P; Garilli, B; Gilli, R; Iovino, A; Kampczyk, P; Knobel, C; Kovac, K; Le Borgne, J F; Le Brun, V; Mignoli, M; Pellò, R; Peng, Y; Montero, E Perez; Ricciardelli, E; Tanaka, M; Tasca, L; Tresse, L; Vergani, D; Vignali, C; Zucca, E; Bottini, D; Cappi, A; Cassata, P; Fumana, M; Griffiths, R; Kartaltepe, J; Marinoni, C; McCracken, H J; Memeo, P; Meneux, B; Oesch, P; Porciani, C; Salvato, M

    2008-01-01

    We present a study of the host galaxies of AGN selected from the zCOSMOS survey to establish if accretion onto supermassive black holes and star formation are explicitly linked up to z~1. We identify 152 galaxies that harbor AGN, based on XMM observations of 7543 galaxies (i<22.5). Star formation rates (SFRs), including those weighted by stellar mass, are determined using the [OII]3727 emission-line, corrected for an AGN contribution. We find that the majority of AGN hosts have significant levels of star formation with a distribution spanning ~1-100 Msun yr^-1. The close association between AGN activity and star formation is further substantiated by an increase in the AGN fraction with the youthfulness of their stars as indicated by the rest-frame color (U-V) and spectral index Dn(4000); we demonstrate that mass-selection alleviates an artifical peak falling in the transition region when using luminosity-limited samples. We also find that the SFRs of AGN hosts evolve with cosmic time in a manner that close...

  10. CO J = 2 - 1 Emission from Evolved Stars in the Galactic Bulge

    CERN Document Server

    Sargent, Benjamin A; Meixner, M; Otsuka, M; Riebel, D; Srinivasan, S

    2014-01-01

    We observe a sample of 8 evolved stars in the Galactic Bulge in the CO J = 2 - 1 line using the Submillimeter Array (SMA) with angular resolution of 1 - 4 arcseconds. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2 - 1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining 5 stars in the sample because of heavy contamination from the galactic foreground CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic Bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 (+/- 2.2) x 10^-5 M_Sun/year and a gas-to-dust ratio of 310 (+/- 89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 (+/- 2.8) x 10^-5 M_Sun/year and a gas-to-dust ratio of 220 (+/- 110). For [SLO2003] A51, we find a ...

  11. Deep Mixing in Evolved Stars. II. Interpreting Li Abundances in RGB and AGB Stars

    CERN Document Server

    Palmerini, S; Busso, M; Abia, C; Uttenthaler, S; Gialanella, L; Maiorca, E

    2011-01-01

    We reanalyze the problem of Li abundances in red giants of nearly solar metallicity. After an outline of the problems affecting our knowledge of the Li content in low-mass stars (M<3Mo), we discuss deep-mixing models for the RGB stages suitable to account for the observed trends and for the correlated variations of the carbon isotope ratio; we find that Li destruction in these phases is limited to masses below about 2.3 Mo. Subsequently, we concentrate on the final stages of evolution for both O-rich and C-rich AGB stars. Here, the constraints on extra-mixing phenomena previously derived from heavier nuclei (from C to Al), coupled to recent updates in stellar structure models (including both the input physics and the set of reaction rates used), are suitable to account for the observations of Li abundances below A(Li)= log e(Li) = 1.5 (and sometimes more). Also their relations with other nucleosynthesis signatures of AGB phases (like the abundance of F, the C/O and 12C/13C ratios) can be explained. This re...

  12. Chemical composition of evolved stars in the young open clusters NGC 4609 and NGC 5316

    CERN Document Server

    Drazdauskas, Arnas; Smiljanic, Rodolfo; Bagdonas, Vilius; Chorniy, Yuriy

    2016-01-01

    High-resolution spectral analysis is performed for the first time in evolved stars of two young open clusters: NGC 4609 and NGC 5316, of about 80 and 100 Myr in age, respectively, and turn-off masses above 5 Msun. Stellar evolution models predict an extra-mixing event in evolved stars, which follows the first dredge-up and happens later on the red giant branch. However, it is still not understood how this process affects stars of different masses. In this study, we determine abundances of the mixing sensitive elements carbon and nitrogen, carbon isotope 12C/13C ratios, as well as 20 other elements produced by different nucleosynthetic processes (O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Y, Zr, Ba, La, Ce, Pr, Nd, and Eu). We compared our results with the latest theoretical models of evolutionary mixing processes. We find that the obtained 12C/13C and C/N ratios and [Na/Fe] agree quite well with the model which takes into account thermohaline- and rotation-induced mixing but within error limits also agree...

  13. Planetary Companions to Three Evolved Intermediate-Mass Stars: HD 2952, HD 120084, and ω Serpentis

    Science.gov (United States)

    Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Liu, Yu-Juan; Izumiura, Hideyuki; Kambe, Eiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru

    2013-08-01

    We report on the detections of planetary companions orbiting around three evolved intermediate-mass stars based on precise radial velocity measurements at Okayama Astrophysical Observatory. HD 2952 (K0III, 2.5 M⊙ ) and ω Ser (G8III, 2.2 M⊙ ) host a relatively low-mass planet with minimum masses of m2 sini = 1.6 MJ and 1.7 MJ in nearly circular orbits with periods of P = 312 and 277 d, respectively. HD 120084 (G7 III, 2.4 M⊙ ) hosts an eccentric planet with m2sini = 4.5 MJ in an orbit with P = 2082 d and an eccentricity of e = 0.66. The planet has one of the largest eccentricities among those ever discovered around evolved intermediate-mass stars, almost all of which have an eccentricity smaller than 0.4. We also show that the radial-velocity variations of stellar oscillations for G giants can be averaged out below a level of a few m s-1 , at least on a timescale of a week by high-cadence observations. This enables us to detect a super-Earth and a Neptune-mass planet in short-period orbits even around such giant stars.

  14. Rotten Egg Nebula: The magnetic field of a binary evolved star

    CERN Document Server

    Leal-Ferreira, M L; Diamond, P J; Kemball, A; Amiri, N; Desmurs, J -F

    2012-01-01

    Most of PNe are not spherical. The loss of spherical symmetry occurs somewhere between the AGB and PN phase. The cause of this change of morphology is not yet well known, but magnetic fields are one of the possible agents. Its origin remains to be determined, and potentially requires the presence of a massive companion to the AGB star. Therefore, further detections of the magnetic field around evolved stars (in particular those thought to be part of a binary system) are crucial to improve our understanding of the origin and role of magnetism on evolved stars. One such binaries is the pre-PN OH231.8, around which a magnetic field was detected in the OH maser region of the outer circumstellar envelope. We aim to detect and infer the properties of the magnetic field of this source in the water maser region. We observed the 6_{1,6}-5_{2,3} water maser rotational transition to determine its linear and circular polarization. These emissions are located within the inner regions of OH231.8 (at few tens of AU). We det...

  15. Bridging the Gap between Coronal and Non-Coronal Evolved Stars

    Science.gov (United States)

    Carpenter, Kenneth G.; Nielsen, Krister E.; Kober, Gladys V.

    2017-01-01

    The Hubble Space Telescope (HST) Treasury Program "Advanced Spectral Library (ASTRAL)" enables investigations of a broad range of problems including the character and dynamics of the wind and chromosphere of cool stars. This paper presents an investigation of the change in spectral characteristics when transitioning from the cool non-coronal objects with fluorescent emission spectra from the iron group elements, molecular hydrogen, and carbon monoxide to the warmer stars on the blue side of the Linsky-Haish dividing line in the HR diagram. These warmer objects exhibit chromospheric emission from significantly hotter environments in addition to coronal signatures, while the hybrid stars overlap in the HR-diagram with some of the non-coronal objects and share many spectral characteristics but show differences in the wind properties. We show how the wind, fluorescent features, and hot stellar signatures dramatically change with spectral class by comparing the already analyzed non-coronal objects (Alpha Ori, Gamma Cru) with the hybrid stars (Gamma Dra, Beta Gem and Alpha Aqr) and the coronal object Beta Dra. We aim to gain understanding of the physical processes in these objects' outer atmospheres and their evolutionary tracks.

  16. Evidence of Resonant Mode Coupling in the Hot B Subdwarf Star KIC 10139564

    Directory of Open Access Journals (Sweden)

    Zong W.

    2015-01-01

    Full Text Available The Kepler spacecraft provides new opportinuties to observe long term frequency and amplitude modulations of oscillation modes in pulsating stars. We analyzed more than three years of uninterrupted data obtained with this instrument on the hot B subdwarf (sdB star KIC 10139564 and found clear signatures of nonlinear resonant mode coupling affecting several multiplets. The observed periodic frequency and amplitude modulations may allow for new asteroseismic diagnostics, providing in particular ways to measure linear growth rates of pulsation modes in hot subdwarf stars for the first time.

  17. Evolved stars and the origin of abundance trends in planet hosts

    Science.gov (United States)

    Maldonado, J.; Villaver, E.

    2016-04-01

    Context. Detailed chemical abundance studies have revealed different trends between samples of planet and non-planet hosts. Whether these trends are related to the presence of planets or not is strongly debated. At the same time, tentative evidence that the properties of evolved stars with planets may be different from what we know for main-sequence hosts has recently been reported. Aims: We aim to test whether evolved stars with planets show any chemical peculiarity that could be related to the planet formation process. Methods: In a consistent way, we determine the metallicity and individual abundances of a large sample of evolved (subgiants and red giants) and main-sequence stars that are with and without known planetary companions, and discuss their metallicity distribution and trends. Our methodology is based on the analysis of high-resolution échelle spectra (R ≳ 57 000) from 2-3 m class telescopes. It includes the calculation of the fundamental stellar parameters, as well as individual abundances of C, O , Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, and Zn. Results: No differences in the ⟨[X/Fe]⟩ vs. condensation temperature (TC) slopes are found between the samples of planet and non-planet hosts when all elements are considered. However, if the analysis is restricted to only refractory elements, differences in the TC-slopes between stars with and without known planets are found. This result is found to be dependent on the stellar evolutionary stage, as it holds for main-sequence and subgiant stars, while there seems to be no difference between planet and non-planet hosts among the sample of giants. A search for correlations between the TC-slope and the stellar properties reveals significant correlations with the stellar mass and the stellar age. The data also suggest that differences in terms of mass and age between main-sequence planet and non-planet hosts may be present. Conclusions: Our results are well explained by radial mixing in the

  18. CO J = 2-1 EMISSION FROM EVOLVED STARS IN THE GALACTIC BULGE

    Energy Technology Data Exchange (ETDEWEB)

    Sargent, Benjamin A.; Meixner, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Patel, N. A. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Otsuka, M.; Srinivasan, S. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Riebel, D., E-mail: baspci@rit.edu [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2013-03-01

    We observe a sample of eight evolved stars in the Galactic bulge in the CO J = 2-1 line using the Submillimeter Array with angular resolution of 1''-4''. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2-1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining five stars in the sample because of heavy contamination from the galactic CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 ({+-}2.2) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 310 ({+-}89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 ({+-}2.8) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 220 ({+-}110). For [SLO2003] A51, we find a gas mass-loss rate of 3.4 ({+-}3.0) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 160 ({+-}140), reflecting the low quality of our tentative detection of the CO J = 2-1 emission from A51. We find that the CO J = 2-1 detections of OH/IR stars in the Galactic bulge require lower average CO J = 2-1 backgrounds.

  19. Turbulence and magnetic spots at the surface of hot massive stars

    CERN Document Server

    Cantiello, Matteo; Brandenburg, Axel; Del Sordo, Fabio; Käpylä, Petri; Langer, Norbert

    2010-01-01

    Hot luminous stars show a variety of phenomena in their photospheres and in their winds which still lack clear physical explanations at this time. Among these phenomena are non-thermal line broadening, line profile variability (LPVs), discrete absorption components (DACs), wind clumping and stochastically excited pulsations. Cantiello et al. (2009) argued that a convection zone close to the surface of hot, massive stars, could be responsible for some of these phenomena. This convective zone is caused by a peak in the opacity due to iron recombination and for this reason is referred as the "iron convection zone" (FeCZ). 3D MHD simulations are used to explore the possible effects of such subsurface convection on the surface properties of hot, massive stars. We argue that turbulence and localized magnetic spots at the surface are the likely consequence of subsurface convection in early type stars.

  20. The Pan-Pacific Planet Search V. Fundamental Parameters for 164 Evolved Stars

    CERN Document Server

    Wittenmyer, Robert A; Wang, Liang; Casagrande, Luca; Johnson, John Asher; Tinney, C G

    2016-01-01

    We present spectroscopic stellar parameters for the complete target list of 164 evolved stars from the Pan-Pacific Planet Search, a five-year radial velocity campaign using the 3.9m Anglo-Australian Telescope. For 87 of these bright giants, our work represents the first determination of their fundamental parameters. Our results carry typical uncertainties of 100 K, 0.15 dex, and 0.1 dex in $T_{\\rm eff}$, $\\log g$, and [Fe/H] and are consistent with literature values where available. The derived stellar masses have a mean of $1.31^{+0.28}_{-0.25}$ Msun, with a tail extending to $\\sim$2 Msun, consistent with the interpretation of these targets as "retired" A-F type stars.

  1. 28 SiO v=0 J=1-0 emission from evolved stars

    CERN Document Server

    de Vicente, P; Díaz-Pulido, A; Albo, C; Alcolea, J; Barcia, A; Barbas, L; Bolaño, R; Colomer, F; Diez, M C; Gallego, J D; Gómez-González, J; López-Fernández, I; López-Fernández, J A; López-Pérez, J A; Malo, I; Moreno, A; Patino, M; Serna, J M; Tercero, F; Vaquero, B

    2016-01-01

    Observations of 28SiO v=0 J=1-0 line emission (7-mm wavelength) from AGB stars show in some cases peculiar profiles, composed of a central intense component plus a wider plateau. Very similar profiles have been observed in CO lines from some AGB stars and most post-AGB nebulae and, in these cases, they are clearly associated with the presence of conspicuous axial symmetry and bipolar dynamics. We present systematic observations of 28SiO v=0 J=1-0 emission in 28 evolved stars, performed with the 40~m radio telescope of the IGN in Yebes, Spain. We find that the composite core plus plateau profiles are almost always present in O-rich Miras, OH/IR stars, and red supergiants. They are also found in one S-type Mira ($\\chi$ Cyg), as well as in two semiregular variables (X Her and RS Cnc) that are known to show axial symmetry. In the other objects, the profiles are simpler and similar to those of other molecular lines. The composite structure appears in the objects in which SiO emission is thought to come from the ve...

  2. 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.

  3. Stellar parameters and chemical abundances of 223 evolved stars with and without planets

    CERN Document Server

    Jofré, E; Saffe, C; Saker, L; de la Villarmois, E Artur; Chavero, C; Gómez, M; Mauas, P

    2014-01-01

    We present fundamental stellar parameters and chemical abundances for a sample of 86 evolved stars with planets and for a control sample of 137 stars without planets. The analysis was based on both high S/N and resolution echelle spectra. The goals of this work are i) to investigate chemical differences between stars with and without planets; ii) to explore potential differences between the properties of the planets around giants and subgiants; and iii) to search for possible correlations between these properties and the chemical abundances of their host stars. In agreement with previous studies, we find that subgiants with planets are, on average, more metal-rich than subgiants without planets by ~ 0.16 dex. The [Fe/H] distribution of giants with planets is centered at slightly subsolar metallicities and there is no metallicity enhancement relative to the [Fe/H] distribution of giants without planets. Furthermore, contrary to recent results, we do not find any clear difference between the metallicity distrib...

  4. Asteroseismology from multi-month Kepler photometry: the evolved Sun-like stars KIC 10273246 and KIC 10920273

    NARCIS (Netherlands)

    T.L. Campante; R. Handberg; S. Mathur; T. Appourchaux; T.R. Bedding; W.J. Chaplin; B. Mosser; O. Benomar; A. Bonanno; E. Corsaro; S.T. Fletcher; P. Gaulme; S. Hekker; C. Karoff; D. Salabert; G.A. Verner; T.R. White; G. Houdek; I.M. Brandao; O.L. Creevey; G. Dogan; M. Bazot; J. Christensen-Dalsgaard; M.S. Cunha; Y. Elsworth; D. Huber; H. Kjeldsen; M. Lundkvist; J. Molenda-Zakowicz; M.J.P.F.G. Monteiro; D. Stello; B.D. Clarke; F.R. Girouard; J.R. Hall; R.A. Garcia; C. Regulo

    2011-01-01

    Context. The evolved main-sequence Sun-like stars KIC 10273246 (F-type) and KIC 10920273 (G-type) were observed with the NASA Kepler satellite for approximately ten months with a duty cycle in excess of 90%. Such continuous and long observations are unprecedented for solar-type stars other than the

  5. Identification of oxygen-rich evolved stars by maser surveys and statistical studies on infrared data

    Science.gov (United States)

    Yung, Bosco H.-K.

    2013-10-01

    The post-asymptotic giant branch (post-AGB) phase is a short episode in the life of a star with mass between 0.8 to 8 M⊙. It comes after the AGB phase, and before the planetary nebula phase. A rapid change in many physical properties of a star is suggested to happen in this phase, for example the onset of jets. However, a lot of details are still unknown. In this thesis, three major problems are addressed: insufficient samples of post-AGB stars, identification of post-AGB stars, and the true status of a special class of objects called the "water fountains (WFs)". WFs are evolved stars associated with high velocity collimated bipolar jets that can be traced by H2O maser emissions. For the first two problems, new searching criteria are introduced with two new maser surveys on oxygen-rich post-AGB stars. It is necessary to collect more samples of post-AGB stars for further studies. Nonetheless, there has been no systematic searching method because most of the post-AGB stars are dim in optical and near-infrared wavelengths, which increases the difficulty in identification. Maser thus becomes a good alternative tool. In the first survey which focused only on H2O masers, over 200 AGB or post-AGB star candidates have been selected and observed. Those candidates were mainly chosen by new colour criteria with the far-infrared AKARI data. In particular, four characteristic maser sources were found, and they are currently suggested as possible very young post-AGB stars. In the second survey, another 100 objects were observed in OH and/or H2O masers. Three possible high velocity objects were discovered, including a new rare member of WFs. The colour criteria are proved to be quite sensitive in distinguishing post-AGB stars from AGB stars or other types of objects, even though there are still some contamination from young stellar objects. A follow-up study shows that the Q-parameters are effective in isolating objects with spherical or aspherical envelopes, which are also

  6. Hot subdwarf stars in the Galactic halo Tracers of prominent events in late stellar evolution

    Science.gov (United States)

    Geier, Stephan; Kupfer, Thomas; Schaffenroth, Veronika; Heber, Ulrich

    2016-08-01

    Hot subdwarf stars (sdO/Bs) are the stripped cores of red giants located at the bluest extension of the horizontal branch. They constitute the dominant population of UV-bright stars in old stellar environments and are most likely formed by binary interactions. We perform the first systematic, spectroscopic analysis of a sample of those stars in the Galactic halo based on data from SDSS. In the course of this project we discovered 177 close binary candidates. A significant fraction of the sdB binaries turned out to have close substellar companions, which shows that brown dwarfs and planets can significantly influence late stellar evolution. Close hot subdwarf binaries with massive white dwarf companions on the other hand are good candidates for the progenitors of type Ia supernovae. We discovered a hypervelocity star, which not only turned out to be the fastest unbound star known in our Galaxy, but also the surviving companion of such a supernova explosion.

  7. A selection of hot subluminous stars in the GALEX survey I. Correlation with the Guide Star Catalog

    CERN Document Server

    Vennes, S; Nemeth, P

    2010-01-01

    We assembled a catalogue of bright, hot subdwarf and white dwarf stars extracted from a joint ultraviolet, optical, and infrared source list. The selection is secured using colour criteria that correlate well with effective temperatures T_eff ~> 12,000 K. We built a N_UV-V versus V-J diagram for more than 60,000 bright sources using the Galaxy Evolution Explorer (GALEX) N_UV magnitude (N_UV<14), and the associated Guide Star Catalog (GSC2.3.2) photographic quick-V magnitude and the Two Micron All Sky Survey (2MASS) J and H magnitudes. This distillation process delivered a catalogue of approximately 700 sources with N_UV-V<0.5 comprising ~160 known hot subdwarf stars and another ~60 known white dwarf stars. A reduced proper-motion diagram built using the proper-motion measurements extracted from the Naval Observatory Merged Astrometric Dataset allowed us to identify an additional ~120 new hot subdwarf candidates and ~10 hot white dwarf candidates. We present a spectroscopic study of a subset of 52 subdwa...

  8. A Hot Water Bottle for Aging Neutron Stars

    DEFF Research Database (Denmark)

    Alford, Mark; Jotwani, Pooja; Kouvaris, Christoforos

    2004-01-01

    The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat l...

  9. Influence of XUV radiation on Pv ionization fraction in hot star winds

    CERN Document Server

    Krticka, Jiri

    2012-01-01

    Different diagnostics of hot star wind mass-loss rates provide results that are difficult to reconcile with each other. The widely accepted presence of clumping in hot star winds implies a significant reduction of observational mass-loss rate estimates from diagnostics that depend on the square of the density. Moreover, the ultraviolet Pv resonance lines indicate a possible need for even stronger reduction of hot star mass-loss rates, provided that Pv is a dominant ionization stage of phosphorus at least in some hot stars. The latter assumption is challenged by a possible presence of the XUV radiation. Here we study the influence of the XUV radiation on the Pv ionization fraction in the hot star winds. By a detailed solution of the hydrodynamical, radiative transfer, and statistical equilibrium equations we confirm that sufficiently strong XUV radiation source may decrease the Pv ionization fraction, possibly depreciating the Pv lines as a reliable mass-loss rate indicator. On the other hand, the XUV radiatio...

  10. A hot Jupiter orbiting a 2-Myr-old solar-mass T Tauri star

    CERN Document Server

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

    2016-01-01

    Hot Jupiters are giant Jupiter-like exoplanets that orbit 100x closer to their host stars than Jupiter does to the Sun. These planets presumably form in the outer part of the primordial disc 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 still embedded within protoplanetary discs, or later, once multiple planets are formed and interact. Although numerous hot Jupiters were 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 show that hot Jupiters around young stars can be revealed from extended sets of high-resolution spectra. Once filtered-out from the activity, radial velocities of V830 Tau derived from new data collected in late 2015 exhibit a sine wave of...

  11. Chemical composition of evolved stars in the young open clusters NGC 4609 and NGC 5316

    Science.gov (United States)

    Drazdauskas, Arnas; Tautvaišienė, Gražina; Smiljanic, Rodolfo; Bagdonas, Vilius; Chorniy, Yuriy

    2016-10-01

    High-resolution spectral analysis is performed for the first time in evolved stars of two young open clusters: NGC 4609 and NGC 5316, of about 80 and 100 Myr in age, respectively, and turn-off masses above 5 M⊙. Stellar evolution models predict an extra-mixing event in evolved stars, which follows the first dredge-up and happens later on the red giant branch. However, it is still not understood how this process affects stars of different masses. In this study, we determine abundances of the mixing sensitive elements carbon and nitrogen, carbon isotope 12C/13C ratios, as well as 20 other elements produced by different nucleosynthetic processes (O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Y, Zr, Ba, La, Ce, Pr, Nd, and Eu). We compared our results with the latest theoretical models of evolutionary mixing processes. We find that the obtained 12C/13C and C/N ratios and [Na/Fe] agree quite well with the model which takes into account thermohaline- and rotation-induced mixing but within error limits also agree with the standard first dredge-up model. Comparison of oxygen, magnesium, and other α-elements with theoretical models of Galactic chemical evolution revealed that both clusters follow the thin disc α-element trends. Neutron-capture element abundances in NGC 4609 are apparently reflecting its birthplace in the thin disc, while NGC 5316 has marginally higher abundances, which would indicate its birthplace in an environment more enriched with neutron-capture elements.

  12. Evolved stars as complex chemical laboratories - the quest for gaseous chemistry

    Science.gov (United States)

    Katrien Els Decin, Leen

    2015-08-01

    At the end of their life, most stars lose a large fraction of their mass through a stellar wind. The stellar winds of evolved (super)giant stars are the dominant suppliers for the pristine building blocks of the interstellar medium (ISM). Crucial to the understanding of the chemical life cycle of the ISM is hence a profound insight in the chemical and physical structure governing these stellar winds.These winds are really unique chemical laboratories in which currently more than 70 different molecules and 15 different dust species are detected. Several chemical processes such as neutral-neutral and ion-molecule gas-phase reactions, dust nucleation and growth, and photo-processes determine the chemical content of these winds. However, gas-phase and dust-nucleation chemistry for astronomical environments still faces many challenges. One should realize that only ˜15% of the rate coefficients for gas-phase reactions considered to occur in (inter/circum)stellar regions at temperatures (T) below 300K have been subject to direct laboratory determinations and that the temperature dependence of the rate constants is often not known; only ˜2% have rate constants at Teducated guesses’ for these unknown rates, sometimes forcing the network to yield predictions concurring with (astronomical) observations. Large uncertainties are inherent in this type of ‘optimized’ chemical schemes.Thanks to an ERC-CoG grant, we are now in the position to solve some riddles involved in understanding the gas-phase chemistry in evolved stars. In this presentation, I will demonstrate the need for accurate temperature-dependent gas-phase reaction rate constants and will present our new laboratory equipment built to measure the rate constants for species key in stellar wind chemistry. Specifically, we aim to obtain the rate constants of reactions involving silicon- and sulphur bearing species and HCCO for 30

  13. A Hot Water Bottle for Aging Neutron Stars

    CERN Document Server

    Alford, M; Kouvaris, C; Kundu, J; Rajagopal, K; Alford, Mark; Jotwani, Pooja; Kouvaris, Chris; Kundu, Joydip; Rajagopal, Krishna

    2004-01-01

    The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat loss by neutrino emission L_\

  14. Evidence of the evolved nature of the B[e] star MWC 137

    Energy Technology Data Exchange (ETDEWEB)

    Muratore, M. F.; Arias, M. L.; Cidale, L. [Departamento de Espectroscopía Estelar, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, and Instituto de Astrofísica de La Plata, CCT La Plata, CONICET-UNLP, Paseo del Bosque S/N, B1900FWA, La Plata (Argentina); Kraus, M.; Oksala, M. E. [Astronomický ústav, Akademie věd České Republiky, Fričova 298, 251 65 Ondřejov (Czech Republic); Fernandes, M. Borges [Observatório Nacional, Rua General José Cristino 77, 20921-400 São Cristovão, Rio de Janeiro (Brazil); Liermann, A., E-mail: fmuratore@carina.fcaglp.unlp.edu.ar [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2015-01-01

    The evolutionary phase of B[e] stars is difficult to establish due to the uncertainties in their fundamental parameters. For instance, possible classifications for the Galactic B[e] star MWC 137 include pre-main-sequence and post-main-sequence phases, with a large range in luminosity. Our goal is to clarify the evolutionary stage of this peculiar object, and to study the CO molecular component of its circumstellar medium. To this purpose, we modeled the CO molecular bands using high-resolution K-band spectra. We find that MWC 137 is surrounded by a detached cool (T=1900±100 K) and dense (N=(3±1)×10{sup 21} cm{sup −2}) ring of CO gas orbiting the star with a rotational velocity, projected to the line of sight, of 84 ± 2 km s{sup −1}. We also find that the molecular gas is enriched in the isotope {sup 13}C, excluding the classification of the star as a Herbig Be. The observed isotopic abundance ratio ({sup 12}C/{sup 13}C = 25 ± 2) derived from our modeling is compatible with a proto-planetary nebula, main-sequence, or supergiant evolutionary phase. However, based on some observable characteristics of MWC 137, we propose that the supergiant scenario seems to be the most plausible. Hence, we suggest that MWC 137 could be in an extremely short-lived phase, evolving from a B[e] supergiant to a blue supergiant with a bipolar ring nebula.

  15. Analysis of strange-mode instability with time-dependent convection in hot massive stars

    CERN Document Server

    Sonoi, Takafumi

    2013-01-01

    We carry out nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection (TDC) for the first time. Although convective luminosity in envelopes of hot massive stars is not as dominative as in stars near the red edge of the classical Cepheid instability strip in the Hertzsprung-Russell (H-R) diagram, we have found that the strange-mode instability can be affected by the treatment of convection. However, existence of the instability around and over the Humphreys-Davidson (H-D) limit is independent of the treatment. This implies that the strange-mode instability could be responsible for the lack of observed stars over the H-D limit regardless of uncertainties on convection theories.

  16. A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets

    CERN Document Server

    Mulders, Gijs D; Apai, Daniel; Frasca, Antonio; Molenda-Zakowicz, Joanna

    2016-01-01

    The host star metallicity provide a measure of the conditions in protoplanetary disks at the time of planet formation. Using a sample of over 20,000 Kepler stars with spectroscopic metallicities from the LAMOST survey, we explore how the exoplanet population depends on host star metallicity as a function of orbital period and planet size. We find that exoplanets with orbital periods less than 10 days are preferentially found around metal-rich stars ([Fe/H]~ 0.15 +- 0.05 dex). The occurrence rates of these hot exoplanets increases to ~30% for super-solar metallicity stars from ~10% for stars with a sub-solar metallicity. Cooler exoplanets, that resides at longer orbital periods and constitute the bulk of the exoplanet population with an occurrence rate of >~ 90%, have host-star metallicities consistent with solar. At short orbital periods, P<10 days, the difference in host star metallicity is largest for hot rocky planets (<1.7 R_Earth), where the metallicity difference is [Fe/H] =~ 0.25 +- 0.07 dex. The...

  17. Kepler-14b: A massive hot Jupiter transiting an F star in a close visual binary

    OpenAIRE

    Buchhave, Lars A.; Latham, David W.; Carter, Joshua A.; Désert, Jean-Michel; Torres, Guillermo; Adams, Elisabeth R.; Bryson, Stephen T.; Charbonneau, David B.; Ciardi, David R.; Kulesa, Craig; Dupree, Andrea K.; Fischer, Debra A.; Fressin, François; Gautier III, Thomas N.; Gilliland, Ronald L.

    2011-01-01

    We present the discovery of a hot Jupiter transiting an F star in a close visual (0.3" sky projected angular separation) binary system. The dilution of the host star's light by the nearly equal magnitude stellar companion (~ 0.5 magnitudes fainter) significantly affects the derived planetary parameters, and if left uncorrected, leads to an underestimate of the radius and mass of the planet by 10% and 60%, respectively. Other published exoplanets, which have not been observed with high-resolut...

  18. Radiation-Hydrodynamic Models of the evolving Circumstellar Medium around Massive Stars

    CERN Document Server

    Toalá, J A

    2011-01-01

    We study the evolution of the interstellar and circumstellar media around massive stars (M > 40M_{\\odot}) from the main sequence through to the Wolf-Rayet stage by means of radiationhydrodynamic simulations. We use publicly available stellar evolution models to investigate the different possible structures that can form in the stellar wind bubbles around Wolf-Rayet stars. We find significant differences between models with and without stellar rotation, and between models from different authors. More specifically, we find that the main ingredients in the formation of structures in the Wolf-Rayet wind bubbles are the duration of the Red Supergiant (or Luminous Blue Variable) phase, the amount of mass lost, and the wind velocity during this phase, in agreement with previous authors. Thermal conduction is also included in our models. We find that main-sequence bubbles with thermal conduction are slightly smaller, due to extra cooling which reduces the pressure in the hot, shocked bubble, but that thermal conducti...

  19. CO and HI emission from the circumstellar envelopes of some evolved stars

    CERN Document Server

    Diep, P N; Nhung, P T; Tuan-Anh, P; Bertre, T Le; Winters, J M; Matthews, L D; Phuong, N T; Thao, N T; Darriulat, P

    2015-01-01

    Studies of the CO and HI radio emission of some evolved stars are presented using data collected by the IRAM Plateau de Bure interferometer and Pico Veleta telescope, the Nan\\c{c}ay Radio Telescope and the JVLA and ALMA arrays. Approximate axial symmetry of the physical and kinematic properties of the circumstellar envelope (CSE) are observed in CO emission, in particular, from RS Cnc, EP Aqr and the Red Rectangle. A common feature is the presence of a bipolar outflow causing an enhanced wind velocity in the polar directions. HI emission extends to larger radial distances than probed by CO emission and displays features related to the interaction between the stellar outflow and interstellar matter. With its unprecedented sensitivity, FAST will open a new window on such studies. Its potential in this domain is briefly illustrated.

  20. On Magnesium Sulfide as the Carrier of the 30micron Emission Feature in Evolved Stars

    CERN Document Server

    Zhang, Ke; Li, Aigen

    2009-01-01

    A large number of carbon-rich evolved objects (asymptotic giant branch stars, protoplanetary nebulae, and planetary nebulae) in both the Milky Way galaxy and the Magellanic Clouds exhibit an enigmatic broad emission feature at 30 micron. This feature, extending from 24 micron to 45 micron, is very strong and accounts for up to 30% of the total infrared luminosity of the object. In literature it is tentatively attributed to magnesium sulfide (MgS) dust. Using the prototypical protoplanetary nebula around HD 56126 for illustrative purpose, however, in this work we show that in order for MgS to be responsible for the 30 micron feature, one would require an amount of MgS mass substantially exceeding what would be available in this source. We therefore argue that MgS is unlikely the carrier of the 30 micron feature seen in this source and in other sources as well.

  1. RV variable, hot post-AGB stars from the MUCHFUSS project - Classification, atmospheric parameters, formation scenarios

    CERN Document Server

    Reindl, N; Kupfer, T; Bloemen, S; Schaffenroth, V; Heber, U; Barlow, B N; Østensen, R H

    2016-01-01

    In the course of the MUCHFUSS project we have recently discovered four radial velocity (RV) variable, hot (Teff $\\approx$ 80,000 - 110,000 K) post-asymptotic giant branch (AGB) stars. Among them, we found the first known RV variable O(He) star, the only second known RV variable PG 1159 close binary candidate, as well as the first two naked (i.e., without planetary nebula (PN)) H-rich post-AGB stars of spectral type O(H) that show significant RV variations. We present a non-LTE spectral analysis of these stars along with one further O(H)-type star whose RV variations were found to be not significant. We also report the discovery of an far-infrared excess in the case of the PG 1159 star. None of the stars in our sample displays nebular emission lines, which can be explained well in terms of a very late thermal pulse evolution in the case of the PG 1159 star. The "missing" PNe around the O(H)-type stars seem strange, since we find that several central stars of PNe have much longer post-AGB times. Besides the non...

  2. Toward A Self Consistent MHD Model of Chromospheres and Winds From Late Type Evolved Stars

    CERN Document Server

    Airapetian, V S; Carpenter, K G

    2014-01-01

    We present the first magnetohydrodynamic model of the stellar chromospheric heating and acceleration of the outer atmospheres of cool evolved stars, using alpha Tau as a case study. We used a 1.5D MHD code with a generalized Ohm's law that accounts for the effects of partial ionization in the stellar atmosphere to study Alfven wave dissipation and wave reflection. We have demonstrated that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfven waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of alpha Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere due to resistive (Joule) dissipation of electric currents, induced by ...

  3. Crystalline silicate dust around evolved stars II. The crystalline silicate complexes

    CERN Document Server

    Molster, F J; Tielens, A G G M

    2002-01-01

    This is the second paper in a series of three in which we present an exhaustive inventory of the 49 solid state emission bands observed in a sample of 17 oxygen-rich dust shells surrounding evolved stars. Most of these emission bands are concentrated in well defined spectral regions (called complexes). We define 7 of these complexes; the 10, 18, 23, 28, 33, 40 and 60 micron complex. We derive average properties of the individual bands. Comparison with laboratory data suggests that both olivines (Mg(2x)Fe(2-2x)SiO(4)) and pyroxenes (Mg(x)Fe(1-x)SiO(3)) are present, with x close to 1, i.e. the minerals are very Mg-rich and Fe-poor. This composition is similar to that seen in disks surrounding young stars and in the solar system comet Hale-Bopp. A significant fraction of the emission bands cannot be identified with either olivines or pyroxenes. Possible other materials that may be the carriers of these unidentified bands are briefly discussed. There is a natural division into objects that show a disk-like geomet...

  4. Galactic encounters our majestic and evolving star-system, from the big bang to time's end

    CERN Document Server

    Sheehan, William

    2015-01-01

    Written by William Sheehan, a noted historian of astronomy, and Christopher J. Conselice, a professional astronomer specializing in galaxies in the early universe, this book tells the story of how astronomers have pieced together what is known about the vast and complicated systems of stars and dust known as galaxies. The first galaxies appeared as violently disturbed exotic objects when the Universe was only a few 100 million years old.  From that tortured beginning, they have evolved though processes of accretion, merging and star formation into the majestic spirals and massive ellipticals that dominate our local part of the Universe. This of course includes the Milky Way, to which the Sun and Solar System belong; it is our galactic home, and the only galaxy we will ever know from the inside.  Sheehan and Conselice show how astronomers’ understanding has grown from the early catalogs of Charles Messier and William Herschel; developed through the pioneering efforts of astronomers like E.E. Barnard, V.M. ...

  5. 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.

  6. The Magnetic Coupling of Chromospheres and Winds From Late Type Evolved Stars: Role of MHD Waves

    Science.gov (United States)

    Airapetian, Vladimir; Leake, James; Carpenter, Kenneth

    2015-08-01

    Stellar chromospheres and winds represent universal attributes of stars on the cool portion of H-R diagram. In this paper we derive observational constrains for the chromospheric heating and wind acceleration from cool evolved stars and examine the role of Alfven waves as a viable source of energy dissipation and momentum deposition. We use a 1.5D magnetohydrodynamic code with a generalized Ohm's law to study propagation of Alfven waves generated along a diverging magnetic field in a stellar photosphere at a single frequency. We demonstrate that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfven waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of α Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere model due to resistive (Joule) dissipation of electric currents on Pedersen resistivity are consistent with observational constraints on the net radiative losses in UV lines and the continuum from α Tau. At the top of the chromosphere, Alfven waves experience significant reflection, producing downward propagating transverse waves that interact with upward propagating waves and produce velocity shear in the chromosphere. Our simulations also suggest that momentum deposition by non-linear Alfven waves becomes significant in the outer chromosphere within 1 stellar radius from the photosphere that initiates a slow and massive winds from red giants and supergiants.

  7. Observational Study of Morphological Changes in Medium-mass Evolved Stars

    Science.gov (United States)

    Chong, Sze-Ning

    2014-02-01

    Medium-mass (or intermediate-mass) stars refer to main sequence stars with masses ranging from 0.4 to 8 solar masses. These stars are believed to finally evolve into the central stars of planetary nebulae (PNe) and white dwarfs. One of the fascinating aspects of PNe is their diverse morphology. To understand the mechanisms of the morphological changes from spherical circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars to those forming highly diversified PNe, it is necessary to investigate the true three-dimensional (3D) morphology of PNe from two-dimensional images, and the short transition phase in-between the two phases should also be explored. "Water Fountain" (WF) sources belong to transition phase objects; they are AGB or post-AGB stars with collimated jets traced by high velocity water maser emissions in their CSEs. This thesis comprises of four chapters. The results can be divided into two major parts. Chapter 1 is the introduction on the related fields with brief reviews of previous observational studies on PNe and the rapidly evolving transition phase objects. Basic theories necessary for understanding the next chapters were also described, including those explaining the commonly observed Hα emission in PNe, the formation of multipolar PNe, the maser emission and the role of shock in circumstellar materials. The first major part of the results, about the morphological classification of multipolar PNe, is presented in Chapter 2. At the beginning of the chapter, the problems on the previous classification methods were pointed out. Then a three-lobed model was introduced. By changing the combination of the orientations of the three pairs of lobes, simulations using the model produced statistical results in classification and quantified the errors of misidentification. Assuming that all PNe observed have the true structure of three lobes, due to projection effect, only 49% of them would be correctly classified. 46% and 5% of them would be

  8. FUV and Optical Spectroscopy of Hot Post-AGB Stars in Globular Clusters

    Science.gov (United States)

    Dixon, William V.

    2004-01-01

    The goal of this program was to determine the atmospheric parameters (effective temperature and surface gravity) and abundances of the hot, post-AGB (PAGB) stars in globular clusters observed with the Hopkins Ultraviolet Telescope (HUT) on the Astro-l and 2 missions.

  9. Hot subdwarfs: Small stars marking important events in stellar evolution. Ludwig Biermann Award Lecture 2014

    Science.gov (United States)

    Geier, S.

    2015-06-01

    Hot subdwarfs are considered to be the compact helium cores of red giants which lost almost their entire hydrogen envelope. What causes this enormous mass loss is still unclear. Binary interactions are invoked, and a significant fraction of the hot subdwarf population is indeed found in close binaries. In a large project we search for close binary sdBs with the most and the least massive companions. Significantly enhancing the known sample of close binary sdBs we performed the first comprehensive study of this population. Triggered by the discovery of two sdB binaries with close brown dwarf companions in the course of this project, we were able to show that the interaction of stars with substellar companions is an important channel to form sdB stars. Finally, we discovered a unique and very compact binary system consisting of an sdB and a massive white dwarf which qualifies as a progenitor candidate for a supernova of type Ia. In addition to that, we could connect those explosions to the class of hypervelocity hot subdwarf stars which we consider as the surviving companions of such events. Being the stripped cores of red giants, hot subdwarfs turned out to be important markers of peculiar events in stellar evolution ranging all the way from star-planet interactions to the progenitors of stellar explosions used to measure the expansion of our Universe.

  10. Theory of Winds from Hot, Luminous Massive Stars

    CERN Document Server

    Owocki, Stanley

    2014-01-01

    The high luminosities of massive stars drive strong stellar winds, through line scattering of the star's continuum radiation. This paper reviews the dynamics of such line driving, building first upon the standard CAK model for steady winds, and deriving the associated analytic scalings for the mass loss rate and wind velocity law. It next summarizes the origin and nature of the strong Line Deshadowing Instability (LDI) intrinsic to such line-driving, including also the role of a diffuse-line-drag effect that stabilizes the wind base, and then describes how both instability and drag are incorporated in the Smooth Source Function (SSF) method for time-dependent simulations of the nonlinear evolution of the resulting wind structure. The review concludes with a discussion of the effect of the resulting extensive structure in temperature, density and velocity for interpreting observational diagnostics. In addition to the usual clumping effect on density-squared diagnostics, the spatial porosity of optically thick ...

  11. Maximum mass of a hot neutron star with a quark core

    Institute of Scientific and Technical Information of China (English)

    Tayebeh Yazdizadeh; Gholam Hossein Bordbar

    2011-01-01

    We have considered a hot neutron star with a quark core, a mixed phase of quark-hadron matter, and a hadronic matter crust and have determined the equation of state of the hadronic phase and the quark phase. We have then found the equation of state of the mixed phase under the Gibbs conditions. Finally, we have computed the structure of a hot neutron star with a quark core and compared our results with those of the neutron star without a quark core. For the quark matter calculations, we have used the MIT bag model in which the total energy of the system is considered as the kinetic energy of the particles plus a bag constant. For the hadronic matter calculations, we have used the lowest order constrained variational formalism. Our calculations show that the results for the maximum gravitational mass of a hot neutron star with a quark core are substantially different from those of a neutron star without the quark core.

  12. Dust photophoretic transport in a disk irradiated by an evolving PMS star

    Science.gov (United States)

    Cordier, D.; Moroni, P.; Tognelli, E.

    2014-04-01

    As reported by Tielens et al. (2005) [14] the interstellar medium (ISM) is very poor in crystalline solids. For instance, Kemper et al. (2004) [7] well reproduce the interstellar absorption band using a mixture of 15.1% amorphous pyroxene and 84.9% of amorphous olivine by mass, leading to a crystalline fraction of the interstellar silicates around 0.2% by mass. The proto-solar nebula is supposed to be formed from the material coming from the ISM. As a consequence, the primordial dust in the solar system should be composed of amorphous solids excepted grains which have undergone thermal annealing in high temperature regions (i.e. around 1000-1500 K) close to the star (i.e. r . 1 - 2 AU). Besides this, comets are presumed to have formed in the cold outer part of the solar nebula. Campins & Ryan (1989) have found that crystalline olivine is a major component of the silicates in comet Halley. Stardust samples of comet 81P/Wild 2 include large singleminerals crystals and X-raymicroscopic analysis leads to a crystal mass fraction fcryst larger than ~ 50% (Ogliore et al. 2009, Brownlee et al. 2006). More generally comets have a fcryst larger than ~ 20% (Lindsay et al. 2013, Kelley & Wooden, 2009). This discrepancy between ISMgrains crystallinity and comets one is the mark of a radial transport process occuring in the accretion disk. Several transport processes have been proposed to explain the presence of these refractory material in comets: annealing by shock waves in the outer solar nebula (Harker & Desch 2002) [3], radial mixing processes by turbulent diffusion (Gail, 2001; Wehrstedt & Gail, 2002; Bockelée-Morvan et al., 2002) or transport by photophoresis (Mousis et al., 2007 andMoudens et al., 2011). In this paper, we focus on this last process for which we employ a 1+1D accretion disk model irradiated by a pre-main sequence (PMS) star. The model of nebula and the model of star are both evolving. Concerning the photophoresis itself, essentially, we have followed the

  13. From hot lattice QCD to cold quark stars

    Energy Technology Data Exchange (ETDEWEB)

    Schulze, Robert

    2011-02-22

    A thermodynamic model of the quark-gluon plasma using quasiparticle degrees of freedom based on the hard thermal loop self-energies is introduced. It provides a connection between an established phenomenological quasiparticle model - following from the former using a series of approximations - and QCD - from which the former is derived using the Cornwall-Jackiw-Tomboulis formalism and a special parametrization of the running coupling. Both models allow for an extrapolation of first-principle QCD results available at small chemical potentials using Monte-Carlo methods on the lattice to large net baryon densities with remarkably similar results. They are used to construct equations of state for heavy-ion collider experiments at SPS and FAIR as well as quark and neutron star interiors. A mixed-phase construction allows for a connection of the SPS equation of state to the hadron resonance gas. An extension to the weak sector is presented as well as general stability and binding arguments for compact stellar objects are developed. From the extrapolation of the most recent lattice results the existence of bound pure quark stars is not suggested. However, quark matter might exist in a hybrid phase in cores of neutron stars. (orig.)

  14. Dynamical ejecta from precessing neutron star-black hole mergers with a hot, nuclear-theory based equation of state

    Science.gov (United States)

    Foucart, F.; Desai, D.; Brege, W.; Duez, M. D.; Kasen, D.; Hemberger, D. A.; Kidder, L. E.; Pfeiffer, H. P.; Scheel, M. A.

    2017-02-01

    Neutron star-black hole binaries are among the strongest sources of gravitational waves detectable by current observatories. They can also power bright electromagnetic signals (gamma-ray bursts, kilonovae), and may be a significant source of production of r-process nuclei. A misalignment of the black hole spin with respect to the orbital angular momentum leads to precession of that spin and of the orbital plane, and has a significant effect on the properties of the post-merger remnant and of the material ejected by the merger. We present a first set of simulations of precessing neutron star-black hole mergers using a hot, composition dependent, nuclear-theory based equation of state (DD2). We show that the mass of the remnant and of the dynamical ejecta are broadly consistent with the result of simulations using simpler equations of state, while differences arise when considering the dynamics of the merger and the velocity of the ejecta. We show that the latter can easily be understood from assumptions about the composition of low-density, cold material in the different equations of state, and propose an updated estimate for the ejecta velocity which takes those effects into account. We also present an updated mesh-refinement algorithm which allows us to improve the numerical resolution used to evolve neutron star-black hole mergers.

  15. Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory

    CERN Document Server

    Rauch, Thomas; Ziegler, Marc; Koesterke, Lars; Kruk, Jeffrey W

    2008-01-01

    Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived at a high level of sophistication: fully line-blanketed model atmospheres which consider opacities of all elements from H to Ni allow the reliable determination of photospheric parameters of hot, compact stars. Such models provide a crucial test of stellar evolutionary theory: recent abundance determinations of trace elements like, e.g., F, Ne, Mg, P, S, Ar, Fe, and Ni are suited to investigate on AGB nucleosynthesis. E.g., the strong Fe depletion found in hydrogen-deficient post-AGB stars is a clear indication of an efficient s-process on the AGB where Fe is transformed into Ni or even heavier trans iron-group elements. We present results of recent spectral analyses based on high-resolution UV observations of hot stars.

  16. C/O Ratios of Stars with Transiting Hot Jupiter Exoplanets

    CERN Document Server

    Teske, Johanna K; Smith, Verne V; Schuler, Simon C; Griffith, Caitlin A

    2014-01-01

    The relative abundances of carbon and oxygen have long been recognized as fundamental diagnostics of stellar chemical evolution. Now, the growing number of exoplanet observations enable estimation of these elements in exoplanetary atmospheres. In hot Jupiters, the C/O ratio affects the partitioning of carbon in the major observable molecules, making these elements diagnostic of temperature structure and composition. Here we present measurements of carbon and oxygen abundances in 16 stars that host transiting hot Jupiter exoplanets, and compare our C/O ratios to those measured in larger samples of host stars, as well as those estimated for the corresponding exoplanet atmospheres. With standard stellar abundance analysis we derive stellar parameters as well as [C/H] and [O/H] from multiple abundance indicators, including synthesis fitting of the [O I] 6300 {\\AA} line and NLTE corrections for the O I triplet. Our results, in agreement with recent suggestions, indicate that previously-measured exoplanet host star...

  17. Evidence of the Evolved Nature of the B[e] Star MWC 137

    Science.gov (United States)

    Muratore, M. F.; Kraus, M.; Oksala, M. E.; Arias, M. L.; Cidale, L.; Borges Fernandes, M.; Liermann, A.

    2015-01-01

    The evolutionary phase of B[e] stars is difficult to establish due to the uncertainties in their fundamental parameters. For instance, possible classifications for the Galactic B[e] star MWC 137 include pre-main-sequence and post-main-sequence phases, with a large range in luminosity. Our goal is to clarify the evolutionary stage of this peculiar object, and to study the CO molecular component of its circumstellar medium. To this purpose, we modeled the CO molecular bands using high-resolution K-band spectra. We find that MWC 137 is surrounded by a detached cool (T=1900+/- 100 K) and dense (N=(3+/- 1)× {{10}21} {{cm}-2}) ring of CO gas orbiting the star with a rotational velocity, projected to the line of sight, of 84 ± 2 km s-1. We also find that the molecular gas is enriched in the isotope 13C, excluding the classification of the star as a Herbig Be. The observed isotopic abundance ratio (12C/13C = 25 ± 2) derived from our modeling is compatible with a proto-planetary nebula, main-sequence, or supergiant evolutionary phase. However, based on some observable characteristics of MWC 137, we propose that the supergiant scenario seems to be the most plausible. Hence, we suggest that MWC 137 could be in an extremely short-lived phase, evolving from a B[e] supergiant to a blue supergiant with a bipolar ring nebula. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), under program IDs GN-2011B-Q-24 and GN-2013B-Q-11.

  18. The mass-loss return from evolved stars to the Large Magellanic Cloud V. The GRAMS carbon-star model grid

    CERN Document Server

    Srinivasan, Sundar; Meixner, Margaret

    2011-01-01

    The total dust return rate from AGB and RSG star outflows is an important constraint to galactic chemical evolution models. However, this requires detailed radiative transfer (RT) modeling of individual stars, which becomes impractical for large data sets. Another approach is to select the best-fit spectral energy distribution (SED) from a grid of dust shell models, allowing for a faster determination of the luminosities and mass-loss rates for entire samples. We have developed the Grid of RSG and AGB ModelS (GRAMS) to measure the mass-loss return from evolved stars. The models span the range of stellar, dust shell and grain properties relevant to evolved stars. In this paper we present the carbon-star grid and compare our results with data of Large Magellanic Cloud (LMC) carbon stars from the SAGE and SAGE-Spec programs. We generate spherically symmetric dust shell models using the 2Dust code, with hydrostatic models for the central stars. We explore five values of the inner radius R_in of the dust shell (1....

  19. How many hot subdwarf stars were rejected from the PG survey?

    CERN Document Server

    Wade, R A; Green, R F

    2004-01-01

    The Palomar-Green (PG) survey for UV-excess objects selected objects with U-B<-0.46 for spectroscopic follow-up. The color selection was done from photographic photometry, with typical error sigma(U-B) = 0.38. Spectroscopic detection of the Ca II K line in color-selected candidates was thought to indicate that a metal-weak cool star (sdF-sdG) had entered the list owing to photometric errors. About 1100 such "K-line" stars were rejected on this basis from the final published PG catalog, as not having "genuine" UV excesses. However, another possibility is that some of these objects are composite (binary) stars, consisting of a hot subdwarf (sdB or sdO) and a cool companion (F-G-K). Recent interest in binary-star formation channels for sdB stars in particular has brought renewed attention to the issue of completeness of lists of known hot subdwarfs, especially ones with cool companions. In this contribution, we attempt to determine that nature of the "rejected" PG candidate stars, by assembling available info...

  20. Hot super-Earths stripped by their host stars

    CERN Document Server

    Lundkvist, M S; Albrecht, S; Davies, G R; Basu, S; Huber, D; Justesen, A B; Karoff, C; Aguirre, V Silva; Van Eylen, V; Vang, C; Arentoft, T; Barclay, T; Bedding, T R; Campante, T L; Chaplin, W J; Christensen-Dalsgaard, J; Elsworth, Y P; Gilliland, R L; Handberg, R; Hekker, S; Kawaler, S D; Lund, M N; Metcalfe, T S; Miglio, A; Rowe, J F; Stello, D; Tingley, B; White, T R

    2016-01-01

    Simulations predict that hot super-Earth sized exoplanets can have their envelopes stripped by photo-evaporation, which would present itself as a lack of these exoplanets. However, this absence in the exoplanet population has escaped a firm detection. Here we demonstrate, using asteroseismology on a sample of exoplanets and exoplanet candidates observed during the Kepler mission that, while there is an abundance of super-Earth sized exoplanets with low incident fluxes, none are found with high incident fluxes. We do not find any exoplanets with radii between 2.2 and 3.8 Earth radii with incident flux above 650 times the incident flux on Earth. This gap in the population of exoplanets is explained by evaporation of volatile elements and thus supports the predictions. The confirmation of a hot-super-Earth desert caused by evaporation will add an important constraint on simulations of planetary systems, since they must be able to reproduce the dearth of close-in super-Earths.

  1. Coupled evolutions of the stellar obliquity, orbital distance, and planet's radius due to the Ohmic dissipation induced in a diamagnetic hot Jupiter around a magnetic T Tauri star

    CERN Document Server

    Chang, Yu-Ling; Gu, Pin-Gao

    2012-01-01

    We revisit the calculation of the Ohmic dissipation in a hot Jupiter presented in Laine et al. (2008) by considering more realistic interior structures, stellar obliquity, and the resulting orbital evolution. In this simplified approach, the young hot Jupiter of one Jupiter mass is modelled as a diamagnetic sphere with a finite resistivity, orbiting across tilted stellar magnetic dipole fields in vacuum. Since the induced Ohmic dissipation occurs mostly near the planet's surface, we find that the dissipation is unable to significantly expand the young hot Jupiter. Nevertheless, the planet inside a small co-rotation orbital radius can undergo orbital decay by the dissipation torque and finally overfill its Roche lobe during the T Tauri star phase. The stellar obliquity can evolve significantly if the magnetic dipole is parallel/anti-parallel to the stellar spin. Our results are validated by the general torque-dissipation relation in the presence of the stellar obliquity. We also run the fiducial model in Laine...

  2. Planetary Companions to Evolved Intermediate-Mass Stars: 14 Andromedae, 81 Ceti, 6 Lyncis, and HD 167042

    CERN Document Server

    Sato, Bun'ei; Omiya, Masashi; Izumiura, Hideyuki; Kambe, Eiji; Masuda, Seiji; Takeda, Yoichi; Itoh, Yoichi; Ando, Hiroyasu; Yoshida, Michitoshi; Kokubo, Eiichiro; Ida, Shigeru

    2008-01-01

    We report on the detection of four extrasolar planets orbiting evolved intermediate-mass stars from a precise Doppler survey of G and K giants at Okayama Astrophysical Observatory. All of the host stars are considered to be formerly early F-type or A-type dwarfs when they were on the main sequence. 14 And (K0 III) is a clump giant with a mass of 2.2 M_solar and has a planet of minimum mass m_2sin i=4.8 M_Jup in a nearly circular orbit with a 186 day period. This is one of the innermost planets around evolved intermediate-mass stars and such planets have only been discovered in clump giants. 81 Cet (G5 III) is a clump giant with 2.4 M_solar hosting a planet of m_2sin i=5.3 M_Jup in a 953 day orbit with an eccentricity of e=0.21. 6 Lyn (K0 IV) is a less evolved subgiant with 1.7 M_solar and has a planet of m_2sin i=2.4 M_Jup in a 899 day orbit with e=0.13. HD 167042 (K1 IV) is also a less evolved star with 1.5 M_solar hosting a planet of m_2sin i=1.6 M_Jup in a 418 day orbit with e=0.10. This planet was indepen...

  3. Toward A Self Consistent MHD Model of Chromospheres and Winds From Late Type Evolved Stars

    Science.gov (United States)

    Airapetian, V. S.; Leake, J. E.; Carpenter, Kenneth G.

    2015-01-01

    We present the first magnetohydrodynamic model of the stellar chromospheric heating and acceleration of the outer atmospheres of cool evolved stars, using α Tau as a case study. We used a 1.5D MHD code with a generalized Ohm's law that accounts for the effects of partial ionization in the stellar atmosphere to study Alfvén wave dissipation and wave reflection. We have demonstrated that due to inclusion of the effects of ion-neutral collisions in magnetized weakly ionized chromospheric plasma on resistivity and the appropriate grid resolution, the numerical resistivity becomes 1-2 orders of magnitude smaller than the physical resistivity. The motions introduced by non-linear transverse Alfvé waves can explain non-thermally broadened and non-Gaussian profiles of optically thin UV lines forming in the stellar chromosphere of α Tau and other late-type giant and supergiant stars. The calculated heating rates in the stellar chromosphere due to resistive (Joule) dissipation of electric currents, induced by upward propagating non-linear Alfvé waves, are consistent with observational constraints on the net radiative losses in UV lines and the continuum from α Tau. At the top of the chromosphere, Alfvé waves experience significant reflection, producing downward propagating transverse waves that interact with upward propagating waves and produce velocity shear in the chromosphere. Our simulations also suggest that momentum deposition by non-linear Alfvé waves becomes significant in the outer chromosphere at 1 stellar radius from the photosphere. The calculated terminal velocity and the mass loss rate are consistent with the observationally derived wind properties in α Tau.

  4. QPO emission from moving hot spots on the surface of neutron stars: a model

    CERN Document Server

    Bachetti, Matteo; Kulkarni, Akshay; Burderi, Luciano; di Salvo, Tiziana

    2009-01-01

    We present recent results of 3D magnetohydrodynamic simulations of neutron stars with small misalignment angles, as regards the features in light curves produced by regular movements of the hot spots during accretion onto the star. In particular, we show that the variation of position of the hot spot created by the infalling matter, as observed in 3D simulations, can produce high frequency Quasi Periodic Oscillations with frequencies associated with the inner zone of the disk. Simulations show that the usual assumption of a fixed hot spot near the polar region is valid only for misalignment angles relatively large. Otherwise, two phenomena challenge the assumption: one is the presence of Rayleigh-Taylor instabilities at the disk-magnetospheric boundary (e.g. Kulkarni & Romanova 2008), which produce tongues of accreting matter that can reach the star almost anywhere between the equator and the polar region; the other one is the motion of the hot spot around the magnetic pole during stable accretion (e.g. R...

  5. Light and heavy metal abundances in hot central stars of planetary nebulae

    CERN Document Server

    Werner, K; Jahn, D; Rauch, T; Reiff, E; Traulsen, I; Kruk, J W; Dreizler, S

    2005-01-01

    We present new results from our spectral analyses of very hot central stars achieved since the last IAU Symposium on planetary nebulae held in Canberra 2001. The analyses are mainly based on UV and far-UV spectroscopy performed with the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer but also on ground-based observations performed at the Very Large Telescope and other observatories. We report on temperature, gravity, and abundance determinations for the CNO elements of hydrogen-rich central stars. In many hydrogen-deficient central stars (spectral type PG1159) we discovered particular neon and fluorine lines, which are observed for the very first time in any astrophysical object. Their analysis strongly confirms the idea that these stars exhibit intershell matter as a consequence of a late helium-shell flash.

  6. Oscillations of hot, young neutron stars: Gravitational wave frequencies and damping times

    CERN Document Server

    Burgio, G F; Gualtieri, L; Schulze, H J

    2011-01-01

    We study how the frequencies and damping times of oscillations of a newly born, hot proto-neutron star depend on the physical quantities which characterize the star quasi-stationary evolution which follows the bounce. Stellar configurations are modeled using a microscopic equation of state obtained within the Brueckner-Hartree-Fock, nuclear many-body approach, extended to the finite-temperature regime. We discuss the mode frequency behaviour as function of the lepton composition, and of the entropy gradients which prevail in the interior of the star. We find that, in the very early stages, gravitational wave emission efficiently competes with neutrino processes in dissipating the star mechanical energy residual of the gravitational collapse.

  7. A search for new hot subdwarfs stars by means of Virtual Observatory tools.

    Science.gov (United States)

    Solano, E.; Pérez-Fernández, E.; Ulla, A.; Oreiro, R.; Rodrigo, C.

    2017-03-01

    We present here a selection strategy to find new, uncatalogued hot subdwarfs making use of Virtual Observatory (VO) tools. We used large area catalogues (GALEX, SDSS, Super-Cosmos, 2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cut-off, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates, which represents an increase of 17% in the census of known hot subdwarfs. Visual inspection of the 68 candidates with SDSS specrum showed that 65 can be classified as hot subdwarfs: 5 sdOs, 25 sdOBs and 35 sdBs. This success rate above 95 per cent proves the robustness and efficiency of our methodology. Taking advantage of the VOSA capabilities, we built the Spectral Energy Distribution (SED) of our candidates. 45 per cent of the SEDs showed infrared excesses, a signature of their probable binary nature. The stellar companions of the binary systems so detected are expected to be late-type main sequence stars. A more detailed description of the methodology, the analysis and results can be found at Pérez-Fernández et al. (2016)

  8. On the Relation of Silicates and SiO Maser in Evolved Stars

    Science.gov (United States)

    Liu, Jiaming; Jiang, Biwei

    2017-04-01

    The SiO molecule is one of the candidates for the seed of silicate dust in the circumstellar envelope of evolved stars, but this opinion is challenged. In this work we investigate the relation of the SiO maser emission power and the silicate dust emission power. With both our own observation by using the PMO/Delingha 13.7 m telescope and archive data, a sample is assembled of 21 SiO v = 1, J = 2 - 1 sources and 28 SiO v = 1, J = 1 - 0 sources that exhibit silicate emission features in the ISO/SWS spectrum as well. The analysis of their SiO maser and silicate emission power indicates a clear correlation, which is not against the hypothesis that the SiO molecules are the seed nuclei of silicate dust. On the other hand, no correlation is found between SiO maser and silicate crystallinity, which may imply that silicate crystallinity does not correlate with mass-loss rate.

  9. All Known Hot RCB Stars Are Fading Fast Over the Last Century

    CERN Document Server

    Schaefer, Bradley E

    2016-01-01

    The R Coronae Borealis (RCB) stars are cool supergiants that display irregular and deep dips in their light curves, caused by dust formation. There are four known hot RCB stars (DY Cen, MV Sgr, V348 Sgr, and HV 2671), with surface temperatures of 15,000--25,000 K, and prior work has suggested that three of these have secular fading in brightness. I have tested this result by measuring century-long light curves in the Johnson B-band with modern comparison star magnitudes, and I have extended this by measuring many magnitudes over a wide time range as well as for the fourth hot RCB star. In all four cases, the B-band magnitude of the maximum light is now fast fading. The fading rates (in units of magnitudes per century) are 2.5 for DY Cen after 1960, 1.3 for MV Sgr, 1.3 for V348 Sgr, and 0.7 for HV 2671. This secular fading is caused by the expected evolution of the star across the top of the HR diagram at constant luminosity, as the temperature rises and the bolometric correction changes. For DY Cen, the brigh...

  10. First detections of 610 MHz radio emission from hot magnetic stars

    CERN Document Server

    Chandra, P; Sundqvist, J O; Oberoi, D; Grunhut, J H; ud-Doula, A; Petit, V; Cohen, D H; Oksala, M E; David-Uraz, A

    2015-01-01

    We have carried out a study of radio emission from a small sample of magnetic O- and B-type stars using the Giant Metrewave Radio Telescope, with the goal of investigating their magnetospheres at low frequencies. These are the lowest frequency radio measurements ever obtained of hot magnetic stars. The observations were taken at random rotational phases in the 1390 and the 610 MHz bands. Out of the 8 stars, we detect five B-type stars in both the 1390 and the 610 MHz bands. The O-type stars were observed only in the 1390 MHz band, and no detections were obtained. We explain this result as a consequence of free-free absorption by the free-flowing stellar wind exterior to the closed magnetosphere. We also study the variability of individual stars. One star - HD 133880 - exhibits remarkably strong and rapid variability of its low frequency flux density. We discuss the possibility of this emission being coherent emission as reported for CU Vir by Trigilio et al. (2000).

  11. Mechanical Equilibrium of Hot, Large-Scale Magnetic Loops on T Tauri Stars

    CERN Document Server

    Aarnio, Alicia; Jardine, Moira; Gregory, Scott G

    2011-01-01

    The most extended, closed magnetic loops inferred on T Tauri stars confine hot, X-ray emitting plasma at distances from the stellar surface beyond the the X-ray bright corona and closed large-scale field, distances comparable to the corotation radius. Mechanical equilibrium models have shown that dense condensations, or "slingshot prominences", can rise to great heights due to their density and temperatures cooler than their environs. On T Tauri stars, however, we detect plasma at temperatures hotter than the ambient coronal temperature. By previous model results, these loops should not reach the inferred heights of tens of stellar radii where they likely no longer have the support of the external field against magnetic tension. In this work, we consider the effects of a stellar wind and show that indeed, hot loops that are negatively buoyant can attain a mechanical equilibrium at heights above the typical extent of the closed corona and the corotation radius.

  12. The Magellanic zoo: Mid-infrared Spitzer spectroscopy of evolved stars and circumstellar dust in the Magellanic Clouds

    CERN Document Server

    Sloan, G C; Wood, P R; Zijlstra, A A; Bernard-Salas, J; Devost, D; Houck, J R

    2008-01-01

    We observed a sample of evolved stars in the Large and Small Magellanic Clouds (LMC and SMC) with the Infrared Spectrograph on the Spitzer Space Telescope. Comparing samples from the SMC, LMC, and the Galaxy reveals that the dust-production rate depends on metallicity for oxygen-rich stars, but carbon stars with similar pulsation properties produce similar quantities of dust, regardless of their initial metallicity. Other properties of the oxygen-rich stars also depend on metallicity. As the metallicity decreases, the fraction of naked (i.e. dust-free) stars increases, and among the naked stars, the strength of the 8 um absorption band from SiO decreases. Our sample includes several massive stars in the LMC with long pulsation periods which produce significant amounts of dust, probably because they are young and relatively metal rich. Little alumina dust is seen in circumstellar shells in the SMC and LMC, unlike in Galactic samples. Three oxygen-rich sources also show emission from magnesium-rich crystalline ...

  13. Kepler-6b: A transiting Hot Jupitere Orbiting a Metal-rich Star

    DEFF Research Database (Denmark)

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

    2010-01-01

    We announce the discovery of Kepler-6b, a transiting hot Jupiter orbiting a star with unusually high metallicity, . The planet's mass is about 2/3 that of Jupiter, M P = 0.67 M J, and the radius is 30% larger than that of Jupiter, R P = 1.32 R J, resulting in a density of ¿P = 0.35 g cm–3, a fairly...

  14. Nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection

    Directory of Open Access Journals (Sweden)

    Sonoi Takafumi

    2015-01-01

    Full Text Available We carry out nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection (TDC. We find that the instability of the modes excited at the Fe bump is weaker with TDC than with frozen-in convection (FC. But the instability still remains with TDC, and could be a possible candidate for the trigger of luminous blue variable (LBV phenomena.

  15. Non-LTE Line Formation in the Near-IR: Hot Stars

    CERN Document Server

    Przybilla, Norbert

    2010-01-01

    Line-formation calculations in the Rayleigh-Jeans tail of the spectral energy distribution are complicated by an amplification of non-LTE effects. For hot stars this can make quantitative modelling of spectral lines in the near-IR challenging. An introduction to the modelling problems is given and several examples in the context of near-IR line formation for hydrogen and helium are discussed.

  16. VizieR Online Data Catalog: Bolometric flux estimation for cool evolved stars (van Belle+, 2016)

    Science.gov (United States)

    van Belle, G. T.; Creech-Eakman, M. J.; Ruiz-Velasco, A. E.

    2016-09-01

    The target data come from 84 observations of 60 objects found in Dyck et al. (1974ApJ...189...89D), all of which are cool evolved stars at spectral types M4.0III and later. Two objects have measurements at four separate epochs, three objects have three epochs, and 11 have two epochs. These 60 objects include contemporaneous flux measurements in logFlambda (in W/cm/μm) across up to 12 bands from 0.55 to 10.2μm, along with epoch-specific spectral-type determinations for 70 of the 84 observations, and 34FBOL determinations. Broadband filters representing the V, J, H, K, L, M, and N passbands were used, along with narrowband filters at 0.78, 0.87, 0.88, 1.04, and 1.05μm. The data from Dyck et al. (1974ApJ...189...89D) were "obtained with the Kitt Peak National Observatory 0.9- and 1.3-meter telescopes during 1971 using three different photometric systems. Infrared observations at 1.25, 1.65, 2.2, and 3.4μ were made with a lead sulfide detector, while observations at 2.2, 3.4, 5.0, and 10.2μ employed a gallium-doped germanium bolometer. The broad-band filters used duplicated as far as possible the standard J, H, K, L, M, and N passbands. In the visible and near-infrared regions, data were obtained with an S-1 photomultiplier and various photometers using a broad-band filter combination at 0.55μ approximating the V passband, and narrow-band filters at 0.78, 0.87, 0.88, 1.04, and 1.05μ. The latter were chosen to isolate TiO and VO molecular bands and nearby relatively uncontaminated continuum regions in M stars so that photometric spectral types can be determined from the band strengths". For the purposes of this study, we have taken the data in Dyck et al. (1974ApJ...189...89D) and converted it into Janskys (Jy), which can be found in Table2. (2 data files).

  17. Close-in planets around giant stars. Lack of hot-Jupiters and prevalence of multi-planetary systems

    CERN Document Server

    Lillo-Box, J; Correia, A C M

    2016-01-01

    Extrasolar planets abound in almost any possible configuration. However, until five years ago, there was a lack of planets orbiting closer than 0.5 au to giant or subgiant stars. Since then, recent detections have started to populated this regime by confirming 13 planetary systems. We discuss the properties of these systems in terms of their formation and evolution off the main sequence. Interestingly, we find that $70.0\\pm6.6$ % of the planets in this regime are inner components of multiplanetary systems. This value is 4.2$\\sigma$ higher than for main-sequence hosts, which we find to be $42.4\\pm0.1$ %. The properties of the known planets seem to indicate that the closest-in planets (a < 0.06 au) to main-sequence stars are massive (i.e., hot Jupiters) and isolated and that they are subsequently engulfed by their host as it evolves to the red giant branch, leaving only the predominant population of multiplanetary systems in orbits 0.06 < a < 0.5 au. We discuss the implications of this emerging observa...

  18. A search for new hot subdwarf stars by means of Virtual Observatory tools II

    CERN Document Server

    Pérez-Fernández, Esther; Solano, Enrique; Oreiro, Raquel; Rodrigo, Carlos

    2016-01-01

    Recent massive sky surveys in different bandwidths are providing new opportunities to modern astronomy. The Virtual Observatory (VO) represents the adequate framework to handle the huge amount of information available and filter out data according to specific requirements. In this work, we applied a selection strategy to find new, uncatalogued hot subdwarfs making use of VO tools. We used large area catalogues (GALEX, SDSS, SuperCosmos, 2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cutoff, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates. Based on previous results, we expect our procedure to have an overall efficiency of at least 80 per cent. Visual inspection of the 68 candidates with SDSS spectrum showed that 65 can be classif...

  19. The infrared spectral features of circumstellar envelope of evolved low-and intermediate-mass stars

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ke; JIANG BiWei

    2008-01-01

    The circumstellar envelope of evolved stars of low-and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib-uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

  20. The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib- uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

  1. Hot Subdwarf Stars Observed in LAMOST DR1 - Atmospheric parameters from single-lined spectra

    CERN Document Server

    Luo, Yangping; Liu, Chao; Deng, Licai; Han, Zhanwen

    2016-01-01

    We present a catalog of 166 spectroscopically identified hot subdwarf stars from LAMOST DR1, 44 of which show the characteristics of cool companions in their optical spectra. Atmospheric parameters of 122 non-composite spectra subdwarf stars were measured by fitting the profiles of hydrogen (H) and helium (He) lines with synthetic spectra from non-LTE model atmospheres. Most of the sdB stars scatter near the Extreme Horizontal Branch in the $T_{\\rm eff}-\\log{g}$ diagram and two well defined groups can be outlined. A clustering of He-enriched sdO stars appears near $T_{\\rm eff}=45\\,000$ K and $\\log(g) = 5.8$. The sdB population separates into several nearly parallel sequences in the $T_{\\rm eff}-{\\rm He}$ abundance diagram with clumps corresponding to those in the $T_{\\rm eff}-\\log{g}$ diagram. Over $38\\,000$ K (sdO) stars show abundance extremes, they are either He-rich or He-deficient and we observe only a few stars in the $ -1 < \\log(y) < 0$ abundance range. With increasing temperature these extremes ...

  2. WASP-41b: A Transiting Hot Jupiter Planet Orbiting a Magnetically Active G8V Star

    Science.gov (United States)

    Maxted, P. F. L.; Anderson, D. R.; Collier Cameron, A.; Hellier, C.; Queloz, D.; Smalley, B.; Street, R. A.; Triaud, A. H. M. J.; West, R. G.; Gillon, M.; Lister, T. A.; Pepe, F.; Pollacco, D.; Ségransan, D.; Smith, A. M. S.; Udry, S.

    2011-05-01

    We report the discovery of a transiting planet with an orbital period of 3.05 days orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8 V star (V = 11.6) with a metallicity close to solar ([Fe/H] = -0.08 ± 0.09). The star shows evidence of moderate chromospheric activity, both from emission in the cores of the Ca ii H and K ines and photometric variability with a period of 18.4 days and an amplitude of about 1%. We use a new method to show quantitatively that this periodic signal has a low false-alarm probability. The rotation period of the star implies a gyrochronological age for WASP-41 of 1.8 Gyr with an error of about 15%. We have used a combined analysis of the available photometric and spectroscopic data to derive the mass and radius of the planet (0.92 ± 0.06 MJup, 1.20 ± 0.06 RJup). Further observations of WASP-41 can be used to explore the connections between the properties of hot Jupiter planets and the level of chromospheric activity in their host stars.

  3. Stability Analysis of Strange-Modes in Hot Massive Stars with Time-Dependent Convection

    CERN Document Server

    Sonoi, Takafumi

    2014-01-01

    We carry out a nonadiabatic analysis of strange-modes in hot massive stars with time-dependent convection (TDC). In envelopes of such stars, convective luminosity is not so dominant as that in envelopes of stars in the redder side of the classical instability strip. Around the Fe opacity bump, however, convection non-negligibly contributes to energy transfer. Indeed, instability of modes excited at the Fe bump is likely to be suppressed with TDC compared with the case of adopting the frozen-in convection approximation. But we make sure that unstable strange-modes certainly appear in hot massive stars even by taking into account TDC. We also examine properties of the strange-mode instability, which is related to destabilization of strange-modes without adiabatic counterparts. In this type of instability, the phase lag between density and pressure varies from 0 to $180^{\\circ}$ in an excitation zone unlike the case of the $\\kappa$-mechanism. In addition, we confirm by comparing models with $Z=0$ and $Z=0.02$ th...

  4. Herschel/PACS observations of the 69 μm band of crystalline olivine around evolved stars

    NARCIS (Netherlands)

    Blommaert, J.A.D.L.; de Vries, B.L.; Waters, L.B.F.M.; Waelkens, C.; Min, M.; Van Winckel, H.; Molster, F.; Decin, L.; Groenewegen, M.A.T.; Barlow, M.; García-Lario, P.; Kerschbaum, F.; Posch, T.; Royer, P.; Ueta, T.; Vandenbussche, B.; Van de Steene, G.; van Hoof, P.

    2014-01-01

    Context. We present 48 Herschel/PACS spectra of evolved stars in the wavelength range of 67−72 μm. This wavelength range covers the 69 μm band of crystalline olivine (Mg2−2xFe(2x)SiO4). The width and wavelength position of this band are sensitive to the temperature and composition of the crystalline

  5. The carrier of the "30" micron emission feature in evolved stars. A simple model using magnesium sulfide

    CERN Document Server

    Hony, S; Tielens, A G G M

    2002-01-01

    We present 2-45 micron spectra of a large sample of carbon-rich evolved stars in order to study the ``30'' micron feature. We find the ``30'' micron feature in sources in a wide range of sources: low mass loss carbon stars, extreme carbon-stars, post-AGB objects and planetary nebulae. We extract the profiles from the sources by using a simple systematic approach to model the continuum. We find large variations in the wavelength and width of the extracted profiles of the ``30'' micron feature. We modelled the whole range of profiles in a simple way by using magnesium sulfide (MgS) dust grains with a MgS grain temperature different from the continuum temperature. The systematic change in peak positions can be explained by cooling of MgS grains as the star evolves off the AGB. In several sources we find that a residual emission excess at ~26 micron can also be fitted using MgS grains but with a different grains shape distribution. The profiles of the ``30'' micron feature in planetary nebulae are narrower than o...

  6. Rings and arcs around evolved stars - I. Fingerprints of the last gasps in the formation process of planetary nebulae

    Science.gov (United States)

    Ramos-Larios, G.; Santamaría, E.; Guerrero, M. A.; Marquez-Lugo, R. A.; Sabin, L.; Toalá, J. A.

    2016-10-01

    Evolved stars such as asymptotic giant branch stars (AGB), post-AGB stars, proto-planetary nebulae (proto-PNe), and planetary nebulae (PNe) show rings and arcs around them and their nebular shells. We have searched for these morphological features in optical Hubble Space Telescope and mid-infrared Spitzer Space Telescope images of ˜650 proto-PNe and PNe and discovered them in 29 new sources. Adding those to previous detections, we derive a frequency of occurrence ≃8 per cent. All images have been processed to remove the underlying envelope emission and enhance outer faint structures to investigate the spacing between rings and arcs and their number. The averaged time lapse between consecutive rings and arcs is estimated to be in the range 500-1200 yr. The spacing between them is found to be basically constant for each source, suggesting that the mechanism responsible for the formation of these structures in the final stages of evolved stars is stable during time periods of the order of the total duration of the ejection. In our sample, this period of time spans ≤4500 yr.

  7. Collisions of Free Floating Planets with Evolved Stars in Globular Clusters

    CERN Document Server

    Soker, N; Fregeau, J M; Soker, Noam; Rappaport, Saul; Fregeau, John

    2001-01-01

    We estimate the rate of collisions between stars and free-floating planets (FFPs) in globular clusters, in particular the collision of FFPs with red giant branch (RGB) stars. Recent dynamical simulations imply that the density of such objects could exceed million per cubic parsec near the cores of rich globular clusters. We show that in these clusters 5-10 per cents of all RGB stars near the core would suffer a collision with a FFP, and that such a collision can spin up the RGB star's envelope by an order of magnitude. In turn, the higher rotation rates may lead to enhanced mass-loss rates on the RGB, which could result in bluer horizontal branch (HB) stars. Hence, it is plausible that the presence of a large population of FFPs in a globular cluster can influence the distribution of stars on the HB of that cluster to a detectable degree.

  8. Self-Similar Hot Accretion Flow onto a Rotating Neutron Star Structure and Stability

    CERN Document Server

    Medvedev, M V; Medvedev, Mikhail; Narayan, Ramesh

    2001-01-01

    We present analytical and numerical solutions which describe a hot, viscous, two-temperature accretion flow onto a rotating neutron star or any other rotating compact star with a surface. We assume Coulomb coupling between the protons and electrons, and free-free cooling from the electrons. Outside a thin boundary layer, where the accretion flow meets the star, we show that there is an extended settling region which is well-described by two self-similar solutions: (i) a two-temperature solution which is valid in an inner zone $r\\le10^{2.5}$ ($r$ is in Schwarzchild units), and (ii) a one-temperature solution at larger radii. In both zones, $\\rho\\propto r^{-2}, \\Omega\\propto r^{-3/2}, v\\propto r^0, T_p\\propto r^{-1}$; in the two-temperature zone, $T_e\\propto r^{-1/2}$. The luminosity of the settling zone arises from the rotational energy of the star as the star is braked by viscosity. Hence the luminosity and the flow parameters (density, temperature, angular velocity) are independent of $\\dot M$. The settling ...

  9. A hot Jupiter around the very active weak-line T Tauri star TAP 26

    Science.gov (United States)

    Yu, L.; Donati, J.-F.; Hébrard, E. M.; Moutou, C.; Malo, L.; Grankin, K.; Hussain, G.; Collier Cameron, A.; Vidotto, A. A.; Baruteau, C.; Alencar, S. H. P.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G.; Gregory, S. G.; Jardine, M.; Morin, J.; Ménard, F.; Matysse Collaboration

    2017-05-01

    We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the Magnetic Topologies of Young Stars and the Survival of close-in massive Exoplanets (MaTYSSE) programme with the Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) spectropolarimeter at the 3.6-m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging (ZDI) to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using ZDI and one Gaussian-process regression (GPR), with a false-alarm probability smaller than 6 × 10-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79 ± 0.14 d followed by 8.99 ± 0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass Msin i of 1.66 ± 0.31 MJup and orbits at 0.0968 ± 0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).

  10. New binaries among UV-selected, hot subdwarf stars and population properties

    CERN Document Server

    Kawka, A; O'Toole, S; Nemeth, P; Burton, D; Kotze, E; Buckley, D A H

    2015-01-01

    We have measured the orbital parameters of seven close binaries, including six new objects, in a radial velocity survey of 38 objects comprising a hot subdwarf star with orbital periods ranging from ~0.17 to 3 d. One new system, GALEX J2205-3141, shows reflection on a M dwarf companion. Three other objects show significant short-period variations, but their orbital parameters could not be constrained. Two systems comprising a hot subdwarf paired with a bright main-sequence/giant companion display short-period photometric variations possibly due to irradiation or stellar activity and are also short-period candidates. All except two candidates were drawn from a selection of subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our new identifications also include a low-mass subdwarf B star and likely progenitor of a low mass white dwarf (GALEX J0805-1058) paired with an unseen, possibly substellar, companion. The mass functions of the newly identified binaries imply minimum secondary masses...

  11. Oxygen isotope systematics in an evolving geothermal system: Coso Hot Springs, California

    Science.gov (United States)

    Etzel, Thomas M.; Bowman, John R.; Moore, Joseph N.; Valley, John W.; Spicuzza, Michael J.; McCulloch, Jesse M.

    2017-01-01

    Oxygen isotope and clay mineralogy studies have been made on whole rock samples and feldspar separates from three wells along the high temperature West Flank of the Coso geothermal system, California. The reservoir rocks have experienced variable 18O/16O depletion, with δ18O values ranging from primary values of + 7.5‰ down to - 4.6‰. Spatial patterns of clay mineral distributions in the three wells are not closely correlated with the distributions expected from measured, pre-production temperature profiles, but do correlate with spatial patterns of 18O/16O depletion, indicating that the stability of clay minerals in the three wells is a function of fluid-rock interaction in addition to temperature. Detailed δ18O measurements in the three wells identify a limited number of localized intervals of extensive 18O/16O depletion. These intervals document localized zones of higher permeability in the geothermal system that have experienced significant fluid infiltration, water-rock interaction and oxygen isotopic exchange with the geothermal fluids. The local zones of maximum 18O/16O depletion in each well correspond closely with current hot water production zones. Most feldspar separates have measured δ18O values too high to have completely attained oxygen isotope exchange equilibrium with the reservoir fluid at pre-production temperatures. In general, the lower the δ18O value of the feldspar, the closer the feldspar approaches exchange equilibrium with the geothermal fluid. This correlation suggests that fracture-induced increases in permeability increase both fluid infiltration and the surface area of the host rock exposed to geothermal fluid, promoting fluid-rock interaction and oxygen isotope exchange. The two most 18O/16O-depleted feldspar samples have δ18O values too low to be in exchange equilibrium with the pre-production reservoir fluid at pre-production temperatures. These discrepancies suggest that the reservoir fluid in the West Flank of the Coso

  12. B field in OB stars (BOB): The outstandingly strong magnetic field in the evolved He-strong star CPD -62° 2124

    Science.gov (United States)

    Castro, N.; Fossati, L.; Hubrig, S.; Järvinen, S. P.; Przybilla, N.; Nieva, M.-F.; Ilyin, I.; Carroll, T. A.; Schöller, M.; Langer, N.; Schneider, F. R. N.; Simón-Díaz, S.; Morel, T.; Butler, K.; BOB Collaboration

    2017-01-01

    The origin and evolution of magnetism in OB stars is far from being well understood. With approximately 70 magnetic OB stars known, any new object with unusual characteristics may turn out to be a key piece of the puzzle. We report the detection of an exceptionally strong magnetic field in the He-strong B2IV star CPD -62° 2124. Spectropolarimetric FORS2 and HARPSpol observations were analysed by two independent teams and procedures, concluding on a strong longitudinal magnetic field of approximately 5.2 kG. The quantitative characterisation of the stellar atmosphere yields an effective temperature of 23 650 ± 250 K, a surface gravity of 3.95 ± 0.10 dex and a surface helium fraction of 0.35 ± 0.02 by number. The metal composition is in agreement with the cosmic abundance standard, except for Mg, Si and S, which are slightly non-solar. The strong and broad ( 300 km s-1) disc-like emission displayed by the Hα line suggests a centrifugal magnetosphere supported by the strong magnetic field. Our results imply that CPD -62° 2124 is an early B-type star hosting one of the strongest magnetic fields discovered to date, and one of the most evolved He-strong stars known, with a fractional main-sequence lifetime of approximately 0.6. Based on observations made with ESO telescopes at the La Silla and Paranal observatories under programme ID 191.D-0255(G,I).

  13. HOT STAR

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    01孔垂楠×黄礼格独家棚拍花絮曝光孔垂楠×黄礼格棚拍花絮照抢先看|《类似爱情》系列剧主演孔垂楠与黄礼格近日做客Easy杂志拍摄大片,男友力爆发。02话题度及人气始终直线UP的陈伟霆近日与Easy独家对话,谈及他的“2015女皇派对”生日会与多部将于明年上映的影片。

  14. HOT STAR

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    01陈伟霆独家棚拍花絮曝光陈伟霆独家专访棚拍花絮照抢先看|陈伟霆近日接受了Easy的独家专访并拍摄大片,时而可爱卖萌,时而性感无比,各种造型毫无压力。

  15. Bipolar rings from jet-inflated bubbles around evolved binary stars

    CERN Document Server

    Akashi, Muhammad

    2016-01-01

    We show that a fast wind that expands into a bipolar nebula composed of two opposite jet-inflated bubbles can form a pair of bipolar rings around giant stars. Our model assumes three mass loss episodes: a spherical slow and dense shell, two opposite jets, and a spherical fast wind. We use the FLASH hydrodynamical code in three-dimensions to simulate the flow, and obtain the structure of the nebula. We assume that the jets are launched from an accretion disk around a stellar companion to the giant star. The accretion disk is assumed to be formed when the primary giant star and the secondary star suffer a strong interaction accompanied by a rapid mass transfer process from the primary to the secondary star, mainly a main sequence star. Later in the evolution the primary star is assumed to shrink and blow a fast tenuous wind that interacts with the dense gas on the surface of the bipolar structure. We assume that the dense mass loss episode before the jets are launched is spherically symmetric. Our results might...

  16. The Mass Loss Return from Evolved Stars to the Large Magellanic Cloud : Oxygen-Rich Asymptotic Giant Branch Stars

    NARCIS (Netherlands)

    Sargent, Benjamin A.; Srinivasan, S.; Meixner, M.; Kemper, F.; Tielens, X.; Speck, A.; Matsuura, M.; Bernard, J.; Hony, S.; Gordon, K.; Indebetouw, R.; Marengo, M.; Sloan, G.; Woods, P.; Vijh, U. P.

    2010-01-01

    The Spitzer Space Telescope Legacy program Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) has observed over 6 million stars in the Large Magellanic Cloud with both the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments to explore the lif

  17. The Mass Loss Return from Evolved Stars to the Large Magellanic Cloud: Oxygen-Rich Asymptotic Giant Branch Stars

    NARCIS (Netherlands)

    Sargent, Benjamin A.; Srinivasan, S.; Meixner, M.; Kemper, F.; Tielens, X.; Speck, A.; Matsuura, M.; Bernard, J.; Hony, S.; Gordon, K.; Indebetouw, R.; Marengo, M.; Sloan, G.; Woods, P.; Vijh, U. P.

    2010-01-01

    The Spitzer Space Telescope Legacy program Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) has observed over 6 million stars in the Large Magellanic Cloud with both the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments to explore the lif

  18. WASP-135b: a highly irradiated, inflated hot Jupiter orbiting a G5V star

    CERN Document Server

    Spake, Jessica J; Doyle, Amanda P; Hébrard, Guillaume; McCormac, James; Armstrong, David J; Pollacco, Don; Chew, Yilen Gómez Maqueo; Anderson, David R; Barros, Susana C C; Bouchy, François; Boumis, Panayotis; Bruno, Giovanni; Cameron, Andrew Collier; Courcol, Bastien; Davies, Guy R; Faedi, Francesca; Hellier, Coel; Kirk, James; Lam, Kristine W F; Liakos, Alexios; Louden, Tom; Maxted, Pierre F L; Osborn, Hugh P; Palle, Enric; Arranz, Jorge Prieto; Udry, Stéphane; Walker, Simon R; West, Richard G; Wheatley, Peter J

    2015-01-01

    We report the discovery of a new transiting planet from the WASP survey. WASP-135b is a hot Jupiter with a radius of 1.30 pm 0.09 Rjup, a mass of 1.90 pm 0.08 Mjup and an orbital period of 1.401 days. Its host is a Sun-like star, with a G5 spectral type and a mass and radius of 0.98 pm 0.06 Msun and 0.96 pm 0.05 Rsun respectively. The proximity of the planet to its host means that WASP-135b receives high levels of insolation, which may be the cause of its inflated radius. Additionally, we find weak evidence of a transfer of angular momentum from the planet to its star.

  19. Temperature Scale and Iron Abundances of Very Hot Central Stars of Planetary Nebulae

    CERN Document Server

    Werner, K; Dreizler, S; Rauch, T; Kruk, J W

    2002-01-01

    The determination of effective temperatures of very hot central stars (Teff>70000K) by model atmosphere analyses of optical H and He line profiles is afflicted with considerable uncertainty, primarily due to the lack of neutral helium lines. Ionization balances of metals, accessible only with UV lines, allow more precise temperature estimates. The potential of iron lines is pointed out. At the same time iron and other metal abundances, hardly investigated until today, may be derived from UV spectra. We describe recent HST spectroscopy performed for this purpose. A search for iron lines in FUV spectra of the hottest H-deficient central stars (PG1159-type, Teff>100000K) taken with FUSE was unsuccessful. The derived deficiency is interpreted in terms of iron depletion due to n-capture nucleosynthesis in intershell matter, which is now exposed at the stellar surface as a consequence of a late He shell flash.

  20. Hot third family of compact stars and the possibility of core-collapse supernova explosions

    Science.gov (United States)

    Hempel, Matthias; Heinimann, Oliver; Yudin, Andrey; Iosilevskiy, Igor; Liebendörfer, Matthias; Thielemann, Friedrich-Karl

    2016-11-01

    A phase transition to quark matter can lead to interesting phenomenological consequences in core-collapse supernovae, e.g., triggering an explosion in spherically symmetric models. However, until now, this explosion mechanism was only shown to be working for equations of state that are in contradiction with recent pulsar mass measurements. Here, we identify that this explosion mechanism is related to the existence of a third family of compact stars. For the equations of state investigated, the third family is only pronounced in the hot, early stages of the protocompact star and absent or negligibly small at zero temperature and thus represents a novel kind of third family. This interesting behavior is a result of unusual thermal properties induced by the phase transition, e.g., characterized by a decrease of temperature with increasing density for isentropes, and can be related to a negative slope of the phase transition line in the temperature-pressure phase diagram.

  1. A hydrodynamic scheme for two-component winds from hot stars

    CERN Document Server

    Votruba, V; Kubát, J; Rätzel, D

    2007-01-01

    We have developed a time-dependent two-component hydrodynamics code to simulate radiatively-driven stellar winds from hot stars. We use a time-explicit van Leer scheme to solve the hydrodynamic equations of a two-component stellar wind. Dynamical friction due to Coulomb collisions between the passive bulk plasma and the line-scattering ions is treated by a time-implicit, semi-analytic method using a polynomial fit to the Chandrasekhar function. This gives stable results despite the stiffness of the problem. This method was applied to model stars with winds that are both poorly and well-coupled. While for the former case we reproduce the mCAK solution, for the latter case our solution leads to wind decoupling.

  2. Kepler-14b: A massive hot Jupiter transiting an F star in a close visual binary

    CERN Document Server

    Buchhave, Lars A; Carter, Joshua A; Désert, Jean-Michel; Torres, Guillermo; Adams, Elisabeth R; Bryson, Stephen T; Charbonneau, David B; Ciardi, David R; Kulesa, Craig; Dupree, Andrea K; Fischer, Debra A; Fressin, François; Gautier, Thomas N; Gilliland, Ronald L; Howel, Steve B; Isaacson, Howard; Jenkins, Jon M; Marcy, Geoffrey W; McCarthy, Donald W; Rowe, Jason F; Batalha, Natalie M; Borucki, William J; Brown, Timothy M; Caldwell, Douglas A; Christiansen, Jessie L; Cochran, William D; Deming, Drake; Dunham, Edward W; Everett, Mark; Ford, Eric B; Fortney, Jonathan J; Geary, John C; Girouard, Forrest R; Haas, Michael R; Holman, Matthew J; Horch, Elliott; Klaus, Todd C; Knutson, Heather A; Koch, David G; Kolodziejczak, Jeffrey; Lissauer, Jack J; Machalek, Pavel; Mullally, Fergal; Still, Martin D; Quinn, Samuel N; Seager, Sara; Thompson, Susan E; Van Cleve, Jeffrey

    2011-01-01

    We present the discovery of a hot Jupiter transiting an F star in a close visual (0.3" sky projected angular separation) binary system. The dilution of the host star's light by the nearly equal magnitude stellar companion (~ 0.5 magnitudes fainter) significantly affects the derived planetary parameters, and if left uncorrected, leads to an underestimate of the radius and mass of the planet by 10% and 60%, respectively. Other published exoplanets, which have not been observed with high-resolution imaging, could similarly have unresolved stellar companions and thus have incorrectly derived planetary parameters. Kepler-14b (KOI-98) has a period of P = 6.790 days and correcting for the dilution, has a mass of Mp = 8.40 +0.19-0.18 MJ and a radius of Rp = 1.136 +0.073-0.054 RJ, yielding a mean density of rho = 7.1 +- 1.1 g cm-3.

  3. A search for new hot subdwarf stars by means of virtual observatory tools II

    Science.gov (United States)

    Pérez-Fernández, E.; Ulla, A.; Solano, E.; Oreiro, R.; Rodrigo, C.

    2016-04-01

    Recent massive sky surveys in different bandwidths are providing new opportunities to modern astronomy. The Virtual Observatory (VO) represents the adequate framework to handle the huge amount of information available and filter out data according to specific requirements. In this work, we applied a selection strategy to find new, uncatalogued hot subdwarfs making use of VO tools. We used large area catalogues like GALEX, Sloan Digital Sky Survey (SDSS), SuperCosmos and Two Micron All Sky Survey (2MASS) to retrieve photometric and astrometric information of stellar objects. To these objects, we applied colour and proper motion filters, together with an effective temperature cutoff, aimed at separating hot subdwarfs from other blue objects such as white dwarfs, cataclysmic variables or main-sequence OB stars. As a result, we obtained 437 new, uncatalogued hot subdwarf candidates. Based on previous results, we expect our procedure to have an overall efficiency of at least 80 per cent. Visual inspection of the 68 candidates with SDSS spectrum showed that 65 can be classified as hot subdwarfs: 5 sdOs, 25 sdOBs and 35 sdBs. This success rate above 95 per cent proves the robustness and efficiency of our methodology. The spectral energy distribution of 45 per cent of the subdwarf candidates showed infrared excesses, a signature of their probable binary nature. The stellar companions of the binary systems so detected are expected to be late-type main-sequence stars. A detailed determination of temperatures and spectral classification of the cool companions will be presented in a forthcoming work.

  4. The VLT-FLAMES Tarantula Survey - XI. A census of the hot luminous stars and their feedback in 30 Doradus

    CERN Document Server

    Doran, E I; de Koter, A; Evans, C J; McEvoy, C; Walborn, N R; Bastian, N; Bestenlehner, J M; Grafener, G; Herrero, A; Kohler, K; Apellaniz, J Maiz; Najarro, F; Puls, J; Sana, H; Schneider, F R N; Taylor, W D; van Loon, J Th; Vink, J S

    2013-01-01

    We compile the first comprehensive census of hot luminous stars in the 30 Doradus (30 Dor) star forming region of the LMC. The census extends to a radius of 10arcmin (150pc) from the central cluster, R136. Stars were selected photometrically and combined with the latest spectral types. 1145 candidate hot luminous stars were identified of which >700 were considered genuine early type stars that contribute to feedback. We assess the spectroscopic completeness to be 85% in outer regions (>5pc) but fall to 35% in the vicinity of R136, giving a total of 500 hot luminous stars with spectroscopy. Stellar calibrations and models were used to obtain their physical parameters before integrated values were compared to global observations and the population synthesis code, Starburst99. The 31 W-R and Of/WN stars made large contributions to the total ionising and wind luminosities of ~40% and ~50%, respectively. Stars with Minit>100Msun also showed high contributions to the global feedback, ~25% in both cases. Such massiv...

  5. The iron abundance in hot central stars of planetary nebulae derived from IUE spectra

    CERN Document Server

    Deetjen, J L; Rauch, T; Werner, K

    1999-01-01

    We present the first attempt to determine the iron abundance in hot central stars of planetary nebulae. We perform an analysis with fully metal-line blanketed NLTE model atmospheres for a sample of ten stars (T_eff >= 70.000 K) for which high-resolution UV spectra are available from the IUE archive. In all cases lines of Fe VI or Fe VII can be identified. As a general trend, the iron abundance appears to be subsolar by 0.5-1 dex, however, the S/N of the IUE spectra is not sufficient to exclude a solar abundance in any specific case. Improved spectroscopy by either FUSE or HST is necessary to verify the possibility of a general iron deficiency in central stars. The suspected deficiency may be the result of gravitational settling in the case of three high-gravity objects. For the other stars with low gravity and high luminosity dust fractionation during the previous AGB phase is a conceivable origin.

  6. A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters

    CERN Document Server

    Németh, Péter; Vennes, Stéphane

    2012-01-01

    We present an update of our low-resolution spectroscopic follow-up and model atmosphere analysis of hot subdwarf stars from the Galaxy Evolution Explorer (GALEX) survey. Targets were selected on the basis of colour indices calculated from the GALEX GR6 N_UV, Guide Star Catalogue (GSC2.3.2) V and the Two Micron All Sky Survey (2MASS) J and H photometry. High signal-to-noise ratio spectra were obtained at the European Southern Observatory (ESO) and the Kitt Peak National Observatory (KPNO) over the course of three years. Detailed H, He and CNO abundance analysis helped us improve our T_eff, log g and He abundance determination and to constrain CNO abundances. We processed 191 observations of 180 targets and found 124 sdB and 42 sdO stars in this sample while some blue horizontal branch stars were also found in this programme. With quantitative binary decomposition of 29 composite spectra we investigated the incidence of A, F and G type companions. The incidence of late G and K type companions and their effects ...

  7. The Unseen Population of F to K-type Companions to Hot Subdwarf Stars

    CERN Document Server

    Girven, J; Heber, U; Gänsicke, B T; Marsh, T R; Breedt, E; Copperwheat, C M; Pyrzas, S; Peña, P Longa

    2012-01-01

    We present a method to select hot subdwarf stars with A to M-type companions using photometric selection criteria. We cover a wide range in wavelength by combining GALEX ultraviolet data, optical photometry from the SDSS and the Carlsberg Meridian telescope, near-infrared data from 2MASS and UKIDSS. We construct two complimentary samples, one by matching GALEX, CMC and 2MASS, as well as a smaller, but deeper, sample using GALEX, SDSS and UKIDSS. In both cases, a large number of composite subdwarf plus main-sequence star candidates were found. We fit their spectral energy distributions with a composite model in order to estimate the subdwarf and companion star effective temperatures along with the distance to each system. The distribution of subdwarf effective temperature was found to primarily lie in the 20,000 - 30,000 K regime, but we also find cooler subdwarf candidates, making up ~5-10 per cent. The most prevalent companion spectral types were seen to be main-sequence stars between F0 and K0, while subdwa...

  8. The far-ultraviolet spectra of two hot PG1159 stars

    CERN Document Server

    Werner, K; Kruk, J W

    2016-01-01

    PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85,000-140,000 K). Here we report on the results for two even hotter stars (PG1520+525 and PG1144+005, both with Teff = 150,000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the a...

  9. Properties of Hot Stars in the Wolf-Rayet galaxy NGC5253 from ISO Spectroscopy

    CERN Document Server

    Crowther, P A; Willis, A J; Conti, P S; Morris, P W; Sutherland, R S; Crowther, Paul A.; Willis, Allan J.; Conti, Peter S.; Morris, Pat W.; Sutherland, Ralph S.

    1998-01-01

    ISO-SWS spectroscopy of the WR galaxy NGC5253 is presented, and analysed to provide estimates of its hot young star population. Our approach differs from previous investigations in that we are able to distinguish between the regions in which different infrared fine-structure lines form, using complementary ground-based observations. The high excitation nebular [SIV] emission is formed in a very compact region, which we attribute to the central super-star-nucleus, and lower excitation [NeII] nebular emission originates in the galactic core. We use photo-ionization modelling coupled with the latest theoretical O-star flux distributions to derive effective stellar temperatures and ionization parameters of Teff>38kK, logQ=8.25 for the compact nucleus, with Teff=35kK, logQ<8 for the larger core. Results are supported by more sophisticated calculations using evolutionary synthesis models. We assess the contribution that Wolf-Rayet stars may make to highly ionized nebular lines (e.g. [OIV]). From our Br(alpha) fl...

  10. Low resolution spectroscopy of hot post-AGB candidates II. LS, LSS, LSE stars and additional IRAS sources

    CERN Document Server

    Parthasarathy, M; Vijapurkar, J; Takeda, Y

    2011-01-01

    Hot (OB) post-AGB stars are immediate progenitors of planetary nebulae (PNe). Very few hot post-AGB stars are known. Detecting new hot post-AGB candidates and follow-up multiwavelength studies will enable us to further understand the processes during the post-AGB evolution that lead to the formation of PNe. Case-Hamburg OB star surveys and their extension (LS, LSS, and LSE catalogues) and IRAS (point source) catalogues are good sources for detecting new hot post-AGB candidates from low resolution spectroscopy. Spectral types are determined from low resolution optical spectra of 44 stars selected from the LS, LSS, and LSE catalogues. Unlike the stars in the first paper, the stars in this paper were selected using criteria other than positional coincidence with an IRAS source with far IR (IRAS) colours similar to post-AGB supergiants and planetary nebulae. These included high galactic latitude, spectral types of O, B, A supergiants, emission lines in the spectrum and known spectral peculiarity. From the present...

  11. Magnetic Fields in Evolved Stars: Imaging the Polarized Emission of High-Frequency SiO Masers

    CERN Document Server

    Vlemmings, W H T; Franco-Hernández, R

    2011-01-01

    We present Submillimeter Array observations of high frequency SiO masers around the supergiant VX Sgr and the semi-regular variable star W Hya. The J=5-4, v=1 28SiO and v=0 29SiO masers of VX Sgr are shown to be highly linearly polarized with a polarization from ~5-60%. Assuming the continuum emission peaks at the stellar position, the masers are found within ~60 mas of the star, corresponding to ~100 AU at a distance of 1.57 kpc. The linear polarization vectors are consistent with a large scale magnetic field, with position and inclination angles similar to that of the dipole magnetic field inferred in the H2O and OH maser regions at much larger distances from the star. We thus show for the first time that the magnetic field structure in a circumstellar envelope can remain stable from a few stellar radii out to ~1400 AU. This provides further evidence supporting the existence of large scale and dynamically important magnetic fields around evolved stars. Due to a lack of parallactic angle coverage, the linear...

  12. WASP-32b: A Transiting Hot Jupiter Planet Orbiting a Lithium-Poor, Solar-Type Star

    Science.gov (United States)

    Maxted, P. F. L.; Anderson, D. R.; Collier Cameron, A.; Gillon, M.; Hellier, C.; Queloz, D.; Smalley, B.; Triaud, A. H. M. J.; West, R. G.; Enoch, R.; Lister, T. A.; Pepe, F.; Pollacco, D. L.; Ségransan, D.; Skillen, I.; Udry, S.

    2010-12-01

    We report the discovery of a transiting planet orbiting the star TYC 2-1155-1. The star, WASP-32, is a moderately bright (V = 11.3) solar-type star (Teff = 6100 ± 100 K, [Fe/H] = -0.13 ± 0.10). The light curve of the star obtained with the WASP-South and WASP-North instruments shows periodic transitlike features with a depth of about 1% and a duration of 0.10 day every 2.72 days. The presence of a transitlike feature in the light curve is confirmed using z -band photometry obtained with Faulkes Telescope North. High-resolution spectroscopy obtained with the Coralie spectrograph confirms the presence of a planetary mass companion. From a combined analysis of the spectroscopic and photometric data, assuming that the star is a typical main-sequence star, we estimate that the planet has a mass Mp of 3.60 ± 0.07 MJup and a radius Rp = 1.19 ± 0.06 RJup. WASP-32 is one of a small group of hot Jupiters with masses greater than 3 MJup. We find that some stars with hot Jupiter companions and with masses M⋆ ≈ 1.2 M⊙, including WASP-32, are depleted in lithium and that the majority of these stars have lithium abundances similar to field stars.

  13. A bimodal correlation between host star chromospheric emission and the surface gravity of hot Jupiters

    CERN Document Server

    Fossati, L; Lanza, A F

    2015-01-01

    The chromospheric activity index logR'HK of stars hosting transiting hot Jupiters appears to be correlated with the planets' surface gravity. One of the possible explanations is based on the presence of condensations of planetary evaporated material located in a circumstellar cloud that absorbs the CaII H&K and MgII h&k resonance line emission flux, used to measure chromospheric activity. A larger column density in the condensations, or equivalently a stronger absorption in the chromospheric lines, is obtained when the evaporation rate of the planet is larger, which occurs for a lower gravity of the planet. We analyze here a sample of stars hosting transiting hot Jupiters tuned in order to minimize systematic effects (e.g., interstellar medium absorption). Using a mixture model, we find that the data are best fit by a two-linear-regression model. We interpret this result in terms of the Vaughan-Preston gap. We use a Monte Carlo approach to best take into account the uncertainties, finding that the two...

  14. A Search for Rapidly Pulsating Hot Subdwarf Stars in the GALEX Survey

    Science.gov (United States)

    Boudreaux, Thomas M.; Barlow, Brad N.; Fleming, Scott W.; Vasquez Soto, Alan; Million, Chase; Reichart, Dan E.; Haislip, Josh B.; Linder, Tyler R.; Moore, Justin P.

    2017-08-01

    NASA’s Galaxy Evolution Explorer (GALEX) provided near- and far-UV observations for approximately 77% of the sky over a 10-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX, with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft’s short visit durations, uneven gaps between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBV r class of variable stars.

  15. 3-D Radiative Transfer Modeling of Structured Winds in Massive Hot Stars with Wind3D

    CERN Document Server

    Lobel, A; Blomme, R

    2010-01-01

    We develop 3-D models of the structured winds of massive hot stars with the Wind3D radiative transfer (RT) code. We investigate the physical properties of large-scale structures observed in the wind of the B-type supergiant HD 64760 with detailed line profile fits to Discrete Absorption Components (DACs) and rotational modulations observed with IUE in Si IV {\\lambda}1395. We develop parameterized input models Wind3D with large-scale equatorial wind density- and velocity-structures, or so-called `Co-rotating Interaction Regions' (CIRs) and `Rotational Modulation Regions' (RMRs). The parameterized models offer important advantages for high-performance RT calculations over ab-initio hydrodynamic input models. The acceleration of the input model calculations permits us to simulate and investigate a wide variety of physical conditions in the extended winds of massive hot stars. The new modeling method is very flexible for constraining the dynamic and geometric wind properties of RMRs in HD 64760. We compute that t...

  16. A hot Jupiter around the very active weak-line T Tauri star TAP 26

    Science.gov (United States)

    Yu, L.; Donati, J.-F.; Hébrard, E. M.; Moutou, C.; Malo, L.; Grankin, K.; Hussain, G.; Collier Cameron, A.; Vidotto, A. A.; Baruteau, C.; Alencar, S. H. P.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G.; Gregory, S. G.; Jardine, M.; Morin, J.; Ménard, F.; Matysse Collaboration

    2017-01-01

    We report the results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star TAP 26, carried out within the MaTYSSE programme with the ESPaDOnS spectropolarimeter at the 3.6 m Canada-France-Hawaii Telescope. Applying Zeeman-Doppler Imaging to our observations, concentrating in 2015 November and 2016 January and spanning 72 d in total, 16 d in 2015 November and 13 d in 2016 January, we reconstruct surface brightness and magnetic field maps for both epochs and demonstrate that both distributions exhibit temporal evolution not explained by differential rotation alone. We report the detection of a hot Jupiter (hJ) around TAP 26 using three different methods, two using Zeeman-Doppler Imaging (ZDI) and one Gaussian-Process Regression (GPR), with a false-alarm probability smaller than 6 10-4. However, as a result of the aliasing related to the observing window, the orbital period cannot be uniquely determined; the orbital period with highest likelihood is 10.79±0.14 d followed by 8.99±0.09 d. Assuming the most likely period, and that the planet orbits in the stellar equatorial plane, we obtain that the planet has a minimum mass Msin i of 1.66±0.31 MJup and orbits at 0.0968±0.0032 au from its host star. This new detection suggests that disc type II migration is efficient at generating newborn hJs, and that hJs may be more frequent around young T Tauri stars than around mature stars (or that the MaTYSSE sample is biased towards hJ-hosting stars).

  17. Hot Bottom Burning in Asymptotic Giant Branch Stars and the Turbulent Convection Model

    Science.gov (United States)

    D'Antona, Francesca; Mazzitelli, Italo

    1996-10-01

    We investigate the effect of two different local turbulent convection models on the structure of intermediate-mass stars (IMSs, 3.5 Msun ≤ M ≤7 Msun) in the asymptotic giant branch (AGB) phase where, according to observations, they should experience hot bottom burning (HBB). Evolutionary models adopting either the mixing length theory (MLT) or the Canuto & Mazzitelli (CM) description of stellar convection are discussed. It is found that, while the MLT structures require some degree of tuning to achieve, at the bottom of the convective envelope, the large temperatures required for HBB, the CM structures spontaneously achieve these conditions. Since the observational evidence for HBB (existence of a class of very luminous, lithium-rich AGB stars in the Magellanic Clouds showing low 12C/13C ratios) is quite compelling, the above result provides a further, successful test for the CM convective model, in stellar conditions far from solar. With the aid of the CM model, we then explore a number of problems related to the late evolution of this class of objects, and give first results for (1) the luminosity evolution of IMSs in the AGB phase (core mass-luminosity relation and luminosity range in which HBB occurs) for Population I and Population II structures, (2) the minimum core mass for semidegenerate carbon ignition (˜1.05 Msun), (3) the relation between initial mass and final white dwarf (WD) mass (also based on some observational evidences about the upper AGB stars), and (4) the expected mass function of massive WDs. Confirmation of the theoretical framework could arise from an observational test: the luminosity function of AGB stars is expected to show a gap at Mbol ˜ -6, which would distinguish between the low-luminosity regime, in which AGBs become carbon stars, and the upper luminosities, at which they undergo HBB, have very low 12C/13C ratios, and become lithium rich.

  18. Photometric Observations of Omega Centauri Multi-Wavelength Observations of Evolved Stars

    CERN Document Server

    Hughes, J; Van Leeuwen, F W; Hughes, Joanne; Wallerstein, George; Leeuwen, Floor van

    2001-01-01

    We present multi-wavelength observations of the northern population of Omega Cen from the main-sequence turn-off to high on the red giant branch. We show that the best information about the metallicity and age of the stars can be gained from combining vby, B-I and V-I colors (in the absence of spectroscopy). We confirm our results for the main-sequence turn-off stars: there is at least a 3 Gyr age spread. We use proper motion studies to confirm cluster membership at and above the level of the horizontal branch, and we show that the age spread is maintained amongst stars from the subgiant branch through the red giants. The available evidence suggests that Omega Cen is the core of a disrupted dwarf galaxy.

  19. EVIDENCE OF HOT HIGH VELOCITY PHOTOIONIZED PLASMA FALLING ON ACTIVELY ACCRETING T TAURI STARS

    Energy Technology Data Exchange (ETDEWEB)

    Gómez de Castro, Ana Ines [Grupo de Investigación Complutense AEGORA and S.D. Astronomía y Geodesia, Fac. de CC Matemáticas, Universidad Complutense, E-28040 Madrid (Spain)

    2013-10-01

    The He II (1640 Å) line and the resonance doublet of N V (UV1) provide a good diagnostic tool to constrain the excitation mechanism of hot (T{sub e} > 40,000 K) atmospheric/magnetospheric plasmas in T Tauri stars (TTSs). Making use of the data available in the Hubble Space Telescope archive, this work shows that there are at least two distinct physical components contributing to the radiation in these tracers: the accretion flow sliding on the magnetosphere and the atmosphere. The N V profiles in most sources are symmetric and at rest with respect to the star. The velocity dispersion of the profile increases from non-accreting (σ = 40 km s{sup –1}) to accreting (σ = 120 km s{sup –1}) TTSs, suggesting that the macroturbulence field in the line formation region decreases as the stars approach the main sequence. Evidence of the N V line being formed in a hot solar-like wind has been found in RW Aur, HN Tau, and AA Tau. The He II profile has a strong narrow component that dominates the line flux; the dispersion of this component ranges from 20 to 60 km s{sup –1}. Current data suggest that both accretion shocks and atmospheric emission might contribute to the line flux. In some sources, the He II line shows a broad and redward-shifted emission component often accompanied by semiforbidden O III] emission that has a critical electron density of ∼3.4 × 10{sup 10} cm{sup 3}. In spite of their different origins (inferred from the kinematics of the line formation region), N V and He II fluxes are strongly correlated, with only the possible exception of some of the heaviest accretors.

  20. Solar hot water demonstration project at Red Star Industrial Laundry, Fresno, California

    Energy Technology Data Exchange (ETDEWEB)

    None

    1980-07-01

    The Final Report of the Solar Hot Water System located at the Red Star Industrial Laundry, 3333 Sabre Avenue, Fresno, California, is presented. The system was designed as an integrated wastewater heat recovery and solar preheating system to supply a part of the hot water requirements. It was estimated that the natural gas demand for hot water heating could be reduced by 56 percent (44 percent heat reclamation and 12 percent solar). The system consists of a 16,500 gallon tube-and-shell wastewater heat recovery subsystem combined with a pass-through 6,528 square foot flat plate Ying Manufacturing Company Model SP4120 solar collector subsystem, a 12,500 gallon fiber glass water storage tank subsystem, pumps, heat exchangers, controls, and associated plumbing. The design output of the solar subsystem is approximately 2.6 x 10/sup 9/ Btu/year. Auxiliary energy is provided by a gas fired low pressure boiler servicing a 4,000 gallon service tank. This project is part of the US Department of Energy's Solar Demonstration Program with DOE sharing $184,841 of the $260,693 construction cost. The system was turned on in July 1977, and acceptance tests completed in September 1977. The demonstration period for this project ends September 2, 1982.

  1. Signatures of nonlinear mode interactions in the pulsating hot B subdwarf star KIC 10139564

    Science.gov (United States)

    Zong, W.; Charpinet, S.; Vauclair, G.

    2016-10-01

    Context. The unprecedented photometric quality and time coverage offered by the Kepler spacecraft has opened up new opportunities to search for signatures of nonlinear effects that affect oscillation modes in pulsating stars. Aims: The data accumulated on the pulsating hot B subdwarf KIC 10139564 are used to explore in detail the stability of its oscillation modes, focusing in particular on evidences of nonlinear behaviors. Methods: We analyzed 38 months of contiguous short-cadence data, concentrating on mode multiplets induced by the star rotation and on frequencies forming linear combinations that show intriguing behaviors during the course of the observations. Results: We find clear signatures that point toward nonlinear effects predicted by resonant mode coupling mechanisms. These couplings can induce various mode behaviors for the components of multiplets and for frequencies related by linear relationships. We find that a triplet at 5760 μHz, a quintuplet at 5287 μHz and a (ℓ > 2) multiplet at 5412 μHz, all induced by rotation, show clear frequency and amplitude modulations which are typical of the so-called intermediate regime of a resonance between the components. One triplet at 316 μHz and a doublet at 394 μHz show modulated amplitude and constant frequency which can be associated with a narrow transitory regime of the resonance. Another triplet at 519 μHz appears to be in a frequency-locked regime where both frequency and amplitude are constant. Additionally, three linear combinations of frequencies near 6076 μHz also show amplitude and frequency modulations, which are likely related to a three-mode direct resonance of the type ν0 ~ ν1 + ν2. Conclusions: The identified frequency and amplitude modulations are the first clear-cut signatures of nonlinear resonant couplings occurring in pulsating hot B subdwarf stars. However, the observed behaviors suggest that the resonances occurring in these stars usually follow more complicated patterns than

  2. VLT/MUSE discovers a jet from the evolved B[e] star MWC 137

    CERN Document Server

    Mehner, A; Groh, J H; Oudmaijer, R D; Baade, D; Rivinius, T; Selman, F; Boffin, H M J; Martayan, C

    2016-01-01

    Not all stars exhibiting the optical spectral characteristics of B[e] stars share the same evolutionary stage. The Galactic B[e] star MWC 137 is a prime example of an object with uncertain classification, with previous work suggesting pre- and post-main sequence classification. Our goal is to settle this debate and provide reliable evolutionary classification. Integral field spectrograph observations with VLT MUSE of the cluster SH 2-266 are used to analyze the nature of MWC 137. A collimated outflow is discovered that is geometrically centered on MWC 137. The central position of MWC 137 in the cluster SH 2-266 within the larger nebula suggests strongly that it is a member of this cluster and that it is both at the origin of the nebula and the newly discovered jet. Comparison of the color-magnitude diagram of the brightest cluster stars with stellar evolutionary models results in a distance of about 5.2$\\pm$1.4 kpc. We estimate that the cluster is at least 3 Myr old. The jet extends over 66" (1.7 pc) projecte...

  3. Combining observational techniques to constrain convection in evolved massive star models

    CERN Document Server

    Georgy, C; Meynet, G

    2014-01-01

    Recent stellar evolution computations indicate that massive stars in the range ~ 20 - 30 Msun are located in the blue supergiant (BSG) region of the Hertzsprung-Russell diagram at two different stages of their life: immediately after the main sequence (MS, group 1) and during a blueward evolution after the red supergiant phase (group 2). From the observation of the pulsationnal properties of a subgroup of variable BSGs (alpha Cyg variables), one can deduce that these stars belongs to group 2. It is however difficult to simultaneously fit the observed surface abundances and gravity for these stars, and this allows to constrain the physical processes of chemical species transport in massive stars. We will show here that the surface abundances are extremely sensitive to the physics of convection, particularly the location of the intermediate convective shell that appears at the ignition of the hydrogen shell burning after the MS. Our results show that the use of the Ledoux criterion to determine the convective r...

  4. A Precise Asteroseismic Age and Radius for the Evolved Sun-like Star KIC 11026764

    DEFF Research Database (Denmark)

    Metcalfe, Travis S.; Monteiro, Mario J.P.F.G.; Thompson, Michael J.

    2010-01-01

    that attempt to match the asteroseismic and spectroscopic constraints simultaneously. We determine both the radius and the age of KIC 11026764 with a precision near 1%, and an accuracy near 2% for the radius and 15% for the age. Continued observations of this star promise to reveal additional oscillation...

  5. Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud

    CERN Document Server

    Jones, O C; Srinivasan, S; McDonald, I; Sloan, G C; Zijlstra, A A

    2014-01-01

    In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars we have computed a grid of modust radiative-transfer models for a range of dust compositions, mass-loss rates, dust shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5$-$35-$\\mu$m Spitzer infrared spectrograph (IRS) spectra and broadband photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range $\\sim 8\\times10^{-8}$ to $5\\times10^{-6}$ M$_{\\odot}\\ \\mathrm{yr}^{-1}$, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron provides...

  6. Mass-loss predictions for evolved very metal-poor massive stars

    CERN Document Server

    Muijres, Lianne; de Koter, A; Hirschi, R; Langer, N; Yoon, S -C

    2012-01-01

    (shortened) The first couple of stellar generations may have been massive, of order 100 Msun, and to have played a dominant role in galaxy formation and the chemical enrichment of the early Universe. Some fraction of these objects may have died as pair-instability supernovae or gamma-ray bursts. The winds if these stars may have played an important role in determining these outcomes. As the winds are driven by radiation pressure on spectral lines, their strengths are expected to vary with metallicity. Until now, most mass-loss predictions for metal-poor O-type stars have assumed a scaled-down solar-abundance pattern. However, Population III evolutionary tracks show significant surface enrichment through rotational mixing of CNO-processed material, because even metal-poor stars switch to CNO-burning early on. We address the question of whether the CNO surface enhanced self-enrichment in the first few generations of stars could impact their mass-loss properties. For this, we employ Monte Carlo simulations to es...

  7. Hot and dense matter in compact stars - from nuclei to quarks

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Matthias

    2010-10-19

    This dissertation deals with the equation of state of hot and dense matter in compact stars, with special focus on first order phase transitions. A general classification of first order phase transitions is given and the properties of mixed phases are discussed. Aspects of nucleation and the role of local constraints are investigated. The derived theoretical concepts are applied to matter in neutron stars and supernovae, in the hadron-quark and the liquid-gas phase transition. For the detailed description of the liquid-gas phase transition a new nuclear statistical equilibrium model is developed. It is based on a thermodynamic consistent implementation of relativistic mean-field interactions and excluded volume effects. With this model different equation of state tables are calculated and the composition and thermodynamic properties of supernova matter are analyzed. As a first application numerical simulations of core-collapse supernovae are presented. For the hadron-quark phase transition two possible scenarios are studied in more detail. First the appearance of a new mixed phase in a proto neutron star and the implications on its evolution. In the second scenario the consequences of the hadron-quark transition in corecollapse supernovae are investigated. Simulations show that the appearance of quark matter has clear observable signatures and can even lead to the generation of an explosion. (orig.)

  8. The Giant Branches of ω Centauri: Multiwavelength Observations of Evolved Stars

    Science.gov (United States)

    Hughes, Joanne; Wallerstein, George; van Leeuwen, Floor; Hilker, Michael

    2004-02-01

    We have obtained photometric observations in a 182 arcmin2 area, 25' to the north of the center of the globular cluster ω Centauri. The Strömgren vby and broadband BI filters were used to obtain measurements for some 2500 stars. Preliminary examinations of parts of the data have been presented previously (Hughes & Wallerstein, published in 2000; Hughes, Wallerstein, & van Leeuwen, published in 2002). Here we present the complete data set, study the giant branches, and use the B-I color index as a tool for assessing the ages of the populations within ω Cen. Our results confirm previous results for the main-sequence turnoff stars: there appears to be an age spread of about 3-5 Gyr among the stars of ω Cen. We use the proper-motion study by van Leeuwen et al. (published in 2000) to confirm cluster membership above B~16.5 and calibrate our photometry to that of Hilker and Hilker & Richtler (both published in 2000) in order to use the improved methods described by these authors for deriving metallicity estimates from the Strömgren photometry. We use data on 25 ROA stars in our field and 40 stars from Hilker to look at the enrichment history of ω Cen. We support previous findings that there is another red giant branch, redder (Lee et al., published in 1999, and Pancino et al., published in 2000), and younger than the main giant branch but containing few stars. Even though this so-called RGB-a population appears to be younger than the bulk of the stellar population, it does not seem to be younger than the most metal-rich tail of the bulk population. This last property suggests that the RGB-a may not have been the last burst of star formation in ω Cen and could support the idea, presented by Ferraro et al. and Pancino et al. (both in 2002), that it represents an accreted stellar system.

  9. CNO abundances and carbon isotope ratios in evolved stars of the open clusters NGC 2324, NGC 2477, and NGC 3960

    CERN Document Server

    Tautvaisiene, Grazina; Bragaglia, Angela; Randich, Sofia; Zenoviene, Renata

    2016-01-01

    Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters NGC 2324, NGC 2477, and NGC 3960, which have turn-off masses of about 2 Msun, and to compare them with predictions of theoretical models. High-resolution spectra were analysed using a differential synthetic spectrum method. Abundances of carbon were derived using the C2 Swan (0,1) band heads at 5135 and 5635.5 A. The wavelength interval 7940-8130 A with strong CN features was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [Oi] line at 6300 A. The mean values of the CNO abundances are [C/Fe]=-0.35+-0.06 (s.d.), [N/Fe]=0.28+-0.05, and [O/Fe]=-0.02+-0.10 in seven stars of NGC 2324; [C/Fe]=-0.26+-0.02, [N/Fe]=0.39+-0.04, and [O/Fe]=-0.11+-0.06 in six stars of NGC 2477; and [C/Fe]=-0.39+-0.04, [N/Fe]=0.32+-0.05, and [O/Fe]=-0.19+-0.06 in six stars of NGC 3960. The mean C/N ratio is equal to 0.92+-0.12, 0.91+-0.09, and 0.80+-0.13, resp...

  10. The far-ultraviolet spectra of two hot PG 1159 stars

    Science.gov (United States)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2016-09-01

    PG 1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85 000-140 000 K). Here we report on the results for two even hotter stars (PG 1520+525 and PG 1144+005, both with Teff = 150 000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the abundances of some species are confirmed, while results on others (Si, P, S) are revised. In particular, a solar abundance of sulphur is measured in contrast to earlier claims of a strong S deficiency that contradicted stellar evolution models. For the first time, we assess the abundances of Na, Al, and Cl with newly constructed non-LTE model atoms. Besides the main constituents (He, C, O), we determine the abundances (or upper limits) of N, F, Ne, Na, Al, Si, P, S, Cl, Ar, and Fe. Generally, good agreement with stellar models is found.

  11. The weather report from IRC+10216: Evolving irregular clouds envelop carbon star

    CERN Document Server

    Stewart, P N; Monnier, J D; Ireland, M J; Hedman, M M; Nicholson, P D; Lacour, S

    2015-01-01

    High angular resolution images of IRC+10216 are presented in several near infrared wavelengths spanning more than 8 years. These maps have been reconstructed from interferometric observations obtained at both Keck and the VLT, and also from stellar occultations by the rings of Saturn observed with the Cassini spacecraft. The dynamic inner regions of the circumstellar environment are monitored over eight epochs ranging between January 2000 and July 2008. The system is shown to experience substantial evolution within this period including the fading of many previously reported persistent features, some of which had been identified as the stellar photosphere. These changes are discussed in context of existing models for the nature of the underlying star and the circumstellar environment. With access to these new images, we are able to report that none of the previously identified bright spots in fact contain the star, which is buried in its own dust and not directly visible in the near infrared.

  12. Delivery of complex organic compounds from evolved stars to the solar system.

    Science.gov (United States)

    Kwok, Sun

    2011-12-01

    Stars in the late stages of evolution are able to synthesize complex organic compounds with aromatic and aliphatic structures over very short time scales. These compounds are ejected into the interstellar medium and distributed throughout the Galaxy. The structures of these compounds are similar to the insoluble organic matter found in meteorites. In this paper, we discuss to what extent stellar organics has enriched the primordial Solar System and possibly the early Earth.

  13. Variable Evolved Stars and YSOs Discovered in the Large Magellanic Cloud using the SAGE Survey

    CERN Document Server

    Vijh, Uma P; Babler, B; Block, M; Bracker, S; Engelbracht, C W; For, B; Gordon, K; Hora, J; Indebetouw, R; Leitherer, C; Meade, M; Misselt, K; Sewilo, M; Srinivasan, S; Whitney, B

    2008-01-01

    We present initial results and source lists of variable sources in the Large Magellanic Cloud (LMC) for which we detect thermal infrared variability from the SAGE (Surveying the Agents of a Galaxy's Evolution) survey, which had 2 epochs of photometry separated by three months. The SAGE survey mapped a 7 degree by 7 degree region of the LMC using the IRAC and the MIPS instruments on board Spitzer. Variable sources are identified using a combination of the IRAC 3.6, 4.5, 5.8, 8.0 \\micron bands and the MIPS 24 \\micron bands. An error-weighted flux difference between the two epochs is used to assess the variability. Of the ~ 3 million sources detected at both epochs we find ~ 2,000 variable sources for which we provide electronic catalogs. Most of the variable sources can be classified as asymptotic giant branch (AGB) stars. A large fraction (> 66%) of the extreme AGB stars are variable and only smaller fractions of carbon-rich (6.1%) and oxygen-rich (2.0%) stars are detected as variable. We also detect a populat...

  14. Magnetic fields around evolved stars: further observations of H$_2$O maser polarization

    CERN Document Server

    Leal-Ferreira, M L; Kemball, A; Amiri, N

    2013-01-01

    We aim to detect the magnetic field and infer its properties around four AGB stars using H$_2$O maser observations. The sample we observed consists of the following sources: the semi-regular variable RT Vir and the Mira variables AP Lyn, IK Tau, and IRC+60370. We observed the 6$_{1,6}-5_{2,3}$ H$_2$O maser rotational transition, in full-polarization mode, to determine its linear and circular polarization. Based on the Zeeman effect, one can infer the properties of the magnetic field from the maser polarization analysis. We detected a total of 238 maser features, in three of the four observed sources. No masers were found toward AP Lyn. The observed masers are all located between 2.4 and 53.0 AU from the stars. Linear and circular polarization was found in 18 and 11 maser features, respectively. We more than doubled the number of AGB stars in which magnetic field has been detected from H$_2$O maser polarization, as our results confirm the presence of fields around IK Tau, RT Vir and IRC+60370. The strength of ...

  15. The hot Jupiter of the magnetically active weak-line T Tauri star V830 Tau

    Science.gov (United States)

    Donati, J.-F.; Yu, L.; Moutou, C.; Cameron, A. C.; Malo, L.; Grankin, K.; Hébrard, E.; Hussain, G. A. J.; Vidotto, A. A.; Alencar, S. H. P.; Haywood, R. D.; Bouvier, J.; Petit, P.; Takami, M.; Herczeg, G. J.; Gregory, S. G.; Jardine, M. M.; Morin, J.; MaTYSSE Collaboration

    2017-03-01

    We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme, were spread over 91 d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6-m Canada-France-Hawaii, the 2-m Bernard Lyot, and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies, and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced redshifted emission in multiple spectral activity proxies. With three different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2 km s-1) that V830 Tau generates, successfully retrieve the 68 ± 11 m s-1 RV planet signal hiding behind the jitter, further confirm the existence of V830 Tau b, and better characterize its orbital parameters. We find that the method based on Gaussian-process regression performs best thanks to its higher ability at modelling not only the activity jitter, but also its temporal evolution over the course of our observations, and succeeds at reproducing our RV data down to an rms precision of 35 m s-1. Our result provides new observational constraints on scenarios of star/planet formation and demonstrates the scientific potential of large-scale searches for close-in giant planets around T Tauri stars.

  16. Theory review: Line-driven instability and other causes of structure and variability in hot-star winds

    Science.gov (United States)

    Owocki, Stanley P.

    1994-01-01

    The winds of the hot, luminous, OB stars are driven by the line-scattering of the star's continuum radiation flux. Several kinds of observational evidence indicate that such winds are highly structured and variable. This paper will review possible theoretical causes of such wind structure. For relatively small-scale, stochastic variability, I review the role of the strong intrinsic instability of the line-driving process itself. for larger scale structure, I describe recent efforts to examine how disturbances from the underlying, rotating star can be translated outward into propagating features in the wind.

  17. The evolved-star dust budget of the Small Magellanic Cloud: the critical role of a few key players

    Science.gov (United States)

    Srinivasan, S.; Boyer, M. L.; Kemper, F.; Meixner, M.; Sargent, B. A.; Riebel, D.

    2016-04-01

    The life cycle of dust in the interstellar medium is heavily influenced by outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars, a large fraction of which is contributed by a few very dusty sources. We compute the dust input to the Small Magellanic Cloud (SMC) by fitting the multi-epoch mid-infrared spectral energy distributions of AGB/RSG candidates with models from the Grid of RSG and AGB ModelS grid, allowing us to estimate the luminosities and dust-production rates (DPRs) of the entire population. By removing contaminants, we guarantee a high-quality data set with reliable DPRs and a complete inventory of the dustiest sources. We find a global AGB/RSG dust-injection rate of (1.3 ± 0.1) × 10-6 M⊙ yr-1, in agreement with estimates derived from mid-infrared colours and excess fluxes. As in the Large Magellanic Cloud, a majority (66 per cent) of the dust arises from the extreme AGB stars, which comprise only ≈7 per cent of our sample. A handful of far-infrared sources, whose 24 μm fluxes exceed their 8 μm fluxes, dominate the dust input. Their inclusion boosts the global DPR by ≈1.5×, making it necessary to determine whether they are AGB stars. Model assumptions, rather than missing data, are the major sources of uncertainty; depending on the choice of dust shell expansion speed and dust optical constants, the global DPR can be up to ≈10 times higher. Our results suggest a non-stellar origin for the SMC dust, barring as yet undiscovered evolved stars with very high DPRs.

  18. HAT-P-55b: A Hot Jupiter Transiting a Sun-like Star

    CERN Document Server

    Juncher, D; Hartman, J D; Bakos, G Á; Bieryla, A; Kovács, T; Boisse, I; Latham, D W; Kovács, G; Bhatti, W; Csubry, Z; Penev, K; de Val-Borro, M; Falco, E; Torres, G; Noyes, R W; Lázár, J; Papp, I; Sári, P

    2015-01-01

    We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The planet orbits a V = 13.207 +/- 0.039 sun-like star with a mass of 1.013 +/- 0.037 solar masses, a radius of 1.011 +/- 0.036 solar radii and a metallicity of -0.03 +/- 0.08. The planet itself is a typical hot Jupiter with a period of 3.5852467 +/- 0.0000064 days, a mass of 0.582 +/- 0.056 Jupiter masses and a radius of 1.182 +/- 0.055 Jupiter radii. This discovery adds to the increasing sample of transiting planets with measured bulk densities, which is needed to put constraints on models of planetary structure and formation theories.

  19. WASP-32b: A transiting hot Jupiter planet orbiting a lithium-poor, solar-type star

    CERN Document Server

    Maxted, P F L; Cameron, A Collier; Gillon, M; Hellier, C; Queloz, D; Smalley, B; Triaud, A H M J; West, R G; Enoch, R; Lister, T A; Pepe, F; Pollacco, D L; Ségransan, D; Skillen, I; Udry, S

    2010-01-01

    We report the discovery of a transiting planet orbiting the star TYC 2-1155-1. The star, WASP-32, is a moderately bright (V=11.3) solar-type star (Teff=6100 +- 100K, [Fe/H] = -0.13 +- 0.10). The lightcurve of the star obtained with the WASP-South and WASP-North instruments shows periodic transit-like features with a depth of about 1% and a duration of 0.10d every 2.72d. The presence of a transit-like feature in the lightcurve is confirmed using z-band photometry obtained with Faulkes Telescope North. High resolution spectroscopy obtained with the CORALIE spectrograph confirms the presence of a planetary mass companion. From a combined analysis of the spectroscopic and photometric data, assuming that the star is a typical main-sequence star, we estimate that the planet has a mass M_p = 3.60 +- 0.07 M_Jup and a radius R_p = 1.19 +- 0.06R_Jup. WASP-32 is one of a small group of hot Jupiters with masses M_p > 3M_Jup. We find that some stars with hot Jupiter companions and with masses M_* =~ 1.2M_sun, including WA...

  20. CNO abundances and carbon isotope ratios in evolved stars of the open clusters NGC 2324, NGC 2477, and NGC 3960

    Science.gov (United States)

    Tautvaišienė, Gražina; Drazdauskas, Arnas; Bragaglia, Angela; Randich, Sofia; Ženovienė, Renata

    2016-10-01

    Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters NGC 2324, NGC 2477, and NGC 3960, which have turn-off masses of about 2 M⊙, and to compare them with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential synthetic spectrum method. Abundances of carbon were derived using the C2 Swan (0, 1) band heads at 5135 and 5635.5 Å. The wavelength interval 7940-8130 Å with strong CN features was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Results: The mean values of the CNO abundances are [C/Fe] = -0.35 ± 0.06 (s.d.), [N/Fe] = 0.28 ± 0.05, and [O/Fe] = -0.02 ± 0.10 in seven stars of NGC 2324; [C/Fe] = -0.26 ± 0.02, [N/Fe] = 0.39 ± 0.04, and [O/Fe] = -0.11 ± 0.06 in six stars of NGC 2477; and [C/Fe] = -0.39 ± 0.04, [N/Fe] = 0.32 ± 0.05, and [O/Fe] = -0.19 ± 0.06 in six stars of NGC 3960. The mean C/N ratio is equal to 0.92 ± 0.12, 0.91 ± 0.09, and 0.80 ± 0.13, respectively. The mean 12C /13C ratio is equal to 21 ± 1, 20 ± 1, and 16 ± 4, respectively. The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. Conclusions: The mean values of the 12C /13C and C/N ratios in NGC 2324 and NGC 2477 agree well with the first dredge-up and thermohaline-induced extra-mixing models, which are similar for intermediate turn-off mass stars. The 12C /13C ratios in the investigated clump stars of NGC 3960 span from 10 to 20. The mean carbon isotope and C/N ratios in NGC 3960 are close to predictions of the model in which the thermohaline- and rotation-induced (if rotation velocity at the zero-age main sequence was 30% of the critical velocity) extra-mixing act together. Based on observations collected at ESO telescopes under programmes 072.D-0550 and 074.D-0571.

  1. K2-111 b - a short period super-Earth transiting a metal poor, evolved old star

    Science.gov (United States)

    Fridlund, Malcolm; Gaidos, Eric; Barragán, Oscar; Persson, Carina M.; Gandolfi, Davide; Cabrera, Juan; Hirano, Teruyuki; Kuzuhara, Masayuki; Csizmadia, Sz.; Nowak, Grzegorz; Endl, Michael; Grziwa, Sascha; Korth, Judith; Pfaff, Jeremias; Bitsch, Bertram; Johansen, Anders; Mustill, Alexander J.; Davies, Melvyn B.; Deeg, Hans J.; Palle, Enric; Cochran, William D.; Eigmüller, Philipp; Erikson, Anders; Guenther, Eike; Hatzes, Artie P.; Kiilerich, Amanda; Kudo, Tomoyuki; MacQueen, Phillip; Narita, Norio; Nespral, David; Pätzold, Martin; Prieto-Arranz, Jorge; Rauer, Heike; Van Eylen, Vincent

    2017-07-01

    Context. From a light curve acquired through the K2 space mission, the star K2-111(EPIC 210894022) has been identified as possibly orbited by a transiting planet. Aims: Our aim is to confirm the planetary nature of the object and derive its fundamental parameters. Methods: We analyse the light curve variations during the planetary transit using packages developed specifically for exoplanetary transits. Reconnaissance spectroscopy and radial velocity observations have been obtained using three separate telescope and spectrograph combinations. The spectroscopic synthesis package SME has been used to derive the stellar photospheric parameters that were used as input to various stellar evolutionary tracks in order to derive the parameters of the system. The planetary transit was also validated to occur on the assumed host star through adaptive imaging and statistical analysis. Results: The star is found to be located in the background of the Hyades cluster at a distance at least 4 times further away from Earth than the cluster itself. The spectrum and the space velocities of K2-111 strongly suggest it to be a member of the thick disk population. The co-added high-resolution spectra show that that it is a metal poor ([Fe/H] = - 0.53 ± 0.05 dex) and α-rich somewhat evolved solar-like star of spectral type G3. We find Teff = 5730 ± 50 K, log g⋆ = 4.15 ± 0.1 cgs, and derive a radius of R⋆ = 1.3 ± 0.1 R⊙ and a mass of M⋆ = 0.88 ± 0.02 M⊙. The currently available radial velocity data confirms a super-Earth class planet with a mass of 8.6 ± 3.9 M⊕ and a radius of 1.9 ± 0.2 R⊕. A second more massive object with a period longer than about 120 days is indicated by a long-term radial velocity drift. Conclusions: The radial velocity detection together with the imaging confirms with a high level of significance that the transit signature is caused by a planet orbiting the star K2-111. This planet is also confirmed in the radial velocity data. A second more

  2. Abundances of neutron-capture elements in the Hot Extreme-Helium Stars V1920 Cygni and HD 124448

    CERN Document Server

    Pandey, G; Rao, N K; Jeffery, C S; Pandey, Gajendra; Lambert, David L.

    2004-01-01

    Analysis of HST STIS ultraviolet spectra of two hot extreme helium stars (EHes): V1920 Cyg and HD 124448 provide the first measurements of abundances of neutron-capture elements for EHes. Although the two stars have similar abundances for elements up through the iron-group, they differ strikingly in their abundances of heavier elements: V1920 Cyg is enriched by a factor of 30 in light neutron-capture elements (Y/Fe, Zr/Fe) relative to HD 124448. These differences in abundances of neutron-capture elements among EHes mirrors that exhibited by the RCrB stars, and is evidence supporting the view that there is an evolutionary connection between these two groups of hydrogen-deficient stars. Also, the abundances of Y and Zr in V1920 Cyg provide evidence that at least one EHe star went through a s-process synthesis episode in its earlier evolution.

  3. Coupled Evolutions of the Stellar Obliquity, Orbital Distance, and Planet's Radius due to the Ohmic Dissipation Induced in a Diamagnetic Hot Jupiter around a Magnetic T Tauri Star

    Science.gov (United States)

    Chang, Yu-Ling; Bodenheimer, Peter H.; Gu, Pin-Gao

    2012-10-01

    We revisit the calculation of the ohmic dissipation in a hot Jupiter presented by Laine et al. by considering more realistic interior structures, stellar obliquity, and the resulting orbital evolution. In this simplified approach, the young hot Jupiter of one Jupiter mass is modeled as a diamagnetic sphere with a finite resistivity, orbiting across tilted stellar magnetic dipole fields in vacuum. Since the induced ohmic dissipation occurs mostly near the planet's surface, we find that the dissipation is unable to significantly expand the young hot Jupiter. Nevertheless, the planet inside a small corotation orbital radius can undergo orbital decay by the dissipation torque and finally overfill its Roche lobe during the T Tauri star phase. The stellar obliquity can evolve significantly if the magnetic dipole is parallel/antiparallel to the stellar spin. Our results are validated by the general torque-dissipation relation in the presence of the stellar obliquity. We also run the fiducial model of Laine et al. and find that the planet's radius is sustained at a nearly constant value by the ohmic heating, rather than being thermally expanded to the Roche radius as suggested by the authors.

  4. EK Eridani: the tip of the iceberg of giants which have evolved from magnetic Ap stars

    CERN Document Server

    Aurière, M; Petit, P; Charbonnel, C; Dintrans, B; Lignières, F; Roudier, T; Alecian, E; Donati, J F; Landstreet, J D; Wade, G A

    2008-01-01

    We observe the slowly-rotating, active, single giant, EK Eri, to study and infer the nature of its magnetic field directly. We used the spectropolarimeter NARVAL at the Telescope Bernard Lyot, Pic du Midi Observatory, and the Least Square Deconvolution method to create high signal-to-noise ratio Stokes V profiles. We fitted the Stokes V profiles with a model of the large-scale magnetic field. We studied the classical activity indicators, the CaII H and K lines, the CaII infrared triplet, and H\\alpha line. We detected the Stokes V signal of EK Eri securely and measured the longitudinal magnetic field Bl for seven individual dates spanning 60% of the rotational period. The measured longitudinal magnetic field of EK Eri reached about 100 G and was as strong as fields observed in RSCVn or FK Com type stars: this was found to be extraordinary when compared with the weak fields observed at the surfaces of slowly-rotating MS stars or any single red giant previously observed with NARVAL. From our modeling, we infer t...

  5. Abundance analysis of a sample of evolved stars in the outskirts of Omega Centauri

    CERN Document Server

    Villanova, Sandro; Scarpa, Riccardo; Marconi, Gianni

    2009-01-01

    The globular cluster $\\omega$ Centauri (NGC 5139) is a puzzling stellar system harboring several distinct stellar populations whose origin still represents a unique astrophysical challenge. Current scenarios range from primordial chemical inhomogeneities in the mother cloud to merging of different sub-units and/or subsequent generations of enriched stars - with a variety of different pollution sources- within the same potential well. In this paper we study the chemical abundance pattern in the outskirts of Omega Centauri, half-way to the tidal radius (covering the range of 20-30 arcmin from the cluster center), and compare it with chemical trends in the inner cluster regions, in an attempt to explore whether the same population mix and chemical compositions trends routinely found in the more central regions is also present in the cluster periphery.We extract abundances of many elements from FLAMES/UVES spectra of 48 RGB stars using the equivalent width method and then analyze the metallicity distribution func...

  6. Deep Mixing in Evolved Stars: I. The Effect of Reaction Rate Revisions from C to Al

    CERN Document Server

    Palmerini, S; Cristallo, S; Busso, M

    2010-01-01

    We present computations of nucleosynthesis in low-mass red-giant-branch and asymptotic-giant-branch stars of Population I experiencing extended mixing. We adopt the updated version of the FRANEC evolutionary model, a new post-process code for non-convective mixing and the most recent revisions for solar abundances. In this framework, we discuss the effects of recent improvements in relevant reaction rates for proton captures on intermediate-mass nuclei (from carbon to aluminum). For each nucleus we briefly discuss the new choices and their motivations. The calculations are then performed on the basis of a parameterized circulation, where the effects of the new nuclear inputs are best compared to previous works. We find that the new rates (and notably the one for the 14N(p,g)15O reaction) imply considerable modifications in the composition of post-main sequence stars. In particular, the slight temperature changes due to the reduced efficiency of proton captures on 14N induce abundance variations at the first d...

  7. VizieR Online Data Catalog: Hot Jupiter exoplanets host stars EW and abundances (Teske+, 2014)

    Science.gov (United States)

    Teske, J. K.; Cunha, K.; Smith, V. V.; Schuler, S. C.; Griffith, C. A.

    2017-07-01

    Our target list was chosen to include some of the best-studied hot Jupiter host stars that are observable from the Northern Hemisphere, as well as a range of planet radii, masses, and orbital periods. All but three of the planetary hosts in this sample have at least the 3.6 um, 4.5 um, 5.8 um, and 8.0 um diagnostic measurements of secondary eclipse depth from the Spitzer Infrared Array Camera (IRAC; Fazio et al. 2004ApJS..154...10F). These data cover wavelengths with features of CH4, CO, CO2, and H2O, which are the most abundant oxygen and carbon molecules in hot Jupiter atmospheres. There are three sources of observations for this project: the High Dispersion Spectrograph (HDS; Noguchi et al. 2002PASJ...54..855N) on the 8.2 m Subaru Telescope at Mauna Kea Observatory, the High Resolution Echelle Spectrometer (HIRES; Vogt et al. 1994SPIE.2198..362V) at the Keck I Telescope, and the Keck/HIRES archive. (2 data files).

  8. An extremely fast halo hot subdwarf star in a wide binary system

    CERN Document Server

    Németh, Péter; Irrgang, Andreas; Geier, Stephan; Fürst, Felix; Kupfer, Thomas; Heber, Ulrich

    2016-01-01

    New spectroscopic observations of the halo hyper-velocity star candidate SDSS J121150.27+143716.2 ($V=17.92$ mag) revealed a cool companion to the hot subdwarf primary. The components have a very similar radial velocity and their absolute luminosities are consistent with the same distance, confirming the physical nature of the binary, which is the first double-lined hyper-velocity candidate. Our spectral decomposition of the Keck/ESI spectrum provided an sdB+K3V pair, analogous to many long-period subdwarf binaries observed in the Galactic disk. We found the subdwarf atmospheric parameters: $T_{\\rm eff}=30\\,600\\pm500$ K, $\\log{g}=5.57\\pm0.06$ cm s$^{-2}$ and He abundance $\\log(n{\\rm He}/n{\\rm H})=-3.0\\pm0.2$. Oxygen is the most abundant metal in the hot subdwarf atmosphere, and Mg and Na lines are the most prominent spectral features of the cool companion, consistent with a metallicity of $[{\\rm Fe}/{\\rm H}]=-1.3$. The non-detection of radial velocity variations suggest the orbital period to be a few hundred ...

  9. Chemical segregation toward massive hot cores: The AFGL2591 star forming region

    CERN Document Server

    Jimenez-Serra, I; Viti, S; Martin-Pintado, J; de Wit, W -J

    2012-01-01

    We present high angular resolution observations (0.5"x0.3") carried out with the Submillimeter Array (SMA) toward the AFGL2591 high-mass star forming region. Our SMA images reveal a clear chemical segregation within the AFGL2591 VLA 3 hot core, where different molecular species (Type I, II and III) appear distributed in three concentric shells. This is the first time that such a chemical segregation is ever reported at linear scales <3000 AU within a hot core. While Type I species (H2S and 13CS) peak at the AFGL2591 VLA 3 protostar, Type II molecules (HC3N, OCS, SO and SO2) show a double-peaked structure circumventing the continuum peak. Type III species, represented by CH3OH, form a ring-like structure surrounding the continuum emission. The excitation temperatures of SO2, HC3N and CH3OH (185+-11 K, 150+-20 K and 124+-12 K, respectively) show a temperature gradient within the AFGL2591 VLA 3 envelope, consistent with previous observations and modeling of the source. By combining the H2S, SO2 and CH3OH imag...

  10. OBLIQUITIES OF HOT JUPITER HOST STARS: EVIDENCE FOR TIDAL INTERACTIONS AND PRIMORDIAL MISALIGNMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Albrecht, Simon; Winn, Joshua N. [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Johnson, John A. [Department of Astrophysics, California Institute of Technology, MC249-17, Pasadena, CA 91125 (United States); Howard, Andrew W.; Marcy, Geoffrey W. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Butler, R. Paul [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Arriagada, Pamela [Department of Astronomy, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Hirano, Teruyuki [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Bakos, Gaspar; Hartman, Joel D. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States)

    2012-09-20

    We provide evidence that the obliquities of stars with close-in giant planets were initially nearly random, and that the low obliquities that are often observed are a consequence of star-planet tidal interactions. The evidence is based on 14 new measurements of the Rossiter-McLaughlin effect (for the systems HAT-P-6, HAT-P-7, HAT-P-16, HAT-P-24, HAT-P-32, HAT-P-34, WASP-12, WASP-16, WASP-18, WASP-19, WASP-26, WASP-31, Gl 436, and Kepler-8), as well as a critical review of previous observations. The low-obliquity (well-aligned) systems are those for which the expected tidal timescale is short, and likewise the high-obliquity (misaligned and retrograde) systems are those for which the expected timescale is long. At face value, this finding indicates that the origin of hot Jupiters involves dynamical interactions like planet-planet interactions or the Kozai effect that tilt their orbits rather than inspiraling due to interaction with a protoplanetary disk. We discuss the status of this hypothesis and the observations that are needed for a more definitive conclusion.

  11. A NLTE analysis of the hot subdwarf O star BD+28 4211. II. The optical spectrum

    CERN Document Server

    Latour, M; Green, E M; Brassard, P

    2015-01-01

    We present the second part of our detailed analysis of the hot sdO and spectroscopic standard star BD+28 4211, in which we focus on the optical spectrum. In the first part of our study, we determined the abundances of some 11 metals detected in the atmosphere of BD+28 4211 using UV spectra of the star and corroborated the fundamental parameters estimated in past studies (Teff $\\sim$ 82,000 K, log g $\\sim$ 6.2, and solar N(He)/N(H)). In this work, we aim at rederiving these secured parameters on the sole basis of high-quality optical spectra. A first grid of non-LTE line-blanketed model atmospheres, including metals with the abundances derived from the UV spectrum, does not give satisfactory results when we apply a standard simultaneous fitting procedure to the observed H and He lines of our optical spectra. The line profiles are not finely reproduced and the resulting effective temperatures, in particular, are too low by $\\sim$10,000 K. We next investigate the probable cause of this failure, that is, the impo...

  12. Hot planetary winds near a star: dynamics, wind-wind interactions, and observational signatures

    Science.gov (United States)

    Carroll-Nellenback, Jonathan; Frank, Adam; Liu, Baowei; Quillen, Alice C.; Blackman, Eric G.; Dobbs-Dixon, Ian

    2017-04-01

    Signatures of 'evaporative' winds from exoplanets on short (hot) orbits around their host star have been observed in a number of systems. In this paper, we present global adaptive mesh refinement simulations that track the launching of the winds, their expansion through the circumstellar environment, and their interaction with a stellar wind. We focus on purely hydrodynamic flows including the anisotropy of the wind launching and explore the orbital/fluid dynamics of the resulting flows in detail. In particular, we find that a combination of the tidal and Coriolis forces strongly distorts the planetary 'Parker' wind creating 'up-orbit' and 'down-orbit' streams. We characterize the flows in terms of their orbital elements that change depending on their launch position on the planet. We find that the anisotropy in the atmospheric temperature leads to significant backflow on to the planet. The planetary wind interacts strongly with the stellar wind creating instabilities that may cause eventual deposition of planetary gas on to the star. We present synthetic observations of both transit and absorption line-structure for our simulations. For our initial conditions, we find that the orbiting wind material produces absorption signatures at significant distances from the planet and substantial orbit-to-orbit variability. Lyα absorption shows red- and blueshifted features out to 70 km s-1. Finally, using semi-analytic models we constrain the effect of radiation pressure, given the approximation of uniform stellar absorption.

  13. Hot planetary winds near a star: dynamics, wind-wind interactions, and observational signatures

    CERN Document Server

    Carroll-Nellenback, Jonathan; Liu, Baowei; Quillen, Alice C; Blackman, Eric G; Dobbs-Dixon, Ian

    2016-01-01

    Signatures of "evaporative" winds from exo-planets on short (hot) orbits around their host star have been observed in a number of systems. In this paper we present global AMR simulations that track the launching of the winds, their expansion through the circumstellar environment, and their interaction with a stellar wind. We focus on purely hydrodynamic flows including the anisotropy of the wind launching and explore the orbital/fluid dynamics of the resulting flows in detail. In particular we find that a combination of the tidal and Coriolis forces strongly distorts the planetary "Parker" wind creating "up-orbit" and "down-orbit" streams. We characterize the flows in terms of their orbital elements which change depending on their launch position on the planet. We find that the anisotropy in the atmospheric temperature leads to significant backflow on to the planet. The planetary wind interacts strongly with the stellar wind creating instabilities that cause eventual deposition of planetary gas onto the star....

  14. The Mass-Loss Return from Evolved Stars to the Large Magellanic Cloud IV: Construction and Validation of a Grid of Models for Oxygen-Rich AGB Stars, Red Supergiants, and Extreme AGB Stars

    CERN Document Server

    Sargent, Benjamin A; Meixner, M

    2014-01-01

    To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically-symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores 4 parameters - stellar effective temperature from 2100 K - 4700 K; luminosity from 10^3-10^6 L_Sun; dust shell inner radii of 3, 7, 11, and 15 R_Star; and 10.0 micron optical depth from 10^-4 to 26. From an initial grid of ~1200 2Dust models, we create a larger grid of ~69,000 models by scaling to cover the luminosity range required by the data. These models are offered to the public on a website. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR star...

  15. Evolved stars with complex atmospheres - the high spectral resolution, mid-IR view

    CERN Document Server

    Ryde, N; Richter, M J; Josselin, E; Harper, G M; Eriksson, K; Boogert, A; DeWitt, C; Encrenaz, T; Greathouse, T; Jaffe, D; Kulas, K; McKelvey, M; Najita, J; Vacca, W

    2014-01-01

    The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to non-classical atmosphere models to interpret these regions. This region's properties is of importance, not the least, for the understanding of the mass-loss mechanism for these stars, which is not still understood. Here, we present observational constraints of the outer regions of red giants, based on mid-IR, high spectral resolution spectra. We also discuss possible non-LTE effects and highlight a new non-LTE code that will be used to analyse the spectra of these atmospheric layers. We conclude by mentioning our new SOFIA/EXES observations of red giants at 6 microns, where the vibration-rotation lines of water vapour can be detected and spectrally resolved for the first time.

  16. The Dust Properties of Two Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: in Search of a Possible Link

    CERN Document Server

    Clayton, Geoffrey C; Whitney, B A; Babler, B; Gallagher, J S; Nordhaus, J; Speck, A K; Wolff, M J; Freeman, W R; Camp, K A; Lawson, W A; Roman-Duval, J; Misselt, K A; Meade, M; Sonneborn, G; Matsuura, M; Meixner, M

    2011-01-01

    We present new Spitzer/IRS spectra of two hot R Coronae Borealis (RCB) stars, one in the Galaxy,V348 Sgr, and one lying in the LMC, HV 2671. These two objects may constitute a link between the RCB stars and the late Wolf-Rayet ([WCL]) class of central stars of planetary nebula (CSPNe) such as CPD -56 8032 that has little or no hydrogen in their atmospheres. HV 2671 and V348 Sgr are members of a rare subclass that has significantly higher effective temperatures than most RCB stars, but sharing the traits of hydrogen deficiency and dust formation that define the cooler RCB stars. The [WC] CSPNe star, CPD -56 8032, displays evidence for dual-dust chemistry showing both PAHs and crystalline silicates in its mid-IR spectrum. HV 2671 shows strong PAH emission but shows no sign of having crystalline silicates. The spectrum of V348 Sgr is very different from those of CPD -56 8032 and HV 2671. The PAH emission seen strongly in the other two stars is not present. Instead, the spectrum is dominated by a broad emission c...

  17. HATS-11b AND HATS-12b: Two Transiting Hot Jupiters Orbiting Subsolar Metallicity Stars Selected for the K2 Campaign 7

    Science.gov (United States)

    Rabus, M.; Jordán, A.; Hartman, J. D.; Bakos, G. Á.; Espinoza, N.; Brahm, R.; Penev, K.; Ciceri, S.; Zhou, G.; Bayliss, D.; Mancini, L.; Bhatti, W.; de Val-Borro, M.; Csbury, Z.; Sato, B.; Tan, T.-G.; Henning, T.; Schmidt, B.; Bento, J.; Suc, V.; Noyes, R.; Lázár, J.; Papp, I.; Sári, P.

    2016-10-01

    We report the discovery of two transiting extrasolar planets from the HATSouth survey. HATS-11, a V = 14.1 G0-star shows a periodic 12.9 mmag dip in its light curve every 3.6192 days and a radial velocity variation consistent with a Keplerian orbit. HATS-11 has a mass of 1.000+/- 0.060 {M}⊙ , a radius of 1.444+/- 0.057 {R}⊙ and an effective temperature of 6060+/- 150 K, while its companion is a 0.85+/- 0.12 {M}{{J}}, 1.510+/- 0.078 {R}{{J}} planet in a circular orbit. HATS-12 shows a periodic 5.1 mmag flux decrease every 3.1428 days and Keplerian RV variations around a V = 12.8 F-star. HATS-12 has a mass of 1.489+/- 0.071 {M}⊙ , a radius of 2.21+/- 0.21 {R}⊙ , and an effective temperature of 6408+/- 75 K. For HATS-12b, our measurements indicate that this is a 2.38+/- 0.11 {M}{{J}}, 1.35+/- 0.17 {R}{{J}} planet in a circular orbit. Both host stars show subsolar metallicities of -0.390+/- 0.060 dex and -0.100+/- 0.040 dex, respectively, and are (slightly) evolved stars. In fact, HATS-11 is among the most metal-poor and, HATS-12, with a {log}{g}\\star of 3.923+/- 0.065, is among the most evolved stars hosting a hot-Jupiter planet. Importantly, HATS-11 and HATS-12 have been observed in long cadence by Kepler as part of K2 campaign 7 (EPIC216414930 and EPIC218131080 respectively). 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 data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based in part on

  18. Radio variability and non-thermal components in stars evolving towards planetary nebulae

    Science.gov (United States)

    Cerrigone, L.; Umana, G.; Trigilio, C.; Leto, P.; Buemi, C. S.; Ingallinera, A.

    2017-07-01

    We present new Karl G. Jansky Very Large Array multifrequency measurements of a set of stars in transition from the post-AGB to the planetary nebula phase monitored in the radio range over several years. Clear variability is found for five sources. Their light curves show increasing and decreasing patterns. New radio observations at high angular resolution are also presented for two sources. Among these is IRAS 18062 + 2410, whose radio structure is compared to near-infrared images available in the literature. With these new maps, we can estimate inner and outer radii of 0.03 and 0.08 arcsec for the ionized shell, an ionized mass of 3.2 × 10-4 M⊙ and a density at the inner radius of 7.7 × 105 cm-3, obtained by modelling the radio shell with the new morphological constraints. The combination of multifrequency data and, where available, spectral-index maps leads to the detection of spectral indices not due to thermal emission, contrary to what one would expect in planetary nebulae. Our results allow us to hypothesize the existence of a link between radio variability and non-thermal emission mechanisms in the nebulae. This link seems to hold for IRAS 22568 + 6141 and may generally hold for those nebulae where the radio flux decreases over time.

  19. Self-consistent modelling of line-driven hot-star winds with Monte Carlo radiation hydrodynamics

    CERN Document Server

    Noebauer, U M

    2015-01-01

    Radiative pressure exerted by line interactions is a prominent driver of outflows in astrophysical systems, being at work in the outflows emerging from hot stars or from the accretion discs of cataclysmic variables, massive young stars and active galactic nuclei. In this work, a new radiation hydrodynamical approach to model line-driven hot-star winds is presented. By coupling a Monte Carlo radiative transfer scheme with a finite-volume fluid dynamical method, line-driven mass outflows may be modelled self-consistently, benefiting from the advantages of Monte Carlo techniques in treating multi-line effects, such as multiple scatterings, and in dealing with arbitrary multidimensional configurations. In this work, we introduce our approach in detail by highlighting the key numerical techniques and verifying their operation in a number of simplified applications, specifically in a series of self-consistent, one-dimensional, Sobolev-type, hot-star wind calculations. The utility and accuracy of our approach is dem...

  20. Discovery of XO-6b: A Hot Jupiter Transiting a Fast Rotating F5 Star on an Oblique Orbit

    Science.gov (United States)

    Crouzet, N.; McCullough, P. R.; Long, D.; Montanes Rodriguez, P.; Lecavelier des Etangs, A.; Ribas, I.; Bourrier, V.; Hébrard, G.; Vilardell, F.; Deleuil, M.; Herrero, E.; Garcia-Melendo, E.; Akhenak, L.; Foote, J.; Gary, B.; Benni, P.; Guillot, T.; Conjat, M.; Mékarnia, D.; Garlitz, J.; Burke, C. J.; Courcol, B.; Demangeon, O.

    2017-03-01

    Only a few hot Jupiters are known to orbit around fast rotating stars. These exoplanets are harder to detect and characterize and may be less common than around slow rotators. Here, we report the discovery of the transiting hot Jupiter XO-6b, which orbits a bright, hot, and fast rotating star: V = 10.25, T eff⋆ = 6720 ± 100 K, v sin i ⋆ = 48 ± 3 km s‑1. We detected the planet from its transits using the XO instruments and conducted a follow-up campaign. Because of the fast stellar rotation, radial velocities taken along the orbit do not yield the planet’s mass with a high confidence level, but we secure a 3σ upper limit M p orbit with a sky-projected obliquity {\\boldsymbol{λ }}=-20\\buildrel{\\circ}\\over{.} 7+/- 2\\buildrel{\\circ}\\over{.} 3. The rotation period of the star is shorter than the orbital period of the planet: P rot P orb = 3.77 days. Thus, this system stands in a largely unexplored regime of dynamical interactions between close-in giant planets and their host stars.

  1. Recent progress in understanding the hot and warm gas phases in the halos of star-forming galaxies

    CERN Document Server

    Strickland, D K; Colbert, E J M; Hoopes, C G; Weaver, K A

    2002-01-01

    In this contribution we present a few selected examples of how the latest generation of space-based instrumentation -- NASA's Chandra X-ray Observatory and the Far-Ultraviolet Spectroscopic Explorer (FUSE) -- are finally answering old questions about the influence of massive star feedback on the warm and hot phases of the ISM and IGM. In particular, we discuss the physical origin of the soft thermal X-ray emission in the halos of star-forming and starburst galaxies, its relationship to extra-planar H-alpha emission, and plasma diagnostics using FUSE observations of O VI absorption and emission.

  2. On the synthesis of resonance lines in dynamical models of structured hot-star winds

    Science.gov (United States)

    Puls, J.; Owocki, S. P.; Fullerton, A. W.

    1993-01-01

    We examine basic issues involved in synthesizing resonance-line profiles from 1-D, dynamical models of highly structured hot-star winds. Although these models exhibit extensive variations in density as well as velocity, the density scale length is still typically much greater than the Sobolev length. The line transfer is thus treated using a Sobolev approach, as generalized by Rybicki & Hummer (1978) to take proper account of the multiple Sobolev resonances arising from the nonmonotonic velocity field. The resulting reduced-lambda-matrix equation describing nonlocal coupling of the source function is solved by iteration, and line profiles are then derived from formal solution integration using this source function. Two more approximate methods that instead use either a stationary or a structured, local source function yield qualitatively similar line-profiles, but are found to violate photon conservation by 10% or more. The full results suggest that such models may indeed be able to reproduce naturally some of the qualitative properties long noted in observed UV line profiles, such as discrete absorption components in unsaturated lines, or the blue-edge variability in saturated lines. However, these particular models do not yet produce the black absorption troughs commonly observed in saturated lines, and it seems that this and other important discrepancies (e.g., in acceleration time scale of absorption components) may require development of more complete models that include rotation and other 2-D and/or 3-D effects.

  3. Non-LTE models for synthetic spectra of type Ia supernovae/hot stars with extremely extended atmospheres

    CERN Document Server

    Sauer, D N; Pauldrach, A W A

    2006-01-01

    Realistic atmospheric models that link the properties and the physical conditions of supernova ejecta to observable spectra are required for the quantitative interpretation of observational data of type Ia supernovae (SN Ia) and the assessment of the physical merits of theoretical supernova explosion models. The numerical treatment of the radiation transport - yielding the synthetic spectra - in models of SN Ia ejecta in early phases is usually carried out in analogy to atmospheric models of `normal' hot stars. Applying this analogy indiscriminately leads to inconsistencies in SN Ia models because a diffusive lower boundary, while justified for hot stars, is invalid for hydrogen and helium-deficient supernova ejecta. In type Ia supernovae the radiation field does not thermalize even at large depths, and large optical depths are not reached at all wavelengths. We derive an improved description of the lower boundary that allows a more consistent solution of the radiation transfer in SN Ia and therefore yields m...

  4. The Hot Horizontal-Branch Stars in NGC288 - Effects of Diffusion and Stratification on Their Atmospheric Parameters*

    Science.gov (United States)

    Moehler, S.; Dreizler, S.; LeBlanc, F.; Khalack, V.; Michaud, G.; Richer, J.; Sweigart, Allen V.; Grundahl, F.

    2014-01-01

    Context. NGC288 is a globular cluster with a well developed blue horizontal branch covering the so-called u-jump which indicates the onset of diffusion. It is therefore well suited to study the effects of diffusion in blue horizontal branch (HB) stars. Aims. We compare observed abundances to predictions from stellar evolution models calculated with diffusion and from stratified atmospheric models. We verify the effect of using stratified model spectra to derive atmospheric parameters. In addition we investigate the nature of the overluminous blue HB stars around the u-jump. Methods. We define a new photometric index sz from uvby measurements that is gravity sensitive between 8 000K and 12 000 K. Using medium-resolution spectra and Stroemgren photometry we determine atmospheric parameters (Teff, logg) and abundances for the blue HB stars. We use both homogeneous and stratified model spectra for our spectroscopic analyses. Results. The atmospheric parameters and masses of the hot HB stars in NGC288 show a behaviour seen also in other clusters for temperatures between 9 000K and 14 000 K. Outside this temperature range, however, they follow rather the results found for such stars in (omega)Cen. The abundances derived from our observations are for most elements (except He and P) within the abundance range expected from evolutionary models that include the effects of atomic diffusion and assume a surface mixed mass of 10(exp -7) M. The abundances predicted by stratified model atmospheres are generally significantly more extreme than observed, except for Mg. The use of stratified model spectra to determine effective temperatures, surface gravities and masses moves the hotter stars to a closer agreement with canonical evolutionary predictions. Conclusions. Our results show definite promise towards solving the long-standing issue of surface gravity and mass discrepancies for hot HB stars, but there is still much work needed to arrive at a self-consistent solution.

  5. Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low Metallicity Small Magellanic Cloud (SAGE-SMC) II. Cool Evolved Stars

    CERN Document Server

    Boyer, Martha L; van Loon, Jacco Th; McDonald, Iain; Meixner, Margaret; Zaritsky, Dennis; Gordon, Karl D; Kemper, F; Babler, Brian; Block, Miwa; Bracker, Steve; Engelbracht, Charles W; Hora, Joe; Indebetouw, Remy; Meade, Marilyn; Misselt, Karl; Robitaille, Thomas; Sewilo, Marta; Shiao, Bernie; Whitney, Barbara

    2011-01-01

    We investigate the infrared (IR) properties of cool, evolved stars in the Small Magellanic Cloud (SMC), including the red giant branch (RGB) stars and the dust-producing red supergiant (RSG) and asymptotic giant branch (AGB) stars using observations from the Spitzer Space Telescope Legacy program entitled: "Surveying the Agents of Galaxy Evolution in the Tidally-stripped, Low Metallicity SMC", or SAGE-SMC. The survey includes, for the first time, full spatial coverage of the SMC bar, wing, and tail regions at infrared (IR) wavelengths (3.6 - 160 microns). We identify evolved stars using a combination of near-IR and mid-IR photometry and point out a new feature in the mid-IR color-magnitude diagram that may be due to particularly dusty O-rich AGB stars. We find that the RSG and AGB stars each contribute ~20% of the global SMC flux (extended + point-source) at 3.6 microns, which emphasizes the importance of both stellar types to the integrated flux of distant metal-poor galaxies. The equivalent SAGE survey of t...

  6. Emission-line stars discovered in the UKST H-alpha survey of the Large Magellanic Cloud; Part 1: Hot stars

    CERN Document Server

    Reid, Warren A

    2012-01-01

    We present new, accurate positions, spectral classifications, radial and rotational velocities, H-alpha fluxes, equivalent widths and B,V,I,R magnitudes for 579 hot emission-line stars (classes B0 - F9) in the Large Magellanic Cloud which include 469 new discoveries. Candidate emission line stars were discovered using a deep, high resolution H-alpha map of the central 25 deg2 of the LMC obtained by median stacking a dozen 2 hour H-alpha exposures taken with the UK Schmidt Telescope. Spectroscopic follow-up observations on the AAT, UKST, VLT, the SAAO 1.9m and the MSSSO 2.3m telescope have established the identity of these faint sources down to magnitude R~23 for H-alpha (4.5 x 10^-17 ergs cm^2 s^-1 Ang). Confirmed emission-line stars have been assigned an underlying spectral classification through cross-correlation against 131 absorption line template spectra covering the range O1 to F8. We confirm 111 previously identified emission line stars and 64 previously known variable stars with spectral types hotter ...

  7. KELT-7b: A hot Jupiter transiting a bright V=8.54 rapidly rotating F-star

    CERN Document Server

    Bieryla, Allyson; Beatty, Thomas G; Eastman, Jason; Siverd, Robert J; Pepper, Joshua; Gaudi, B Scott; Stassun, Keivan G; Canas, Caleb; Latham, David W; Buchhave, Lars A; Sanchis-Ojeda, Roberto; Winn, Joshua N; Jensen, Eric L N; Kielkopf, John F; McLeod, Kim K; Gregorio, Joao; Colon, Knicole D; Street, Rachel; Ross, Rachel; Penny, Matthew; Mellon, Samuel N; Oberst, Thomas E; Fulton, Benjamin J; Wang, Ji; Berlind, Perry; Calkins, Michael L; Esquerdo, Gilbert A; DePoy, Darren L; Gould, Andrew; Marshall, Jennifer; Pogge, Richard; Trueblood, Mark; Trueblood, Patricia

    2015-01-01

    We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of $1.28 \\pm 0.18$ MJ, radius of $1.53_{-0.047}^{+0.046}$ RJ, and an orbital period of $2.7347749 \\pm 0.0000039$ days. The bright host star (HD33643; KELT-7) is an F-star with $V=8.54$, Teff $=6789_{-49}^{+50}$ K, [Fe/H] $=0.139_{-0.081}^{+0.075}$, and $\\log{g}=4.149 \\pm 0.019$. It has a mass of $1.535_{-0.054}^{+0.066}$ Msun, a radius of $1.732_{-0.045}^{+0.043}$ Rsun, and is the fifth most massive, fifth hottest, and the ninth brightest star known to host a transiting planet. It is also the brightest star around which KELT has discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed characterization given its relatively low surface gravity, high equilibrium temperature, and bright host star. The rapid rotation of the star ($73 \\pm 0.5$ km/s) results in a Rossiter-McLaughlin effect with an unusually large amplitude of several hundred m/s. We find that the orbit normal of the planet is likely to be well-aligned with ...

  8. WASP-41b: A transiting hot Jupiter planet orbiting a magnetically-active G8V star

    CERN Document Server

    Maxted, P F L; Cameron, A Collier; Hellier, C; Queloz, D; Smalley, B; Street, R A; Triaud, A H M J; West, R G; Gillon, M; Lister, T A; Pepe, F; Pollacco, D; Segransan, D; Smith, A M S; Udry, S

    2010-01-01

    We report the discovery of a transiting planet with an orbital period of 3.05d orbiting the star TYC 7247-587-1. The star, WASP-41, is a moderately bright G8V star (V=11.6) with a metallicity close to solar ([Fe/H]=-0.08+-0.09). The star shows evidence of moderate chromospheric activity, both from emission in the cores of the CaII H and K lines and photometric variability with a period of 18.3d and an amplitude of about 1%. The rotation period of the star implies a gyrochronological age for WASP-41 of 1.8Gyr with an error of about 15%. We have used a combined analysis of the available photometric and spectroscopic data to derive the mass and radius of the planet (0.93+-0.06M_Jup, 1.21+-0.06R_Jup). Further observations of WASP-41 can be used to explore the connections between the properties of hot Jupiter planets and the level of chromospheric activity in their host stars.

  9. KELT-17b: A hot-Jupiter transiting an A-star in a misaligned orbit detected with Doppler tomography

    CERN Document Server

    Zhou, George; Collins, Karen A; Beatty, Thomas; Oberst, Thomas; Heintz, Tyler M; Stassun, Keivan G; Latham, David W; Kuhn, Rudolf B; Bieryla, Allyson; Lund, Michael B; Labadie-Bartz, Jonathan; Siverd, Robert J; Stevens, Daniel J; Gaudi, B Scott; Pepper, Joshua; Buchhave, Lars A; Eastman, Jason; Colón, Knicole; Cargile, Phillip; James, David; Gregorio, Joao; Reed, Phillip A; Jensen, Eric L N; Cohen, David H; McLeod, Kim K; Tan, T G; Zambelli, Roberto; Bayliss, Daniel; Bento, Joao; Esquerdo, Gilbert A; Berlind, Perry; Calkins, Michael L; Blancato, Kirsten; Manner, Mark; Samulski, Camile; Stockdale, Christopher; Nelson, Peter; Stephens, Denise; Curtis, Ivan; Kielkopf, John; Fulton, Benjamin J; DePoy, D L; Marshall, Jennifer L; Pogge, Richard; Gould, Andy; Trueblood, Mark; Trueblood, Pat

    2016-01-01

    We present the discovery of a hot-Jupiter transiting the V=9.23 mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a 1.31 -0.29/+0.28 Mj, 1.645 -0.055/+0.060 Rj hot-Jupiter in a 3.08 day period orbit misaligned at -115.9 +/- 4.1 deg to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet over two transits. The nature of the spin-orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates (alpha < 0.30 at 2 sigma significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of 1.635 -0.061/+0.066 Msun, effective temperature of 7454 +/- 49 K, and projected rotational velocity v sin I_* = 44.2 -1.3/+1.5 km/s; it is amongst the most massive, hottest, and most rapidly rotating of know...

  10. KELT-17b: A Hot-Jupiter Transiting an A-star in a Misaligned Orbit Detected with Doppler Tomography

    Science.gov (United States)

    Zhou, George; Rodriguez, Joseph E.; Collins, Karen A.; Beatty, Thomas; Oberst, Thomas; Heintz, Tyler M.; Stassun, Keivan G.; Latham, David W.; Kuhn, Rudolf B.; Bieryla, Allyson; Lund, Michael B.; Labadie-Bartz, Jonathan; Siverd, Robert J.; Stevens, Daniel J.; Gaudi, B. Scott; Pepper, Joshua; Buchhave, Lars A.; Eastman, Jason; Colón, Knicole; Cargile, Phillip; James, David; Gregorio, Joao; Reed, Phillip A.; Jensen, Eric L. N.; Cohen, David H.; McLeod, Kim K.; Tan, T. G.; Zambelli, Roberto; Bayliss, Daniel; Bento, Joao; Esquerdo, Gilbert A.; Berlind, Perry; Calkins, Michael L.; Blancato, Kirsten; Manner, Mark; Samulski, Camile; Stockdale, Christopher; Nelson, Peter; Stephens, Denise; Curtis, Ivan; Kielkopf, John; Fulton, Benjamin J.; DePoy, D. L.; Marshall, Jennifer L.; Pogge, Richard; Gould, Andy; Trueblood, Mark; Trueblood, Pat

    2016-11-01

    We present the discovery of a hot Jupiter transiting the V = 9.23 mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a {1.31}-0.29+0.28 {M}{{J}}, {1.525}-0.060+0.065 {R}{{J}} hot-Jupiter in a 3.08-day period orbit misaligned at ‑115.°9 ± 4.°1 to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet during two transits. The nature of the spin–orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates (α \\lt 0.30 at 2σ significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of {1.635}-0.061+0.066 {M}ȯ , an effective temperature of 7454 ± 49 K, and a projected rotational velocity of v\\sin {I}* ={44.2}-1.3+1.5 {km} {{{s}}}-1; it is among the most massive, hottest, and most rapidly rotating of known planet hosts.

  11. The Mass-Loss Return From Evolved Stars to The Large Magellanic Cloud VI: Luminosities and Mass-Loss Rates on Population Scales

    CERN Document Server

    Riebel, D; Sargent, B; Meixner, M

    2012-01-01

    We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer (RT) models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ~30,000 Asymptotic Giant Branch (AGB) and Red Supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published dataset consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between Oxygen- and Carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 1.5x10^(-5) solar masses/yr, equivalent to a total mass injection rate (including the gas) into t...

  12. Imaging the transition between pre-planetary and planetary nebulae: integral field spectroscopy of hot post-AGB stars with NIFS

    Science.gov (United States)

    Gledhill, T. M.; Forde, K. P.

    2015-02-01

    We present 2-2.4 μm integral field spectroscopy of a sample of hot post-asymptotic giant branch stars with early-B spectral types, using the Near-infrared Integral Field Spectrometer instrument on Gemini North. These stars are just beginning to ionize their immediate environments and turn into planetary nebulae (PNe). We use molecular hydrogen emission lines together with hydrogen and helium recombination lines to explore the distribution of molecular and atomic gas and the extent of the developing ionized region. We see a range of evolutionary stages: IRAS 18062+2410 and IRAS 18379-1707 have recently developed compact and unresolved regions of photoionized H within axisymmetric molecular envelopes, with the former object increasing its Brγ flux by a factor of 5.3 in 14 years; IRAS 22023+5249 and IRAS 20462+3416 have extended Brγ nebulae and in the latter object only weak H2 emission remains; IRAS 19336-0400 is at a more advanced stage of PN formation where H2 is mostly dissociated and we see structure in both the H and He recombination line nebulae. IRAS 19200+3457 is the only object not to show the He I line at 2.058 μm and is probably the least evolved object in our sample; the H2 emission forms a ring around the star and we suggest that this object may be a rare example of a `round' pre-PN in transition to a `round' PN.

  13. The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

    CERN Document Server

    Bower, Richard; Frenk, Carlos S; Theuns, Tom; Schaller, Matthieu; Crain, Robert A; McAlpine, Stuart

    2016-01-01

    Galaxies fall into two clearly distinct types: `blue-sequence' galaxies that are rapidly forming young stars, and `red-sequence' galaxies in which star formation has almost completely ceased. Most galaxies more massive than $3\\times10^{10} M_\\odot$ follow the red-sequence while less massive central galaxies lie on the blue sequence. We show that these sequences are created by a competition between star formation-driven outflows and gas accretion on to the supermassive black hole at the galaxy's center. We develop a simple analytic model for this interaction. In galaxies less massive than $3\\times10^{10} M_\\odot$, young stars and supernovae drive a buoyant outflow that balances the rate of gas inflow. This prevents high gas densities building up in the central regions. More massive galaxies, however, are surrounded by a hot corona. We argue that above a halo mass of $\\sim 10^{12} M_\\odot$, the supernova-driven outflow is no longer buoyant and star formation is unable to prevent the build up of gas in the centr...

  14. Carbon and Oxygen Abundances in the Hot Jupiter Exoplanet Host Star XO-2N and its Binary Companion

    CERN Document Server

    Teske, Johanna K; Cunha, Katia; Smith, Verne V; Griffith, Caitlin A

    2013-01-01

    With the aim of connecting the compositions of stars and planets, we present the abundances of carbon and oxygen, as well as iron and nickel, for the transiting exoplanet host star XO-2N and its wide-separation binary companion XO-2S. Stellar parameters are derived from high-resolution, high-signal-to-noise spectra, and the two stars are found to be similar in their Teff, log g, iron ([Fe/H]), nickel ([Ni/H]) abundances. Their carbon ([C/H]) and oxygen ([O/H]) abundances also overlap within errors, although XO-2N may be slightly more C-rich and O-rich than XO-2S. The C/O ratios of both stars (~0.60+/-0.20) may also be somewhat larger than solar (C/O~0.50). The XO-2 system has a transiting hot Jupiter orbiting one binary component but not the other, allowing us to probe the potential effects planet formation might have on the host star composition. Additionally, with multiple observations of its atmosphere the transiting exoplanet XO-2b lends itself to compositional analysis, which can be compared to the natal...

  15. The Large Magellanic Cloud as a laboratory for Hot Bottom Burning in massive Asymptotic Giant Branch stars

    CERN Document Server

    Ventura, P; Dell'Agli, F; Boyer, M L; García-Hernández, D A; Di Criscienzo, M; Schneider, R

    2015-01-01

    We use Spitzer observations of the rich population of Asymptotic Giant Branch stars in the Large Magellanic Cloud (LMC) to test models describing the internal structure and nucleosynthesis of the most massive of these stars, i.e. those with initial mass above $\\sim 4M_{\\odot}$. To this aim, we compare Spitzer observations of LMC stars with the theoretical tracks of Asymptotic Giant Branch models, calculated with two of the most popular evolution codes, that are known to differ in particular for the treatment of convection. Although the physical evolution of the two models are significantly different, the properties of dust formed in their winds are surprisingly similar, as is their position in the colour-colour (CCD) and colour-magnitude (CMD) diagrams obtained with the Spitzer bands. This model independent result allows us to select a well defined region in the ($[3.6]-[4.5], [5.8]-[8.0]$) plane, populated by AGB stars experiencing Hot Bottom Burning, the progeny of stars with mass $M\\sim 5.5M_{\\odot}$. This...

  16. The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

    Science.gov (United States)

    Bower, Richard G.; Schaye, Joop; Frenk, Carlos S.; Theuns, Tom; Schaller, Matthieu; Crain, Robert A.; McAlpine, Stuart

    2017-02-01

    Galaxies fall into two clearly distinct types: `blue-sequence' galaxies which are rapidly forming young stars, and `red-sequence' galaxies in which star formation has almost completely ceased. Most galaxies more massive than 3 × 1010 M⊙ follow the red sequence, while less massive central galaxies lie on the blue sequence. We show that these sequences are created by a competition between star formation-driven outflows and gas accretion on to the supermassive black hole at the galaxy's centre. We develop a simple analytic model for this interaction. In galaxies less massive than 3 × 1010 M⊙, young stars and supernovae drive a high-entropy outflow which is more buoyant than any tenuous corona. The outflow balances the rate of gas inflow, preventing high gas densities building up in the central regions. More massive galaxies, however, are surrounded by an increasingly hot corona. Above a halo mass of ˜1012 M⊙, the outflow ceases to be buoyant and star formation is unable to prevent the build-up of gas in the central regions. This triggers a strongly non-linear response from the black hole. Its accretion rate rises rapidly, heating the galaxy's corona, disrupting the incoming supply of cool gas and starving the galaxy of the fuel for star formation. The host galaxy makes a transition to the red sequence, and further growth predominantly occurs through galaxy mergers. We show that the analytic model provides a good description of galaxy evolution in the EAGLE hydrodynamic simulations. So long as star formation-driven outflows are present, the transition mass scale is almost independent of subgrid parameter choice.

  17. A high obliquity orbit for the hot-Jupiter HATS-14b transiting a 5400K star

    CERN Document Server

    Zhou, G; Hartman, J D; Fulton, B J; Bakos, G Á; Howard, A W; Isaacson, H; Marcy, G W; Schmidt, B P; Brahm, R; Jordán, A

    2015-01-01

    We report a spin-orbit misalignment for the hot-Jupiter HATS-14b, measuring a projected orbital obliquity of |lambda|= 76 -5/+4 deg. HATS-14b orbits a high metallicity, 5400 K G dwarf in a relatively short period orbit of 2.8 days. This obliquity was measured via the Rossiter-McLaughlin effect, obtained with observations from Keck-HIRES. The velocities were extracted using a novel technique, optimised for low signal-to-noise spectra, achieving a high precision of 4 m/s point-to-point scatter. However, we caution that our uncertainties may be underestimated. Due to the low rotational velocity of the star, the detection significance is dependent on the vsini prior that is imposed in our modelling. Based on trends observed in the sample of hot Jupiters with obliquity measurements, it has been suggested that these planets modify the spin axes of their host stars, with an efficiency that depends on the stellar type and orbital period of the system. In this framework, short-period planets around stars with surface ...

  18. On the consistent treatment of the quasi-hydrostatic layers in hot star atmospheres

    CERN Document Server

    Sander, Andreas; Hainich, Rainer; Gímenez-García, Angel; Todt, Helge; Hamann, Wolf-Rainer

    2015-01-01

    CONTEXT: Spectroscopic analysis remains the most common method to derive masses of massive stars, the most fundamental stellar parameter. While binary orbits and stellar pulsations can provide much sharper constraints on the stellar mass, these methods are only rarely applicable to massive stars. Unfortunately, spectroscopic masses of massive stars heavily depend on the detailed physics of model atmospheres. AIMS: We demonstrate the impact of a consistent treatment of the radiative pressure on inferred gravities and spectroscopic masses of massive stars. Specifically, we investigate the contribution of line and continuum transitions to the photospheric radiative pressure. We further explore the effect of model parameters, e.g., abundances, on the deduced spectroscopic mass. Lastly, we compare our results with the plane-parallel TLUSTY code, commonly used for the analysis of massive stars with photospheric spectra. METHODS: We calculate a small set of O-star models with the Potsdam Wolf-Rayet (PoWR) code using...

  19. New aspects in the theory of magnetic winds from massive hot stars

    CERN Document Server

    Seemann, H

    1998-01-01

    This thesis discusses the influence of magnetic fields on the instability of line-driven winds in O-stars and Wolf-Rayet stars. This combination is an important concept to understand the strong, observed winds from Wolf-Rayet stars. In the second part of the thesis a model is derived which describes the wind outside the equatorial plane. This model allows to use the simple approach of an ordinary differential equation instead of a 2-dim. partial differential equation.

  20. Magnetized Converging Flows toward the Hot Core in the Intermediate/High-mass Star-forming Region NGC 6334 V

    Science.gov (United States)

    Juárez, Carmen; Girart, Josep M.; Zamora-Avilés, Manuel; Tang, Ya-Wen; Koch, Patrick M.; Liu, Hauyu Baobab; Palau, Aina; Ballesteros-Paredes, Javier; Zhang, Qizhou; Qiu, Keping

    2017-07-01

    We present Submillimeter Array (SMA) observations at 345 GHz toward the intermediate/high-mass cluster-forming region NGC 6334 V. From the dust emission we spatially resolve three dense condensations, the brightest one presenting the typical chemistry of a hot core. The magnetic field (derived from the dust polarized emission) shows a bimodal converging pattern toward the hot core. The molecular emission traces two filamentary structures at two different velocities, separated by 2 km s-1, converging to the hot core and following the magnetic field distribution. We compare the velocity field and the magnetic field derived from the SMA observations with magnetohydrodynamic simulations of star-forming regions dominated by gravity. This comparison allows us to show how the gas falls in from the larger-scale extended dense core (˜0.1 pc) of NGC 6334 V toward the higher-density hot core region (˜0.02 pc) through two distinctive converging flows dragging the magnetic field, whose strength seems to have been overcome by gravity.

  1. A survey for hot central stars of planetary nebulae - I. Methods and first results

    Science.gov (United States)

    Kanarek, Graham C.; Shara, Michael M.; Faherty, Jacqueline K.; Zurek, David; Moffat, Anthony F. J.

    2017-02-01

    We present the results of initial spectrographic followup with the Very Large Telescope (UT3, Melipal) for Ks ≥ 14 Galactic plane C IV emission-line candidates in the near-infrared (NIR). These seven faint stars all display prominent He I and/or C IV emission lines characteristic of a carbon-rich Wolf-Rayet star. They have NIR colours which are much too blue to be those of distant, classical WR stars. The magnitudes and colours are compatible with those expected for central stars of planetary nebulae, and are likely to come from massive progenitor populations. Our survey has identified thousands of such candidates.

  2. Iron abundance in hot hydrogen-deficient central stars and white dwarfs from FUSE, HST, and IUE spectroscopy

    CERN Document Server

    Miksa, S; Dreizler, S; Kruk, J W; Rauch, T; Werner, K

    2002-01-01

    We present a first systematic investigation of the iron abundance in very hot (Teff>50,000K) hydrogen-deficient post-AGB stars. Our sample comprises 16 PG1159 stars and four DO white dwarfs. We use recent FUSE observations as well as HST and IUE archival data to perform spectral analyses with line blanketed NLTE model atmospheres. Iron is not detected in any PG1159 star. In most cases this is compatible with a solar iron abundance due to limited quality of HST and IUE data, although the tendency to an iron underabundance may be recognized. However, the absence of iron lines in excellent FUSE spectra suggests an underabundance by at least 1 dex in two objects (K1-16 NGC 7094). A similar result has been reported recently in the [WC]-PG1159 transition object Abell 78 (Werner et al. 2002). We discuss dust fractionation and s-process neutron-captures as possible origins. We also announce the first identification of sulfur in PG1159 stars.

  3. An inflated massive Hot Jupiter transiting a bright F star followed up with K2.0 observations

    CERN Document Server

    Huang, C X; Bakos, G Á; Penev, K; Bhatti, W; Bieryla, A; de Val-Borro, M; Latham, D W; Buchhave, L A; Csubry, Z; Kovács, G; Béky, B; Falco, E; Berlind, P; Calkins, M L; Esquerdo, G A; Lázár, J; Papp, I; Sári, P

    2015-01-01

    We report the discovery of HAT-P-56b by the HATNet survey, an inflated hot Jupiter transiting a bright F type star in Field 0 of NASA's K2 mission. We combine ground-based discovery and follow-up light curves with high precision photometry from K2, as well as ground-based radial velocities from TRES on the FLWO~1.5m telescope to determine the physical properties of this system. HAT-P-56b has a mass of $M_p \\approx 2.18 M_J$, radius of $R_p \\approx 1.47 R_J$, and transits its host star on a near-grazing orbit with a period of $P\\approx$ 2.7908 d. The radius of HAT-P-56b is among the largest known for a planet with $M_p > 2 M_J$. The host star has a V-band magnitude of 10.9, mass of 1.30 $M_\\odot$, and radius of 1.43 $R_\\odot$. The periodogram of the K2 light curve suggests the star is a $\\gamma$ Dor variable. HAT-P-56b is an example of a ground-based discovery of a transiting planet, where space-based observations greatly improve the confidence in the confirmation of its planetary nature, and also improve the ...

  4. The influence of rotation in radiation driven wind from hot stars: New solutions and disk formation in Be stars

    CERN Document Server

    Cur'e, M

    2004-01-01

    The theory of radiation driven wind including stellar rotation is re-examined. After a suitable change of variables, a new equation for the mass loss rate is derived analytically. The solution of this equation remains within 1% confidence when compared with numerical solutions. Also, a non-linear equation for the position of the critical (singular) point is obtained. This equation shows the existence of an additional critical point, besides the standard m--CAK critical point. For a stellar rotation velocity larger than aprox. 0.7 - 0.8 V_{breakup}, there exists only one critical point, located away from the star's surface. Numerical solutions crossing through this new critical point, are attained. In these cases, the wind has a very low terminal velocity and therefore a higher density wind. Disk formation in Be stars is discussed in the frame of this new line driven stellar wind solution.

  5. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Alexander P.; Frebel, Anna [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Simon, Joshua D. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Geha, Marla, E-mail: alexji@mit.edu [Astronomy Department, Yale University, New Haven, CT 06520 (United States)

    2016-01-20

    We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.

  6. Hot Star Extension to the Hubble Space Telescope Stellar Spectral Library

    Science.gov (United States)

    Khan, Islam; Worthey, Guy

    2017-01-01

    CCD spectra of 36 stars were obtained from the Space Telescope Imaging Spectrograph (STIS) installed in the Hubble Space Telescope (HST) using three low resolution gratings - G230LB, G430L, and G750L, combined in processing to make single, continuous spectra from 0.2 to 1.0 micrometers. These spectra will be added to the Next Generation Stellar Library (NGSL) after completing the data analysis, reduction, and the required corrections. The stars include normal O-type stars, helium-burning stars, and post-asymptotic giant branch (PAGB) stars. Difficult steps in the data reduction process were removing the cosmic rays from the raw images and defringing of the G750L spectra using fringe flats. Most stars have detectable dust extinction. To aid in analysis, synthetic spectra were generated with various effective temperatures and surface gravities. A five parameter analytic model for the dust extinction correction was adopted. The parameters were varied in order to fit especially the ultraviolet portion of the observed and comparison synthetic spectra. Cross-correlation was used to bring the spectra to a common, final, zero velocity wavelength scale. Some star temperatures obtained from fitting synthetic versus observed spectra vary significantly from literature values. The dust extinction correction parameters also varied for several stars, mostly O stars, indicating variations in dust properties for different lines of sight. Analysis of scattered light effects showed that it was significant only for our two coolest stars.Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.Support for this work was provided by NASA through grant number HST-GO-14141 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  7. K2-30 b and K2-34 b: Two inflated hot Jupiters around solar-type stars

    Science.gov (United States)

    Lillo-Box, J.; Demangeon, O.; Santerne, A.; Barros, S. C. C.; Barrado, D.; Hébrard, G.; Osborn, H. P.; Armstrong, D. J.; Almenara, J.-M.; Boisse, I.; Bouchy, F.; Brown, D. J. A.; Courcol, B.; Deleuil, M.; Delgado Mena, E.; Díaz, R. F.; Kirk, J.; Lam, K. W. F.; McCormac, J.; Pollacco, D.; Rajpurohit, A.; Rey, J.; Santos, N. C.; Sousa, S. G.; Tsantaki, M.; Wilson, P. A.

    2016-10-01

    We report the discovery of the two hot Jupiters K2-30 b and K2-34 b. The two planets were detected during campaigns 4 and 5 of the extension of the Kepler mission, K2; they transit their main-sequence stars with periods of ~4.099 and ~2.996 days. Subsequent ground-based radial velocity follow-up with SOPHIE, HARPS-N, and CAFE established the planetary nature of the transiting objects. We analyzed the transit signal, radial velocity, and spectral energy distributions of the two systems to characterize their properties. Both planets (K2-30 b and K2-34 b) are bloated hot Jupiters (1.20 RJup and 1.22 RJup) around relatively bright (V = 13.5 and V = 11.5) slow rotating main-sequence (G8 and F9) stars. Thus, these systems are good candidates for detecting the Rossiter-MacLaughlin effect in order to measure their obliquity and for atmospheric studies. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A50

  8. EPIC210957318b and EPIC212110888b: two inflated hot-Jupiters around Solar-type stars

    CERN Document Server

    Lillo-Box, J; Santerne, A; Barros, S C C; Barrado, D; Hébrard, G; Osborn, H P; Armstrong, D J; Almenara, J -M; Boisse, I; Bouchy, F; Brown, D J A; Courcol, B; Deleuil, M; Mena, E Delgado; Díaz, R F; Kirk, J; Lam, K W F; McCormac, J; Pollacco, D; Rajpurohit, A; Rey, J; Santos, N C; Sousa, S G; Tsantaki, M; Wilson, P A

    2016-01-01

    We report the discovery of the two hot-Jupiters EPIC210957318b and EPIC212110888b (hereafter EPIC-318b and EPIC-888b, respectively). The two planets were detected transiting their main-sequence star with periods $\\sim$ 4.099 and $\\sim$ 2.996 days, in campaigns 4 and 5 of the extension of the Kepler mission, K2. Subsequent ground-based radial velocity follow-up with SOPHIE, HARPS-N and CAFE, established the planetary nature of the transiting objects. We analyzed the transit signal, radial velocity and spectral energy distributions of the two systems to characterize their properties. Both planets (EPIC-318b and EPIC-888b) are bloated hot-Jupiters (1.25 $R_{\\rm Jup}$ and 1.33 $R_{\\rm Jup}$) around relatively bright (V =13.5 and V=11.5), slow rotating main-sequence (G8 and F9) stars. Thus, these systems are good candidates for detecting the Rossiter-MacLaughlin effect to measure their obliquity and for atmospheric studies.

  9. A Survey for hot Central Stars of Planetary Nebulae I. Methods and First Results

    CERN Document Server

    Kanarek, Graham C; Faherty, Jacqueline K; Zurek, David; Moffat, Anthony F J

    2016-01-01

    We present the results of initial spectrographic followup with the Very Large Telescope (UT3, Melipal) for $K_s \\ge 14$ Galactic plane CIV emission-line candidates in the near-infrared (NIR). These 7 faint stars all display prominent HeI and CIV emission lines characteristic of a carbon-rich Wolf-Rayet star. They have NIR colours which are much too blue to be those of distant, classical WR stars. The magnitudes and colours are compatible with those expected for central stars of planetary nebulae, and are likely to come from massive progenitor populations, and themselves be more massive than any sample of planetary nebulae known. Our survey has identified thousands of such candidates.

  10. Molecular Astrophysics from Space: the Physical and Chemical Effects of Star Formation and the Destruction of Planetary Systems around Evolved Stars

    Science.gov (United States)

    Neufeld, David

    2005-01-01

    The research conducted during the reporting period is grouped into three sections: 1) Warm molecular gas in the interstellar medium (ISM); 2) Absorption line studies of "cold" molecular clouds; 3) Vaporization of comets around the AGB star IRC+10216.

  11. The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity

    CERN Document Server

    Goldman, Steven R; Zijlstra, Albert A; Green, James A; Wood, Peter R; Nanni, Ambra; Imai, Hiroshi; Whitelock, Patricia A; Matsuura, Mikako; Groenewegen, Martin A T; Gómez, José F

    2016-01-01

    We present the results of our survey of 1612 MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud. We have discovered four new circumstellar maser sources in the LMC, and increased the number of reliable wind speeds from IR stars in the LMC from 5 to 13. Using our new wind speeds, as well as those from Galactic sources, we have derived an updated relation for dust driven winds: $v_{exp} \\propto Z L^{0.4}$. We compare the sub-solar metallicity LMC OH/IR stars with carefully selected samples of more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and Galactic Bulge. For 8 of the Bulge stars we derive pulsation periods for the first time, using near-IR photometry from the VVV survey. We have modeled our LMC OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and mass loss rates by scaling the models to the results from maser profiles. We have done this also for samples in the Galactic...

  12. The Very Massive and Hot LMC Star VFTS 682: Progenitor of a Future Dark Gamma-Ray Burst?

    CERN Document Server

    Zhang, Dong

    2011-01-01

    VFTS 682, a very massive and very hot Wolf-Rayet (WR) star recently discovered in the Large Magellanic Cloud near the famous star cluster R136, might be providing us with a glimpse of a missing link in our understanding of Long Gamma-Ray Bursts (LGRBs), including dark GRBs. It is likely its properties result from chemically homogeneous evolution (CHE), believed to be a key process for a massive star to become a GRB. It is also heavily obscured by dust extinction, which could make it a dark GRB upon explosion. Using Spitzer data we investigate the properties of interstellar dust in the vicinity of R136, and argue that its high obscuration is not unusual for its environment and that it could indeed be a slow runaway ("walkaway") from R136. Unfortunately, based on its current mass loss rate, VFTS 682 is unlikely to become a GRB, because it will lose too much angular momentum at its death. If it were to become a GRB, it probably would also not be dark, either escaping or destroying its surrounding dusty region. N...

  13. The SW Sex-type star 2MASS J01074282+4845188: an unusual bright accretion disk with non-steady emission and a hot white dwarf

    CERN Document Server

    Khruzina, T; Kjurkchieva, D; 10.1051/0004-6361/201220385

    2013-01-01

    We present new photometric and spectral observations of the newly discovered nova-like eclipsing star 2MASS J01074282+4845188. To obtain a light curve solution we used model of a nova-like star whose emission sources are a white dwarf surrounded by an accretion disk, a secondary star filling its Roche lobe, a hot spot and a hot line. 2MASS J01074282+4845188 shows the deepest permanent eclipse among the known nova-like stars. It is reproduced by covering the very bright accretion disk by the secondary component. The luminosity of the disk is much bigger than that of the rest light sources. The determined high temperature of the disk is typical for that observed during the outbursts of CVs. The primary of 2MASS J01074282+4845188 is one of the hottest white dwarfs in CVs. The temperature of 5090 K of its secondary is also quite high and more appropriate for a long-period SW Sex star. It might be explained by the intense heating from the hot white dwarf and the hot accretion disk of the target. The high mass accr...

  14. The Mass-Loss Return From Evolved Stars to the LMC: Empirical Relations for Excess Emission at 8 and 24 \\mu m

    CERN Document Server

    Srinivasan, Sundar; Leitherer, Claus; Vijh, Uma; Volk, Kevin; Blum, Robert D; Babler, Brian L; Block, Miwa; Bracker, Steve; Cohen, Martin; Engelbracht, Charles W; For, Bi-Qing; Gordon, Karl D; Harris, Jason; Hora, Joseph L; Indebetouw, Remy; Markwick-Kemper, Francisca; Meade, Marilyn; Misselt, Karl A; Sewilo, Marta; Whitney, Barbara

    2009-01-01

    We present empirical relations describing excess emission from evolved stars in the Large Magellanic Cloud (LMC) using data from the SAGE (Surveying the Agents of a Galaxy's Evolution) survey which includes the IRAC 3.6, 4.5, 5.8 and 8.0 \\mu m and MIPS 24, 70 and 160 \\mu m bands. We combine the SAGE data with the Two Micron All Sky Survey (2MASS; J, H and Ks) and the optical Magellanic Cloud Photometric Survey (MCPS; U, B, V and I) point source catalogs to create complete spectral energy distributions (SEDs) of the asymptotic giant branch (AGB) star candidates in the LMC. AGB star outflows are among the main producers of dust in a galaxy, and this mass loss results in an excess in the fluxes observed in the 8 and 24 \\mic m bands. We identify oxygen-rich, carbon-rich and extreme AGB star populations in our sample based on their 2MASS and IRAC colors. We calculate excesses fluxes in the mid-IR bands by comparison of the SEDs with model photospheres. We find about 16,000 O-rich, 6300 C-rich and 1000 extreme sour...

  15. VizieR Online Data Catalog: New hot subdwarf stars (Perez-Fernandez+, 2016)

    Science.gov (United States)

    Perez-Fernandez, E.; Ulla, A.; Solano, E.; Oreiro, R.; Rodrigo, C.

    2016-11-01

    In that work, a hot sd selection procedure was defined and tested by means of a thorough retrieval, with the aid of VO tools, of multicolour photometry and astrometric information from stellar catalogues. A filtering procedure to distinguish among different types of objects was designed to obtain a hot sd sample with a low contamination factor. The method was tested on two sky regions: the Kepler FoV2 and a region of 300deg2 around (RA:225°,DE:5°) obtaining a high rate of success (above 80 per cent) in finding new uncatalogued hot sds. Temperatures were provided by fitting their spectral energy distribution (SED), and considering two-atmosphere fits for those objects with a clear infrared (IR) excess, a signature of the possible presence of a cool companion. The complete table can be found at http://svo2.cab.inta-csic.es/vocats/hsa/ (4 data files).

  16. Hot subdwarf stars in close-up view I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions

    CERN Document Server

    Geier, S; Podsiadlowski, Ph; Edelmann, H; Napiwotzki, R; Kupfer, T; Mueller, S

    2010-01-01

    The origin of hot subdwarf B stars (sdBs) is still unclear. About half of the known sdBs are in close binary systems for which common envelope ejection is the most likely formation channel. Little is known about this dynamic phase of binary evolution. Due to the tidal influence of the companion in close binary systems, the rotation of the primary becomes synchronised to its orbital motion. In this case it is possible to constrain the mass of the companion, if the primary mass, its projected rotational velocity as well as its surface gravity are known. For the first time we measured the projected rotational velocities of a large sdB binary sample from high resolution spectra. We analysed a sample of 51 sdB stars in close binaries, 40 of which have known orbital parameters comprising half of all such systems known today. Synchronisation in sdB binaries is discussed both from the theoretical and the observational point of view. The masses and the nature of the unseen companions could be constrained in 31 cases. ...

  17. HAT-P-6b: A Hot Jupiter transiting a bright F star

    CERN Document Server

    Noyes, R W; Torres, G; Pal, A; Kovacs, Geza; Latham, D W; Fernández, J M; Fischer, D A; Butler, R P; Marcy, G W; Sipocz, B; Esquerdo, G A; Kovacs, Gabor; Sasselov, D D; Sato, B; Stefanik, R; Holman, M; Lázár, J; Papp, I; Sari, P

    2007-01-01

    In the ongoing HATNet survey we have detected a giant planet, with radius 1.33 +/- 0.06 RJup and mass 1.06 +/- 0.12 MJup, transiting the bright (V = 10.5) star GSC 03466-00819. The planet is in a circular orbit with period 3.852985 +/- 0.000005 days and mid-transit epoch 2,454,035.67575 +/- 0.00028 (HJD). The parent star is a late F star with mass 1.29 +/- 0.06 Msun, radius 1.46 +/- 0.06 Rsun, Teff ~ 6570 +/- 80 K, [Fe=H] = -0.13 +/- 0.08 and age ~ 2.3+/-^{0.5}_{0.7}Gy. With this radius and mass, HAT-P-6b has somewhat larger radius than theoretically expected. We describe the observations and their analysis to determine physical properties of the HAT-P-6 system, and briefly discuss some implications of this finding.

  18. Hot, Massive Stars in the Extremely Metal-Poor Galaxy, I Zw 18

    Science.gov (United States)

    Heap, Sara R.; Malumuth, Eliot M.

    2010-01-01

    The carbon-enhanced metal-poor galaxy, I Zw 18, is the Rosetta Stone for understanding galaxies in the early universe by providing constraints on the IMF of massive stars, the role of galaxies in reionization of the universe, mixing of newly synthesized material in the ISM, and gamma-ray bursts at low metallicity, and on the earliest generations of stars producing the observed abundance pattern. We describe these constraints as derived from analyses of HST/COS spectra of I Zw 18 including stellar atmosphere analysis and photo-ionization modeling of both the emission and absorption spectra of the nebular material and interstellar medium.

  19. Investigating the origin of cyclical spectral variations in hot, massive stars

    CERN Document Server

    David-Uraz, Alexandre; Petit, Veronique; ud-Doula, Asif

    2013-01-01

    OB stars are known to exhibit various types of wind variability, as detected in their ultraviolet spectra, amongst which are the ubiquitous discrete absorption components (DACs). These features have been associated with large-scale azimuthal structures extending from the base of the wind to its outer regions: corotating interaction regions (CIRs). There are several competing hypotheses as to which physical processes may perturb the star's surface and generate CIRs, including magnetic fields and non radial pulsations (NRPs), the subjects of this paper with a particular emphasis on the former. Although large-scale magnetic fields are ruled out, magnetic spots deserve further investigation, both on the observational and theoretical fronts.

  20. The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity

    Science.gov (United States)

    Goldman, Steven R.; van Loon, Jacco Th.; Zijlstra, Albert A.; Green, James A.; Wood, Peter R.; Nanni, Ambra; Imai, Hiroshi; Whitelock, Patricia A.; Matsuura, Mikako; Groenewegen, Martin A. T.; Gómez, José F.

    2017-02-01

    We present the results of our survey of 1612-MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC). We have discovered four new circumstellar maser sources in the LMC, and increased the number of reliable wind speeds from infrared (IR) stars in the LMC from 5 to 13. Using our new wind speeds, as well as those from Galactic sources, we have derived an updated relation for dust-driven winds: vexp ∝ ZL0.4. We compare the subsolar metallicity LMC OH/IR stars with carefully selected samples of more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and Galactic bulge. We derive pulsation periods for eight of the bulge stars for the first time by using near-IR photometry from the Vista Variables in the Via Lactea survey. We have modelled our LMC OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and mass-loss rates by scaling the models to the results from maser profiles. We have done this also for samples in the Galactic Centre and bulge and derived a new mass-loss prescription which includes luminosity, pulsation period, and gas-to-dust ratio dot{M} = 1.06^{+3.5}_{-0.8} × }10^{-5 (L/10^4 L_{⊙})^{0.9± 0.1}(P/500 {d})^{0.75± 0.3} (r_gd/200)^{-0.03± 0.07} M⊙ yr-1. The tightest correlation is found between mass-loss rate and luminosity. We find that the gas-to-dust ratio has little effect on the mass-loss of oxygen-rich AGB stars and RSGs within the Galaxy and the LMC. This suggests that the mass-loss of oxygen-rich AGB stars and RSGs is (nearly) independent of metallicity between a half and twice solar.

  1. Comoving frame models of hot star winds. II. Reduction of O star wind mass-loss rates in global models

    Science.gov (United States)

    Krtička, J.; Kubát, J.

    2017-10-01

    We calculate global (unified) wind models of main-sequence, giant, and supergiant O stars from our Galaxy. The models are calculated by solving hydrodynamic, kinetic equilibrium (also known as NLTE) and comoving frame (CMF) radiative transfer equations from the (nearly) hydrostatic photosphere to the supersonic wind. For given stellar parameters, our models predict the photosphere and wind structure and in particular the wind mass-loss rates without any free parameters. Our predicted mass-loss rates are by a factor of 2-5 lower than the commonly used predictions. A possible cause of the difference is abandoning of the Sobolev approximation for the calculation of the radiative force, because our models agree with predictions of CMF NLTE radiative transfer codes. Our predicted mass-loss rates agree nicely with the mass-loss rates derived from observed near-infrared and X-ray line profiles and are slightly lower than mass-loss rates derived from combined UV and Hα diagnostics. The empirical mass-loss rate estimates corrected for clumping may therefore be reconciled with theoretical predictions in such a way that the average ratio between individual mass-loss rate estimates is not higher than about 1.6. On the other hand, our predictions are by factor of 4.7 lower than pure Hα mass-loss rate estimates and can be reconciled with these values only assuming a microclumping factor of at least eight.

  2. The Mass-Loss Return from Evolved Stars to the Large Magellanic Cloud II: Dust Properties for Oxygen-Rich Asymptotic Giant Branch Stars

    CERN Document Server

    Sargent, Benjamin A; Meixner, M; Kemper, F; Tielens, A G G M; Speck, A K; Matsuura, M; Bernard, J -Ph; Hony, S; Gordon, Karl D; Indebetouw, R; Marengo, M; Sloan, G C; Woods, Paul M

    2014-01-01

    We model multi-wavelength broadband UBVIJHKs and Spitzer IRAC and MIPS photometry and IRS spectra from the SAGE and SAGE-Spec observing programs of two oxygen-rich asymptotic giant branch (O-rich AGB) stars in the Large Magellanic Cloud (LMC) using radiative transfer models of dust shells around stars. We chose a star from each of the bright and faint O-rich AGB populations found by earlier studies of the SAGE sample in order to derive a baseline set of dust properties to be used in the construction of an extensive grid of radiative transfer models of the O-rich AGB stars found in the SAGE surveys. From the bright O-rich AGB population we chose HV 5715, and from the faint O-rich AGB population we chose SSTISAGE1C J052206.92-715017.6 (SSTSAGE052206). We found the complex indices of refraction of oxygen-deficient silicates from Ossenkopf et al (1992) and a "KMH"-like grain size distribution with gamma of -3.5, a_min of 0.01 microns, and a_0 of 0.1 microns to be reasonable dust properties for these models. There...

  3. The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370

    Science.gov (United States)

    Hrudková, M.; Hatzes, A.; Karjalainen, R.; Lehmann, H.; Hekker, S.; Hartmann, M.; Tkachenko, A.; Prins, S.; Van Winckel, H.; De Nutte, R.; Dumortier, L.; Frémat, Y.; Hensberge, H.; Jorissen, A.; Lampens, P.; Laverick, M.; Lombaert, R.; Pápics, P. I.; Raskin, G.; Sódor, Á.; Thoul, A.; Van Eck, S.; Waelkens, C.

    2017-01-01

    We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 ± 1.0 MJupiter orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our programme to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coudé echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph High Efficiency and Resolution Mercator Echelle Spectrograph of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 ± 4.5 d) variation with a semi-amplitude K = 133 ± 25 m s- 1, superimposed on a long-term trend. A low-mass stellar companion with an orbital period of ˜88 yr in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this system may answer this uncertainty. From Kepler photometry, we find that HD 175370 is most likely a low-mass red giant branch or asymptotic giant branch star.

  4. Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles - II. CO line survey of evolved stars: derivation of mass-loss rate formulae

    CERN Document Server

    De Beck, E; de Koter, A; Justtanont, K; Verhoelst, T; Kemper, F; Menten, K M M

    2010-01-01

    We aim to (1) set up simple and general analytical expressions to estimate mass-loss rates of evolved stars, and (2) from those calculate estimates for the mass-loss rates of asymptotic giant branch (AGB), red supergiant (RSG), and yellow hypergiant stars in our galactic sample. Rotationally excited lines of CO are a very robust diagnostic in the study of circumstellar envelopes (CSEs). When sampling different layers of the CSE, observations of these molecular lines lead to detailed profiles of kinetic temperature, expansion velocity, and density. A state-of-the-art, nonlocal thermal equilibrium, and co-moving frame radiative transfer code that predicts CO line intensities in the CSEs of late-type stars is used in deriving relations between stellar and molecular-line parameters, on the one hand, and mass-loss rate, on the other. We present analytical expressions for estimating the mass-loss rates of evolved stellar objects for 8 rotational transitions of the CO molecule, apply them to our extensive CO data se...

  5. High-Resolution {\\it Chandra} Spectroscopy of tau Scorpii A Narrow-Line X-ray Spectrum From a Hot Star

    CERN Document Server

    Cohen, D H; MacFarlane, J J; Miller, N A; Cassinelli, J P; Owocki, S P; Liedahl, D A; Cohen, David H.; Messi\\`{e}res, Genevi\\`{e}ve E. de; Farlane, Joseph J. Mac; Miller, Nathan A.; Cassinelli, Joseph P.; Owocki, Stanley P.; Liedahl, Duane A.

    2003-01-01

    Long known to be an unusual early-type star by virtue of its hard and strong X-ray emission, tau Scorpii poses a severe challenge to the standard picture of O star wind-shock X-ray emission. The Chandra HETGS spectrum now provides significant direct evidence that this B0.2 star does not fit this standard wind-shock framework. The many emission lines detected with the Chandra gratings are significantly narrower than what would be expected from a star with the known wind properties of tau Sco, although they are broader than the corresponding lines seen in late-type coronal sources. While line ratios are consistent with the hot plasma on this star being within a few stellar radii of the photosphere, from at least one He-like complex there is evidence that the X-ray emitting plasma is located more than a stellar radius above the photosphere. The Chandra spectrum of tau Sco is harder and more variable than those of other hot stars, with the exception of the young magnetized O star theta Ori C. We discuss these new...

  6. Discovery of a close substellar companion to the hot subdwarf star HD 149382 - The decisive influence of substellar objects on late stellar evolution

    CERN Document Server

    Geier, S; Heber, U; Morales-Rueda, L

    2009-01-01

    Substellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star formation process. The evolution of their host stars may have an enourmous impact on these small companions. Vice versa a planet might also influence stellar evolution as has recently been argued. Here we report the discovery of a 8-23 Jupiter-mass substellar object orbiting the hot subdwarf HD 149382 in 2.391 days at a distance of only about five solar radii. Obviously the companion must have survived engulfment in the red-giant envelope. Moreover, the substellar companion has triggered envelope ejection and enabled the sdB star to form. Hot subdwarf stars have been identified as the sources of the unexpected ultravoilet emission in elliptical galaxies, but the formation of these stars is not fully understood. Being the brightest star of its class, HD 149382 offers the best conditions to detect the substellar companion. Hence, undisclosed substellar companions offer a natural solution for the long-standing formation...

  7. 演化晚期恒星中的结晶硅酸盐尘埃%Crystalline Silicates in Evolved Stars

    Institute of Scientific and Technical Information of China (English)

    刘佳明; 姜碧沩

    2014-01-01

    Silicate is the most abundant cosmic dust which may present in two forms:amorphous and crystalline. Due to the difference in structure, the two types of silicate dust can be distinguished from their spectral features in the infrared. The amorphous silicate dust was discovered early in 1960s by their smooth and broad features at 10 and 18 micron. In particular, the all-sky survey by InfraRed Astronomical Satellite/Low Resolution Spectrometer revealed the popularity of amorphous silicate dust in the circumstellar envelope of evolved stars such as AGB and post-AGB stars. Meanwhile, the crystalline silicate outside the solar system was not definitely identified until the successful observation in the even longer wavelength range by the high resolution spectrometers board on the Infrared Space Observatory. It was found that the crystalline silicate dust emits a series of narrow and sharp features spanning the infrared spectrum from 10 to 70 micron, with the most prominent features being the complexes around 10, 18, 23, 28, 33, 40 and 60 micron. These features are detected in various scales, from our solar system ob jects to distant galaxies, including comets, the pre-planetary disk around Herbig Ae/Be and T Tauri stars, the debris disk of main-sequence stars, circumstellar envelop around evolved stars, ultra-luminous infrared galaxies, and even quasars. On the other hand, there has been no clear detection of crystalline silicate in the interstellar medium of the Milky Way galaxy, which addresses a question how the crystalline silicate dust evolves in the interstellar medium. The crystalline silicate dust is detected in every phase of late stellar evolution, i.e, red giants, AGB stars, post-AGB stars, planetary nebulae at the low-mass end, and red supergiants, luminous blue variables, supernova remnants at the high-mass end. The char-acteristics (such as peak wavelength and FWHM) of the spectral features (in particular the features at 33.6 and 69 microns) in the evolved

  8. Evolved Massive Stars in the Local Group. I. Identification of Red Supergiants in NGC 6822, M31, and M33

    Science.gov (United States)

    Massey, Philip

    1998-07-01

    Knowledge of the red supergiant (RSG) population of nearby galaxies allows us to probe massive star evolution as a function of metallicity; however, contamination by foreground Galactic dwarfs dominates surveys for red stars in Local Group galaxies beyond the Magellanic Clouds. Model atmospheres predict that low-gravity supergiants will have B-V values that are redder by several tenths of a magnitude than foreground dwarfs at a given V-R color, a result that is largely independent of reddening. We conduct a BVR survey of several fields in the Local Group galaxies NGC 6822, M33, and M31 as well as neighboring control fields and identify RSG candidates from CCD photometry. The survey is complete to V = 20.5, corresponding to MV = -4.5 or an Mbol of -6.3 for the reddest stars. Follow-up spectroscopy at the Ca II triplet of 130 stars is used to demonstrate that our photometric criterion for identifying RSGs is highly successful (96% for stars brighter than V = 19.5; 82% for V = 19.5-20.5). Classification spectra are also obtained for a number of stars in order to calibrate color with spectral type empirically. We find that there is a marked progression in the average (B-V)0 and (V-R)0 colors of RSGs in these three galaxies, with the higher metallicity systems having a later average spectral type, which is consistent with previous findings by Elias, Frogel, & Humphreys for the Milky Way and Magellanic Clouds. More significantly, we find that there is a clear progression with metallicity in the relative number of the highest luminosity RSGs, a trend that is apparent both in absolute visual magnitude and in bolometric luminosity. Thus any use of RSGs as distance indicators requires correction for the metallicity of the parent galaxy. Our findings are in accord with the predictions of the ``Conti scenario'' in which higher metallicities result in higher mass-loss rates, resulting in a star of a given luminosity spending an increasing fraction of its He-burning lifetime as

  9. Types of Hot Jupiter Atmospheres

    Science.gov (United States)

    Bisikalo, Dmitry V.; Kaygorodov, Pavel V.; Ionov, Dmitry E.; Shematovich, Valery I.

    Hot Jupiters, i.e. exoplanet gas giants, having masses comparable to the mass of Jupiter and semimajor axes shorter than 0.1 AU, are a unique class of objects. Since they are so close to the host stars, their atmospheres form and evolve under the action of very active gas dynamical processes caused by the gravitational field and irradiation of the host star. As a matter of fact, the atmospheres of several of these planets fill their Roche lobes , which results in a powerful outflow of material from the planet towards the host star. The energy budget of this process is so important that it almost solely governs the evolution of hot Jupiters gaseous envelopes. Based on the years of experience in the simulations of gas dynamics in mass-exchanging close binary stars, we have investigated specific features of hot Jupiters atmospheres. The analytical estimates and results of 3D numerical simulations, discussed in this Chapter, show that the gaseous envelopes around hot Jupiters may be significantly non-spherical and, at the same time, stationary and long-lived. These results are of fundamental importance for the interpretation of observational data.

  10. An extreme planetary system around HD219828. One long-period super Jupiter to a hot-neptune host star

    CERN Document Server

    Santos, N C; Faria, J P; Rey, J; Correia, A C M; Laskar, J; Udry, S; Adibekyan, V; Bouchy, F; Delgado-Mena, E; Melo, C; Dumusque, X; Hébrard, G; Lovis, C; Mayor, M; Montalto, M; Mortier, A; Pepe, F; Figueira, P; Sahlmann, J; Ségransan, D; Sousa, S G

    2016-01-01

    With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. We present a full investigation of the HD219828 system, a bright metal-rich star for which a hot neptune has previously been detected. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD219828. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. We announce the discovery of a long period (P=13.1years) massive (msini=15.1MJup) companion (HD219828c) in a very eccentric orbit (e=0.81). The same data confirms the existence of a hot-neptune, HD219828b, with a minimum mass of 21 MEarth and a period of 3.83days. The dynamical analysis shows that the system is stable. The HD219828 system is extreme and unique in several aspects. First, among all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like H...

  11. Abundances in the hot DZ star CBS 127 - How efficient is hydrogen screening

    Energy Technology Data Exchange (ETDEWEB)

    Sion, E.M.; Hammond, G.L.; Wagner, R.M.; Starrfield, S.G.; Liebert, J. (Villanova Univ., PA (USA) South Florida Univ., Tampa, FL (USA) Ohio State Univ., Columbus (USA) Arizona State Univ., Tempe (USA) Steward Observatory, Tucson, AZ (USA))

    1990-10-01

    A revised and updated grid of cool helium-rich model atmospheres which includes the effect of varying hydrogen abundance is used to analyze the temperature and abundance of the DZ white dwarf CBS 127. Comparisons of the star to several other DZ white dwarfs with similar T(e)s show that CBS 137 is the hottest DZ star and lies near the boundary temperature above which it has been proposed that hydrogen accretion may be prevented. Based on the results, a specifically defined single lower boundary temperature for screening is rejected, and it is demonstrated that the propeller must operate over a very broad range of T(eff), down to T(eff) as low as 5800 K, with highly variable efficiency. 39 refs.

  12. A hot horizontal branch star with a close K-type main-sequence companion

    CERN Document Server

    Bidin, C Moni; Montalto, M; Catelan, M; Villanova, S; Piotto, G; Geisler, D

    2015-01-01

    Dynamical interactions in binary systems are thought to play a major role in the formation of extreme horizontal branch stars (EHBs) in the Galactic field. However, it is still unclear if the same mechanisms are at work in globular clusters, where EHBs are predominantly single stars. Here we report on the discovery of a unique close binary system (period ~1.61 days) in the globular cluster NGC6752, comprising an EHB and a main-sequence companion of 0.63+-0.05 Msun. Such a system has no counterpart among nearly two hundred known EHB binaries in the Galactic field. Its discovery suggests that either field studies are incomplete, missing this type of systems possibly because of selection effects, or that a particular EHB formation mechanism is active in clusters but not in the field.

  13. XO-2b: a hot Jupiter with a variable host star that potentially affects its measured transit depth

    CERN Document Server

    Zellem, Robert T; Pearson, Kyle A; Turner, Jake D; Henry, Gregory W; Williamson, Michael W; Fitzpatrick, M Ryleigh; Teske, Johanna K; Biddle, Lauren I

    2015-01-01

    The transiting hot Jupiter XO-2b is an ideal target for multi-object photometry and spectroscopy as it has a relatively bright ($V$-mag = 11.25) K0V host star (XO-2N) and a large planet-to-star contrast ratio (R$_{p}$/R$_{s}\\approx0.015$). It also has a nearby (31.21") binary stellar companion (XO-2S) of nearly the same brightness ($V$-mag = 11.20) and spectral type (G9V), allowing for the characterization and removal of shared systematic errors (e.g., airmass brightness variations). We have therefore conducted a multiyear (2012--2015) study of XO-2b with the University of Arizona's 61" (1.55~m) Kuiper Telescope and Mont4k CCD in the Bessel U and Harris B photometric passbands to measure its Rayleigh scattering slope to place upper limits on the pressure-dependent radius at, e.g., 10~bar. Such measurements are needed to constrain its derived molecular abundances from primary transit observations. We have also been monitoring XO-2N since the 2013--2014 winter season with Tennessee State University's Celestron-...

  14. Dynamical ejecta from precessing neutron star-black hole mergers with a hot, nuclear-theory based equation of state

    CERN Document Server

    Foucart, Francois; Brege, Wyatt; Duez, Matthew D; Kasen, Daniel; Hemberger, Daniel A; Kidder, Lawrence E; Pfeiffer, Harald P; Scheel, Mark A

    2016-01-01

    Neutron star-black hole binaries are among the strongest sources of gravitational waves detectable by current observatories. They can also power bright electromagnetic signals (gamma-ray bursts, kilonovae), and may be a significant source of production of r-process nuclei. A misalignment of the black hole spin with respect to the orbital angular momentum leads to precession of that spin and of the orbital plane, and has a significant effect on the properties of the post-merger remnant and of the material ejected by the merger. We present a first set of simulations of precessing neutron star-black hole mergers using a hot, composition dependent, nuclear-theory based equation of state (DD2). We show that the mass of the remnant and of the dynamical ejecta are broadly consistent with the result of simulations using simpler equations of state, while differences arise when considering the dynamics of the merger and the velocity of the ejecta. We show that the latter can easily be understood from assumptions about ...

  15. Modeling the Structure of Hot Star Disks: a Critical Evaluation of the Viscous Decretion Scenario

    OpenAIRE

    Carciofi, A. C.; Bjorkman, J. E.; Miroshnichenko, A. S.; Magalhães, A.M.; Bjorkman, K. S.

    2006-01-01

    We present self-consistent solutions for the disk structure of classical Be stars. Our disk model is hydrostatically supported in the vertical direction and the radial structure is governed by viscosity ($\\alpha$-disks). We perform three-dimensional non-LTE Monte Carlo simulations to calculate simultaneously both the equilibrium temperature and Hydrogen level populations and to solve self-consistently for the density structure of the disk. We discuss the general properties of the solution for...

  16. HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star

    CERN Document Server

    Bakos, G Á; Bayliss, D; Hartman, J D; Zhou, G; Brahm, R; Mancini, L; deVal-Borro, M; Bhatti, W; Jordán, A; Rabus, M; Espinoza, N; Csubry, Z; Howard, A W; Fulton, B J; Buchhave, L A; Ciceri, S; Henning, T; Schmidt, B; Isaacson, H; Noyes, R W; Marcy, G W; Suc, V; Howe, A R; Burrows, A S; Lázár, J; Papp, I; Sári, P

    2015-01-01

    We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120+/-0.012 M_Jup, a radius of 0.563+0.046-0.034 R_Jup, and an orbital period of 3.1853 days. The host star is a moderately bright (V = 13.340+/-0.010 mag, K_S = 10.976+/-0.026 mag) K dwarf star with a mass of 0.849+/-0.027 M_Sun, a radius of 0.815+0.049-0.035 R_Sun, and a metallicity of [Fe/H]= +0.250+/-0.080. The star is photometrically quiet to within the precision of the HATSouth measurements, has low RV jitter, and shows no evidence for chromospheric activity in its spectrum. HATS-7b is the second smallest radius planet discovered by a wide-field ground-based transit survey, and one of only a handful of Neptune-size planets with mass and radius determined to 10% precision. Theoretical modeling of HATS-7b yields a hydrogen-helium fraction of 18+/-4% (rock-iron core and H2-He envelope), or 9+/-4% (ice core and H2-He envelope), i.e.it has a composition broadly similar to that of Uranus and Neptune, and ve...

  17. The mass-loss return from evolved stars to the Large Magellanic Cloud III. Dust properties for carbon-rich asymptotic giant branch stars

    CERN Document Server

    Srinivasan, Sundar; Matsuura, M; Meixner, M; Kemper, F; Tielens, A G G M; Volk, K; Speck, A K; Woods, Paul M; Gordon, K; Marengo, M; Sloan, G C

    2010-01-01

    We present a 2Dust model for the dust shell around a LMC long-period variable (LPV) previously studied as part of the OGLE survey. OGLE LMC LPV 28579 (SAGE J051306.40-690946.3) is a carbon-rich asymptotic giant branch (AGB) star for which we have photometry and spectra from the Spitzer SAGE and SAGE-Spec programs along with UBVIJHK_s photometry. By modeling this source, we obtain a baseline set of dust properties to be used in the construction of a grid of models for carbon stars. We reproduce its spectral energy distribution using a mixture of AmC and SiC (15% by mass). The grain sizes are distributed according to the KMH model. The best-fit model has an optical depth of 0.28 for the shell at the peak of the SiC feature, with R_in~1430 R_sun or 4.4 R_star. The temperature at this inner radius is 1310 K. Assuming an expansion velocity of 10 km s^-1, we obtain a dust mass-loss rate of 2.5x10^-9 M_sun yr-1. We calculate a 15% variation in this rate by testing the fit sensitivity against variation in input param...

  18. The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370

    CERN Document Server

    Hrudková, M; Karjalainen, R; Lehmann, H; Hekker, S; Hartmann, M; Tkachenko, A; Prins, S; van Winckel, H; de Nutte, R; Dumortier, L; Frémat, Y; Hensberge, H; Jorissen, A; Lampens, P; Laverick, M; Lombaert, R; Pápics, P I; Raskin, G; Sódor, Á; Thoul, A; van Eck, S; Waelkens, C

    2016-01-01

    We report on the discovery of a planetary companion candidate with a minimum mass Msini = 4.6 M_J orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our program to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coude echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph HERMES of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 days) variation with a semi-amplitude K = 133 m/s, superimposed on a long-term trend. A low-mass stellar companion with an orbital period of ~88 years in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-...

  19. Hardening in a Time--Evolving Stellar Background: Hyper--Velocity Stars, Orbital Decay and Prediction for Lisa

    CERN Document Server

    Haardt, F; Madau, P

    2006-01-01

    We study the long-term evolution of massive black hole binaries (MBHBs) at the centers of galaxies using detailed full three-body scattering experiments. Stars, drawn from a distribution unbound to the binary, are ejected by the gravitational slingshot. We quantify the effect of secondary slingshots -- stars returning on small impact parameter orbits to have a second super-elastic scattering with the MBHB -- on binary separation. Even in the absence of two-body relaxation or gas dynamical processes, very unequal mass binaries of mass M=10^7 solar masses can shrink to the gravitational wave emission regime in less than a Hubble time, and are therefore a target for the planned Laser Interferometer Space Antenna (LISA). Three-body interactions create a subpopulation of hypervelocity stars on nearly radial, corotating orbits, with a spatial distribution that is initially highly flattened in the inspiral plane of the MBHB, but becomes more isotropic with decreasing binary separation. The mass ejected is ~0.7 times...

  20. Hot subdwarf formation: Confronting theory with observation

    Directory of Open Access Journals (Sweden)

    Geier S.

    2013-03-01

    Full Text Available The formation of hot subdwarf stars is still unclear. Both single-star and binary scenarios have been proposed to explain the properties of these evolved stars situated at the extreme blue end of the horizontal branch. The observational evidence gathered in the last decade, which revealed high fractions of binaries, shifted the focus from the single-star to the binary formation scenarios. Common envelope ejection, stable Roche lobe overflow and the merger of helium white dwarfs seemed to be sufficient to explain the formation of both the binary as well as the remaining single hot subdwarfs. However, most recent and rather unexpected observations challenge the standard binary evolution scenarios.

  1. HATS-7b: A Hot Super Neptune Transiting a Quiet K Dwarf Star

    Science.gov (United States)

    Bakos, G. Á.; Penev, K.; Bayliss, D.; Hartman, J. D.; Zhou, G.; Brahm, R.; Mancini, L.; de Val-Borro, M.; Bhatti, W.; Jordán, A.; Rabus, M.; Espinoza, N.; Csubry, Z.; Howard, A. W.; Fulton, B. J.; Buchhave, L. A.; Ciceri, S.; Henning, T.; Schmidt, B.; Isaacson, H.; Noyes, R. W.; Marcy, G. W.; Suc, V.; Howe, A. R.; Burrows, A. S.; Lázár, J.; Papp, I.; Sári, P.

    2015-11-01

    We report the discovery by the HATSouth network of HATS-7b, a transiting Super-Neptune with a mass of 0.120 ± 0.012 {M}{{J}}, a radius of {0.563}-0.034+0.046 {R}{{J}}, and an orbital period of 3.1853 days. The host star is a moderately bright (V=13.340\\+/- 0.010 mag, {K}S=10.976\\+/- 0.026 mag) K dwarf star with a mass of 0.849 ± 0.027 {M}⊙ , a radius of {0.815}-0.035+0.049 {R}⊙ , and a metallicity of [{Fe}/{{H}}] =+0.250\\+/- 0.080. The star is photometrically quiet to within the precision of the HATSouth measurements, has low RV jitter, and shows no evidence for chromospheric activity in its spectrum. HATS-7b is the second smallest radius planet discovered by a wide-field ground-based transit survey, and one of only a handful of Neptune-size planets with mass and radius determined to 10% precision. Theoretical modeling of HATS-7b yields a hydrogen-helium fraction of 18 ± 4% (rock-iron core and H2-He envelope), or 9 ± 4% (ice core and H2-He envelope), i.e., it has a composition broadly similar to that of Uranus and Neptune, and very different from that of Saturn, which has 75% of its mass in H2-He. Based on a sample of transiting exoplanets with accurately (Mauna Kea, the MPG 2.2 m and ESO 3.6 m telescopes at the ESO Observatory in La Silla. This paper uses observations obtained with facilities of the Las Cumbres Observatory Global Telescope.

  2. HAT-P-25b: a Hot-Jupiter Transiting a Moderately Faint G Star

    CERN Document Server

    Quinn, S N; Hartman, J; Torres, G; Kovács, G; Latham, D W; Noyes, R W; Fischer, D A; Johnson, J A; Marcy, G W; Howard, A W; Szentgyorgyi, A; Fürész, G; Buchhave, L A; Béky, B; Sasselov, D D; Stefanik, R P; Perumpilly, G; Everett, M; Lázár, J; Papp, I; Sári, P

    2010-01-01

    We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 +/- 0.000019 days, transit epoch Tc = 2455176.85173 +/- 0.00047 (BJD), and transit duration 0.1174 +/- 0.0017 days. The host star has mass of 1.01 +/- 0.03 M(Sun), radius of 0.96 +(0.05)-(0.04) R(Sun), effective temperature 5500 +/- 80 K, and metallicity [Fe/H] = +0.31 +/- 0.08. The planetary companion has a mass of 0.567 +/- 0.022 M(Jup), and radius of 1.190 +(0.081)-(0.056) R(Jup) yielding a mean density of 0.42 +/- 0.07 g cm-3. Comparing these observations with recent theoretical models, we find that HAT-P-25b is consistent with a hydrogen-helium dominated gas giant planet with negligible core mass and age 3.2 +/- 2.3 Gyr. The properties of HAT-P-25b support several previously observed correlations for planets in the mass range 0.4 < M < 0.7 M(Jup), including those of core mass vs. metallicity, planet radius vs. equilibrium temperature, and orbital perio...

  3. HATS-3b: An inflated hot Jupiter transiting an F-type star

    CERN Document Server

    Bayliss, D; Penev, K; Bakos, G; Hartman, J; Jordán, A; Mancini, L; Mohler, M; Suc, V; Rabus, M; Béky, B; Csubry, Z; Buchhave, L; Henning, T; Nikolov, N; Csák, B; Brahm, R; Espinoza, N; Noyes, R; Schmidt, B; Conroy, P; Wright, D; Tinney, C; Addison, B; Sackett, P; Sasselov, D; Lázár, J; Papp, I; Sári, P

    2013-01-01

    We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V=12.4 F-dwarf star. HATS-3b has a period of P = 3.5479d, mass of Mp = 1.07MJ, and radius of Rp = 1.38RJ. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsini = 9.0km/s), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces logg and Teff parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1 km/s.

  4. HATS-4b: A Dense Hot-Jupiter Transiting a Super Metal-Rich G Star

    CERN Document Server

    Jordán, A; Bakos, G Á; Bayliss, D; Penev, K; Hartman, J D; Zhou, G; Mancini, L; Mohler-Fischer, M; Ciceri, S; Sato, B; Csubry, Z; Rabus, M; Suc, V; Espinoza, N; Bhatti, W; Borro, M de Val; Buchhave, L; Csák, B; Henning, T; Schmidt, B; Tan, T G; Noyes, R W; Béky, B; Butler, R P; Shectman, S; Crane, J; Thompson, I; Williams, A; Martin, R; Contreras, C; Lázár, J; Papp, I; Sári, P

    2014-01-01

    We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V=13.46 mag G star. HATS-4b has a period of P = 2.5167 d, mass of Mp = 1.32 Mj, radius of Rp = 1.02 Rj and density of rho_p = 1.55 +- 0.16 g/cm^3 ~ 1.24 rhoj. The host star has a mass of 1.00 Msun, a radius of 0.92 Rsun and a very high metallicity [Fe/H]= 0.43 +- 0.08. HATS-4b is among the densest known planets with masses between 1-2 Mj and is thus likely to have a significant content of heavy elements of the order of 75 Mearth. In this paper we present the data reduction, radial velocity measurement and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique to estimate simultaneously vsini and macroturbulence using high resolution spectra.

  5. Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators

    CERN Document Server

    Van Winckel, Hans; Briquet, Maryline; De Cat, Peter; Degroote, Pieter; De Meester, Wim; De Ridder, Joris; Deroo, Pieter; Desmet, Maarten; Drummond, Rachel; Eyer, Laurent; Groenewegen, Martin A T; Kolenberg, Katrien; Kilkenny, David; Ladjal, Djazia; Lefever, Karolien; Maas, Thomas; Marang, Fred; Martinez, Peter; Østensen, Roy H; Raskin, Gert; Reyniers, Maarten; Royer, Pierre; Saesen, Sophie; Uytterhoeven, Katrien; Vanautgaerden, Jan; Vandenbussche, Bart; van Wyk, Francois; Vučković, Maja; Waelkens, Christoffel; Zima, Wolfgang

    2009-01-01

    While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their Spectral Energy Distribution (SED) allowed us to launch a more systematic search for binaries. We selected post-AGB objects which show a broad dust excess often starting already at H or K, pointing to the presence of a gravitationally bound dusty disc in the system. We started a very extensive multi-wavelength study of those systems and here we report on our radial velocity and photometric monitoring results for six stars of early F type, which are pulsators of small amplitude. To determine the radial velocity of low signal-to-noise time-series, we constructed dedicated auto-correlation masks. The radial velocity variations were subjected to detailed analysis to differentiate between pulsational variability and variability due to orbital motion. Finally orbital minimalisation was performed to constrain the orbital elements. All of the six objects are binaries, with orbital periods ranging from 120 to 1...

  6. HATS-3b: AN INFLATED HOT JUPITER TRANSITING AN F-TYPE STAR

    Energy Technology Data Exchange (ETDEWEB)

    Bayliss, D.; Zhou, G.; Schmidt, B. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Penev, K.; Bakos, G. Á.; Hartman, J. D.; Csubry, Z. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Jordán, A.; Suc, V.; Rabus, M.; Brahm, R.; Espinoza, N. [Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Mancini, L.; Mohler-Fischer, M.; Henning, T.; Nikolov, N.; Csák, B. [Max Planck Institute for Astronomy, Heidelberg (Germany); Béky, B.; Noyes, R. W. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Buchhave, L., E-mail: daniel@mso.anu.edu.au [Niels Bohr Institute, Copenhagen University (Denmark); and others

    2013-11-01

    We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V = 12.4 F dwarf star. HATS-3b has a period of P = 3.5479 days, mass of M{sub p} = 1.07 M {sub J}, and radius of R{sub p} = 1.38 R {sub J}. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsin i = 9.0 km s{sup –1}), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low-/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces log g and T {sub eff} parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1 km s{sup –1}.

  7. HATS-4b: A dense hot Jupiter transiting a super metal-rich G star

    Energy Technology Data Exchange (ETDEWEB)

    Jordán, Andrés; Brahm, Rafael; Rabus, M.; Suc, V.; Espinoza, N. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Bakos, G. Á.; Penev, K.; Hartman, J. D.; Csubry, Z.; Bhatti, W.; De Val Borro, M. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Bayliss, D.; Zhou, G. [The Australian National University, Canberra (Australia); Mancini, L.; Mohler-Fischer, M.; Ciceri, S.; Csák, B.; Henning, T. [Max Planck Institute for Astronomy, Heidelberg (Germany); Sato, B. [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Buchhave, L. [Niels Bohr Institute, Copenhagen University (Denmark); and others

    2014-08-01

    We report the discovery by the HATSouth survey of HATS-4b, an extrasolar planet transiting a V = 13.46 mag G star. HATS-4b has a period of P ≈ 2.5167 days, mass of M{sub p} ≈ 1.32 M {sub Jup}, radius of R{sub p} ≈ 1.02 R {sub Jup}, and density of ρ {sub p} = 1.55 ± 0.16 g cm{sup –3} ≈1.24 ρ{sub Jup}. The host star has a mass of 1.00 M {sub ☉}, a radius of 0.92 R {sub ☉}, and a very high metallicity [Fe/H]=0.43 ± 0.08. HATS-4b is among the densest known planets with masses between 1 and 2 M {sub J} and is thus likely to have a significant content of heavy elements of the order of 75 M {sub ⊕}. In this paper we present the data reduction, radial velocity measurements, and stellar classification techniques adopted by the HATSouth survey for the CORALIE spectrograph. We also detail a technique for simultaneously estimating vsin i and macroturbulence using high resolution spectra.

  8. WASP-50b: a hot Jupiter transiting a moderately active solar-type star

    CERN Document Server

    Gillon, M; Lendl, M; Maxted, P F L; Triaud, A H M J; Anderson, D R; Barros, S C C; Bento, J; Collier-Cameron, A; Enoch, B; Faedi, F; Hellier, C; Jehin, E; Magain, P; Montalban, J; Pepe, F; Pollacco, D; Queloz, D; Smalley, B; Segransan, D; Smith, A M S; Southworth, J; Udry, S; West, R G; Wheatley, P J

    2011-01-01

    We report the discovery by the WASP transit survey of a giant planet in a close orbit (0.0295+-0.0009 AU) around a moderately bright (V=11.6, K=10) G9 dwarf (0.89+-0.08 M_sun, 0.84+-0.03 R_sun) in the Southern constellation Eridanus. Thanks to high-precision follow-up photometry and spectroscopy obtained by the telescopes TRAPPIST and Euler, the mass and size of this planet, WASP-50b, are well constrained to 1.47+-0.09 M_jup and 1.15+-0.05 R_jup, respectively. The transit ephemeris is 2455558.6120 (+-0.0002) + N x 1.955096 (+-0.000005) HJD_UTC. The size of the planet is consistent with basic models of irradiated giant planets. The chromospheric activity (log R'_HK = -4.67) and rotational period (P_rot = 16.3+-0.5 days) of the host star suggest an age of 0.8+-0.4 Gy that is discrepant with a stellar-evolution estimate based on the measured stellar parameters (rho_star = 1.48+-0.10 rho_sun, Teff = 5400+-100 K, [Fe/H]= -0.12+-0.08) which favours an age of 7+-3.5 Gy. This discrepancy could be explained by the tid...

  9. Some Like it Hot: The X-Ray Emission of The Giant Star YY Mensae

    CERN Document Server

    Audard, M; Güdel, M; Skinner, S L; Pallavicini, R; Mitra-Kraev, U; Audard, Marc; Telleschi, Alessandra; Guedel, Manuel; Skinner, Stephen L.; Pallavicini, Roberto; Mitra-Kraev, Urmila

    2004-01-01

    (Abridged abstract) We present an analysis of the X-ray emission of the rapidly rotating giant star YY Mensae observed by Chandra HETGS and XMM-Newton. Although no obvious flare was detected, the X-ray luminosity changed by a factor of two between the XMM-Newton and Chandra observations taken 4 months apart. The coronal abundances and the emission measure distribution have been derived from three different methods using optically thin collisional ionization equilibrium models. The abundances show an inverse first ionization potential (FIP) effect. We further find a high N abundance which we interpret as a signature of material processed in the CNO cycle. The corona is dominated by a very high temperature (20-40 MK) plasma, which places YY Men among the magnetically active stars with the hottest coronae. Lower temperature plasma also coexists, albeit with much lower emission measure. Line broadening is reported, which we interpret as Doppler thermal broadening, although rotational broadening due to X-ray emitt...

  10. Pilot VLBI Survey of SiO v=3 J=1--0 Maser Emission around Evolved Stars

    CERN Document Server

    Imai, Hiroshi; Chong, Sze Ning; Nakagawa, Akiharu; Kurayama, Tomoharu; Nakashima, Jun-ichi; Matsumoto, Naoko; Nagayama, Takumi; Oyama, Tomoaki; Mizuno, Shota; Deguchi, Shuji; Cho, Se-Hyung

    2012-01-01

    In this Letter, we report detections of SiO v=3 J=1--0 maser emission in very long baseline interferometric (VLBI) observations towards 4 out of 12 long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections towards WX Psc and T Cep are new ones. We also present successful astrometric observations of SiO v=2 and v=3 J=1--0 maser emissions associated with two stars: WX Psc and W Hya and their position-reference continuum sources: J010746.0+131205 and J135146.8-291218 with the VLBI Exploration of Radio Astrometry (VERA). The relative coordinates of the position-reference continuum source and SiO v=3 maser spots were measured with respect to those of an SiO v=2 maser spot adopted as fringe-phase reference. Thus the faint continuum sources were inversely phase-referenced to the bright maser sources. It implies possible registration of multiple SiO maser line maps onto a common coordinate system with 10 microarcsecond-level accuracy.

  11. The young low-mass star ISO-Oph-50: Extreme variability induced by a clumpy, evolving circumstellar disk

    CERN Document Server

    Scholz, Aleks; Geers, Vincent

    2015-01-01

    ISO-Oph-50 is a young low-mass object in the ~Myr old Ophiuchus star forming region undergoing dramatic changes in its optical/near/mid-infrared brightness by 2-4 mag. We present new multi-band photometry and near-infrared spectra, combined with a synopsis of the existing literature data. Based on the spectroscopy, the source is confirmed as a mid M dwarf, with evidence for ongoing accretion. The near-infrared lightcurves show large-scale variations, with 2-4 mag amplitude in the bands IJHK, with the object generally being bluer when faint. Near its brightest state, the object shows colour changes consistent with variable extinction of dAV~7 mag. High-cadence monitoring at 3.6mu reveals quasi-periodic variations with a typical timescale of 1-2 weeks. The best explanation for these characteristics is a low-mass star seen through circumstellar matter, whose complex variability is caused by changing inhomogeneities in the inner parts of the disk. When faint, the direct stellar emission is blocked; the near-infra...

  12. Planets around evolved intermediate-mass stars. I. Two substellar companions in the open clusters NGC 2423 and NGC 4349

    CERN Document Server

    Lovis, C

    2007-01-01

    Context. Many efforts are being made to characterize extrasolar planetary systems and unveil the fundamental mechanisms of planet formation. An important aspect of the problem, which remains largely unknown, is to understand how the planet formation process depends on the mass of the parent star. In particular, as most planets discovered to date orbit a solar-mass primary, little is known about planet formation around more massive stars. Aims. To investigate this point, we present first results from a radial velocity planet search around red giants in the clump of intermediate-age open clusters. We choose clusters harbouring red giants with masses between 1.5 and 4 M_sun, using the well-known cluster parameters to accurately determine the stellar masses. We are therefore exploring a poorly-known domain of primary masses, which will bring new insights into the properties of extrasolar planetary systems. Methods. We are following a sample of about 115 red giants with the Coralie and HARPS spectrographs to obtai...

  13. The evolved-star dust budget of the Small Magellanic Cloud: the critical role of a few key players

    CERN Document Server

    Srinivasan, Sundar; Kemper, Francisca; Meixner, Margaret; Riebel, David; Sargent, Benjamin A

    2016-01-01

    The lifecycle of dust in the interstellar medium (ISM) is heavily influenced by outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars, a large fraction of which is contributed by a few very dusty sources. We compute the dust input to the Small Magellanic Cloud (SMC) by fitting the multi-epoch mid-infrared spectral energy distributions (SEDs) of AGB/RSG candidates with models from the {\\em G}rid of {\\em R}SG and {\\em A}GB {\\em M}odel{\\em S} (GRAMS) grid, allowing us to estimate the luminosities and dust-production rates (DPRs) of the entire population. By removing contaminants, we guarantee a high-quality dataset with reliable DPRs and a complete inventory of the dustiest sources. We find a global AGB/RSG dust-injection rate of $(1.3\\pm 0.1)\\times 10^{-6}$ \\msunperyr, in agreement with estimates derived from mid-infrared colours and excess fluxes. As in the LMC, a majority (66\\%) of the dust arises from the extreme AGB stars, which comprise only $\\approx$7\\% of our sample. A handful of far...

  14. The evolving relation between star-formation rate and stellar mass in the VIDEO Survey since $z=3$

    CERN Document Server

    Johnston, Russell; Jarvis, Matt; Smith, Mathew; Giovannoli, Elodie; Häußler, Boris; Prescott, Matthew

    2015-01-01

    We investigate the star-formation rate (SFR) and stellar mass ($M_*$) relation of a star-forming (SF) galaxy sample in the XMM-LSS field to $z\\sim 3.0$ using the near-infrared data from the VISTA Deep Extragalactic Observations (VIDEO) survey. Combining VIDEO with broad-band photometry, we use the SED fitting algorithm CIGALE to derive SFRs and $M_*$ and have adapted it to account for the full photometric redshift PDF uncertainty. Applying a SF selection using the D4000 index, we find evidence for strong evolution in the normalisation of the SFR-$M_*$ relation out to $z\\sim 3$ and a roughly constant slope of (SFR $\\propto M_*^{\\alpha}$) $\\alpha=0.69\\pm0.02$ to $z\\sim 1.7$. We find this increases close to unity toward $z\\sim2.65$. Alternatively, if we apply a colour selection, we find a distinct turnover in the SFR-$M_*$ relation between $0.7\\lesssim z\\lesssim2.0$ at the high mass end, and suggest that this is due to an increased contamination from passive galaxies. We find evolution of the specific SFR $\\prop...

  15. Bow shock nebulae of hot massive stars in a magnetized medium

    CERN Document Server

    Meyer, D M -A; Kuiper, R; Raga, A; Kley, W

    2016-01-01

    A significant fraction of OB-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ISM). Their strong stellar winds interact with their surroundings where the typical strength of the local ISM magnetic field is about 3.5-7 micro-G, which can result in the formation of bow shock nebulae. We investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures. Our axisymmetric, magneto-hydrodynamical simulations with optically-thin radiative cooling, heating and anisotropic thermal conduction show that the presence of the background ISM magnetic field affects the projected optical emission our bow shocks at Ha and [OIII] lambda 5007 which become fainter by about 1-2 orders of magnitude, respectively. Radiative transfer calculations against dust opacity indicate that the magnetic field slightly diminishes their projected infrared emission and that our bow shoc...

  16. HAT-P-25b: A Hot-Jupiter Transiting a Moderately Faint G Star

    Science.gov (United States)

    Quinn, S. N.; Bakos, G. Á.; Hartman, J.; Torres, G.; Kovács, G.; Latham, D. W.; Noyes, R. W.; Fischer, D. A.; Johnson, J. A.; Marcy, G. W.; Howard, A. W.; Szentgyorgyi, A.; Fűrész, G.; Buchhave, L. A.; Béky, B.; Sasselov, D. D.; Stefanik, R. P.; Perumpilly, G.; Everett, M.; Lázár, J.; Papp, I.; Sári, P.

    2012-01-01

    We report the discovery of HAT-P-25b, a transiting extrasolar planet orbiting the V = 13.19 G5 dwarf star GSC 1788-01237, with a period P = 3.652836 ± 0.000019 days, transit epoch Tc = 2455176.85173 ± 0.00047 (BJD—barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time, UTC), and transit duration 0.1174 ± 0.0017 days. The host star has a mass of 1.01 ± 0.03 M ⊙, radius of 0.96+0.05 - 0.04 R ⊙, effective temperature 5500 ± 80 K, and metallicity [Fe/H] = +0.31 ± 0.08. The planetary companion has a mass of 0.567 ± 0.022 M J and radius of 1.190+0.081 - 0.056 R J yielding a mean density of 0.42 ± 0.07 g cm-3. Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO (A201Hr), NASA (N018Hr and N167Hr), and the NASA Gemini-Keck time-exchange program (G329Hr). Based in part on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

  17. HATS-3b: An Inflated Hot Jupiter Transiting an F-type Star

    Science.gov (United States)

    Bayliss, D.; Zhou, G.; Penev, K.; Bakos, G. Á.; Hartman, J. D.; Jordán, A.; Mancini, L.; Mohler-Fischer, M.; Suc, V.; Rabus, M.; Béky, B.; Csubry, Z.; Buchhave, L.; Henning, T.; Nikolov, N.; Csák, B.; Brahm, R.; Espinoza, N.; Noyes, R. W.; Schmidt, B.; Conroy, P.; Wright, D. J.; Tinney, C. G.; Addison, B. C.; Sackett, P. D.; Sasselov, D. D.; Lázár, J.; Papp, I.; Sári, P.

    2013-11-01

    We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V = 12.4 F dwarf star. HATS-3b has a period of P = 3.5479 days, mass of Mp = 1.07 M J, and radius of Rp = 1.38 R J. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsin i = 9.0 km s-1), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low-/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces log g and T eff parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1 km s-1. The HATSouth network is operated by a collaboration consisting of Princeton University (PU), the Max Planck Institute für Astronomie (MPIA), and the Australian National University (ANU). The station at Las Campanas Observatory (LCO) of the Carnegie Institute is operated by PU in conjunction with collaborators at the Pontificia Universidad Católica de Chile (PUC), the station at the High Energy Spectroscopic Survey (HESS) site is operated in conjunction with MPIA, and the station at Siding Spring Observatory (SSO) is operated jointly with ANU.

  18. On the Weak-Wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in mu Columbae

    Science.gov (United States)

    Huenemoerder, David P.; Oskinova, Lidia M.; Ignace, Richard; Waldron, Wayne L.; Todt, Helge; Hamaguchi, Kenji; Kitamoto, Shunji

    2012-01-01

    Mu Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the "weak-wind problem"--identified from cool wind UV/optical spectra--is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are "weak-wind" stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.

  19. Angular momentum redistribution by mixed modes in evolved low-mass stars. II. Spin-down of the core of red giants induced by mixed modes

    CERN Document Server

    Belkacem, K; Goupil, M J; Mosser, B; Sonoi, T; Ouazzani, R M; Dupret, M A; Mathis, S; Grosjean, M

    2015-01-01

    The detection of mixed modes in subgiants and red giants by the CoRoT and \\emph{Kepler} space-borne missions allows us to investigate the internal structure of evolved low-mass stars. In particular, the measurement of the mean core rotation rate as a function of the evolution places stringent constraints on the physical mechanisms responsible for the angular momentum redistribution in stars. It showed that the current stellar evolution codes including the modelling of rotation fail to reproduce the observations. An additional physical process that efficiently extracts angular momentum from the core is thus necessary. Our aim is to assess the ability of mixed modes to do this. To this end, we developed a formalism that provides a modelling of the wave fluxes in both the mean angular momentum and the mean energy equations in a companion paper. In this article, mode amplitudes are modelled based on recent asteroseismic observations, and a quantitative estimate of the angular momentum transfer is obtained. This i...

  20. Rest-frame UV--Optically Selected Galaxies at 2.3Star-forming and Passively-Evolving Galaxies

    CERN Document Server

    Guo, Yicheng; Cassata, Paolo; Ferguson, Henry C; Williams, Christina C; Dickinson, Mark; Koekemoer, Anton M; Grogin, Norman A; Chary, Ranga-Ram; Messias, Hugo; Tundo, Elena; Lin, Lihwai; Lee, Seong-Kook; Salimbeni, Sara; Fontana, Adriano; Grazian, Andrea; Kocevski, Dale; Lee, Kyoung-Soo; Villanueva, Edward; van der Wel, Arjen

    2011-01-01

    A new set of color selection criteria (VJL) analogous with the BzK method is designed to select both star-forming galaxies (SFGs) and passively-evolving galaxies (PEGs) at 2.310^{10}M_{Sun}) galaxies at 2.30.4) SFGs, which however, only account for ~20% of the number density of massive SFGs. We also use the mid-infrared fluxes to clean our PEG sample, and find that galaxy size can be used as a secondary criterion to effectively eliminate the contamination of dusty SFGs. The redshift distribution of the cleaned PEG sample peaks at z~2.5. We find 6 PEG candidates at z>3 and discuss possible methods to distinguish them from dusty contamination. We conclude that at least part of our candidates are real PEGs at z~3, implying that this type of galaxies began to form their stars at z>5. We measure the integrated stellar mass density of PEGs at z~2.5 and set constraints on it at z>3. We find that the integrated stellar mass density grows by at least about factor of 10 in 1 Gyr at 3

  1. Hot Organic Molecules Toward a Young Low-Mass Star: A Look at Inner Disk Chemistry

    CERN Document Server

    Lahuis, F; Boogert, A C A; Dullemond, C P; Hogerheijde, M R; Jørgensen, J K; Kessler-Silacci, J E; Knez, C; Pontoppidan, K M; Van Dishoeck, E F

    2006-01-01

    Spitzer Space Telescope spectra of the low mass young stellar object (YSO) IRS 46 (L_bol ~ 0.6 L_sun) in Ophiuchus reveal strong vibration-rotation absorption bands of gaseous C2H2, HCN, and CO2. This is the only source out of a sample of ~100 YSO's that shows these features and the first time they are seen in the spectrum of a solar-mass YSO. Analysis of the Spitzer data combined with Keck L- and M-band spectra gives excitation temperatures of > 350 K and abundances of 10(-6)-10(-5) with respect to H2, orders of magnitude higher than those found in cold clouds. In spite of this high abundance, the HCN J=4-3 line is barely detected with the James Clerk Maxwell Telescope, indicating a source diameter less than 13 AU. The (sub)millimeter continuum emission and the absence of scattered light in near-infrared images limits the mass and temperature of any remnant collapse envelope to less than 0.01 M_sun and 100 K, respectively. This excludes a hot-core type region as found in high-mass YSO's. The most plausible o...

  2. A NLTE analysis of the hot subdwarf O star Bd+28 4211. I. The UV spectrum

    CERN Document Server

    Latour, M; Chayer, P; Brassard, P

    2013-01-01

    We present a detailed analysis of the UV spectrum of the calibration star Bd+28 4211 using high-quality spectra obtained with the HST and FUSE satellites. To this aim, we compare quantitatively the observed data with model spectra obtained from state-of-the-art NLTE metal line-blanketed model atmospheres and synthetic spectra calculated with TLUSTY and SYNSPEC. We thus determine in a self-consistent way the abundances of eleven elements with well-defined lines in the UV, namely those of C, N, O, F, Mg, Si, P, S, Ar, Fe, and Ni. The derived abundances range from about solar to 1/10 solar. We find that the overall quality of the derived spectral fits is very satisfying. Our spectral analysis can be used to constrain rather tigthly the effective temperature of Bd+28 to a value of teff = 82,000 +/- 5000 K. We also estimate conservatively that its surface gravity falls in the range log g = 6.2 -0.1/+0.3. Assuming that the Hipparcos measurement for Bd+28 is fully reliable and that our model atmospheres are reasonab...

  3. A pulsation zoo in the hot subdwarf B star KIC 10139564 observed by Kepler

    CERN Document Server

    Baran, A S; Stello, D; Ostensen, R H; Telting, J H; Pakstiene, E; O'Toole, S J; Silvotti, R; Degroote, P; Bloemen, S; Hu, H; Van Grootel, V; Clarke, B D; Van Cleve, J; Thompson, S E; Kawaler, S D

    2012-01-01

    We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B star. Ten of the periodicities were found in the low-frequency region, and we associate them with nonradial g-modes. The other periodicities were found in the high-frequency region, which are likely p-modes. We discovered that most of the periodicities are components of multiplets with a common spacing. Assuming that multiplets are caused by rotation, we derive a rotation period of 25.6(1.8) days. The multiplets also allow us to identify the pulsations to an unprecedented extent for this class of pulsator. We also detect l<=2 multiplets, which are sensitive to the pulsation inclination and can constrain limb darkening via geometric cancellation factors. While most periodicities are stable, we detected several regions that show complex patterns. Detailed analyses showed these regions are complicated by several factors....

  4. Signatures of nonlinear mode interactions in the pulsating hot B subdwarf star KIC 10139564

    CERN Document Server

    Zong, Weikai; Vauclair, Gérard

    2016-01-01

    We analyse 38-month of contiguous short-cadence data, concentrating on mode multiplets induced by the star rotation and on frequencies forming linear combinations that show intriguing behaviors during the course of the observations. We find clear signatures that point toward nonlinear effects predicted by resonant mode coupling mechanisms. These couplings can induce various mode behaviors for the components of multiplets and for frequencies related by linear relationships. We find that a triplet at 5760\\,$\\mu$Hz, a quintuplet at 5287\\,$\\mu$Hz and a ($\\ell>2$) multiplet at 5412\\,$\\mu$Hz, all induced by rotation, show clear frequency and amplitude modulations which are typical of the so-called intermediate regime of a resonance between the components. One triplet at 316\\,$\\mu$Hz and a doublet at 394\\,$\\mu$Hz show modulated amplitude and constant frequency which can be associated with a narrow transitory regime of the resonance. Another triplet at 519\\,$\\mu$Hz appears to be in a frequency lock regime where both ...

  5. On the X-ray emission from massive star clusters and their evolving superbubbles II. Detailed analytics and observational effects

    CERN Document Server

    Añorve-Zeferino, G A; Silich, S

    2009-01-01

    In this work, we present a comprehensive X-ray picture of the interaction between a super star cluster and the ISM. In order to do that, we compare and combine the X-ray emission from the superwind driven by the cluster with the emission from the wind-blown bubble. Detailed analytical models for the hydrodynamics and X-ray luminosity of fast polytropic superwinds are presented. The superwind X-ray luminosity models are an extension of the results obtained in Paper I of this series. Here, the superwind polytropic character allows to parameterize a wide variety of effects, for instance, radiative cooling. Additionally, X-ray properties that are valid for all bubble models taking thermal evaporation into account are derived. The final X-ray picture is obtained by calculating analytically the expected surface brightness and weighted temperature of each component. All of our X-ray models have an explicit dependence on metallicity and admit general emissivities as functions of the hydrodynamical variables. We consi...

  6. Tidal and Magnetic Interactions between a Hot Jupiter and its Host Star in the Magnetospheric Cavity of a Protoplanetary Disk

    CERN Document Server

    Chang, Shih-Hsin; Bodenheimer, Peter

    2009-01-01

    We present a simplified model to study the orbital evolution of a young hot Jupiter inside the magnetospheric cavity of a proto-planetary disk. The model takes into account the disk locking of stellar spin as well as the tidal and magnetic interactions between the star and the planet. We focus on the orbital evolution starting from the orbit in the 2:1 resonance with the inner edge of the disk, followed by the inward and then outward orbital migration driven by the tidal and magnetic torques as well as the Roche-lobe overflow of the tidally inflated planet. The goal in this paper is to study how the orbital evolution inside the magnetospheric cavity depends on the cavity size, planet mass, and orbital eccentricity. In the present work, we only target the mass range from 0.7 to 2 Jupiter masses. In the case of the large cavity corresponding to the rotational period ~ 7 days, the planet of mass >1 Jupiter mass with moderate initial eccentricities (>~ 0.3) can move to the region < 0.03 AU from its central sta...

  7. Ultraviolet spectra of HZ Herculis/Hercules X-1 from HST: Hot gas during total eclipse of the neutron star

    Science.gov (United States)

    Anderson, Scott F.; Wachter, Stefanie; Margon, Bruce; Downes, Ronald A.; Blair, William P.; Halpern, Jules P.

    1994-01-01

    The Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST) has been used in the UV to observe the prototypical X-ray pulsar Her X-1 and its companion HZ Her. Optical spectra were also obtained contemporaneously at the Kitt Peak National Observatory (KPNO) 2.1 m. The FOS spectra encompass the 1150-3300 A range near binary orbital phases 0.5 (X-ray maximum) and at 0.0 (mid-X-ray eclipse). The maximum light spectra show strong, narrow C III, N V, O V, Si IV + O IV), N IV), C IV, He II, and N IV emission lines, extending previous IUE results; the O III lambda 3133 Bowen resonance line is also prominent, confirming that the Bowen mechanism is the source of the strong lambda lambda 4640, 4650 emission complex, also seen at maximum light. Most remarkable, however, are the minimum light spectra, where the object is too faint for reasonable observations from IUE. Despite the total eclipse of the X-ray-emitting neutron star, our spectra show strong emission at N V lambda 1240, S IV + O IV) whose emission dominates the UV light at phase 0.0 might be associated with the 'accretion disk corona,' it is more likely the source is somewhat less hot (but extended) gas above and around the disk, or perhaps circumstellar material such as a stellar wind.

  8. The Evolving Interstellar Medium of Star Forming Galaxies Since z=2 as Probed by Their Infrared Spectral Energy Distributions

    CERN Document Server

    Magdis, Georgios E; Bethermin, M; Sargent, M; Elbaz, D; Pannella, M; Dickinson, M; Dannerbauer, H; Da Cunha, E; Walter, F; Rigopoulou, D; Charmandaris, V; Hwang, H -S; Kartaltepe, J

    2012-01-01

    Using data from the mid-infrared to millimeter wavelengths for individual galaxies and for stacked ensembles at 0.5, which is proportional to the dust mass weighted luminosity (LIR/Mdust), and the primary parameter defining the shape of the SED, is equivalent to SFE/Z. For MS galaxies we measure this quantity, , showing that it does not depend significantly on either the stellar mass or the sSFR. This is explained as a simple consequence of the existing correlations between SFR-M*, M*-Z and Mgas-SFR. Instead, we show that (or LIR/Mdust) does evolve, with MS galaxies having harder radiation fields and thus warmer temperatures as redshift increases from z=0 to 2, a trend which can also be understood based on the redshift evolution of the M*-Z and SFR-M* relations. These results motivate the construction of a universal set of SED templates for MS galaxies which vary as a function of redshift with only one parameter, .

  9. Mean-field study of hot beta-stable protoneutron star matter: Impact of the symmetry energy and nucleon effective mass

    CERN Document Server

    Tan, Ngo Hai; Khoa, Dao T; Margueron, Jerome

    2016-01-01

    A consistent Hartree-Fock study of the equation of state (EOS) of asymmetric nuclear matter at finite temperature has been performed using realistic choices of the effective, density dependent nucleon-nucleon (NN) interaction, which were successfully used in different nuclear structure and reaction studies. Given the importance of the nuclear symmetry energy in the neutron star formation, EOS's associated with different behaviors of the symmetry energy were used to study hot asymmetric nuclear matter. The slope of the symmetry energy and nucleon effective mass with increasing baryon density was found to affect the thermal properties of nuclear matter significantly. Different density dependent NN interactions were further used to study the EOS of hot protoneutron star (PNS) matter of the $npe\\mu\

  10. The metallicity distribution and hot Jupiter rate of the Kepler field: Hectochelle High-resolution spectroscopy for 776 Kepler target stars

    Science.gov (United States)

    Guo, Xueying; Johnson, John A.; Mann, Andrew W.; Kraus, Adam L.; Curtis, Jason L.; Latham, David W.

    2017-01-01

    The occurrence rate of hot Jupiters from the Kepler transit survey is roughly half that of radial velocity surveys targeting solar neighborhood stars. One hypothesis to explain this difference is that the two surveys target stars with different stellar metallicity distributions. To test this hypothesis, we measure the metallicity distribution of the Kepler targets using the Hectochelle multi-fiber, high-resolution spectrograph. Limiting our spectroscopic analysis to 610 dwarf stars in our sample with log(g) > 3.5, we measure a metallicity distribution characterized by a mean of [M/H]_{mean} = -0.045 +/- 0.009, in agreement with previous studies of the Kepler field target stars. In comparison, the metallicity distribution of the California Planet Search radial velocity sample has a mean of [M/H]_{CPS, mean} = -0.005 +\\- 0.006, and the samples come from different parent populations according to a Kolmogorov-Smirnov test. We refit the exponential relation between the fraction of stars hosting a close-in giant planet and the host star metallicity using a sample of dwarf stars from the California Planet Search with updated metallicities. The best-fit relation tells us that the difference in metallicity between the two samples is insufficient to explain the discrepant Hot Jupiter occurrence rates; the metallicity difference would need to be 0.2-0.3 dex for perfect agreement. We also show that (sub)giant contamination in the Kepler sample cannot reconcile the two occurrence calculations. We conclude that other factors, such as binary contamination and imperfect stellar properties, must also be at play.

  11. Ultraviolet Radiation from Evolved Stellar Populations -- I. Models

    CERN Document Server

    Dorman, B; O'Connell, R

    1993-01-01

    This series of papers comprises a systematic exploration of the hypothesis that the far ultraviolet radiation from star clusters and elliptical galaxies originates from extremely hot horizontal-branch (HB) stars and their post-HB progeny. This first paper presents an extensive grid of calculations of stellar models from the Zero Age Horizontal Branch through to a point late in post-HB evolution or a point on the white dwarf cooling track. We use the term `Extreme Horizontal Branch' (EHB) to refer to HB sequences of constant mass that do not reach the thermally-pulsing stage on the AGB. These models evolve after core helium exhaustion

  12. The hot Jupiter of the magnetically-active weak-line T Tauri star V830 Tau

    CERN Document Server

    Donati, J -F; Moutou, C; Cameron, A C; Malo, L; Grankin, K; Hébrard, E; Hussain, G A J; Vidotto, A A; Alencar, S H P; Haywood, R D; Bouvier, J; Petit, P; Takami, M; Herczeg, G J; Gregory, S G; Jardine, M M; Morin, J

    2016-01-01

    We report results of an extended spectropolarimetric and photometric monitoring of the weak-line T Tauri star V830 Tau and its recently-detected newborn close-in giant planet. Our observations, carried out within the MaTYSSE programme, were spread over 91d, and involved the ESPaDOnS and Narval spectropolarimeters linked to the 3.6m Canada-France-Hawaii, the 2m Bernard Lyot and the 8-m Gemini-North Telescopes. Using Zeeman-Doppler Imaging, we characterize the surface brightness distributions, magnetic topologies and surface differential rotation of V830 Tau at the time of our observations, and demonstrate that both distributions evolve with time beyond what is expected from differential rotation. We also report that near the end of our observations, V830 Tau triggered one major flare and two weaker precursors, showing up as enhanced red-shifted emission in multiple spectral activity proxies. With 3 different filtering techniques, we model the radial velocity (RV) activity jitter (of semi-amplitude 1.2km/s) tha...

  13. K2-31B, a Grazing Transiting Hot Jupiter on a 1.26-day Orbit around a Bright G7V Star

    Science.gov (United States)

    Grziwa, Sascha; Gandolfi, Davide; Csizmadia, Szilard; Fridlund, Malcolm; Parviainen, Hannu; Deeg, Hans J.; Cabrera, Juan; Djupvik, Amanda A.; Albrecht, Simon; Palle, Enric B.; Pätzold, Martin; Béjar, Victor J. S.; Prieto-Arranz, Jorge; Eigmüller, Philipp; Erikson, Anders; Fynbo, Johan P. U.; Guenther, Eike W.; Hatzes, Artie P.; Kiilerich, Amanda; Korth, Judith; Kuutma, Teet; Montañés-Rodríguez, Pilar; Nespral, David; Nowak, Grzegorz; Rauer, Heike; Saario, Joonas; Sebastian, Daniel; Slumstrup, Ditte

    2016-11-01

    We report the discovery of K2-31b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. K2-31b is a 1.8-Jupiter-mass planet on a 1.26-day orbit around a G7 V star ({M}\\star =0.91 M ⊙, {R}\\star =0.78 R ⊙). The planetary radius is poorly constrained (0.7 < R p < 1.4 R Jup),15 owing to the grazing transit and the low sampling rate of the K2 photometry.16

  14. HAT-P-56b: A bright highly inflated massive Hot Jupiter around An F star in K2.0 field

    Science.gov (United States)

    Huang, Xu; Bakos, Gaspar; Hartman, Joel

    2015-08-01

    We report the discovery of HAT-P-56b, a transiting high inflated hot-jupiter orbiting a F type star in the field 0 of the NASA K2 mission, by the HATNet survey. We combine ground-based photometric light curves with the highprecision photometry obervation by the K2 mission, as well as radial velocity to determine the physical properties of this system. HAT-P-56b has a mass around ~2.2 Mjunp, a radius of ~1.5 Rjup, and transits its host star with a period of 2.79d. The host star has a V band magnitude of 10.9, Mass of 1.29 Msun, and radius of 1.433 Rsun. The radius of HAT-P-56b is among one of the largest compare to planets with similar mass, making it an interesting target for following up atmospherical observations.

  15. The Case of the Tail Wagging the Dog: HD 189733 - Evidence of Hot Jupiter Exoplanets Spinning-up Their Host Stars

    Science.gov (United States)

    Guinan, E. F.

    2013-06-01

    (Abstract only) HD 189733A is an eighth mag K1.5V star that has attracted much attention because it hosts a short period, transiting, hot-Jupiter planet. This planet, HD 189733b, has one of the shortest known orbital periods (P = 2.22 days) and is only 0.031 AU from its host star. Because the system undergoes eclipses and is bright, HD 189733 has been extensively studied. The planet's atmosphere has been found to contain water vapor, methane, CO2, and sodium and possible haze. Spitzer IR observations indicate planet temperature, varying ~970 K to ~1,200 K over its surface (Tinetti (2007). Based on measurements of the K-star's P(rot) from starspot modulations of ~11.95 d, strong coronal X-ray emission and chromospheric Ca II-HK emission indicate a young age of ~0.7 Gyr. But this apparent young age is discrepant with a much older age (> 4 Gyr) inferred from the star's very low Lithium abundance. However, the age of the HD 189733 system can be independently determined by the presence of a faint dM4 companion (HD 189733B) some 12" away. Our Age-Activity relations for this star (no detectable coronal X-ray emission and no H-alpha emission) indicate an age > 4 Gyr (and < 8 Gyr from kinematics and metallicity). This age should apply to its K star companion and its planet. The fast rotation and resultant high activity levels of the K star can best be explained from the increase in its (rotation) angular momentum (AM) from the orbital AM of the planet. This AM transfer occurs from tidal and magnetic interactions of the K star with its planet. Determining the possible decrease in the planet's orbital period is possible from studying the planet eclipse times (which can be done by AAVSO members with CCD photometry). We also discuss the properties of other related short-period exoplanet systems found by the Kepler Mission that show similar behavior - in that close-in hot Jupiter size planets appear to be physically interacting with their host stars. This work is supported by

  16. A high spatial resolution X-ray and H-alpha study of hot gas in the halos of star-forming disk galaxies. II. Quantifying supernova feedback

    CERN Document Server

    Strickland, D K; Colbert, E J M; Hoopes, C G; Weaver, K A

    2004-01-01

    We investigate how the empirical properties of hot X-ray-emitting gas in a sample of 7 starburst and 3 normal edge-on spiral galaxies correlate with the size, mass, star formation rate and star formation intensity in the host galaxies. From this analysis we investigate various aspects of mechanical energy feedback on galactic scales. We demonstrate, using a variety of multi-wavelength star formation rate and intensity indicators, that the diffuse X-ray emission is ultimately driven by mechanical energy feedback from massive stars. We find that the luminosity of the extra-planar diffuse X-ray emission is proportional to proxies of the star formation rate of the host galaxy, for example the FIR or 1.4 GHz radio luminosity. Larger galaxies tend to have more extended X-ray-emitting halos, but galaxy mass appears to play no role in determining the properties of the disk or extra-planar X-ray emitting plasma. Accretion of gas from the IGM does not appear to be a significant contributor to the diffuse X-ray emission...

  17. Some Like it Hot: Linking Diffuse X-Ray Luminosity, Baryonic Mass, and Star Formation Rate in Compact Groups of Galaxies

    Science.gov (United States)

    Desjardins, Tyler D.; Gallagher, Sarah C.; Hornschemeier, Ann E.; Mulchaey, John S.; Walker, Lisa May; Brandt, Willian N.; Charlton, Jane C.; Johnson, Kelsey E.; Tzanavaris, Panayiotis

    2014-01-01

    We present an analysis of the diffuse X-ray emission in 19 compact groups (CGs) of galaxies observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in L(x-T) and (L(x-sigma), even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify Hickson CGs 19, 22, 40, and 42, and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and Hi masses are great than or equal to 10(sup (11.3) solar mass are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 micron star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due togas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

  18. HOT STARS AND INTERFEROMETRY

    Directory of Open Access Journals (Sweden)

    F. Millour

    2010-01-01

    junto con las débiles, pero ya convincentes capacidades de imágenes, hacen que esta técnica alcance un estado \\maduro". No discutiré aquí los detalles de la técnica, ya que muchos libros en el tema son publicados, pero describo qué hace que la interferometría estelar de gran línea de base sea atractiva para el campo de la astrofísica de estrellas calientes.

  19. EPIC 204129699b, a grazing transiting hot Jupiter on an 1.26-day orbit around a bright solar like star

    CERN Document Server

    Grziwa, S; Csizmadia, Sz; Fridlund, M; Parviainen, H; Deeg, H J; Cabrera, J; Djupvik, A A; Albrecht, S; Palle, E B; Pätzold, M; Béjar, V J S; Arranz, J P; Eigmüller, P; Erikson, A; Fynbo, J P U; Guenther, E W; Hatzes, A P; Kiilerich, A; Korth, J; Kuutma, T; Montanés-Rodríguez, P; Nespral, D; Nowak, G; Rauer, H; Saario, J; Sebastian, D; Slumstrup, D

    2015-01-01

    We report the discovery of EPIC 204129699b, the first confirmed transiting hot Jupiter detected by the K2 space mission. We combined K2 photometry with FastCam lucky imaging and FIES and HARPS high-resolution spectroscopy to confirm the planetary nature of the transiting object and derived the system parameters. EPIC 204129699b is a 1.8-Jupiter-mass planet on an 1.26-day-orbit around a G7V star (M* = 0.91 Msun, R* = 0.78 Rsun). The planetary radius is poorly constrained (0.7 < Rp < 1.4 RJup ), owing to the grazing transit and the low sampling rate of the K2 photometry. The short orbital period and the brightness of the host star (V = 10.8 mag) make the system amenable to atmospheric characterization.

  20. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    OpenAIRE

    Kuzmychov, O.; Berdyugina, S. V.

    2013-01-01

    We investigated the Paschen-Back effect in the (0,0) band of the A6{\\Sigma}+-X6{\\Sigma}+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field pertur...

  1. XMM-Newton Observations of HD189733 During Planetary Transits. X-rays Interaction Between Hot Jupiters and the Host Star.

    Science.gov (United States)

    Pillitteri, Ignazio; Wolk, S. J.; Cohen, O.; Kashyap, V.; Knutson, H.; Lisse, C. M.

    2010-03-01

    The irradiation of X-rays from host stars on their nearby gas-giant planets can cause excess heating of the planet which can induce mass loss. Further, it has been argued that the magnetic fields of the two bodies can interact. We present XMM-Newton observations of HD 189733 during the eclipse and planetary transit of its hot jupiter planet HD 189733b in order to investigate any effects of the interaction between the host star and the planet in X-rays. We observe a softening of X-ray spectrum at level of 2 sigmas during the 2009 secondary eclipse. It is followed at 3 ks by an enhancement of the X-ray flux likely due to a flare. No remarkable effects are seen in 2007 transit. Magneto-Hydro-Dynamical (MHD) simulations show that the plasma spectrum could get softer during the eclipse. Further, a region of high plasma density on the stellar corona, and displaced from the planet-star line, should form due to the interaction of magnetic fields of star and planet. The magnetic activity in this region is enhanced and should cause frequent transients. The X-ray observations suggest that these model predictions are globally correct. Despite the simple model adopted and the lack of precise parameters, effects of the interaction of stars and their nearby planets appear to observable in X-rays. X-ray observations allow to probe the structuring and the strength of the complex magnetosphere of the star+planet system.

  2. HATS-11b and HATS-12b: Two transiting Hot Jupiters orbiting sub-solar metallicity stars selected for the K2 Campaign 7

    CERN Document Server

    Rabus, M; Hartman, J D; Bakos, G Á; Espinoza, N; Brahm, R; Penev, K; Ciceri, S; Zhou, G; Bayliss, D; Mancini, L; Bhatti, W; de Val-Borro, M; Csbury, Z; Sato, B; Tan, T -G; Henning, T; Schmidt, B; Bento, J; Suc, V; Noyes, R; Lázár, J; Papp, I; Sári, P

    2016-01-01

    We report the discovery of two transiting extrasolar planets from the HATSouth survey. HATS-11, a V=14.1 G0-star shows a periodic 12.9 mmag dip in its light curve every 3.6192 days and a radial velocity variation consistent with a Keplerian orbit. HATS-11 has a mass of 1.000 $\\pm$ 0.060 M$_{\\odot}$, a radius of 1.444 $\\pm$ 0.057 M$_{\\odot}$ and an effective temperature of 6060 $\\pm$ 150 K, while its companion is a 0.85 $\\pm$ 0.12 M$_J$, 1.510 $\\pm$ 0.078 R$_J$ planet in a circular orbit. HATS-12 shows a periodic 5.1 mmag flux decrease every 3.1428 days and Keplerian RV variations around a V=12.8 F-star. HATS-12 has a mass of 1.489 $\\pm$ 0.071 M$_{\\odot}$, a radius of 2.21 $\\pm$ 0.21 R$_{\\odot}$, and an effective temperature of 6408 $\\pm$ 75 K. For HATS-12, our measurements indicate that this is a 2.38 $\\pm$ 0.11 M$_J$, 1.35 $\\pm$ 0.17 R$_J$ planet in a circular orbit. Both host stars show sub-solar metallicity of -0.390 $\\pm$ 0.060 dex and -0.100 $\\pm$ 0.040 dex, respectively and are (slightly) evolved stars....

  3. SOPHIE velocimetry of Kepler transit candidates. XV. KOI-614b, KOI-206b, and KOI-680b: a massive warm Jupiter orbiting a G0 metallic dwarf and two highly inflated planets with a distant companion around evolved F-type stars

    CERN Document Server

    Almenara, J M; Bouchy, F; Havel, M; Bruno, G; Hébrard, G; Diaz, R F; Deleuil, M; Barros, S C C; Boisse, I; Bonomo, A; Montagnier, G; Santerne, A

    2015-01-01

    We report the validation and characterization of three new transiting exoplanets using SOPHIE radial velocities: KOI-614b, KOI-206b, and KOI-680b. KOI-614b has a mass of $2.86\\pm0.35~{\\rm M_{Jup}}$ and a radius of $1.13^{+0.26}_{-0.18}~{\\rm R_{Jup}}$, and it orbits a G0, metallic ([Fe/H]=$0.35\\pm0.15$) dwarf in 12.9 days. Its mass and radius are familiar and compatible with standard planetary evolution models, so it is one of the few known transiting planets in this mass range to have an orbital period over ten days. With an equilibrium temperature of $T_{eq}=1000 \\pm 45$ K, this places KOI-614b at the transition between what is usually referred to as "hot" and "warm" Jupiters. KOI-206b has a mass of $2.82\\pm 0.52~{\\rm M_{Jup}}$ and a radius of $1.45\\pm0.16~{\\rm R_{Jup}}$, and it orbits a slightly evolved F7-type star in a 5.3-day orbit. It is a massive inflated hot Jupiter that is particularly challenging for planetary models because it requires unusually large amounts of additional dissipated energy in the ...

  4. WASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars

    Science.gov (United States)

    Anderson, D. R.; Collier Cameron, A.; Hellier, C.; Lendl, M.; Lister, T. A.; Maxted, P. F. L.; Queloz, D.; Smalley, B.; Smith, A. M. S.; Triaud, A. H. M. J.; Brown, D. J. A.; Gillon, M.; Neveu-VanMalle, M.; Pepe, F.; Pollacco, D.; Ségransan, D.; Udry, S.; West, R. G.; Wheatley, P. J.

    2015-03-01

    We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 MJup; 1.46 RJup) in a 4.9-day, near-aligned (λ = 12.7 ± 4.2°) orbit around CD-24 102 (V = 10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91 MJup; 1.21 RJup) in a 3.4-day, near-aligned (λ = 8 ± 18°) orbit around a V = 12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7+ 2-1 Gyr and 6000 ± 100 K for WASP-20; 5+ 3-2 Gyr and 6100 ± 150 K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation. Based on observations made with: the WASP-South (South Africa) and SuperWASP-North (La Palma) photometric survey instruments; the C2 and EulerCam cameras and the CORALIE spectrograph, all mounted on the 1.2-m Euler-Swiss telescope (La Silla); the HARPS spectrograph on the ESO 3.6-m telescope (La Silla) under programs 072.C-0488, 082.C-0608, 084.C-0185, and 085.C-0393; and LCOGT's Faulkes Telescope North (Maui) and Faulkes Telescope South (Siding Spring).Full Tables 2 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61

  5. Investigating the origin of cyclical wind variability in hot, massive stars - I. On the dipolar magnetic field hypothesis

    CERN Document Server

    David-Uraz, A; Petit, V; ud-Doula, A; Sundqvist, J O; Grunhut, J; Shultz, M; Neiner, C; Alecian, E; Henrichs, H F; Bouret, J -C

    2014-01-01

    OB stars exhibit various types of spectral variability associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These are proposed to be caused by either magnetic fields or non-radial pulsations (NRPs). In this paper, we evaluate the possible relation between large-scale, dipolar magnetic fields and the DAC phenomenon by investigating the magnetic properties of a sample of 13 OB stars exhibiting well-documented DAC behaviour. Using high-precision spectropolarimetric data acquired in part in the context of the Magnetism in Massive Stars (MiMeS) project, we find no evidence for surface dipolar magnetic fields in any of these stars. Using Bayesian inference, we compute upper limits on the strengths of the fields and use these limits to assess two potential mechanisms by which the field may influence wind outflow: magnetic wind confinement and local photospheric brightness enhancements. Within the limits we derive, both mechanisms fail to provide a systematic pro...

  6. HAT-P-24b: An inflated hot-Jupiter on a 3.36d period transiting a hot, metal-poor star

    CERN Document Server

    Kipping, D M; Hartman, J; Torres, G; Shporer, A; Latham, D W; Kovacs, Geza; Noyes, R W; Howard, A W; Fischer, D A; Johnson, J A; Marcy, G W; Beky, B; Perumpilly, G; Esquerdo, G A; Sasselov, D D; Stefanik, R P; Lazar, J; Papp, I; Sari, P

    2010-01-01

    We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V=11.818 F8 dwarf star GSC 0774-01441, with a period P = 3.3552464 +/- 0.0000071 d, transit epoch Tc = 2455216.97669 +/- 0.00024 (BJD_UTC), and transit duration 3.653 +/- 0.025 hours. The host star has a mass of 1.186 +/- 0.042 Msun , radius of 1.294 +/- 0.071 Rsun , effective temperature 6373 +/- 80 K, and a low metallicity of [Fe/H] = -0.16 +/- 0.08. The planetary companion has a mass of 0.681 +/- 0.031 MJ , and radius of 1.243 +/- 0.072 RJ yielding a mean density of 0.439 +/- 0.069 g cm-3 . By repeating our global fits with different parameter sets, we have performed a critical investigation of the fitting techniques used for previous HAT planetary discoveries. We find that the system properties are robust against the choice of priors. The effects of fixed versus fitted limb darkening are also examined. HAT-P-24b probably maintains a small eccentricity of e = 0.052 +0.022 -0.017, which is accepted over the c...

  7. An Exoplanet Spinning Up Its Star

    Science.gov (United States)

    Kohler, Susanna

    2016-11-01

    We know that the large masses of stars govern the orbits of the planets that circle them but a large, close-in planet can also influence the rotation of its host star. A recently discovered, unusual hot Jupiter may be causing its star to spin faster than it should.Exotic PlanetsHot Jupiters are gas giants of roughly Jupiters size that orbit close in to their host stars. Though these planets are easy to detect their large sizes and frequent transits mean surveys have a good chance of catching them we havent found many of them, suggesting that planetary systems containing hot Jupiters are fairly unusual.The period-folded light curve of HATS-18, revealing the transit of the hot Jupiter HATS-18b. The period is P=0.8378 days. [Penev et al. 2016]Studying this exotic population of planets, however, can help us to better understand how gas giants form and evolve in planetary systems. New observations of hot Jupiters may also reveal how stars and close-in planets interact through radiation, gravity, and magnetic fields.The recent discovery of a transiting hot Jupiter a little over 2000 light-years away therefore presents an exciting opportunity!A Speeding GiantThe discovery of HATS-18b, a planet of roughly 2 times Jupiters mass and 1.3 times its radius, was announced in a study led by Kaloyan Penev (Princeton University). The planet was discovered using the HATSouth transit survey network, which includes instruments in Chile, Namibia, and Australia, and follow-up photometry and spectroscopy was conducted at a variety of ground-based observatories.HATS-18bs properties are particularly unusual: this hot Jupiter is zipping around its host star which is very similar to the Sun at the incredible pace of one orbit every 0.84 days. HATS-18bs orbit is more than 20 times closer to its host star than Mercurys is to the Sun, bringing it so close it nearly grazes the stars surface!Size of the planetary orbit relative to the stellar radius as a function of the stellar rotation period

  8. Hot subdwarf stars in close-up view IV. Helium abundances and the $^3$He isotopic anomaly of subdwarf B star

    CERN Document Server

    Geier, S; Edelmann, H; Morales-Rueda, L; Kilkenny, D; O'Donoghue, D; Marsh, T R; Copperwheat, C

    2013-01-01

    Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample consists of newly discovered stars from the Edinburgh Cape survey. We showed that effective temperatures and surface gravities can be derived from high resolution echelle spectra with sufficient accuracy. Systematic uncertainties have been determined by comparing the parameters derived from the high resolution data with the ones derived from medium resolution spectra. Helium abundances have been measured with high accuracy. Besides the known correlation of helium abundance with temperature, two distinct sequences in helium abundance have been confirmed. Significant isotopic shifts of helium lines due to an enrichment in $^{3}$He have been found in the spectra of 8 sdBs. Most of these stars cluster in a small temperature range between $27\\,000\\,{\\rm K}$ and $31\\,000\\,{\\rm K}$ very similar to the known $^{3}$He-rich main sequence B stars, which also cluster in such a small strip, but at ...

  9. High mass star formation in the IRAS 17233-3606 region: a new nearby and bright hot core in the southern sky

    CERN Document Server

    Leurini, S; Thorwirth, S; Wyrowski, F; Schilke, P; Menten, K M; Guesten, R; Zapata, L

    2008-01-01

    We present molecular line observations of the massive star forming region IRAS 17233-3606 aimed at studying the molecular core associated with the source. The observations were made using the Atacama Pathfinder Experiment telescope in the CO (3-2) and HCO^+ (4-3) transitions, and in the CH_3OH (6_K-5_K), (7_K-6_K) and CH_3CN (16_K-15_K) bands. For the CO(3-2) and HCO^+ (4-3) transitions, we obtained maps with a size of 70''\\times 70''. The typical angular resolution of the data is ~18''. Our observations reveal an exceptionally rich molecular spectrum, a signpost of hot core activity. Comparisons with two other prominent southern hot cores were made through observations in the same frequency setups. We also detected a bipolar outflow in CO (3-2) and HCO^+ (4-3) lines. Modelling reveals a hot core of size ~3'' and a temperature of 150 K in the IRAS17233-3606 region. The parameters of the molecular outflow are derived through the analysis of the CO (3-2) emission, and are typical of outflows driven by high-mass...

  10. Binaries discovered by the SPY survey. VI. Discovery of a low mass companion to the hot subluminous planetary nebula central star EGB 5 - a recently ejected common envelope?

    Science.gov (United States)

    Geier, S.; Napiwotzki, R.; Heber, U.; Nelemans, G.

    2011-04-01

    Hot subdwarf B stars (sdBs) in close binary systems are assumed to be formed via common envelope ejection. According to theoretical models, the amount of energy and angular momentum deposited in the common envelope scales with the mass of the companion. That low mass companions near or below the core hydrogen-burning limit are able to trigger the ejection of this envelope is well known. The currently known systems have very short periods ≃0.1-0.3 d. Here we report the discovery of a low mass companion (M2 > 0.14 M⊙) orbiting the sdB star and central star of a planetary nebula EGB 5 with an orbital period of 16.5 d at a minimum separation of 23 R⊙. Its long period is only just consistent with the energy balance prescription of the common envelope. The marked difference between the short and long period systems will provide strong constraints on the common envelope phase, in particular if the masses of the sdB stars can be measured accurately. Due to selection effects, the fraction of sdBs with low mass companions and similar or longer periods may be quite high. Low mass stellar and substellar companions may therefore play a significant role for the still unclear formation of hot subdwarf stars. Furthermore, the nebula around EGB 5 may be the remnant of the ejected common envelope making this binary a unique system to study this short und poorly understood phase of binary evolution. Based on observations at the Paranal Observatory of the European Southern Observatory for programmes No. 167.H-0407(A) and 71.D-0383(A). Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). Some of the data used in this work were obtained at the William Herschel Telescope (WHT) operated by the Isaac Newton Group of Telescopes (ING).

  11. Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150, and HD 46966

    Science.gov (United States)

    Blomme, R.; Mahy, L.; Catala, C.; Cuypers, J.; Gosset, E.; Godart, M.; Montalban, J.; Ventura, P.; Rauw, G.; Morel, T.; Degroote, P.; Aerts, C.; Noels, A.; Michel, E.; Baudin, F.; Baglin, A.; Auvergne, M.; Samadi, R.

    2011-09-01

    Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. Aims: We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. Methods: We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. Results: A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. Conclusions: The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany and Spain

  12. NuSTAR Observations of WISE J1036+0449, A Galaxy at Z Approx. 1 Obscured by Hot Dust

    Science.gov (United States)

    Ricci, C.; Assef, R. J.; Stern, D.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A. W.; Boggs, S.; hide

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z > 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z approx. 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (L(BOL) approx. = 8 x 10(exp 46) erg/s). We find evidence of a broadened component in Mg II, which would imply a black hole mass of M(BH) approx. = 2 x 10(exp 8) Stellar Mass and an Eddington ratio of lambda(Edd) approx. = 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of N(H) approx. = (2-15) x 10(exp 23)/sq cm. The source has an intrinsic 2-10 keV luminosity of approx. 6 x 10(exp 44) erg/s, a value significantly lower than that expected from the mid-infrared X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z < or approx. 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  13. NuSTAR Observations of WISE J1036+0449, A Galaxy at zeta approx 1 Obscured by Hot Dust

    Science.gov (United States)

    Ricci, C.; Assef, R. J.; Stern, Daniel K.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A.W.; Zhang, William W.; hide

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer's all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z > 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z approx. 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 (L(sub BOL) approx. = 8 x 10(exp 46) erg/s). We find evidence of a broadened component in Mg II, which would imply a black hole mass of M(BH) approx. = 2 x 10(exp 8) Stellar Mass and an Eddington ratio of lambda(sub Edd) approx. = 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of N(sub H) approx. = (2-15) x 10(exp 23)/sq cm. The source has an intrinsic 2-10 keV luminosity of approx. 6 x 10(exp 44) erg/s, a value significantly lower than that expected from the mid-infrared X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z < or approx. 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  14. NuSTAR Observations of WISE J1036+0449, a Galaxy at z~1 Obscured by Hot Dust

    Science.gov (United States)

    Ricci, C.; Assef, R. J.; Stern, D.; Nikutta, R.; Alexander, D. M.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Blain, A. W.; Boggs, S.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Chang, C. S.; Chen, C.-T. J.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Díaz-Santos, T.; Eisenhardt, P. R.; Farrah, D.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Jun, H. D.; Koss, M. J.; LaMassa, S.; Lansbury, G. B.; Markwardt, C. B.; Stalevski, M.; Stanley, F.; Treister, E.; Tsai, C.-W.; Walton, D. J.; Wu, J. W.; Zappacosta, L.; Zhang, W. W.

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer’s all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z> 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 hot DOG candidates at z∼ 1, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot DOGs for one of these objects, WISE J1036+0449 ({L}{Bol}≃ 8× {10}46 {erg} {{{s}}}-1). We find evidence of a broadened component in Mg ii, which would imply a black hole mass of {M}{BH}≃ 2× {10}8 {M}ȯ and an Eddington ratio of {λ }{Edd}≃ 2.7. WISE J1036+0449 is the first hot DOG detected by the Nuclear Spectroscopic Telescope Array, and observations show that the source is heavily obscured, with a column density of {N}{{H}}≃ (2{--}15)× {10}23 {{cm}}-2. The source has an intrinsic 2–10 keV luminosity of ∼ 6× {10}44 {erg} {{{s}}}-1, a value significantly lower than that expected from the mid-infrared/X-ray correlation. We also find that other hot DOGs observed by X-ray facilities show a similar deficiency of X-ray flux. We discuss the origin of the X-ray weakness and the absorption properties of hot DOGs. Hot DOGs at z≲ 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the X-ray emitting plasma at extreme values of the Eddington ratio.

  15. SOPHIE velocimetry of Kepler transit candidates. XV. KOI-614b, KOI-206b, and KOI-680b: a massive warm Jupiter orbiting a G0 metallic dwarf and two highly inflated planets with a distant companion around evolved F-type stars

    Science.gov (United States)

    Almenara, J. M.; Damiani, C.; Bouchy, F.; Havel, M.; Bruno, G.; Hébrard, G.; Diaz, R. F.; Deleuil, M.; Barros, S. C. C.; Boisse, I.; Bonomo, A. S.; Montagnier, G.; Santerne, A.

    2015-03-01

    We report the validation and characterization of three new transiting exoplanets using SOPHIE radial velocities: KOI-614b, KOI-206b, and KOI-680b. KOI-614b has a mass of 2.86 ± 0.35 MJup and a radius of 1.13 +0.26-0.18 RJup, and it orbits a G0, metallic ([ Fe/H ] = 0.35 ± 0.15) dwarf in 12.9 days. Its mass and radius are familiar and compatible with standard planetary evolution models, so it is one of the few known transiting planets in this mass range to have an orbital period over ten days. With an equilibrium temperature of Teq = 1000 ± 45 K, this places KOI-614b at the transition between what is usually referred to as "hot" and "warm" Jupiters. KOI-206b has a mass of 2.82 ± 0.52 MJup and a radius of 1.45 ± 0.16 RJup, and it orbits a slightly evolved F7-type star in a 5.3-day orbit. It is a massive inflated hot Jupiter that is particularly challenging for planetary models because it requires unusually large amounts of additional dissipated energy in the planet. On the other hand, KOI-680b has a much lower mass of 0.84 ± 0.15 MJup and requires less extra-dissipation to explain its uncommonly large radius of 1.99 ± 0.18 RJup. It is one of the biggest transiting planets characterized so far, and it orbits a subgiant F9-star well on its way to the red giant stage, with an orbital period of 8.6 days. With host stars of masses of 1.46 ± 0.17 M⊙ and 1.54 ± 0.09 M⊙, respectively, KOI-206b, and KOI-680b are interesting objects for theories of formation and survival of short-period planets around stars more massive than the Sun. For those two targets, we also find signs of a possible distant additional companion in the system. Based on observations made with SOPHIE on the 1.93-m telescope at the Observatoire de Haute-Provence (CNRS), France.Figures 11-14 are available in electronic form at http://www.aanda.org

  16. Hot subdwarfs from the ESO Supernova Ia Progenitor Survey - I. Atmospheric parameters and cool companions of sdB stars

    CERN Document Server

    Lisker, T; Napiwotzki, R; Christlieb, N; Han, Z; Homeier, D; Reimers, D

    2004-01-01

    We present the analysis of a high-resolution, high-quality sample of optical spectra for 76 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey (SPY). Effective temperature, surface gravity, and photospheric helium abundance are determined simultaneously by fitting the profiles of hydrogen and helium lines using synthetic spectra calculated from LTE and NLTE model atmospheres. We perform a detailed comparison of our measurements with theoretical calculations, both for single star evolution and for binary population synthesis models of close binary evolution. The luminosity evolution given by the standard EHB evolutionary tracks from Dorman et al. (1993) shows an overall agreement in shape with our observations, although a constant offset in luminosity exists. The various simulation sets for binary formation channels of sdB stars calculated by Han et al. (2003) are compared individually to our data for testing our current understanding of sdB formation processes and the physical effects involved...

  17. HAT-P-24b: An Inflated Hot Jupiter on a 3.36 Day Period Transiting a Hot, Metal-poor Star

    Science.gov (United States)

    Kipping, D. M.; Bakos, G. Á.; Hartman, J.; Torres, G.; Shporer, A.; Latham, D. W.; Kovács, Géza; Noyes, R. W.; Howard, A. W.; Fischer, D. A.; Johnson, J. A.; Marcy, G. W.; Béky, B.; Perumpilly, G.; Esquerdo, G. A.; Sasselov, D. D.; Stefanik, R. P.; Lázár, J.; Papp, I.; Sári, P.

    2010-12-01

    We report the discovery of HAT-P-24b, a transiting extrasolar planet orbiting the moderately bright V = 11.818 F8 dwarf star GSC 0774-01441, with a period P = 3.3552464 ± 0.0000071 days, transit epoch Tc = 2455216.97669 ± 0.00024 (BJD)11, and transit duration 3.653 ± 0.025 hr. The host star has a mass of 1.191 ± 0.042 M sun, radius of 1.317 ± 0.068 R sun, effective temperature 6373 ± 80 K, and a low metallicity of [Fe/H] = -0.16 ± 0.08. The planetary companion has a mass of 0.681 ± 0.031 M J and radius of 1.243 ± 0.072 R J yielding a mean density of 0.439 ± 0.069 g cm-3. By repeating our global fits with different parameter sets, we have performed a critical investigation of the fitting techniques used for previous Hungarian-made Automated Telescope planetary discoveries. We find that the system properties are robust against the choice of priors. The effects of fixed versus fitted limb darkening are also examined. HAT-P-24b probably maintains a small eccentricity of e = 0.052+0.022 -0.017, which is accepted over the circular orbit model with false alarm probability 5.8%. In the absence of eccentricity pumping, this result suggests that HAT-P-24b experiences less tidal dissipation than Jupiter. Due to relatively rapid stellar rotation, we estimate that HAT-P-24b should exhibit one of the largest known Rossiter-McLaughlin effect amplitudes for an exoplanet (ΔV RM ~= 95 m s-1) and thus a precise measurement of the sky-projected spin-orbit alignment should be possible. Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO and NASA.

  18. Multiplicity in 5 Msun Stars

    CERN Document Server

    Evans, Nancy Remage

    2011-01-01

    Multiwavelength opportunities have provided important new insights into the properties of binary/multiple 5 Msun stars. The combination of cool evolved primaries and hot secondaries in Cepheids (geriatric B stars) has yielded detailed information about the distribution of mass ratios. It has also provided a surprisingly high fraction of triple systems. Ground-based radial velocity orbits combined with satellite data from Hubble, FUSE, IUE, and Chandra can provide full information about the systems, including the masses. In particular, X-ray observations can identify low mass companions which are young enough to be physical companions. These multiwavelength observations provide important tests for star formation scenarios including diffenences between high and low mass results and differences between close and wide binaries.

  19. Three irradiated and bloated hot Jupiters: WASP-76b, WASP-82b & WASP-90b

    CERN Document Server

    West, R G; Anderson, D R; Bouchy, F; Brown, D J A; Cameron, A Collier; Deleuil, M; Delrez, L; Doyle, A P; Faedi, F; Fumel, A; Gillon, M; Hebrard, G; Hellier, C; Jehin, E; Lendl, M; Maxted, P F L; Pepe, F; Pollacco, D; Queloz, D; Segransan, D; Smalley, B; Smith, A M S; Triaud, A H M J; Udry, S

    2016-01-01

    We report three new transiting hot-Jupiter planets discovered from the WASP surveys combined with radial velocities from OHP/SOPHIE and Euler/CORALIE and photometry from Euler and TRAPPIST. All three planets are inflated, with radii 1.7-1.8 Rjup. All orbit hot stars, F5-F7, and all three stars have evolved, post-MS radii (1.7-2.2 Rsun). Thus the three planets, with orbits of 1.8-3.9 d, are among the most irradiated planets known. This reinforces the correlation between inflated planets and stellar irradiation.

  20. Investigating the origin of cyclical wind variability in hot, massive stars - I. On the dipolar magnetic field hypothesis

    NARCIS (Netherlands)

    A. David-Uraz; G.A. Wade; V. Petit; A. ud-Doula; J.O. Sundqvist; J. Grunhut; M. Schultz; C. Neiner; E. Alecian; H.F. Henrichs; J.-C. Bouret

    2014-01-01

    OB stars exhibit various types of spectral variability associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These are proposed to be caused by either magnetic fields or non-radial pulsations. In this paper, we evaluate the possible relation betw

  1. Kepler-4b: Hot Neptune-Like Planet of a G0 Star Near Main-Sequence Turnoff

    CERN Document Server

    Borucki, William J; Brown, Timothy M; Basri, Gibor; Batalha, Natalie; Caldwell, Douglas A; Cochran, William D; Dunham, Edward W; Gautier, Thomas N; Geary, John C; Gilliland, Ronald L; Howell, Steve B; Jenkins, Jon M; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Monet, David; Rowe, Jason F; Sasselov, Dimitar

    2010-01-01

    Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at RA = 19h02m27.68s, Dec = +50:08:08.7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10^{-3} and a duration of about 3.95 hours. Radial velocity measurements from the Keck HIRES spectrograph show a reflex Doppler signal of 9.3 (+1.1 -1.9) m/s, consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the radial velocities for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223 (+0.053 -0.091) solar masses and 1.487 (+0.071 -0.084) solar radii. We estimate the planet mass and radius to be 24.5 +/- 3.8 Earth masses and 3.99 +/- 0.21 Earth radi...

  2. Observational Asteroseismology of Hot Subdwarf Stars with the Mont4K/Kuiper Combination at the Steward Observatory Mount Bigelow Station

    CERN Document Server

    Fontaine, G; Charpinet, S; Latour, M; Randall, S K; Van Grootel, V; Brassard, P; Arizona, several undergraduate students at University of

    2013-01-01

    In the last few years, we have carried out several extensive observational campaigns on pulsating hot subdwarf stars using the Mont4K CCD camera attached to the 1.55 m Kuiper Telescope on Mount Bigelow. The Mont4K is a joint partnership between the University of Arizona and Universite de Montreal. It was designed and built at Steward Observatory. Using the Mont4K/Kuiper combination, we have so far, and among others, gathered high-sensitivity broadband light curves for PG 1219+534, PB8783, HS 0702+6043, and Feige 48. We report very briefly on some of the most interesting observational results that came out of these campaigns.

  3. A HOT URANUS ORBITING THE SUPER METAL-RICH STAR HD 77338 AND THE METALLICITY-MASS CONNECTION

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, J. S.; Hoyer, S.; Jones, M. I.; Rojo, P.; Day-Jones, A. C.; Ruiz, M. T. [Departamento de Astronomia, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Casilla 36-D (Chile); Jones, H. R. A.; Tuomi, M.; Barnes, J. R.; Pavlenko, Y. V.; Pinfield, D. J. [Center for Astrophysics, University of Hertfordshire, College Lane Campus, Hatfield, Hertfordshire, AL10 9AB (United Kingdom); Murgas, F. [Instituto de Astrofisica de Canarias, Via Lactea, E-38205 La Laguna, Tenerife (Spain); Ivanyuk, O. [Main Astronomical Observatory of National Academy of Sciences of Ukraine, 27 Zabolotnoho, Kyiv 127, 03680 (Ukraine); Jordan, A., E-mail: jjenkins@das.uchile.cl [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile)

    2013-04-01

    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{sup -1}, we find a minimum mass of 15.9{sup +4.7}{sub -5.3} M{sub Circled-Plus }. The best-fit eccentricity from this solution is 0.09{sup +0.25}{sub -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 {approx}4.5{sigma} 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.

  4. The first planet detected in the WTS: an inflated hot-Jupiter in a 3.35 day orbit around a late F-star

    CERN Document Server

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

    2012-01-01

    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. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J=16 were constructed for 60000 stars and searched for periodic transit signals. For one of the most promising transiting candidates, high-resolution spectra taken at the Hobby-Eberly Telescope 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 days, a planetary mass of 4.01+-0.35 Mj and a planetary radius of 1.49+-0.17 Rj. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 Mj.

  5. Hot Bottom Burning and s-process nucleosynthesis in massive AGB stars at the beginning of the thermally-pulsing phase

    CERN Document Server

    Garcia-Hernandez, D A; Yagüe, A; Uttenthaler, S; Karakas, A I; Lugaro, M; Ventura, P; Lambert, D L

    2013-01-01

    We report the first spectroscopic identification of massive Galactic Asymptotic Giant Branch (AGB) stars at the beginning of the thermally-pulsing (TP) phase. These stars are the most Li-rich ('super Li-rich' with logE(Li)~3-4) massive AGBs found to date. The high Li overabundances are accompanied by weak or no s-process element (i.e., Rb and Zr) enhancements. A comparison of our observations with the most recent Hot Bottom Burning (HBB) and s-process nucleosynthesis models confirms that HBB is strongly activated during the first TPs but the 22Ne neutron source needs much more TPs and Third Dredge-Up episodes to produce enough Rb at the stellar surface. We also show that the short-lived element Tc - usually used as an indicator of AGB genuineness - is not detected in massive AGBs in agreement with the theoretical predictions when the 22Ne neutron source dominates the s-process nucleosynthesis.

  6. Imaging the transition between pre-planetary and planetary nebulae: Integral Field Spectroscopy of hot post-AGB stars with NIFS

    CERN Document Server

    Gledhill, T M

    2014-01-01

    We present 2 to 2.4 micron integral field spectroscopy of a sample of hot post-AGB stars with early-B spectral types, using the NIFS instrument on Gemini North. These stars are just beginning to ionize their immediate environments and turn into planetary nebulae (PNe).We use molecular hydrogen emission lines together with hydrogen and helium recombination lines to explore the distribution of molecular and atomic gas and the extent of the developing ionized region. We see a range of evolutionary stages: IRAS 18062+2410 and IRAS 18379-1707 have recently developed compact and unresolved regions of photoionized H within axisymmetric molecular envelopes, with the former object increasing its Br-Gamma flux by a factor of 5.3 in 14 years; IRAS 22023+5249 and IRAS 20462+3416 have extended Br-Gamma nebulae and in the latter object only weak H2 emission remains; IRAS 19336-0400 is at a more advanced stage of PN formation where H2 is mostly dissociated and we see structure in both the H and He recombination line nebulae...

  7. The first planet detected in the WTS: an inflated hot-Jupiter in a 3.35 day orbit around a late F-star [ERRATUM

    CERN Document Server

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

    2014-01-01

    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 August 2007. Light curves comprising almost 1200 epochs with a photometric precision of better than 1 per cent to J ~ 16 were constructed for ~60000 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 days, a planetary mass of 4.01 +- 0.35 Mj and a planetary radius of 1.49+0.16-0.18 Rj. WTS-1b has one of the largest radius anomalies among the known hot Jupiters in the mass range 3-5 Mj. The h...

  8. Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150 and HD 46966

    CERN Document Server

    Blomme, R; Catala, C; Cuypers, J; Gosset, E; Godart, M; Montalban, J; Ventura, P; Rauw, G; Morel, T; Degroote, P; Aerts, C; Noels, A; Michel, E; Baudin, F; Baglin, A; Auvergne, M; Samadi, R

    2011-01-01

    The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and we search for pulsational frequencies, which we then compare to theoretical model predictions. We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic p...

  9. Life Cycle of Stars

    Science.gov (United States)

    1999-01-01

    In this stunning picture of the giant galactic nebula NGC 3603, the crisp resolution of NASA's Hubble Space Telescope captures various stages of the life cycle of stars in one single view. To the upper left of center is the evolved blue supergiant called Sher 25. The star has a unique circumstellar ring of glowing gas that is a galactic twin to the famous ring around the supernova 1987A. The grayish-bluish color of the ring and the bipolar outflows (blobs to the upper right and lower left of the star) indicates the presence of processed (chemically enriched) material. Near the center of the view is a so-called starburst cluster dominated by young, hot Wolf-Rayet stars and early O-type stars. A torrent of ionizing radiation and fast stellar winds from these massive stars has blown a large cavity around the cluster. The most spectacular evidence for the interaction of ionizing radiation with cold molecular-hydrogen cloud material are the giant gaseous pillars to the right of the cluster. These pillars are sculptured by the same physical processes as the famous pillars Hubble photographed in the M16 Eagle Nebula. Dark clouds at the upper right are so-called Bok globules, which are probably in an earlier stage of star formation. To the lower left of the cluster are two compact, tadpole-shaped emission nebulae. Similar structures were found by Hubble in Orion, and have been interpreted as gas and dust evaporation from possibly protoplanetary disks (proplyds). This true-color picture was taken on March 5, 1999 with the Wide Field Planetary Camera 2.

  10. Young, Star-forming Galaxies and their local Counterparts: the Evolving Relationship of Mass-SFR-Metallicity since z ~ 2.1

    CERN Document Server

    Gebhardt, Henry S Grasshorn; Ciardullo, Robin; Gronwall, Caryl; Hagen, Alex; Bridge, Joanna S; Schneider, Donald P; Trump, Jonathan R

    2015-01-01

    We explore the evolution of the Stellar Mass-Star Formation Rate-Metallicity Relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90 3 . 10^40 ergs s^-1) local galaxies, and this offset cannot be explained by simple systematic offsets in the derived quantities. At stellar masses above ~10^9 Msol and star formation rates above ~10 Msol yr^-1, the z ~ 2.1 galaxies have higher oxygen abundances than their local counterparts, while the opposite is true for lower-mass, lower-SFR systems.

  11. KELT-6b: A P~7.9 d Hot Saturn Transiting a Metal-Poor Star with a Long-Period Companion

    CERN Document Server

    Collins, Karen A; Beatty, Thomas G; Siverd, Robert J; Gaudi, B Scott; Pepper, Joshua; Kielkopf, John F; Johnson, John Asher; Howard, Andrew W; Fischer, Debra A; Manner, Mark; Bieryla, Allyson; Latham, David W; Fulton, Benjamin J; Gregorio, Joao; Buchhave, Lars A; Jensen, Eric L N; Stassun, Keivan G; Penev, Kaloyan; Crepp, Justin R; Hinkley, Sasha; Street, Rachel A; Cargile, Phillip; Mack, Claude E; Oberst, Thomas E; Avril, Ryan L; Mellon, Samuel N; McLeod, Kim K; Penny, Matthew T; Stefanik, Robert P; Berlind, Perry; Calkins, Michael L; Mao, Qingqing; Richert, Alexander J W; DePoy, Darren L; Esquerdo, Gilbert A; Gould, Andrew; Marshall, Jennifer L; Oelkers, Ryan J; Pogge, Richard W; Trueblood, Mark; Trueblood, Patricia

    2013-01-01

    We report the discovery of KELT-6b, a mildly-inflated Saturn-mass planet transiting a metal-poor host. The initial transit signal was identified in KELT-North survey data, and the planetary nature of the occulter was confirmed using a combination of follow-up photometry, high-resolution imaging, high-resolution spectroscopy, and precise radial velocity measurements. The fiducial model from a global analysis including constraints from isochrones indicates that the V=10.38 host star (TYC 2532-556-1) is a mildly evolved, late-F star with T_eff=6102 \\pm 43 K, log(g_*)=4.07_{-0.07}^{+0.04} and [Fe/H]=-0.28 \\pm 0.04, with an inferred mass M_*=1.09 \\pm 0.04 M_sun and radius R_*=1.58_{-0.09}^{+0.16} R_sun. The planetary companion has mass M_p=0.43 \\pm 0.05 M_Jup, radius R_p=1.19_{-0.08}^{+0.13} R_Jup, surface gravity log(g_p)=2.86_{-0.08}^{+0.06}, and density rho_p=0.31_{-0.08}^{+0.07} g cm^{-3}. The planet is on an orbit with semimajor axis a=0.079 \\pm 0.001 AU and eccentricity e=0.22_{-0.10}^{+0.12}, which is rough...

  12. How does stellar irradiation make hot Jupiters puffy?

    Science.gov (United States)

    Wei, Yu-Jie; Gu, Pin-Gao

    2017-06-01

    Hot Jupiters appear to be re-inflated as their host stars evolve and become more luminous, shedding more light on the intriguing correlation between stellar irradiation and the size of hot Jupiters. To account for the phenomenon, one of the well-known models is the thermal-tide scenario proposed by Arras and Socrates. We present a linear analysis of semi-diurnal thermal tides in a hot Jupiter. The Coriolis effect is added to our equation, which generates more wave modes than non-rotating models, such as Rossby, Yanai, and inertial waves. We attempt to investigate where and which mode contributes most of the torque that maintains the planet in an asynchronous state against gravitational tides, leading to re-inflation of a hot Jupiter.

  13. Gas giants in hot water: inhibiting giant planet formation and planet habitability in dense star clusters through cosmic time

    Science.gov (United States)

    Thompson, Todd A.

    2013-05-01

    I show that the temperature of nuclear star clusters, starburst clusters in M82, compact high-z galaxies and some globular clusters of the Galaxy likely exceeded the ice-line temperature (TIce ≈ 150-170 K) during formation for a time comparable to the planet formation time-scale. The protoplanetary discs within these systems will thus, not have an ice line, decreasing the total material available for building protoplanetary embryos, inhibiting the formation of gas- and ice-giants if they form by core accretion, and prohibiting habitability. Planet formation by gravitational instability is similarly suppressed because Toomre's Q > 1 in all but the most massive discs. I show that cluster irradiation can in many cases dominate the thermodynamics and structure of passive and active protoplanetary discs for semi-major axes larger than ˜1-5 au. I discuss these results in the context of the observed lack of planets in 47 Tuc. I predict that a similar search for planets in the globular cluster NGC 6366 ([Fe/H] = -0.82) should yield detections, whereas (counterintuitively) the relatively metal-rich globular clusters NGC 6440, 6441 and 6388 should be devoid of giant planets. The characteristic stellar surface density above which TIce is exceeded in star clusters is ˜ 6 × 103 M⊙ pc- 2 f- 1/2dg, MW, where fdg, MW is the dust-to-gas ratio of the embedding material, normalized to the Milky Way value. Simple estimates suggest that ˜5-50 per cent of the stars in the universe formed in an environment exceeding this surface density. Future microlensing planet searches that directly distinguish between the bulge and disc planet populations of the Galaxy and M31 can test these predictions. Caveats and uncertainties are detailed.

  14. Hot and cool: two emission-line stars with constrasting behaviours in the same XMM-Newton field

    Science.gov (United States)

    Nazé, Y.; Rauw, G.; Ud-Doula, A.

    2010-02-01

    High-energy emissions are good indicators of peculiar behaviours in stars. We have therefore obtained an XMM-Newton observation of HD 155806 and 1RXS J171502.4-333344, and derived their spectral properties for the first time. The X-ray spectrum of HD 155806 appears soft, even slightly softer than usual for O-type stars (as shown by a comparison with the O9 star HD 155889 in the same XMM-Newton field). It is well-fitted with a two-component thermal model with low temperatures (0.2 and 0.6 keV), and it shows no overluminosity (log[L_X/L_BOL] = -6.75). The high-resolution spectrum, though noisy, reveals a few broad, symmetric X-ray lines (FWHM˜2500 km s-1). The X-ray emission is compatible with the wind-shock model and therefore appears unaffected by the putative dense equatorial regions at the origin of the Oe classification. 1RXS J171502.4-333344 is a nearby flaring source of moderate X-ray luminosity (log[L_X/L_BOL] = -3), with a soft thermal spectrum composed of narrow lines and presenting a larger abundance of elements (e.g. Ne) with a high first ionization potential (FIP) compared to lower-FIP elements. All the evidence indicates a coronal origin for the X-ray emission, in agreement with the dMe classification of this source. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).Research Associate FNRS.

  15. Chemical evolution of high-mass stars in close binaries. II. The evolved component of the eclipsing binary V380 Cygni

    CERN Document Server

    Pavlovski, K; Koubsky, P; Southworth, J; Yang, S; Kolbas, V

    2009-01-01

    The eclipsing and double-lined spectroscopic binary V380 Cyg is an extremely important probe of stellar evolution: its primary component is a high-mass star at the brink of leaving the main sequence whereas the secondary star is still in the early part of its main sequence lifetime. We present extensive high-resolution echelle and grating spectroscopy from Ondrejov, Calar Alto, Victoria and La Palma. We apply spectral disentangling to unveil the individual spectra of the two stars and obtain new spectroscopic elements. The secondary star contributes only about 6% of the total light, which remains the main limitation to measuring the system's characteristics. We determine improved physical properties, finding masses 13.1 +/- 0.3 and 7.8 +/- 0.1 M_sun, radii 16.2 +/- 0.3 and 4.06 +/- 0.08 R_sun, and effective temperatures 21750 +/- 280 and 21600 +/- 550 K, for the primary and secondary components respectively. We perform a detailed abundance analysis by fitting non-LTE theoretical line profiles to the disentang...

  16. Cold gas in hot star clusters: the wind from the red supergiant W26 in Westerlund 1

    Science.gov (United States)

    Mackey, Jonathan; Castro, Norberto; Fossati, Luca; Langer, Norbert

    2015-10-01

    The massive red supergiant W26 in Westerlund 1 is one of a growing number of red supergiants shown to have winds that are ionized from the outside in. The fate of this dense wind material is important for models of second generation star formation in massive star clusters. Mackey et al. (2014, Nature, 512, 282) showed that external photoionization can stall the wind of red supergiants and accumulate mass in a dense static shell. We use spherically symmetric radiation-hydrodynamic simulations of an externally photoionized wind to predict the brightness distribution of Hα and [N II] emission arising from photoionized winds both with and without a dense shell. We analyse spectra of the Hα and [N II] emission lines in the circumstellar environment around W26 and compare them with simulations to investigate whether W26 has a wind that is confined by external photoionization. Simulations of slow winds that are decelerated into a dense shell show strongly limb-brightened line emission, with line radial velocities that are independent of the wind speed. Faster winds (≳22 km s-1) do not form a dense shell, have less limb-brightening, and the line radial velocity is a good tracer of the wind speed. The brightness of the [N II] and Hα lines as a function of distance from W26 agrees reasonably well with observations when only the line flux is considered. The radial velocity of the simulated winds disagrees with observations, however: the brightest observed emission is blueshifted by ≈25 km s-1 relative to the radial velocity of the star, whereas a spherically symmetric wind has the brightest emission at zero radial velocity because of limb brightening. Our results show that the bright nebula surrounding W26 must be asymmetric, and we suggest that it is confined by external ram pressure from the extreme wind of the nearby supergiant W9. We obtain a lower limit on the nitrogen abundance within the nebula of 2.35 times solar. The line ratio strongly favours photoionization

  17. Asteroseismology of hot pre-white dwarf stars: the case of the DOV stars PG 2131+066 and PG 1707+427, and the PNNV star NGC 1501

    CERN Document Server

    Córsico, A H; Bertolami, M M Miller; García--Berro, E

    2009-01-01

    We present an asteroseismological study on the two high-gravity pulsating PG1159 (GW Vir or DOV) stars, PG 2131+066 and PG 1707+427, and on the pulsating [WCE] star NGC 1501. We compute adiabatic $g$-mode pulsation periods on PG1159 evolutionary models with stellar masses ranging from 0.530 to 0.741 Msun. These models take into account the complete evolution of progenitor stars, through the thermally pulsing AGB phase, and born-again episode. We constrain the stellar mass of PG 2131+066, PG 1707+427 and NGC 1501 by comparing the observed period spacing with the asymptotic period spacing and with the average of the computed period spacings. We also employ the individual observed periods in search of representative seismological models for each star. This work closes our short series of asteroseismological studies on pulsating pre-white dwarf stars. Our results demonstrate the usefulness of asteroseismology for probing the internal structure and evolutionary status of pre-white dwarf stars. In particular, aster...

  18. Cold gas in hot star clusters: the wind from the red supergiant W26 in Westerlund 1

    CERN Document Server

    Mackey, Jonathan; Fossati, Luca; Langer, Norbert

    2015-01-01

    The massive red supergiant (RSG) W26 in Westerlund 1 is one of a growing number of RSGs shown to have winds that are ionized from the outside in. The fate of this dense wind material is important for models of second generation star formation in massive star clusters. Mackey et al. (2014) showed that external photoionization can stall the wind of RSGs and accumulate mass in a dense static shell. We use 1D R-HD simulations of an externally photoionized wind to predict the Halpha and [NII] emission arising from photoionized winds both with and without a dense shell. We analyse spectra of the Halpha and [NII] emission in the environment around W26 and compare them with predicted synthetic emission. Simulations of slow winds that are decelerated into a dense shell show strongly limb-brightened line emission, with line radial velocities that are independent of the wind speed. Faster winds (>22 km/s) do not form a dense shell, have less limb-brightening, and the line radial velocity is a good tracer of the wind spe...

  19. Massive Stars

    Science.gov (United States)

    Livio, Mario; Villaver, Eva

    2009-11-01

    Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

  20. Ultraviolet spectroscopy of hot young stars with infrared excesses - NGC 2264-W46, W90, and W100

    Science.gov (United States)

    Meade, M. R.; Sitko, M. L.; Simon, T.

    1984-01-01

    New ultraviolet data are combined with optical data to investigate the wavelength-dependent extinction of the stars W46, W90, and W100 in the young galactic cluster NGC 2264. The observations of W90 confirm the existence of anomalous (circumstellar) dust extinction with a ratio of total to selective extinction, R greater than 7. This extinction is most easily explained by a graphite-silicate mixture with larger mean sizes than are present in the diffuse interstellar medium. For W46 and W100, the grains are likely to be gray, but the possibility of nongray extinction cannot be excluded because of uncertainties arising from the very small ultraviolet optical depths of the circumstellar dust.

  1. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    Science.gov (United States)

    Kuzmychov, O.; Berdyugina, S. V.

    2013-10-01

    Aims: We investigated the Paschen-Back effect in the (0,0) band of the A6Σ+ - X6Σ+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. Methods: We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field perturbation (the Paschen-Back effect) was consistently taken into account. Then, we calculated frequencies and strengths of transitions between magnetic sublevels. Employing these results and solving numerically a set of the radiative transfer equations for polarized radiation, we calculated Stokes parameters for both the individual lines and the (0,0) band depending on the strength and orientation of the magnetic field. Results: We demonstrate that magnetic splitting of the individual CrH lines shows a significant asymmetry due to the Paschen-Back effect already at 1 G field. This leads to a considerable signal in both circular and linear polarization, up to 30% at the magnetic field strength of ≥3 kG in early L dwarfs. The polarization does not cancel out completely even at very low spectral resolution and is seen as broad-band polarization of a few percent. Since the line asymmetry depends only on the magnetic field strength and not on the filling factor, CrH lines provide a very sensitive tool for direct measurement of the stellar magnetic fields on faint cool objects, such as brown dwarfs and hot Jupiters, observed with low spectral resolution.

  2. Transiting exoplanets from the CoRoT space mission. XXVII. CoRoT-28b, a planet orbiting an evolved star, and CoRoT-29b, a planet showing an asymmetric transit

    Science.gov (United States)

    Cabrera, J.; Csizmadia, Sz.; Montagnier, G.; Fridlund, M.; Ammler-von Eiff, M.; Chaintreuil, S.; Damiani, C.; Deleuil, M.; Ferraz-Mello, S.; Ferrigno, A.; Gandolfi, D.; Guillot, T.; Guenther, E. W.; Hatzes, A.; Hébrard, G.; Klagyivik, P.; Parviainen, H.; Pasternacki, Th.; Pätzold, M.; Sebastian, D.; Tadeu dos Santos, M.; Wuchterl, G.; Aigrain, S.; Alonso, R.; Almenara, J.-M.; Armstrong, J. D.; Auvergne, M.; Baglin, A.; Barge, P.; Barros, S. C. C.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Carpano, S.; Chaffey, C.; Deeg, H. J.; Díaz, R. F.; Dvorak, R.; Erikson, A.; Grziwa, S.; Korth, J.; Lammer, H.; Lindsay, C.; Mazeh, T.; Moutou, C.; Ofir, A.; Ollivier, M.; Pallé, E.; Rauer, H.; Rouan, D.; Samuel, B.; Santerne, A.; Schneider, J.

    2015-07-01

    Context. We present the discovery of two transiting extrasolar planets by the satellite CoRoT. Aims: We aim at a characterization of the planetary bulk parameters, which allow us to further investigate the formation and evolution of the planetary systems and the main properties of the host stars. Methods: We used the transit light curve to characterize the planetary parameters relative to the stellar parameters. The analysis of HARPS spectra established the planetary nature of the detections, providing their masses. Further photometric and spectroscopic ground-based observations provided stellar parameters (log g, Teff, v sin i) to characterize the host stars. Our model takes the geometry of the transit to constrain the stellar density into account, which when linked to stellar evolutionary models, determines the bulk parameters of the star. Because of the asymmetric shape of the light curve of one of the planets, we had to include the possibility in our model that the stellar surface was not strictly spherical. Results: We present the planetary parameters of CoRoT-28b, a Jupiter-sized planet (mass 0.484 ± 0.087 MJup; radius 0.955 ± 0.066 RJup) orbiting an evolved star with an orbital period of 5.208 51 ± 0.000 38 days, and CoRoT-29b, another Jupiter-sized planet (mass 0.85 ± 0.20 MJup; radius 0.90 ± 0.16 RJup) orbiting an oblate star with an orbital period of 2.850 570 ± 0.000 006 days. The reason behind the asymmetry of the transit shape is not understood at this point. Conclusions: These two new planetary systems have very interesting properties and deserve further study, particularly in the case of the star CoRoT-29. The CoRoT space mission, launched on December 27th 2006, was developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain. Based on observations obtained with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland

  3. KELT-10b: the first transiting exoplanet from the KELT-South survey - a hot sub-Jupiter transiting a V = 10.7 early G-star

    Science.gov (United States)

    Kuhn, Rudolf B.; Rodriguez, Joseph E.; Collins, Karen A.; Lund, Michael B.; Siverd, Robert J.; Colón, Knicole D.; Pepper, Joshua; Stassun, Keivan G.; Cargile, Phillip A.; James, David J.; Penev, Kaloyan; Zhou, George; Bayliss, Daniel; Tan, T. G.; Curtis, Ivan A.; Udry, Stephane; Segransan, Damien; Mawet, Dimitri; Dhital, Saurav; Soutter, Jack; Hart, Rhodes; Carter, Brad; Gaudi, B. Scott; Myers, Gordon; Beatty, Thomas G.; Eastman, Jason D.; Reichart, Daniel E.; Haislip, Joshua B.; Kielkopf, John; Bieryla, Allyson; Latham, David W.; Jensen, Eric L. N.; Oberst, Thomas E.; Stevens, Daniel J.

    2016-07-01

    We report the discovery of KELT-10b, the first transiting exoplanet discovered using the KELT-South telescope. KELT-10b is a highly inflated sub-Jupiter mass planet transiting a relatively bright V = 10.7 star (TYC 8378-64-1), with Teff = 5948 ± 74 K, log g = 4.319_{-0.030}^{+0.020} and [Fe/H] = 0.09_{-0.10}^{+0.11}, an inferred mass M* = 1.112_{-0.061}^{+0.055} M⊙ and radius R* = 1.209_{-0.035}^{+0.047} R⊙. The planet has a radius Rp = 1.399_{-0.049}^{+0.069} RJ and mass Mp = 0.679_{-0.038}^{+0.039} MJ. The planet has an eccentricity consistent with zero and a semimajor axis a = 0.052 50_{-0.000 97}^{+0.000 86} au. The best-fitting linear ephemeris is T0 = 2457 066.720 45 ± 0.000 27 BJDTDB and P = 4.166 2739 ± 0.000 0063 d. This planet joins a group of highly inflated transiting exoplanets with a larger radius and smaller mass than that of Jupiter. The planet, which boasts deep transits of 1.4 per cent, has a relatively high equilibrium temperature of Teq = 1377_{-23}^{+28} K, assuming zero albedo and perfect heat redistribution. KELT-10b receives an estimated insolation of 0.817_{-0.054}^{+0.068} × 109 erg s-1 cm-2, which places it far above the insolation threshold above which hot Jupiters exhibit increasing amounts of radius inflation. Evolutionary analysis of the host star suggests that KELT-10b may not survive beyond the current subgiant phase, depending on the rate of in-spiral of the planet over the next few Gyr. The planet transits a relatively bright star and exhibits the third largest transit depth of all transiting exoplanets with V < 11 in the Southern hemisphere, making it a promising candidate for future atmospheric characterization studies.

  4. AG Carinae III. The 1990 hot phase of the star and the physical structure of the circumstellar environment

    CERN Document Server

    Viotti, R; Rossi, C

    1993-01-01

    Long slit spectra of the region around the Luminous Blue Variable AG Car obtained in June 1990, just before the onset of its new brightening phase, indicate that AG Car was in the hottest phase so far recorded. The spectrum shows strong broad emissions of He II 468.6 nm, and [Fe III] 465.8-470.1 nm, and He I, N II, Si III, Al III and Fe III with a P Cygni profile. We have also identified weak lines of C II and O II. A faint continuum emission has been detected within the whole ring nebula. We also find that the spectrum of some regions is partially due to scattered star's light. This provides evidence of the presence of dust grains, and indicates that even in present times dust is condensing from AG Car wind. The sharp outer edge of the ring suggest the presence of a shock front. We have also identified an extended low density H II $halo$, which should be associated with the residual of the stellar wind of a previous cooler evolutionary phase of AG Car. In the halo the H$\\alpha$/[N II] ratio is strengthened w...

  5. Gas Giants in Hot Water: Inhibiting Giant Planet Formation and Planet Habitability in Dense Star Clusters Through Cosmic Time

    CERN Document Server

    Thompson, Todd A

    2012-01-01

    I show that the temperature of nuclear star clusters, starburst clusters in M82, compact high-z galaxies, and some globular clusters of the Galaxy likely exceeded the ice line temperature (T_Ice ~ 150-170 K) during formation for a time comparable to the planet formation timescale. The protoplanetary disks within these systems will thus not have an ice line, decreasing the total material available for building protoplanetary embryos, inhibiting the formation of gas- and ice-giants if they form by core accretion, and prohibiting habitability. Planet formation by gravitational instability is similarly suppressed because Toomre's Q > 1 in all but the most massive disks. I discuss these results in the context of the observed lack of planets in 47 Tuc. I predict that a similar search for planets in the globular cluster NGC 6366 ([Fe/H] = -0.82) should yield detections, whereas (counterintuitively) the relatively metal-rich globular clusters NGC 6440, 6441, and 6388 should be devoid of giant planets. The characteris...

  6. Abundance Ratios in Stars vs. Hot Gas in Elliptical Galaxies: the Chemical Evolution Modeller Point of View

    CERN Document Server

    Pipino, A

    2009-01-01

    I will present predictions from chemical evolution model aimed at a self-consistent study of both optical (i.e. stellar) and X-ray (i.e.gas) properties of present-day elliptical galaxies. Detailed cooling and heating processes in the interstellar medium (ISM) are taken into and allow a reliable modelling of the SN-driven galactic wind. SNe Ia activity, in fact, may power a galactic wind lasting for a considerable amount of the galactic lifetime, even in the case for which the efficiency of energy transfer into the ISM per SN Ia event is less than unity. The model simultaneously reproduces the mass-metallicity, the colour-magnitude, the L_X - L_B and the L_X - T relations, as well as the observed trend of the [Mg/Fe] ratio as a function of sigma, by adopting the prescriptions of Pipino & Matteucci (2004) for the gas infall and star formation timescales. The "iron discrepancy", namely the too high predicted iron abundance in X-ray haloes of ellipticals compared to observations, can be solved by taking into ...

  7. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    CERN Document Server

    Kuzmychov, O

    2013-01-01

    We investigated the Paschen-Back effect in the (0,0) band of the A6{\\Sigma}+-X6{\\Sigma}+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field perturbation (the Paschen-Back effect) was consistently taken into account. Then, we calculated frequencies and strengths of transitions between magnetic sublevels. Employing these results and solving numerically a set of the radiative transfer equations for polarized radiation, we calculated Stokes parameters for both the individual lines and the (0,0) band depending on the strength and orientation of the magnetic field. We demonstrate that magnetic splitting of the individual CrH lines shows a significant asymmetry due to the...

  8. RADIO EMISSION FROM RED-GIANT HOT JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Yuka [Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550 (Japan); Spiegel, David S. [Analytics and Algorithms, Stitch Fix, San Francisco, CA 94103 (United States); Mroczkowski, Tony [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Nordhaus, Jason [Department of Science and Mathematics, National Technical Institute for the Deaf, Rochester Institute of Technology, Rochester, NY 14623 (United States); Zimmerman, Neil T. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Parsons, Aaron R. [Astronomy Department, University of California, Berkeley, CA (United States); Mirbabayi, Mehrdad [Astrophysics Department, Institute for Advanced Study, Princeton, NJ 08540 (United States); Madhusudhan, Nikku, E-mail: yuka.fujii@elsi.jp [Astronomy Department, University of Cambridge (United Kingdom)

    2016-04-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

  9. Transiting exoplanets from the CoRoT space mission IX. CoRoT-6b: a transiting `hot Jupiter' planet in an 8.9d orbit around a low-metallicity star

    CERN Document Server

    Fridlund, M; Alonso, R; Deleuil, M; Gandolfi, D; Gillon, M; Bruntt, H; Alapini, A; Csizmadia, Sz; Guillot, T; Lammer, H; Aigrain, S; Almenara, J M; Auvergne, M; Baglin, A; Barge, P; Borde, P; Bouchy, F; Cabrera, J; Carone, L; Carpano, S; Deeg, H J; De la Reza, R; Dvorak, R; Erikson, A; Ferraz-Mello, S; Guenther, E; Gondoin, P; Hartog, R den; Hatzes, A; Jorda, L; Leger, A; Llebaria, A; Magain, P; Mazeh, T; Moutou, C; Ollivier, M; Patzold, M; Queloz, D; Rauer, H; Rouan, D; Samuel, B; Schneider, J; Shporer, A; Stecklum, B; Tingley, B; Weingrill, J; Wuchterl, G

    2010-01-01

    The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations - photometric and spectroscopic - carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a `hot Jupiter' planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high $^7$Li abundance. While thelightcurveindicatesamuchhigherlevelof activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Ca ] H&K lines.

  10. NuSTAR observations of WISE J1036+0449, a galaxy at z ∼ 1 obscured by hot dust

    DEFF Research Database (Denmark)

    Ricci, C.; Assef, R. J.; Stern, D.

    2017-01-01

    Hot dust-obscured galaxies (hot DOGs), selected from Wide-Field Infrared Survey Explorer’s all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. Most known hot DOGs are located at z > 1.5, due in par...

  11. The empirical mass distribution of hot B subdwarfs: Implications for stellar evolution theory

    Directory of Open Access Journals (Sweden)

    Green E.M.

    2013-03-01

    Full Text Available Subdwarf B (sdB stars are hot, compact, and evolved objects that form the very hot end of the horizontal branch, the so-called Extreme Horizontal Branch (EHB. Understanding the formation of sdB stars is one of the remaining challenges of stellar evolution theory. Several scenarios have been proposed to account for the existence of such objects, made of He-burning core surrounded by very thin H-rich envelope. They give quite different theoretical mass distributions for the resulting sdB stars. Detailed asteroseismic analyses, including mass estimates, of 15 pulsating hot B subdwarfs have been published since a decade. The masses have also been reliably determined by light curve modeling and spectroscopy for 7 sdB components of eclipsing and/or reflection effect binaries. These empirical mass distributions, although based on small-number statistics, can be compared with the expectations of stellar evolution theory. In particular, the two He white dwarfs merger scenario does not seem to be the dominant channel to form isolated sdB stars, while the post-red giant branch scenario is reinforced. This opens new questions on extreme mass loss of red giants to form EHB stars, possibly in connection with the recently discovered close substellar companions and planets orbiting sdB stars.

  12. Hot subdwarf binaries - Masses and nature of their heavy compact companions

    Energy Technology Data Exchange (ETDEWEB)

    Geier, Stephan; Heber, Uli; Edelmann, Heinz; Kupfer, Thomas [Dr. Remeis-Sternwarte, Institute for Astronomy, University Erlangen-Nuernberg, Sternwartstr. 7, 96049 Bamberg (Germany); Napiwotzki, Ralf [Centre of Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Podsiadlowski, Philipp, E-mail: geier@sternwarte.uni-erlangen.d [Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom)

    2009-06-01

    Neutron stars and stellar-mass black holes are the remnants of massive stars, which ended their lives in supernova explosions. These exotic objects can only be studied in relatively rare cases. If they are interacting with close companions they become bright X-ray sources. If they are neutron stars, they may be detected as pulsars. Only a few hundred such systems are presently known in the Galaxy. However, there should be many more binaries with basically invisible compact objects in non-interacting binaries. Here we report the discovery of unseen compact companions to hot subdwarfs in close binary systems. Hot subdwarfs are evolved helium-core-burning stars that have lost most of their hydrogen envelopes, often due to binary interactions. Using high-resolution spectra and assuming tidal synchronisation of the subdwarfs, we were able to constrain the companion masses of 31 binaries. While most hot subdwarf binaries have white-dwarf or late-type main sequence companions, as predicted by binary evolution models, at least 5% of the observed subdwarfs must have very massive companions: unusually heavy white dwarfs, neutron stars and, in some cases, even black holes. We present evolutionary models which show that such binaries can indeed form if the system has evolved through two common-envelope phases. This new connection between hot subdwarfs, which are numerous in the Galaxy, and massive compact objects may lead to a tremendous increase in the number of known neutron stars and black holes and shed some light on this dark population and its evolutionary link to the X-ray binary population.

  13. Star Shows It Has The Right Stuff

    Science.gov (United States)

    2004-01-01

    Astronomers have used an observation by NASA's Chandra X-ray Observatory to make the best case yet that a star can be engulfed by its companion star and survive. This discovery will help astronomers better understand how closely coupled stars, and perhaps even stars and planets, evolve when one of the stars expands enormously in its red giant phase. The binary star system known as V471 Tauri comprises a white dwarf star (the primary) in a close orbit -- one thirtieth of the distance between Mercury and the Sun -- with a normal Sun-like star (the secondary). Chandra's data showed that the hot upper atmosphere of the secondary star has a deficit of carbon atoms relative to nitrogen atoms. "This deficit of carbon atoms is the first clear observational evidence that the normal star was engulfed by its companion in the past," according to Jeremy Drake of the Smithsonian Astrophysical Observatory in Cambridge, MA, who coauthored an article on V471 in The Astrophysical Journal Letters with Marek Sarna of the N. Copernicus Astronomical Center in Poland. The white dwarf star was once a star several times as massive as the Sun. Nuclear fusion reactions in the core of such a star convert carbon into nitrogen over a period of about a billion years. When the fuel in the core of the star is exhausted, the core collapses, triggering more energetic nuclear reactions that cause the star to expand and transform into a red giant before eventually collapsing to become a white dwarf. The carbon-poor material in the core of the red giant is mixed with outer part of the star, so its atmosphere shows a deficit of carbon, as compared with Sun-like stars. The X-ray spectra of a red giant star (top panel) and a Sun-like star (bottom panel) show the large difference in the peaks due to carbon atoms in the two stars. Theoretical calculations indicate that a red giant in a binary system can completely envelop its companion star and dramatically affect its evolution. During this common envelope

  14. Molecular cloud regulated star formation in galaxies

    CERN Document Server

    Booth, C M; Okamoto, T

    2007-01-01

    We describe a numerical implementation of star formation in disk galaxies, in which the conversion of cooling gas to stars in the multiphase interstellar medium is governed by the rate at which molecular clouds are formed and destroyed. In the model, clouds form from thermally unstable ambient gas and get destroyed by feedback from massive stars and thermal conduction. Feedback in the ambient phase cycles gas into a hot galactic fountain or wind. We model the ambient gas hydrodynamically using smoothed particle hydrodynamics (SPH). However, we cannot resolve the Jeans mass in the cold and dense molecular gas and, therefore, represent the cloud phase with ballistic particles that coagulate when colliding. We show that this naturally produces a multiphase medium with cold clouds, a warm disk, hot supernova bubbles and a hot, tenuous halo. Our implementation of this model is based on the Gadget N-Body code. We illustrate the model by evolving an isolated Milky Way-like galaxy and study the properties of a disk f...

  15. Small Friends of Hot Jupiters

    Science.gov (United States)

    Nunez, Luis Ernesto; Johnson, John A.

    2017-01-01

    Hot Jupiters are Jupiter-sized gas giant exoplanets that closely orbit their host star in periods of about 10 days or less. Early models hypothesized that these exoplanets formed away from the star, then over time drifted to their characteristically closer locations. However, new theories predict that Hot Jupiters form at their close proximity during the process of core accretion (Batygin et al. 2015). In fact, a super-Earth and a Neptune-sized exoplanet have already been detected in the Hot Jupiter-hosting star WASP-47 (Becker et al. 2015). We will present our analysis of radial velocity time series plots to determine whether low-mass, short-period planets have been previously overlooked in systems of stars which host Hot Jupiters.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851.

  16. Discovery of magnetic A supergiants: the descendants of magnetic main-sequence B stars

    Science.gov (United States)

    Neiner, Coralie; Oksala, Mary E.; Georgy, Cyril; Przybilla, Norbert; Mathis, Stéphane; Wade, Gregg; Kondrak, Matthias; Fossati, Luca; Blazère, Aurore; Buysschaert, Bram; Grunhut, Jason

    2017-10-01

    In the context of the high resolution, high signal-to-noise ratio, high sensitivity, spectropolarimetric survey BritePol, which complements observations by the BRITE constellation of nanosatellites for asteroseismology, we are looking for and measuring the magnetic field of all stars brighter than V = 4. In this paper, we present circularly polarized spectra obtained with HarpsPol at ESO in La Silla (Chile) and ESPaDOnS at CFHT (Hawaii) for three hot evolved stars: ι Car, HR 3890 and ε CMa. We detected a magnetic field in all three stars. Each star has been observed several times to confirm the magnetic detections and check for variability. The stellar parameters of the three objects were determined and their evolutionary status was ascertained employing evolution models computed with the Geneva code. ε CMa was already known and is confirmed to be magnetic, but our modelling indicates that it is located near the end of the main sequence, i.e. it is still in a core hydrogen burning phase. ι Car and HR 3890 are the first discoveries of magnetic hot supergiants located well after the end of the main sequence on the Hertzsprung-Russell diagram. These stars are probably the descendants of main-sequence magnetic massive stars. Their current field strength (a few G) is compatible with magnetic flux conservation during stellar evolution. These results provide observational constraints for the development of future evolutionary models of hot stars including a fossil magnetic field.

  17. Secular chaos and its application to Mercury, hot Jupiters, and the organization of planetary systems

    CERN Document Server

    Lithwick, Yoram

    2013-01-01

    In the inner solar system, the planets' orbits evolve chaotically, driven primarily by secular chaos. Mercury has a particularly chaotic orbit, and is in danger of being lost within a few billion years. Just as secular chaos is reorganizing the solar system today, so it has likely helped organize it in the past. We suggest that extrasolar planetary systems are also organized to a large extent by secular chaos. A hot Jupiter could be the end state of a secularly chaotic planetary system reminiscent of the solar system. But in the case of the hot Jupiter, the innermost planet was Jupiter- (rather than Mercury-) sized, and its chaotic evolution was terminated when it was tidally captured by its star. In this contribution, we review our recent work elucidating the physics of secular chaos and applying it to Mercury and to hot Jupiters. We also present new results comparing the inclinations of hot Jupiters thus produced with observations.

  18. Secular chaos and its application to Mercury, hot Jupiters, and the organization of planetary systems.

    Science.gov (United States)

    Lithwick, Yoram; Wu, Yanqin

    2014-09-02

    In the inner solar system, the planets' orbits evolve chaotically, driven primarily by secular chaos. Mercury has a particularly chaotic orbit and is in danger of being lost within a few billion years. Just as secular chaos is reorganizing the solar system today, so it has likely helped organize it in the past. We suggest that extrasolar planetary systems are also organized to a large extent by secular chaos. A hot Jupiter could be the end state of a secularly chaotic planetary system reminiscent of the solar system. However, in the case of the hot Jupiter, the innermost planet was Jupiter (rather than Mercury) sized, and its chaotic evolution was terminated when it was tidally captured by its star. In this contribution, we review our recent work elucidating the physics of secular chaos and applying it to Mercury and to hot Jupiters. We also present results comparing the inclinations of hot Jupiters thus produced with observations.

  19. Hot Money, Hot Potato

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    International hot money flowing into Chinese capital markets has caught the attention of Chinese watchdogs The Chinese are not the only ones feasting on the thriving property and stock markets. Apparently, these markets are the targets of international h

  20. The Massive Star Population in M101

    Science.gov (United States)

    Grammer, Skyler H.

    ratios are discrepant. Though photometry has proven to be a powerful tool to identify candidate evolved massive stars and their effects on their host galaxy, spectroscopy is necessary to study the physical properties of individual stars. We observed moderate-resolution optical spectra for 56 of the brightest stars in the direction to M101 using the Multiple Mirror Telescope. We also created light curves for each target using multi-epoch U BV R images from the Large Binocular Telescope. We separate the spectroscopially confirmed members of M101 into four groups: hot supergiants, intermediate supergiants, emission-line stars, and LBVs. Several stars in each group are discussed in detail. Of the spectroscopically confirmed members, we find that eight meet our criterion for variability. We present light curves for the known LBV candidates, V2, V4, and V9, and introduce a new candidate: 9492 &barbelow;14 &barbelow;11998. Additionally, we identify 20 new variables in M101. Lacking spectra, we separated the variables, by their photometric properties, into three groups: hot, intermediate, and cool. We find two hot stars with V-band variability of +/-1 magnitude; we flag these stars as LBV candidates. Of the intermediate and cool variables, we identify several stars with low- to moderate-amplitude variability (0.1--0.5 magnitudes).

  1. The subdwarf B star SB 290 - A fast rotator on the extreme horizontal branch

    CERN Document Server

    Geier, S; Heuser, C; Classen, L; O'Toole, S J; Edelmann, H

    2013-01-01

    Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose almost all of its hydrogen envelope right at the tip of the red giant branch. In close binary systems, mass transfer to the companion provides the extraordinary mass loss required for their formation. However, apparently single sdBs exist as well and their formation is unclear since decades. The merger of helium white dwarfs leading to an ignition of core helium-burning or the merger of a helium core and a low mass star during the common envelope phase have been proposed. Here we report the discovery of SB 290 as the first apparently single fast rotating sdB star located on the extreme horizontal branch indicating that those stars may form from mergers.

  2. Asteroseismic surface gravity for evolved stars

    CERN Document Server

    Hekker, S; Mosser, B; Kallinger, T; Basu, Sarbani; Chaplin, W J; Stello, D

    2013-01-01

    Context: Asteroseismic surface gravity values can be of importance in determining spectroscopic stellar parameters. The independent log(g) value from asteroseismology can be used as a fixed value in the spectroscopic analysis to reduce uncertainties due to the fact that log(g) and effective temperature can not be determined independently from spectra. Since 2012, a combined analysis of seismically and spectroscopically derived stellar properties is ongoing for a large survey with SDSS/APOGEE and Kepler. Therefore, knowledge of any potential biases and uncertainties in asteroseismic log(g) values is now becoming important. Aims: The seismic parameter needed to derive log(g) is the frequency of maximum oscillation power (nu_max). Here, we investigate the influence of nu_max derived with different methods on the derived log(g) values. The large frequency separation between modes of the same degree and consecutive radial orders (Dnu) is often used as an additional constraint for the determination of log(g). Addit...

  3. Evolved stars in galactic plane surveys

    NARCIS (Netherlands)

    Verbeek, K.

    2013-01-01

    For the first time in history the entire Galactic Plane is digitally mapped from La Palma and Chile by the European Galactic Plane surveys EGAPS (UVEX, IPHAS and VPHAS+, see http://www.uvexsurvey.org http://www.iphas.org and http://www.vphasplus.org). The complete Galactic plane (3600 square degrees

  4. Bolometric Flux Estimation for Cool Evolved Stars

    CERN Document Server

    van Belle, Gerard T; Ruiz-Velasco, Alma

    2016-01-01

    Estimation of bolometric fluxes (F_BOL) is an essential component of stellar effective temperature determination with optical and near-infrared interferometry. Reliable estimation of F_BOL simply from broad-band K-band photometry data is a useful tool in those cases were contemporaneous and/or wide-range photometry is unavailable for a detailed spectral energy distribution (SED) fit, as was demonstrated in Dyck et al. (1974). Recalibrating the intrinsic F_BOL versus observed F_2.2um relationship of that study with modern SED fitting routines, which incorporate the significantly non-blackbody, empirical spectral templates of the INGS spectral library (an update of the library in Pickles 1998) and estimation of reddening, serves to greatly improve the accuracy and observational utility of this relationship. We find that F_BOL values predicted are roughly 11% less than the corresponding values predicted in Dyck et al. (1974), indicating the effects of SED absorption features across bolometric flux curves.

  5. Wobbly walker evolves into soccer star

    NARCIS (Netherlands)

    Verdult, E.

    2012-01-01

    Seventeen years ago, a graduate student of the Faculty of Mechanical, Maritime and Materials Engineering built the first Delft walking robot. Not a walking computer with heavy motors, but an energy-efficient autonomous robot. That quest into human walking has developed into the Delft Biorobotics Lab

  6. Transiting exoplanets from the CoRoT space mission. XIII. CoRoT-13b: a dense hot Jupiter in transit around a star with solar metallicity and super-solar lithium content

    CERN Document Server

    Cabrera, J; Ollivier, M; Diaz, R F; Csizmadia, Sz; Aigrain, S; Alonso, R; Almenara, J -M; Auvergne, M; Baglin, A; Barge, P; Bonomo, A S; Borde, P; Bouchy, F; Carone, L; Carpano, S; Deleuil, M; Deeg, H J; Dvorak, R; Erikson, A; Ferraz-Mello, S; Fridlund, M; Gandolfi, D; Gazzano, J -C; Gillon, M; Guenther, E W; Guillot, T; Hatzes, A; Havel, M; Hebrard, G; Jorda, L; Leger, A; Llebaria, A; Lammer, H; Lovis, C; Mazeh, T; Moutou, C; Ofir, A; von Paris, P; Patzold, M; Queloz, D; Rauer, H; Rouan, D; Santerne, A; Schneider, J; Tingley, B; Titz-Weider, R; Wuchterl, G

    2010-01-01

    We announce the discovery of the transiting planet CoRoT-13b. Ground based follow-up in CFHT and IAC80 confirmed CoRoT's observations. The mass of the planet was measured with the HARPS spectrograph and the properties of the host star were obtained analyzing HIRES spectra from the Keck telescope. It is a hot Jupiter-like planet with an orbital period of 4.04 days, 1.3 Jupiter masses, 0.9 Jupiter radii, and a density of 2.34 g cm-3. It orbits a G0V star with Teff=5945K, M*=1.09 Msun, R*=1.01 Rsun, solar metallicity, a lithium content of +1.45 dex, and an estimated age between 0.12 and 3.15 Gyr. The lithium abundance of the star is consistent with its effective temperature, activity level, and age range derived from the stellar analysis. The density of the planet is extreme for its mass. It implies the existence of an amount of heavy elements with a mass between about 140 and 300 Mearth.

  7. Transiting exoplanets from the CoRoT space mission XIV. CoRoT-11b: a transiting massive "hot-Jupiter" in a prograde orbit around a rapidly rotating F-type star

    CERN Document Server

    Gandolfi, D; Alonso, R; Deleuil, M; Guenther, E W; Fridlund, M; Endl, M; Eigmüller, P; Csizmadia, Sz; Havel, M; Aigrain, S; Auvergne, M; Baglin, A; Barge, P; Bonomo, A S; Bordé, P; Bouchy, F; Bruntt, H; Cabrera, J; Carpano, S; Carone, L; Cochran, W D; Deeg, H J; Dvorak, R; Eislöffel, J; Erikson, A; Ferraz-Mello, S; Gazzano, J -C; Gibson, N P; Gillon, M; Gondoin, P; Guillot, T; Hartmann, M; Hatzes, A; Jorda, L; Kabath, P; Léger, A; Llebaria, A; Lammer, H; MacQueen, P J; Mayor, M; Mazeh, T; Moutou, C; Ollivier, M; Pätzold, M; Pepe, F; Queloz, D; Rauer, H; Rouan, D; Samuel, B; Schneider, J; Stecklum, B; Tingley, B; Udry, S; Wuchterl, G; 10.1051/0004-6361/201015132

    2010-01-01

    The CoRoT exoplanet science team announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a V=12.9 mag F6 dwarf star (M*=1.27 +/- 0.05 Msun, R*=1.37 +/- 0.03 Rsun, Teff=6440 +/- 120 K), with an orbital period of P=2.994329 +/- 0.000011 days and semi-major axis a=0.0436 +/- 0.005 AU. The detection of part of the radial velocity anomaly caused by the Rossiter-McLaughlin effect shows that the transit-like events detected by CoRoT are caused by a planet-sized transiting object in a prograde orbit. The relatively high projected rotational velocity of the star (vsini=40+/-5 km/s) places CoRoT-11 among the most rapidly rotating planet host stars discovered so far. With a planetary mass of mp=2.33+/-0.34 Mjup and radius rp=1.43+/-0.03 Rjup, the resulting mean density of CoRoT-11b (rho=0.99+/-0.15 g/cm^3) can be explained with a model for an inflated hydrogen-planet with a solar composition and a high level of energy dissipation in its interior.

  8. NuSTAR observations of WISE J1036+0449, a Galaxy at z$\\sim1$ obscured by hot dust

    CERN Document Server

    Ricci, C; Stern, D; Nikutta, R; Alexander, D M; Asmus, D; Ballantyne, D R; Bauer, F E; Blain, A W; Boggs, S; Boorman, P G; Brandt, W N; Brightman, M; Chen, C -T J; Christensen, F E; Comastri, A; Craig, W W; Díaz-Santos, T; Eisenhardt, P R; Farrah, D; Gandhi, P; Hailey, C J; Harrison, F A; Jun, H D; Koss, M J; LaMassa, S; Lansbury, G B; Markwardt, C B; Stalevski, M; Stanley, F; Treister, E; Tsai, C -W; Walton, D J; Wu, J W; Zappacosta, L; Zhang, W W

    2016-01-01

    Hot, Dust-Obscured Galaxies (Hot DOGs), selected from the WISE all sky infrared survey, host some of the most powerful Active Galactic Nuclei (AGN) known, and might represent an important stage in the evolution of galaxies. Most known Hot DOGs are at $z> 1.5$, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. We present a new selection method that identifies 153 Hot DOG candidates at $z\\sim 1$, where they are significantly brighter and easier to study. We validate this approach by measuring a redshift $z=1.009$, and an SED similar to higher redshift Hot DOGs for one of these objects, WISE J1036+0449 ($L_{\\rm\\,Bol}\\simeq 8\\times 10^{46}\\rm\\,erg\\,s^{-1}$), using data from Keck/LRIS and NIRSPEC, SDSS, and CSO. We find evidence of a broadened component in MgII, which, if due to the gravitational potential of the supermassive black hole, would imply a black hole mass of $M_{\\rm\\,BH}\\simeq 2 \\times 10^8 M_{\\odot}$, and an Eddington ratio of $\\lambda_{\\rm\\,Edd...

  9. Radiation-driven winds of hot luminous stars. XVIII. The unreliability of stellar and wind parameter determinations from optical vs. UV spectral analysis of selected central stars of planetary nebulae and the possibility of some CSPNs as single-star supernova Ia progenitors

    Science.gov (United States)

    Hoffmann, T. L.; Pauldrach, A. W. A.; Kaschinski, C. B.

    2016-08-01

    Context. The uncertainty in the degree to which radiation-driven winds of hot stars might be affected by small inhomogeneities in the density leads to a corresponding uncertainty in the determination of the atmospheric mass loss rates from the strength of optical recombination lines and - since the mass loss rate is not a free parameter but a function of the stellar parameters mass, radius, luminosity, and abundances - in principle also in the determination of these stellar parameters. Furthermore, the optical recombination lines also react sensitively to even small changes in the density structure resulting from the (often assumed instead of computed) velocity law of the outflow. This raises the question of how reliable the parameter determinations from such lines are. Aims: The currently existing severe discrepancy between central stars of planetary nebulae (CSPN) stellar and wind parameters derived from model fits to the optical spectra and those derived using hydrodynamically consistent model fits to the UV spectra is to be reassessed via a simultaneous optical/UV analysis using a state-of-the-art model atmosphere code. Methods: We have modified our hydrodynamically consistent model atmosphere code with an implementation of the usual ad hoc treatment of clumping (small inhomogeneities in the density) in the wind. This allows us to re-evaluate, with respect to their influence on the appearance of the UV spectra and their compatibility with the observations, the parameters determined in an earlier study that had employed clumping in its models to achieve a fit to the observed optical spectra. Results: The discrepancy between the optical and the UV analyses is confirmed to be the result of a missing consistency between stellar and wind parameters in the optical analysis. While clumping in the wind does significantly increase the emission in the optical hydrogen and helium recombination lines, the influence of the density (velocity field) is of the same order as

  10. Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau

    CERN Document Server

    Donati, JF; Hussain, G; Moutou, C; Malo, L; Grankin, K; Vidotto, AA; Alencar, SHP; Gregory, SG; Jardine, MM; Herczeg, G; Morin, J; Fares, R; Ménard, F; Bouvier, J; Delfosse, X; Doyon, R; Takami, M; Figueira, P; Petit, P; Boisse, I

    2015-01-01

    We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819 Tau and V830 Tau within the MaTYSSE programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ~3 Myr, both stars dissipated their discs recently and are interesting objects for probing star and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magnetic maps for both stars. We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximated at large radii by 350-400 G dipoles tilted at ~30 degrees to the rotation axis. They are significantly weaker than the field of GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both ...

  11. Three irradiated and bloated hot Jupiters:. WASP-76b, WASP-82b, and WASP-90b

    Science.gov (United States)

    West, R. G.; Hellier, C.; Almenara, J.-M.; Anderson, D. R.; Barros, S. C. C.; Bouchy, F.; Brown, D. J. A.; Collier Cameron, A.; Deleuil, M.; Delrez, L.; Doyle, A. P.; Faedi, F.; Fumel, A.; Gillon, M.; Gómez Maqueo Chew, Y.; Hébrard, G.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Smith, A. M. S.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.

    2016-01-01

    We report on three new transiting hot Jupiter planets, discovered from the WASP surveys, which we combine with radial velocities from OHP/SOPHIE and Euler/CORALIE and photometry from Euler and TRAPPIST. The planets WASP-76b, WASP-82b, and WASP-90b are all inflated, with radii of 1.7-1.8 RJup. All three orbit hot stars, of type F5-F7, with orbits of 1.8-3.9 d, and all three stars have evolved, post-main-sequence radii (1.7-2.2 R⊙). Thus the three planets fit a known trend of hot Jupiters that receive high levels of irradiation being highly inflated. We caution, though, about the presence of a selection effect, in that non-inflated planets around ~2 R⊙ post-MS stars can often produce transits too shallow to be detected by the ground-based surveys that have found the majority of transiting hot Jupiters. Tables of the photometry and radial velocity are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A126

  12. Hot subdwarf binaries - Masses and nature of their heavy compact companions

    CERN Document Server

    Geier, Stephan; Edelmann, Heinz; Kupfer, Thomas; Napiwotzki, Ralf; Podsiadlowski, Philipp

    2009-01-01

    Neutron stars and stellar-mass black holes are the remnants of massive stars, which ended their lives in supernova explosions. These exotic objects can only be studied in relatively rare cases. If they are interacting with close companions they become bright X-ray sources. If they are neutron stars, they may be detected as pulsars. Only a few hundred such systems are presently known in the Galaxy. However, there should be many more binaries with basically invisible compact objects in non-interacting binaries. Here we report the discovery of unseen compact companions to hot subdwarfs in close binary systems. Hot subdwarfs are evolved helium-core-burning stars that have lost most of their hydrogen envelopes, often due to binary interactions. Using high-resolution spectra and assuming tidal synchronisation of the subdwarfs, we were able to constrain the companion masses of 32 binaries. While most hot subdwarf binaries have white-dwarf or late-type main sequence companions, as predicted by binary evolution models...

  13. UV spectral analysis of very hot H-deficient [WCE]-type central stars of planetary nebulae: NGC 2867, NGC 5189, NGC 6905, Pb 6, and Sand 3

    CERN Document Server

    Keller, Graziela R; Maciel, Walter J

    2014-01-01

    We analysed UV FUSE, IUE, and HST/STIS spectra of five of the hottest [WCE]-type central stars of planetary nebulae: NGC 2867, NGC 5189, NGC 6905, Pb 6, and Sand 3. The analysis leveraged on our grid of CMFGEN synthetic spectra, which covers the parameter regime of hydrogen deficient central stars of planetary nebulae and allows a uniform and systematic study of the stellar spectra. The stellar atmosphere models calculated by us include many elements and ionic species neglected in previous analyses, which allowed us to improve the fits to the observed spectra considerably and provided an additional diagnostic line: the Ne VII $\\lambda$ 973 $\\mathrm{\\AA}$, which had not been modelled in [WCE] spectra and which presents, in these stars, a strong P-Cygni profile. We report newly derived photospheric and wind parameters and elemental abundances. The central stars of NGC 2867, NGC 5189, and Pb 6 had their temperatures revised upward in comparison with previous investigations and we found the carbon to helium mass ...

  14. ELODIE metallicity-biased search for transiting Hot Jupiters. IV. Intermediate period planets orbiting the stars HD 43691 and HD 132406

    Science.gov (United States)

    da Silva, R.; Udry, S.; Bouchy, F.; Moutou, C.; Mayor, M.; Beuzit, J.-L.; Bonfils, X.; Delfosse, X.; Desort, M.; Forveille, T.; Galland, F.; Hébrard, G.; Lagrange, A.-M.; Loeillet, B.; Lovis, C.; Pepe, F.; Perrier, C.; Pont, F.; Queloz, D.; Santos, N. C.; Ségransan, D.; Sivan, J.-P.; Vidal-Madjar, A.; Zucker, S.

    2007-10-01

    We report here the discovery of two planet candidates as a result of our planet-search programme biased in favour of high-metallicity stars, using the ELODIE spectrograph at the Observatoire de Haute Provence. One candidate has a minimum mass m_2 sin i = 2.5 M_Jup and is orbiting the metal-rich star HD 43691 with period P = 40 days and eccentricity e=0.14. The other planet has a minimum mass m_2 sin{i} = 5.6 M_Jup and orbits the slightly metal-rich star HD 132406 with period P=974 days and eccentricity e = 0.34. Additional observations for both stars were performed using the new SOPHIE spectrograph that replaces the ELODIE instrument, allowing an improved orbital solution for the systems. Based on radial velocities collected with the ELODIE spectrograph mounted on the 193-cm telescope at the Observatoire de Haute Provence, France. Additional observations were made using the new SOPHIE spectrograph (run 06B.PNP.CONS) that replaces ELODIE.

  15. Evolving Galaxies in a Hierachical Universe

    Science.gov (United States)

    Hahn, Changhoon

    2017-01-01

    Observations of galaxies using large surveys (SDSS, COSMOS, PRIMUS, etc.) have firmly established a global view of galaxy properties out to z~1. Galaxies are broadly divided into two classes: blue, typically disk-like star forming galaxies and red, typically elliptical quiescent ones with little star formation. The star formation rates (SFR) and stellar masses of star forming galaxies form an empirical relationship referred to as the "star formation main sequence". Over cosmic time, this sequence undergoes significant decline in SFR and causes the overall cosmic star formation decline. Simultaneously, physical processes cause significant fractions of star forming galaxies to "quench" their star formation. Hierarchical structure formation and cosmological models provide precise predictions of the evolution of the underying dark matter, which serve as the foundation for these detailed trends and their evolution. Whatever trends we observe in galaxy properties can be interpreted within the narrative of the underlying dark matter and halo occupation framework. More importantly, through careful statistical treatment and precise measurements, this connection can be utilized to better constrain and understand key elements of galaxy evolution. In this spirit, for my dissertation I connect observations of evolving galaxy properties to the framework of the hierarchical Universe and use it to better understand physical processes responsible for the cessation of star formation in galaxies. For instance, through this approach, I constrain the quenching timescale of central galaxies and find that they are significantly longer than the quenching timescale of satellite galaxies.

  16. Better Stars, Better Planets: Using Stellar Rotation to Refine Estimates of Stellar Parameters

    Science.gov (United States)

    Van Saders, Jennifer

    2014-01-01

    Rotation is a fundamental property of all stars. Rotation periods are a strong function of age, evolutionary state, and mass for single stars on the main sequence (MS) and subgiant branch (SGB). These rates may differ by up to an order of magnitude when comparing hot or or young stars to cool or evolved stars. Because rotation depends sensitively on underlying stellar parameters that are challenging to measure, namely mass and age, measurements of rotation can be used to constrain and complement stellar parameters inferred through other means. This is particularly crucial in the case of transiting exoplanet host stars. We have produced models of stars with realistic angular momentum loss laws, both on the MS and SGB. Two important features of the rotation distribution are apparent: on the subgiant branch itself, rotation periods can differ by an order of magnitude between stars born above the Kraft break (6250 K) and those born below it. This allows one to infer both masses and radii on the SGB based on rotation. Secondly, subgiants born above the Kraft break can be rapidly rotating and masquerade as young stars in samples in which the luminosity or gravities are not well known. Therefore, when realistic populations of stars are considered, one cannot simply assume that rapid rotation is always an indication of youth. We provide examples with data from Kepler, among other sources, in which the addition of rotation information our understanding of the underlying stellar (and therefore planetary) distribution substantially. Implications for planet demographics are also discussed.

  17. Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostics

    CERN Document Server

    Sundqvist, J O; Owocki, S P

    2014-01-01

    [Abridged] We develop and benchmark a fast and easy-to-use effective-opacity formalism for line and continuum radiative transfer in an accelerating two-component clumpy medium. The formalism bridges the limits of optically thin and thick clumps, and is here used to i) design a simple vorosity-modified Sobolev with exact integration (vmSEI) method for analyzing UV wind resonance lines in hot, massive stars, and ii) derive simple correction factors to the line force driving the outflows of such stars. We show that (for a given ionization factor) UV resonance doublets may be used to analytically predict the upward corrections in empirically inferred mass-loss rates associated with porosity in velocity space (a.k.a. velocity-porosity, or vorosity), but that severe solution degeneracies exist. For an inter-clump density set to 1 % of the mean density, we for O and B supergiants derive upward empirical mass-loss corrections of typically factors of either ~5 or ~50, depending on which of the two applicable solutions...

  18. Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other Supergiants

    CERN Document Server

    Humphreys, Roberta M; Davidson, Kris; Bomans, D J; Burggraf, Birgitta

    2014-01-01

    An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor class, including the most luminous evolved stars, the Luminous Blue Varaibles (LBVs), and the warm and cool hypergiants is now needed for a complete picture of the final pre-SN stages of very massive stars. We have begun a survey of the evolved and un stable luminous star populations in several nearby resolved galaxies. In this second paper on M31 and M33, we review the spectral characteristics, spectral energy distributions, circumstellar ejecta, and evidence for mass loss for 82 luminous and variable stars.We show that many of these stars have warm circumstellar dust including several of the Fe II emission line stars, but conclude that the confirmed LBVs in M31 and M33 do not. The confirmed LBVs have relatively low wind speeds even in their hot, quiesc...

  19. WASP-78b and WASP-79b: Two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus

    CERN Document Server

    Smalley, B; Collier-Cameron, A; Doyle, A P; Gillon, M; Hellier, C; Jehin, E; Lendl, M; Maxted, P F L; Pepe, F; Pollacco, D; Queloz, D; Segransan, D; Smith, A M S; Southworth, J; Triaud, A H M J; Udry, S; West, R G

    2012-01-01

    We report the discovery of WASP-78b and WASP-79b, two highly-bloated Jupiter-mass exoplanets orbiting F-type host stars. WASP-78b orbits its V=12.0 host star (TYC 5889-271-1) every 2.175 days and WASP-79b orbits its V=10.1 host star (CD-30 1812) every 3.662 days. A simultaneous fit to WASP and TRAPPIST transit photometry and CORALIE radial-velocity measurements yields planetary masses of 0.89 +/- 0.08 M_Jup and 0.90 +/- 0.08 M_Jup, and radii of 1.70 +/- 0.11 R_Jup and 2.09 +/- 0.14 R_Jup, for WASP-78b and WASP-79b, respectively. The planetary equilibrium temperature of T_P = 2350 +/- 80 K for WASP-78b makes it one of the hottest of the currently known exoplanets. The radius of WASP-79b suggests that it is potentially the largest known exoplanet.

  20. Hot microswimmers

    Science.gov (United States)

    Kroy, Klaus; Chakraborty, Dipanjan; Cichos, Frank

    2016-11-01

    Hot microswimmers are self-propelled Brownian particles that exploit local heating for their directed self-thermophoretic motion. We provide a pedagogical overview of the key physical mechanisms underlying this promising new technology. It covers the hydrodynamics of swimming, thermophoresis and -osmosis, hot Brownian motion, force-free steering, and dedicated experimental and simulation tools to analyze hot Brownian swimmers.

  1. Analyzing Evolving Social Network 2 (EVOLVE2)

    Science.gov (United States)

    2015-04-01

    COVERED (From - To) JUN 2012 – OCT 2014 4. TITLE AND SUBTITLE ANALYZING EVOLVING SOCIAL NETWORKS 2 (EVOLVE2) 5a. CONTRACT NUMBER FA8750-12-2-0186... jazz 198 2742 274 0.14 connect 1095 7825 783 0.014 hep-th 8710 14254 1425 0.0003 netscience 1461 2742 274 0.0013 imdb 6260 98235 9824 0.005 technological

  2. Schema Evolution for Stars and Snowflakes

    DEFF Research Database (Denmark)

    Kaas, Christian; Pedersen, Torben Bach; Rasmussen, Bjørn

    2004-01-01

    The most common implementation platform for multidimensional data warehouses is RDBMSs storing data in relational star and snowflake schemas. DW schemas evolve over time, which may invalidate existing analysis queries used for reporting purposes. However, the evolution properties of star...

  3. Deciphering The Hot Components in Symbiotic Variables: A Brave New Frontier

    Science.gov (United States)

    Sion, Edward

    We propose to investigate the physical properties of the hot components of symbiotic variable stars. They are binary star systems consisting of a red giant and a white dwarf (WD) orbiting each other close enough to interact. Material from the outflowing stellar wind of the red giant accretes onto the white dwarf, and an accretion disk may or may not form. Much of the outflowing red giant wind material forms a large nebula around the binary that is partially ionized by radiation from the accreting WD and from thermonuclear burning at its surface. The exact nature of the hot component, the efficiency of such wind-fed accretion, the rate of accretion onto the WD, whether accretion disks are even present, and why the hot components are so much hotter than their cataclysmic variable cousins, all remain poorly know. All previous attempts to determine WD temperatures, luminosities and accretion rates relied upon the modified Zanstra method and crude black body fitting. To deepen our understanding of the hot components, we propose to apply synthetic spectra for high gravity stars and accretion disks generated from state-of-the-art computer codes to the far ultraviolet archival spectra of 40 symbiotic stars, obtained with the International Ultraviolet Explorer (IUE) and Far Ultraviolet Spectroscopic Explorer (FUSE) spacecrafts. Since the WD is the most common end-product of stellar evolution ( > 95% of all the stars in the Galaxy evolve into white dwarfs), and the accretion disk whether from wind- fed accretion or Roche lobe overflow, is the most common universal structure resulting from mass transfer with angular momentum, and since both can be directly viewed in CVs in the ultraviolet (UV), an understanding of the consequences of accretion in these systems is the first step in a global understanding of accretion in other systems throughout the universe. These include protostellar objects, X-ray binaries (containing neutron star and black hole accretors), active galactic

  4. Investigating the origin of cyclical wind variability in hot massive stars - II. Hydrodynamical simulations of corotating interaction regions using realistic spot parameters for the O giant ξ Persei

    Science.gov (United States)

    David-Uraz, A.; Owocki, S. P.; Wade, G. A.; Sundqvist, J. O.; Kee, N. D.

    2017-09-01

    OB stars exhibit various types of spectral variability historically associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These features have been proposed to be caused either by magnetic fields or non-radial pulsations. In this second paper of this series, we revisit the canonical phenomenological hydrodynamical modelling used to explain the formation of DACs by taking into account modern observations and more realistic theoretical predictions. Using constraints on putative bright spots located on the surface of the O giant ξ Persei derived from high precision space-based broad-band optical photometry obtained with the Microvariability and Oscillations of Stars (MOST) space telescope, we generate 2D hydrodynamical simulations of corotating interaction regions in its wind. We then compute synthetic ultraviolet (UV) resonance line profiles using Sobolev Exact Integration and compare them with historical timeseries obtained by the International Ultraviolet Explorer (IUE) to evaluate if the observed behaviour of ξ Persei's DACs is reproduced. Testing three different models of spot size and strength, we find that the classical pattern of variability can be successfully reproduced for two of them: the model with the smallest spots yields absorption features that are incompatible with observations. Furthermore, we test the effect of the radial dependence of ionization levels on line driving, but cannot conclusively assess the importance of this factor. In conclusion, this study self-consistently links optical photometry and UV spectroscopy, paving the way to a better understanding of cyclical wind variability in massive stars in the context of the bright spot paradigm.

  5. WASP-78b and WASP-79b: two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus

    Science.gov (United States)

    Smalley, B.; Anderson, D. R.; Collier-Cameron, A.; Doyle, A. P.; Fumel, A.; Gillon, M.; Hellier, , C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smith, A. M. S.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.; West, R. G.

    2012-11-01

    We report the discovery of WASP-78b and WASP-79b, two highly-bloated Jupiter-mass exoplanets orbiting F-type host stars. WASP-78b orbits its V = 12.0 host star (TYC 5889-271-1) every 2.175 days and WASP-79b orbits its V = 10.1 host star (CD-30 1812) every 3.662 days. Planetary parameters have been determined using a simultaneous fit to WASP and TRAPPIST transit photometry and CORALIE radial-velocity measurements. For WASP-78b a planetary mass of 0.89 ± 0.08 MJup and a radius of 1.70 ± 0.11 RJup is found. The planetary equilibrium temperature of TP = 2350 ± 80 K for WASP-78b makes it one of the hottest of the currently known exoplanets. WASP-79b its found to have a planetary mass of 0.90 ± 0.08 MJup, but with a somewhat uncertain radius due to lack of sufficient TRAPPIST photometry. The planetary radius is at least 1.70 ± 0.11 RJup, but could be as large as 2.09 ± 0.14 RJup, which would make WASP-79b the largest known exoplanet. Photometric data 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/547/A61Table 1 is available in electronic form at http://www.aanda.org

  6. A near-infrared interferometric survey of debris disk stars. I. Probing the hot dust content around epsilon Eridani and tau Ceti with CHARA/FLUOR

    CERN Document Server

    Di Folco, E; Augereau, J -C; Mérand, A; Foresto, V Coudé du; Thévenin, F; Defrère, D; Kervella, P; Brummelaar, T A ten; McAlister, H A; Ridgway, S T; Sturmann, J; Sturmann, L; Turner, N H

    2007-01-01

    We probed the first 3AU around tau Ceti and epsilon Eridani with the CHARA array (Mt Wilson, USA) in order to gauge the 2micron excess flux emanating from possible hot dust grains in the debris disks and to also resolve the stellar photospheres. High precision visibility amplitude measurements were performed with the FLUOR single mode fiber instrument and telescope pairs on baselines ranging from 22 to 241m of projected length. The short baseline observations allow us to disentangle the contribution of an extended structure from the photospheric emission, while the long baselines constrain the stellar diameter. We have detected a resolved emission around tau Cet, corresponding to a spatially integrated, fractional excess flux of 0.98 +/- 0.21 x 10^{-2} with respect to the photospheric flux in the K'-band. Around eps Eri, our measurements can exclude a fractional excess of greater than 0.6x10^{-2} (3sigma). We interpret the photometric excess around tau Cet as a possible signature of hot grains in the inner de...

  7. Tidally-driven Roche-Lobe Overflow of Hot Jupiters with MESA

    CERN Document Server

    Valsecchi, Francesca; Rasio, Frederic A; Marchant, Pablo; Rogers, Leslie A

    2015-01-01

    Many exoplanets have now been detected in orbits with ultra-short periods, very close to the Roche limit. Building upon our previous work, we study the possibility that mass loss through Roche lobe overflow (RLO) may affect the evolution of these planets, and could possibly transform a hot Jupiter into a lower-mass planet (hot Neptune or super-Earth). We focus here on systems in which the mass loss occurs slowly ("stable mass transfer" in the language of binary star evolution) and we compute their evolution in detail with the binary evolution code MESA. We include the effects of tides, RLO, irradiation and photo-evaporation of the planet, as well as the stellar wind and magnetic braking. Our calculations all start with a hot Jupiter close to its Roche limit, in orbit around a sun-like star. The initial orbital decay and onset of RLO are driven by tidal dissipation in the star. We confirm that such a system can indeed evolve to produce lower-mass planets in orbits of a few days. The RLO phase eventually ends a...

  8. Temperature of neutron stars

    Science.gov (United States)

    Tsuruta, Sachiko

    2016-07-01

    We start with a brief introduction to the historical background in the early pioneering days when the first neutron star thermal evolution calculations predicted the presence of neutron stars hot enough to be observable. We then report on the first detection of neutron star temperatures by ROSAT X-ray satellite, which vindicated the earlier prediction of hot neutron stars. We proceed to present subsequent developments, both in theory and observation, up to today. We then discuss the current status and the future prospect, which will offer useful insight to the understanding of basic properties of ultra-high density matter beyond the nuclear density, such as the possible presence of such exotic particles as pion condensates.

  9. HOT 2012

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    Undersøgelse af, hvad der er hot - og hvad der burde være hot på læseområdet med 21 læsekyndige. Undersøgelsen er gennemført siden 2010. HOT-undersøgelsen er foretaget af Nationalt Videncenter for Læsning - Professionshøjskolerne i samarb. med Dansklærerforeningen...

  10. Backward Evolving Quantum States

    CERN Document Server

    Vaidman, L

    2006-01-01

    The basic concept of the two-state vector formalism, which is the time symmetric approach to quantum mechanics, is the backward evolving quantum state. However, due to the time asymmetry of the memory's arrow of time, the possible ways to manipulate a backward evolving quantum state differ from those for a standard, forward evolving quantum state. The similarities and the differences between forward and backward evolving quantum states regarding the no-cloning theorem, nonlocal measurements, and teleportation are discussed. The results are relevant not only in the framework of the two-state vector formalism, but also in the framework of retrodictive quantum theory.

  11. Rapidly evolving and luminous transients from Pan-STARRS1

    Energy Technology Data Exchange (ETDEWEB)

    Drout, M. R.; Chornock, R.; Soderberg, A. M.; Sanders, N. E.; McKinnon, R.; Milisavljevic, D.; Margutti, R.; Berger, E.; Calkins, M.; Fong, W.; Kirshner, R. P.; Lunnan, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Rest, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Foley, R. J. [Astronomy Department, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Gezari, S. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Huber, M. E. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Kankare, E.; Mattila, S. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); Leibler, C. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95060 (United States); Marion, G. H., E-mail: mdrout@cfa.harvard.edu [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); and others

    2014-10-10

    In the past decade, several rapidly evolving transients have been discovered whose timescales and luminosities are not easily explained by traditional supernovae (SNe) models. The sample size of these objects has remained small due, at least in part, to the challenges of detecting short timescale transients with traditional survey cadences. Here we present the results from a search within the Pan-STARRS1 Medium Deep Survey (PS1-MDS) for rapidly evolving and luminous transients. We identify 10 new transients with a time above half-maximum (t {sub 1/2}) of less than 12 days and –16.5 > M > –20 mag. This increases the number of known events in this region of SN phase space by roughly a factor of three. The median redshift of the PS1-MDS sample is z = 0.275 and they all exploded in star-forming galaxies. In general, the transients possess faster rise than decline timescale and blue colors at maximum light (g {sub P1} – r {sub P1} ≲ –0.2). Best-fit blackbodies reveal photospheric temperatures/radii that expand/cool with time and explosion spectra taken near maximum light are dominated by a blue continuum, consistent with a hot, optically thick, ejecta. We find it difficult to reconcile the short timescale, high peak luminosity (L > 10{sup 43} erg s{sup –1}), and lack of UV line blanketing observed in many of these transients with an explosion powered mainly by the radioactive decay of {sup 56}Ni. Rather, we find that many are consistent with either (1) cooling envelope emission from the explosion of a star with a low-mass extended envelope that ejected very little (<0.03 M {sub ☉}) radioactive material, or (2) a shock breakout within a dense, optically thick, wind surrounding the progenitor star. After calculating the detection efficiency for objects with rapid timescales in the PS1-MDS we find a volumetric rate of 4800-8000 events yr{sup –1} Gpc{sup –3} (4%-7% of the core-collapse SN rate at z = 0.2).

  12. Star-forming galaxies with hot dust emission in the Sloan Digital Sky Survey discovered by the Wide-field Infrared Survey Explorer (WISE)

    CERN Document Server

    Izotov, Y I; Fricke, K J; Henkel, C

    2011-01-01

    We present the results of a search for Sloan Digital Sky Survey (SDSS) emission-line galaxies with very red 3.4mum - 4.6mum (W1-W2) colours in the Wide-field Infrared Survey Explorer (WISE) Preliminary Release Source Catalogue (PRSC) aiming to find objects with hot dust emission. For this purpose we considered a sample of ~16000 galaxies with strong emission lines selected out of a total of ~900000 SDSS spectra and identified them with the PRSC sources. We find that ~5000 sources out of the ~16000 SDSS galaxies are present in the PRSC, including ~1000 galaxies with sufficiently strong [OIII]4363 emission lines to permit reliable determinations of the oxygen abundance. No correlation of W1-W2 with metallicity is found. On the other hand, there is clear evidence for a redder W1-W2 index in galaxies with higher Hbeta luminosity and higher Hbeta equivalent width, implying that strong UV radiation from young starbursts efficiently heats interstellar dust to high temperatures. However, galaxies with very red colour...

  13. Studying the evolution of AGB stars in the Gaia epoch

    Science.gov (United States)

    Di Criscienzo, M.; Ventura, P.; García-Hernández, D. A.; Dell'Agli, F.; Castellani, M.; Marrese, P. M.; Marinoni, S.; Giuffrida, G.; Zamora, O.

    2016-10-01

    We present asymptotic giant branch (AGB) models of solar metallicity, to allow the interpretation of observations of Galactic AGB stars, whose distances should be soon available after the first release of the Gaia catalogue. We find an abrupt change in the AGB physical and chemical properties, occurring at the threshold mass to ignite hot bottom burning, i.e. 3.5 M⊙. Stars with mass below 3.5 M⊙ reach the C-star stage and eject into the interstellar medium gas enriched in carbon, nitrogen and 17O. The higher mass counterparts evolve at large luminosities, between 3 × 104 and 105 L⊙. The mass expelled from the massive AGB stars shows the imprinting of proton-capture nucleosynthesis, with considerable production of nitrogen and sodium and destruction of 12C and 18O. The comparison with the most recent results from other research groups is discussed, to evaluate the robustness of the present findings. Finally, we compare the models with recent observations of galactic AGB stars, outlining the possibility offered by Gaia to shed new light on the evolution properties of this class of objects.

  14. Dynamical tides in exoplanetary systems containing hot Jupiters: confronting theory and observations

    Science.gov (United States)

    Chernov, S. V.; Ivanov, P. B.; Papaloizou, J. C. B.

    2017-09-01

    We study the effect of dynamical tides associated with the excitation of gravity waves in an interior radiative region of the central star on orbital evolution in observed systems containing hot Jupiters. We consider WASP-43, OGLE-TR-113, WASP-12 and WASP-18 that contain stars on the main sequence (MS). For these systems there are observational estimates regarding the rate of change of the orbital period. We also investigate Kepler-91 that contains an evolved giant star. We adopt the formalism of Ivanov et al. for calculating the orbital evolution. For the MS stars we determine expected rates of orbital evolution under different assumptions about the amount of dissipation acting on the tides, estimate the effect of stellar rotation for the two most rapidly rotating stars and compare results with observations. All cases apart from possibly WASP-43 are consistent with a regime in which gravity waves are damped during their propagation over the star. However, at present this is not definitive as observational errors are large. We find that although it is expected to apply to Kepler-91, linear radiative damping cannot explain this dissipation regime applying to MS stars. Thus, a non-linear mechanism may be needed. Kepler-91 is found to be such that the time-scale for evolution of the star is comparable to that for the orbit. This implies that significant orbital circularization may have occurred through tides acting on the star. Quasi-static tides, stellar winds, hydrodynamic drag and tides acting on the planet have likely played a minor role.

  15. KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star

    CERN Document Server

    Kuhn, Rudolf B; Collins, Karen A; Lund, Michael B; Siverd, Robert J; Colón, Knicole D; Pepper, Joshua; Stassun, Keivan G; Cargile, Phillip A; James, David J; Penev, Kaloyan; Zhou, George; Bayliss, Daniel; Tan, T G; Curtis, Ivan A; Udry, Stephane; Segransan, Damien; Mawet, Dimitri; Soutter, Jack; Hart, Rhodes; Carter, Brad; Gaudi, B Scott; Myers, Gordon; Beatty, Thomas G; Eastman, Jason D; Reichart, Daniel E; Haislip, Joshua B; Kielkopf, John; Bieryla, Allyson; Latham, David W; Jensen, Eric L N; Oberst, Thomas E; Stevens, Daniel J

    2015-01-01

    We report the discovery of KELT-10b, the first transiting exoplanet discovered using the KELT-South telescope. KELT-10b is a highly inflated sub-Jupiter mass planet transiting a relatively bright $V = 10.7$ star (TYC 8378-64-1), with T$_{eff}$ = $5948\\pm74$ K, $\\log{g}$ = $4.319_{-0.030}^{+0.020}$ and [Fe/H] = $0.09_{-0.10}^{+0.11}$, an inferred mass M$_{*}$ = $1.112_{-0.061}^{+0.055}$ M$_{\\odot}$ and radius R$_{*}$ = $1.209_{-0.035}^{+0.047}$ R$_{\\odot}$. The planet has a radius R$_{P}$ = $1.399_{-0.049}^{+0.069}$ R$_{J}$ and mass M$_{P}$ = $0.679_{-0.038}^{+0.039}$ M$_{J}$. The planet has an eccentricity consistent with zero and a semi-major axis $a$ = $0.05250_{-0.00097}^{+0.00086}$ AU. The best fitting linear ephemeris is $T_{0}$ = 2457066.72045$\\pm$0.00027 BJD$_{TDB}$ and P = 4.1662739$\\pm$0.0000063 days. This planet joins a group of highly inflated transiting exoplanets with a radius much larger and a mass much less than those of Jupiter. The planet, which boasts deep transits of 1.4%, has a relatively ...

  16. Detection of hot, metal-enriched outflowing gas around $z\\approx\\,$2.3 star-forming galaxies in the Keck Baryonic Structure Survey

    CERN Document Server

    Turner, Monica L; Steidel, Charles C; Rudie, Gwen C; Strom, Allison L

    2014-01-01

    We use quasar absorption lines to study the physical conditions in the circumgalactic medium of redshift $z\\approx 2.3$ star-forming galaxies taken from the Keck Baryonic Structure Survey (KBSS). In Turner et al. 2014 we used the pixel optical depth technique to show that absorption by HI and the metal ions OVI, NV, CIV, CIII and SiIV is strongly enhanced within $|\\Delta v|\\lesssim170$ km/s and projected distances $|d|\\lesssim180$ proper kpc from sightlines to the background quasars. Here we demonstrate that the OVI absorption is also strongly enhanced at fixed HI, CIV, and SiIV optical depths, and that this enhancement extends out to $\\sim350$ km/s. At fixed HI the increase in the median OVI optical depth near galaxies is 0.3-0.7 dex and is detected at 2--3-$\\sigma$ confidence for all seven HI bins that have $\\log_{10}\\tau_{\\rm HI}\\ge-1.5$. We use ionisation models to show that the observed strength of OVI as a function of HI is consistent with enriched, photoionised gas for pixels with $\\tau_{\\rm HI}\\gtrsim...

  17. Molecules in G1.6-0.25 - 'Hot' Chemistry in the Absence of Star Formation at the Periphery of the Galactic Center Region

    CERN Document Server

    Menten, Karl M; Leurini, Silvia; Schilke, Peter

    2008-01-01

    We present molecular line mapping of the Giant Molecular Cloud G1.6-0.025, which is located at the high longitude end of the Central Molecular Zone of our Galaxy. We assess the degree of star formation activity in that region using several tracers and find very little. We made a large scale, medium (2') resolution map in the J = 2-1 transition of SiO for which we find clumpy emission over a ~0.8 x 0.3 degree-sized region stretching along the Galactic plane. Toward selected positions we also took spectra in the easy to excite J_k=2_k-1_k quartet of CH3OH and the CS 2-1 line. Throughout the cloud these \\meth lines are, remarkably, several times stronger than, both, the CS and the SiO lines. The large widths of all the observed lines, similar to values generally found in the Galactic center, indicate a high degree of turbulence. Several high LSR velocity clumps that have 0-80 km/s higher velocities than the bulk of the molecular cloud appear at the same projected position as "normal" velocity material; this may ...

  18. Infrared spectroscopy of stars

    Science.gov (United States)

    Merrill, K. M.; Ridgway, S. T.

    1979-01-01

    This paper reviews applications of IR techniques in stellar classification, studies of stellar photospheres, elemental and isotopic abundances, and the nature of remnant and ejected matter in near-circumstellar regions. Qualitative IR spectral classification of cool and hot stars is discussed, along with IR spectra of peculiar composite star systems and of obscured stars, and IR characteristics of stellar populations. The use of IR spectroscopy in theoretical modeling of stellar atmospheres is examined, IR indicators of stellar atmospheric composition are described, and contributions of IR spectroscopy to the study of stellar recycling of interstellar matter are summarized. The future of IR astronomy is also considered.

  19. Mira Symbiotic Stars

    Institute of Scientific and Technical Information of China (English)

    Guo-Liang Lü; Chun-Hua Zhu; Zhan-Wen Han

    2007-01-01

    We have carried out a detailed study of Mira symbiotic stars by means of a population synthesis code. We estimate the number of Mira symbiotic stars in the Galaxy as 1700 - 3100 and the Galactic occurrence rate of Mira symbiotic novae as from ~ 0.9 to 6.0 yr-1,depending on the model assumptions. The distributions of the orbital periods, the masses of the components, mass-loss rates of cool components, mass-accretion rates of hot components and Mira pulsation periods in Mira symbiotic stars are simulated. By a comparison of the number ratio of Mira symbiotic stars to all symbiotic stars, we find the model with the stellar wind model of Winters et al. to be reasonable.

  20. BRITE-Constellation: Nanosatellites for precision photometry of bright stars

    Science.gov (United States)

    Weiss, W. W.; Moffat, A. F. J.; Schwarzenberg-Czerny, A.; Koudelka, O. F.; Grant, C. C.; Zee, R. E.; Kuschnig, R.; Mochnacki, St.; Rucinski, S. M.; Matthews, J. M.; Orleański, P.; Pamyatnykh, A. A.; Pigulski, A.; Alves, J.; Guedel, M.; Handler, G.; Wade, G. A.; Scholtz, A. L.; Scholtz

    2014-02-01

    BRITE-Constellation (where BRITE stands for BRIght Target Explorer) is an international nanosatellite mission to monitor photometrically, in two colours, brightness and temperature variations of stars brighter than V ~ 4, with precision and time coverage not possible from the ground. The current mission design consists of three pairs of 7 kg nanosats (hence ``Constellation'') from Austria, Canada and Poland carrying optical telescopes (3 cm aperture) and CCDs. One instrument in each pair is equipped with a blue filter; the other, a red filter. The first two nanosats (funded by Austria) are UniBRITE, designed and built by UTIAS-SFL (University of Toronto Institute for Aerospace Studies-Space Flight Laboratory) and its twin, BRITE-Austria, built by the Technical University Graz (TUG) with support of UTIAS-SFL. They were launched on 25 February 2013 by the Indian Space Agency, under contract to the Canadian Space Agency. Each BRITE instrument has a wide field of view (~ 24 degrees), so up to 15 bright stars can be observed simultaneously in 32 × 32 sub-rasters. Photometry (with reduced precision but thorough time sampling) of additional fainter targets will be possible through on-board data processing. A critical technical element of the BRITE mission is the three-axis attitude control system to stabilize a nanosat with very low inertia. The pointing stability is better than 1.5 arcminutes rms, a significant advance by UTIAS-SFL over any previous nanosatellite. BRITE-Constellation will primarily measure p- and g-mode pulsations to probe the interiors and ages of stars through asteroseismology. The BRITE sample of many of the brightest stars in the night sky is dominated by the most intrinsically luminous stars: massive stars seen at all evolutionary stages, and evolved medium-mass stars at the very end of their nuclear burning phases (cool giants and AGB stars). The Hertzsprung-Russell diagram for stars brighter than mag V=4 from which the BRITE-Constellation sample

  1. Spin-orbit coupling for tidally evolving super-Earths

    CERN Document Server

    Rodríguez, Adrián; Michtchenko, Tatiana A; Hussmann, Hauke

    2012-01-01

    We investigate the spin behavior of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the tidal torque, both raised by the central star, we analyze the possibility of temporary captures in spin-orbit resonances. The results of the numerical simulations of the exact equations of motions indicate that, whenever the planet rotation is trapped in a resonant motion, the orbital decay and the eccentricity damping are faster than the ones in which the rotation follows the so-called pseudo-synchronization. Analytical results obtained through the averaged equations of the spin-orbit problem show a good agreement with the numerical simulations. We apply the analysis to the cases of the recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The simulated dynamical history of these systems indicates the possibility of capture in several spin-orbit resonances...

  2. Transiting exoplanets from the CoRoT space mission XXVIII. CoRoT-28b, a planet orbiting an evolved star, and CoRoT-29b, a planet showing an asymmetric transit

    CERN Document Server

    Cabrera, J; Montagnier, G; Fridlund, M; Eiff, M Ammler-von; Chaintreuil, S; Damiani, C; Deleuil, M; Ferraz-Mello, S; Ferrigno, A; Gandolfi, D; Guillot, T; Guenther, E W; Hatzes, A; Hébrard, G; Klagyivik, P; Parviainen, H; Pasternacki, Th; Pätzold, M; Sebastian, D; Santos, M Tadeu dos; Wuchterl, G; Aigrain, S; Alonso, R; Almenara, J -M; Armstrong, J D; Auvergne, M; Baglin, A; Barge, P; Barros, S C C; Bonomo, A S; Bordé, P; Bouchy, F; Carpano, S; Chaffey, C; Deeg, H J; Díaz, R F; Dvorak, R; Erikson, A; Grziwa, S; Korth, J; Lammer, H; Lindsay, C; Mazeh, T; Moutou, C; Ofir, A; Ollivier, M; Pallé, E; Rauer, H; Rouan, D; Samuel, B; Santerne, A; Schneider, J

    2015-01-01

    Context. We present the discovery of two transiting extrasolar planets by the satellite CoRoT. Aims. We aim at a characterization of the planetary bulk parameters, which allow us to further investigate the formation and evolution of the planetary systems and the main properties of the host stars. Methods. We used the transit light curve to characterize the planetary parameters relative to the stellar parameters. The analysis of HARPS spectra established the planetary nature of the detections, providing their masses. Further photometric and spectroscopic ground-based observations provided stellar parameters (log g,Teff,v sin i) to characterize the host stars. Our model takes the geometry of the transit to constrain the stellar density into account, which when linked to stellar evolutionary models, determines the bulk parameters of the star. Because of the asymmetric shape of the light curve of one of the planets, we had to include the possibility in our model that the stellar surface was not strictly spherical...

  3. HR2875 Spectroscopic discovery of the first B star + white dwarf binary

    CERN Document Server

    Burleigh, M R; Burleigh, Matt; Barstow, Martin

    1998-01-01

    We report the discovery, in an Extreme Ultraviolet Explorer (EUVE) short wavelength spectrum, of an unresolved hot white dwarf companion to the 5th-magnitude B5Vp star HR2875. This is the first time that a non-interacting white dwarf$+$ B star binary has been discovered; previously, the the earliest type star known with a white dwarf companion was Sirius (A1V). Since the white dwarf must have evolved from a main sequence progenitor with a mass greater than that of a B5V star ($\\geq$6.0M$_\\odot$), this places a lower limit on the maximum mass for white dwarf progenitors, with important implications for our knowledge of the initial-final mass relation. Assuming a pure-hydrogen atmospheric composition, we constrain the temperature of the white dwarf to be between 39,000K and 49,000K. We also argue that this degenerate star is likely to have mass significantly greater than the mean mass for white dwarf stars ($\\approx$0.55M$_\\odot$). Finally, we suggest that other bright B stars (e.g.\\ Field Camera and EUVE may a...

  4. F stars: A challenge to stellar evolution

    CERN Document Server

    Suchkov, A A

    2014-01-01

    Many main-sequence F and early G stars are too luminous for their effective temperature, surface gravity, and chemical composition. These {\\it overluminous stars} have two curious properties. First, their kinematics as a function of age from stellar evolution modeling (isochrone fitting) is very different from that of normal stars. Second, while X-ray luminosity of normal stars declines with age, the X-ray luminosity of overluminous F stars changes in the opposite direction, being on average higher for older stars. These properties imply that, in defiance of standard models of stellar evolution, F stars of a given mass and chemical composition can evolve very differently. Assuming that the models correctly describe normal stars, for overluminous F stars they predict too young age and the X-ray emission evolving in the direction opposite to the actually observed trend. This discrepancy between modeling results and observational data suggests that standard stellar evolution models and models of stellar activity...

  5. THE DUST BUDGET OF THE SMALL MAGELLANIC CLOUD: ARE ASYMPTOTIC GIANT BRANCH STARS THE PRIMARY DUST SOURCE AT LOW METALLICITY?

    Energy Technology Data Exchange (ETDEWEB)

    Boyer, M. L.; Gordon, K. D.; Meixner, M.; Sargent, B. A. [STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Srinivasan, S. [UPMC-CNRS UMR7095, Institut d' Astrophysique de Paris, F-75014 Paris (France); Riebel, D. [Department of Physics and Astronomy, The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); McDonald, I. [Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom); Van Loon, J. Th. [Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom); Clayton, G. C. [Department of Physics and Astronomy, Louisiana State University, 233-A Nicholson Hall, Tower Dr., Baton Rouge, LA 70803-4001 (United States); Sloan, G. C., E-mail: mboyer@stsci.edu [Astronomy Department, Cornell University, Ithaca, NY 14853-6801 (United States)

    2012-03-20

    We estimate the total dust input from the cool evolved stars in the Small Magellanic Cloud, using the 8 {mu}m excess emission as a proxy for the dust-production rate (DPR). We find that asymptotic giant branch (AGB) and red supergiant (RSG) stars produce (8.6-9.5) Multiplication-Sign 10{sup -7} M{sub Sun} yr{sup -1} of dust, depending on the fraction of far-infrared sources that belong to the evolved star population (with 10%-50% uncertainty in individual DPRs). RSGs contribute the least (<4%), while carbon-rich AGB stars (especially the so-called extreme AGB stars) account for 87%-89% of the total dust input from cool evolved stars. We also estimate the dust input from hot stars and supernovae (SNe), and find that if SNe produce 10{sup -3} M{sub Sun} of dust each, then the total SN dust input and AGB input are roughly equivalent. We consider several scenarios of SN dust production and destruction and find that the interstellar medium (ISM) dust can be accounted for solely by stellar sources if all SNe produce dust in the quantities seen around the dustiest examples and if most SNe explode in dense regions where much of the ISM dust is shielded from the shocks. We find that AGB stars contribute only 2.1% of the ISM dust. Without a net positive contribution from SNe to the dust budget, this suggests that dust must grow in the ISM or be formed by another unknown mechanism.

  6. Modeling Evolving Innovation Networks

    OpenAIRE

    Koenig, Michael D.; Battiston, Stefano; Schweitzer, Frank

    2007-01-01

    We develop a new framework for modeling innovation networks which evolve over time. The nodes in the network represent firms, whereas the directed links represent unilateral interactions between the firms. Both nodes and links evolve according to their own dynamics and on different time scales. The model assumes that firms produce knowledge based on the knowledge exchange with other firms, which involves both costs and benefits for the participating firms. In order to increase their knowledge...

  7. Evolving digital ecological networks.

    Science.gov (United States)

    Fortuna, Miguel A; Zaman, Luis; Wagner, Aaron P; Ofria, Charles

    2013-01-01

    "It is hard to realize that the living world as we know it is just one among many possibilities" [1]. Evolving digital ecological networks are webs of interacting, self-replicating, and evolving computer programs (i.e., digital organisms) that experience the same major ecological interactions as biological organisms (e.g., competition, predation, parasitism, and mutualism). Despite being computational, these programs evolve quickly in an open-ended way, and starting from only one or two ancestral organisms, the formation of ecological networks can be observed in real-time by tracking interactions between the constantly evolving organism phenotypes. These phenotypes may be defined by combinations of logical computations (hereafter tasks) that digital organisms perform and by expressed behaviors that have evolved. The types and outcomes of interactions between phenotypes are determined by task overlap for logic-defined phenotypes and by responses to encounters in the case of behavioral phenotypes. Biologists use these evolving networks to study active and fundamental topics within evolutionary ecology (e.g., the extent to which the architecture of multispecies networks shape coevolutionary outcomes, and the processes involved).

  8. Evolving digital ecological networks.

    Directory of Open Access Journals (Sweden)

    Miguel A Fortuna

    Full Text Available "It is hard to realize that the living world as we know it is just one among many possibilities" [1]. Evolving digital ecological networks are webs of interacting, self-replicating, and evolving computer programs (i.e., digital organisms that experience the same major ecological interactions as biological organisms (e.g., competition, predation, parasitism, and mutualism. Despite being computational, these programs evolve quickly in an open-ended way, and starting from only one or two ancestral organisms, the formation of ecological networks can be observed in real-time by tracking interactions between the constantly evolving organism phenotypes. These phenotypes may be defined by combinations of logical computations (hereafter tasks that digital organisms perform and by expressed behaviors that have evolved. The types and outcomes of interactions between phenotypes are determined by task overlap for logic-defined phenotypes and by responses to encounters in the case of behavioral phenotypes. Biologists use these evolving networks to study active and fundamental topics within evolutionary ecology (e.g., the extent to which the architecture of multispecies networks shape coevolutionary outcomes, and the processes involved.

  9. Search for giant planets in M67 III: excess of hot Jupiters in dense open clusters

    CERN Document Server

    Brucalassi, A; Saglia, R; Ruiz, M T; Bonifacio, P; Leao, I; Martins, B L Canto; de Medeiros, J R; Bedin, L R; Biazzo, K; Melo, C; Lovis, C; Randich, S

    2016-01-01

    Since 2008 we used high-precision radial velocity (RV) measurements obtained with different telescopes to detect signatures of massive planets around main-sequence and evolved stars of the open cluster (OC) M67. We aimed to perform a long-term study on giant planet formation in open clusters and determine how this formation depends on stellar mass and chemical composition. A new hot Jupiter (HJ) around the main-sequence star YBP401 is reported in this work. An update of the RV measurements for the two HJ host-stars YBP1194 and YBP1514 is also discussed. Our sample of 66 main-sequence and turnoff stars includes 3 HJs, which indicates a high rate of HJs in this cluster (~5.6% for single stars and ~4.5% for the full sample ). This rate is much higher than what has been discovered in the field, either with RV surveys or by transits. High metallicity is not a cause for the excess of HJs in M67, nor can the excess be attributed to high stellar masses. When combining this rate with the non-zero eccentricity of the o...

  10. MASSIVE INFANT STARS ROCK THEIR CRADLE

    Science.gov (United States)

    2002-01-01

    Extremely intense radiation from newly born, ultra-bright stars has blown a glowing spherical bubble in the nebula N83B, also known as NGC 1748. A new NASA Hubble Space Telescope image has helped to decipher the complex interplay of gas and radiation of a star-forming region in a nearby galaxy. The image graphically illustrates just how these massive stars sculpt their environment by generating powerful winds that alter the shape of the parent gaseous nebula. These processes are also seen in our Milky Way in regions like the Orion Nebula. The Hubble telescope is famous for its contribution to our knowledge about star formation in very distant galaxies. Although most of the stars in the Universe were born several billions of years ago, when the Universe was young, star formation still continues today. This new Hubble image shows a very compact star-forming region in a small part of one of our neighboring galaxies - the Large Magellanic Cloud. This galaxy lies only 165,000 light-years from our Milky Way and can easily be seen with the naked eye from the Southern Hemisphere. Young, massive, ultra-bright stars are seen here just as they are born and emerge from the shelter of their pre-natal molecular cloud. Catching these hefty stars at their birthplace is not as easy as it may seem. Their high mass means that the young stars evolve very rapidly and are hard to find at this critical stage. Furthermore, they spend a good fraction of their youth hidden from view, shrouded by large quantities of dust in a molecular cloud. The only chance is to observe them just as they start to emerge from their cocoon - and then only with very high-resolution telescopes. Astronomers from France, the U.S., and Germany have used Hubble to study the fascinating interplay between gas, dust, and radiation from the newly born stars in this nebula. Its peculiar and turbulent structure has been revealed for the first time. This high-resolution study has also uncovered several individual stars

  11. HATS-25b through HATS-30b: A Half-dozen New Inflated Transiting Hot Jupiters from the HATSouth Survey

    CERN Document Server

    Espinoza, N; Hartman, J D; Bakos, G Á; Jordán, A; Zhou, G; Mancini, L; Brahm, R; Ciceri, S; Bhatti, W; Csubry, Z; Rabus, M; Penev, K; Bento, J; de Val-Borro, M; Henning, T; Schmidt, B; Suc, V; Wright, D J; Tinney, C G; Tan, T G; Noyes, R

    2016-01-01

    We report six new inflated hot Jupiters (HATS-25b through HATS-30b) discovered using the HATSouth global network of automated telescopes. The planets orbit stars with $V$ magnitudes in the range $\\sim 12-14$ and have masses in the largely populated $0.5M_J-0.7M_J$ region of parameter space but span a wide variety of radii, from $1.17R_J$ to $1.75 R_J$. HATS-25b, HATS-28b, HATS-29b and HATS-30b are typical inflated hot Jupiters ($R_p = 1.17-1.26R_J$) orbiting G-type stars in short period ($P=3.2-4.6$ days) orbits. However, HATS-26b ($R_p = 1.75R_J$, $P = 3.3024$ days) and HATS-27b ($R_p=1.50R_J$, $P=4.6370$ days) stand out as highly inflated planets orbiting slightly evolved F stars just after and in the turn-off points, respectively, which are among the least dense hot Jupiters, with densities of $0.153$ g cm$^{-3}$ and $0.180$ g cm$^{-3}$, respectively. All the presented exoplanets but HATS-27b are good targets for future atmospheric characterization studies, while HATS-27b is a prime target for Rossiter-McL...

  12. Exploring atmospheres of hot mini-Neptune and extrasolar giant planets orbiting different stars with application to HD 97658b, WASP-12b, CoRoT-2b, XO-1b, and HD 189733b

    Energy Technology Data Exchange (ETDEWEB)

    Miguel, Y.; Kaltenegger, L., E-mail: miguel@mpia.de [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)

    2014-01-10

    We calculated an atmospheric grid for hot mini-Neptune and giant exoplanets that links astrophysical observable parameters—orbital distance and stellar type—with the chemical atmospheric species expected. The grid can be applied to current and future observations to characterize exoplanet atmospheres and serves as a reference to interpret atmospheric retrieval analysis results. To build the grid, we developed a one-dimensional code for calculating the atmospheric thermal structure and linked it to a photochemical model that includes disequilibrium chemistry (molecular diffusion, vertical mixing, and photochemistry). We compare the thermal profiles and atmospheric composition of planets at different semimajor axes (0.01 AU ≤ a ≤ 0.1 AU) orbiting F, G, K, and M stars. Temperature and UV flux affect chemical species in the atmosphere. We explore which effects are due to temperature and which are due to stellar characteristics, showing the species most affected in each case. CH{sub 4} and H{sub 2}O are the most sensitive to UV flux, H displaces H{sub 2} as the most abundant gas in the upper atmosphere for planets receiving a high UV flux. CH{sub 4} is more abundant for cooler planets. We explore vertical mixing, to inform degeneracies on our models and in the resulting spectral observables. For lower pressures, observable species like H{sub 2}O or CO{sub 2} can indicate the efficiency of vertical mixing, with larger mixing ratios for a stronger mixing. By establishing the grid, testing the sensitivity of the results, and comparing our model to published results, our paper provides a tool to estimate what observations could yield. We apply our model to WASP-12b, CoRoT-2b, XO-1b, HD189733b, and HD97658b.

  13. Color-Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M 31 and M 32

    CERN Document Server

    Brown, T M; Stanford, S A; Deharveng, J M

    1998-01-01

    We present Faint Object Camera (FOC) ultraviolet images of the central 14x14'' of Messier 31 and Messier 32. The hot stellar population detected in the composite UV spectra of these nearby galaxies is partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M 31 and 138 stars in M 32, down to detection limits of m_F275W = 25.5 mag and m_F175W = 24.5 mag. We investigate the luminosity functions of the sources, their spatial distribution, their color-magnitude diagrams, and their total integrated far-UV flux. Although M 32 has a weaker UV upturn than M 31, the luminosity functions and color-magnitude diagrams of M 31 and M 32 are surprisingly similar, and are inconsistent with a majority contribution from any of the following: PAGB stars more massive than 0.56 Msun, main sequence stars, or blue stragglers. Both the the luminosity functions and color-magnitude diagrams are consistent with a dominant population of stars that have evolved fr...

  14. Structured Red Giant Winds with Magnetized Hot Bubbles and the Corona/Cool Wind Dividing Line

    CERN Document Server

    Suzuki, T K

    2006-01-01

    (Abridged) By performing magnetohydrodynamical (MHD) simulations, we investigate mass loss of intermediate- and low-mass stars from main sequence to red giant branch phases. Alfven waves, which are excited by the photospheric perturbations due to the surface convections, travel outwardly and dissipate by nonlinear processes to accelerate and heat stellar winds. We dynamically treat these processes in open magnetic field regions from the photospheres to 25 stellar radii. When the star evolves to slightly blueward of the dividing line (Linsky & Haisch), the steady hot corona with temperature, T ~ 10^6 K, suddenly disappears. Instead, many hot (~ 10^6 K) and warm (>~ 10^5 K) bubbles are formed in cool (T <~ 2 x 10^4 K) chromospheric winds because of thermal instability; the RGB star wind is not a steady stream but structured outflow. The densities of the bubbles which are supported by the magnetic pressure can be kept low to reduce the radiative cooling so that the bubbles survive long time. Even in the s...

  15. XEUS : the physics of the hot evolving universe

    NARCIS (Netherlands)

    Arnaud, Monique; Barcons, Xavier; Barret, Didier; Bautz, Marshall; Bellazzini, Ronaldo; Bleeker, Johan; Boehringer, Hans; Boller, Thomas; Brandt, William Nielsen; Cappi, Massimo; Carrera, Francisco; Comastri, Andrea; Costa, Enrico; Courvoisier, Thierry; de Korte, Piet; Dwelly, Tom; Fabian, Andrew; Flanagan, Kathryn; Gilli, Roberto; Griffiths, Richard; Hasinger, Gunther; Kaastra, Jelle; Kahn, Steve; Kelley, Richard; Kunieda, Hideyo; Makishima, Kazuo; Matt, Giorgio; Mendez, Mariano; Mitsuda, Kazuhisa; Nandra, Kirpal; Ohashi, Takaya; Page, Mathew; Palumbo, Giorgio; Pavlinsky, Mikhail; Sciortino, Salvatore; Smith, Alan; Strueder, Lothar; Takahashi, Tadayuki; Tuerler, Marc; Tuerner, Martin; Ueda, Yoshihiro; Vignali, Cristian; Vink, Jacco; Warwick, Robert; Watson, Mike; Willingale, Richard; Zhang, Shuang Nan

    2009-01-01

    This paper describes the next generation X-ray observatory XEUS which has been submitted to the European Space Agency in the framework of the Cosmic Vision 2015-2025 competition and has been selected for an assessment study. The paper summarizes the scientific goals and instrumental concepts of the

  16. XEUS: the physics of the hot evolving universe

    NARCIS (Netherlands)

    Arnaud, M.; Bleeker, J.; Vink, J.

    2009-01-01

    This paper describes the next generation X-ray observatory XEUS which has been submitted to the European Space Agency in the framework of the Cosmic Vision 2015–2025 competition and has been selected for an assessment study. The paper summarizes the scientific goals and instrumental concepts of the

  17. ESA uncovers Geminga's `hot spot'

    Science.gov (United States)

    2004-07-01

    16 July 2004 Astronomers using ESA’s X-ray observatory XMM-Newton have detected a small, bright ‘hot spot’ on the surface of the neutron star called Geminga, 500 light-years away. The hot spot is the size of a football field and is caused by the same mechanism producing Geminga’s X-ray tails. This discovery identifies the missing link between the X-ray and gamma-ray emission from Geminga. hi-res Size hi-res: 1284 kb Credits: ESA, P. Caraveo (IASF, Milan) Geminga's hot spot This figure shows the effects of charged particles accelerated in the magnetosphere of Geminga. Panel (a) shows an image taken with the EPIC instrument on board the XMM-Newton observatory. The bright tails, made of particles kicked out by Geminga’s strong magnetic field, trail the neutron star as it moves about in space. Panel (b) shows how electrically charged particles interact with Geminga’s magnetic field. For example, if electrons (blue) are kicked out by the star, positrons (in red) hit the star’s magnetic poles like in an ‘own goal’. Panel (c) illustrates the size of Geminga’s magnetic field (blue) compared to that of the star itself at the centre (purple). The magnetic field is tilted with respect to Geminga’s rotation axis (red). Panel (d) shows the magnetic poles of Geminga, where charged particles hit the surface of the star, creating a two-million degrees hot spot, a region much hotter than the surroundings. As the star spins on its rotation axis, the hot spot comes into view and then disappears, causing the periodic colour change seen by XMM-Newton. An animated version of the entire sequence can be found at: Click here for animated GIF [low resolution, animated GIF, 5536 KB] Click here for AVI [high resolution, AVI with DIVX compression, 19128 KB] hi-res Size hi-res: 371 kb Credits: ESA, P. Caraveo (IASF, Milan) Geminga's hot spot, panel (a) Panel (a) shows an image taken with the EPIC instrument on board the XMM-Newton observatory. The bright tails, made of

  18. HATS-19b, HATS-20b, HATS-21b: Three Transiting Hot-Saturns Discovered by the HATSouth Survey

    CERN Document Server

    Bhatti, W; Hartman, J D; Zhou, G; Penev, K; Bayliss, D; Jordán, A; Brahm, R; Espinoza, N; Rabus, M; Mancini, L; de Val-Borro, M; Bento, J; Ciceri, S; Csubry, Z; Henning, T; Schmidt, B; Arriagada, P; Butler, R P; Crane, J; Shectman, S; Thompson, I; Tan, T G; Suc, V; Lázár, J; Papp, I; Sári, P

    2016-01-01

    We report the discovery by the HATSouth exoplanet survey of three hot-Saturn transiting exoplanets: HATS-19b, HATS-20b, and HATS-21b. The planet host HATS-19 is a slightly evolved V = 13.0 G0 star with [Fe/H] = 0.240, a mass of 1.303 Msun, and a radius of 1.75 Rsun. HATS-19b is in an eccentric orbit (e = 0.30) around this star with an orbital period of 4.5697 days and has a mass of 0.427 Mjup and a highly inflated radius of 1.66 Rjup. The planet HATS-20b has a Saturn-like mass and radius of 0.273 Mjup and 0.776 Rjup respectively. It orbits the V = 13.8 G9V star HATS-20 (Ms = 0.910 Msun; Rs = 0.892 Rsun) with a period of 3.7993 days. Finally, HATS-21 is a V = 12.2 G4V star with [Fe/H] = 0.300, a mass of 1.080 Msun, and a radius of 1.021 Rsun. Its accompanying planet HATS-21b has a 3.5544-day orbital period, a mass of 0.332 Mjup, and a moderately inflated radius of 1.123 Rjup. With the addition of these three very different planets to the growing sample of hot-Saturns, we re-examine the relations between the ob...

  19. Studying the evolution of AGB stars in the Gaia epoch

    CERN Document Server

    Di Criscienzo, M; Garcia-Hernandez, D A; Dell'Agli, F; Castellani, M; Marrese, P M; Marinoni, S; Giuffrida, G; Zamora, O

    2016-01-01

    We present asymptotic giant branch (AGB) models of solar metallicity, to allow the interpretation of observations of Galactic AGB stars, whose distances should be soon available after the first release of the Gaia catalogue. We find an abrupt change in the AGB physical and chemical properties, occurring at the threshold mass to ignite hot bottom burning,i.e. $3.5M_{\\odot}$. Stars with mass below $3.5 M_{\\odot}$ reach the C-star stage and eject into the interstellar medium gas enriched in carbon , nitrogen and $^{17}O$. The higher mass counterparts evolve at large luminosities, between $3\\times 10^4 L_{\\odot}$ and $10^5 L_{\\odot}$. The mass expelled from the massive AGB stars shows the imprinting of proton-capture nucleosynthesis, with considerable production of nitrogen and sodium and destruction of $^{12}C$ and $^{18}O$. The comparison with the most recent results from other research groups are discussed, to evaluate the robustness of the present findings. Finally, we compare the models with recent observati...

  20. Enigma of Runaway Stars Solved

    Science.gov (United States)

    1997-01-01

    Supernova Propels Companion Star through Interstellar Space The following success story is a classical illustration of scientific progress through concerted interplay of observation and theory. It concerns a 35-year old mystery which has now been solved by means of exciting observations of a strange double star. An added touch is the successive involvement of astronomers connected to the European Southern Observatory. For many years, astronomers have been puzzled by the fact that, among the thousands of very young, hot and heavy stars which have been observed in the Milky Way, there are some that move with exceptionally high velocities. In some cases, motions well above 100 km/sec, or ten times more than normal for such stars, have been measured. How is this possible? Which mechanism is responsible for the large amounts of energy needed to move such heavy bodies at such high speeds? Could it be that these stars are accelerated during the powerful explosion of a companion star as a supernova? Such a scenario was proposed in 1961 by Adriaan Blaauw [1], but until now, observational proof has been lacking. Now, however, strong supporting evidence for this mechanism has become available from observations obtained at the ESO La Silla observatory. The mysterious runaway stars OB-runaway stars [2] are heavy stars that travel through interstellar space with an anomalously high velocity. They have been known for several decades, but it has always been a problem to explain their high velocities. Although most OB-runaway stars are located at distances of several thousands of lightyears, their high velocity results in a measurable change in position on sky photos taken several years apart. The velocity component in the direction of the Earth can be measured very accurately from a spectrogram. From a combination of such observations, it is possible to measure the space velocity of OB-runaways. Bow shocks reveal runaway stars It has also been found that some OB-runaways display