WorldWideScience

Sample records for late type stars

  1. Infrared Observations of Late Type Stars

    Science.gov (United States)

    Merrill, K. M.

    1977-01-01

    Substantive mass loss resulting in appreciable circumstellar dust envelopes is common in late-type stars. The evolutionary history and physical state of a cool star determine the chemistry within the outer stellar atmosphere mirrored by the molecular and particulate material present in the envelope. The observational consequences of this debris determined by moderate spectral resolution infrared spectrophotometry are reviewed. Significant information is provided by observations of the emergent energy flux of both the cool stellar photosphere and of the circumstellar dust envelope. The observation suggests that mass-loss occurs to some degree throughout late stellar evolutionary phases and that occasional periods of high mass loss are not uncommon.

  2. Spectroscopy of late type giant stars

    Science.gov (United States)

    Spaenhauer, A.; Thevenin, F.

    1984-06-01

    An attempt to calibrate broadband RGU colors of late type giant stars in terms of the physical parameters of the objects is reported. The parameters comprise the effective temperature, surface gravity and global metal abundance with respect to the sun. A selection of 21 giant star candidates in the Basel fields Plaut 1, Centaurus III and near HD 95540 were examined to obtain a two color plot. Attention is focused on the G-R color range 1.5-2.15 mag, i.e., spectral types K0-K5. A relationship between R and the metallicity is quantified and shown to have a correlation coefficient of 0.93. No correlation is found between metallicity and gravity or R and the effective temperature.

  3. Einstein Observatory coronal temperatures of late-type stars

    Science.gov (United States)

    Schmitt, J. H. M. M.; Collura, A.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.

    1990-01-01

    The results are presented of a survey of the coronal temperatures of late-type stars using the Einstein Observatory IPC. The spectral analysis shows that the frequently found one- and two-temperature descriptions are mainly influenced by the SNR of the data and that models using continuous emission measure distributions can provide equally adequate and physically more meaningful and more plausible descriptions. Intrinsic differences in differential emission measure distributions are found for four groups of stars. M dwarfs generally show evidence for high-temperature gas in conjunction with lower-temperature material, while main-sequence stars of types F and G have the high-temperature component either absent or very weak. Very hot coronae without the lower-temperature component appearing in dwarf stars are evident in most of the giant stars studied. RS CVn systems show evidence for extremely hot coronae, sometimes with no accompanying lower-temperature material.

  4. The Star Formation History of Late Type Galaxies

    CERN Document Server

    Fernandes, R C

    2007-01-01

    The combination of huge databases of galaxy spectra and advances in evolutionary synthesis models in the past few years has renewed interest in an old question: How to estimate the star formation history of a galaxy out of its integrated spectrum? Fresh approaches to this classical problem are making it possible to extract the best of both worlds, producing exquisite pixel-by-pixel fits to galaxy spectra with state-of-the-art stellar population models while at the same time exploring the fabulous statistics of mega-surveys to derive the star-formation and chemical enrichment histories of different types of galaxies with an unprecedented level of detail. This review covers some of these recent advances, focusing on results for late-type, star-forming galaxies, and outlines some of the issues which will keep us busy in the coming years.

  5. The Near-Ultraviolet Continuum of Late-Type Stars

    CERN Document Server

    Allende-Prieto, C; Allende-Prieto, Carlos; Lambert, David L

    2000-01-01

    Analyses of the near-ultraviolet continuum of late-type stars have led to controversial results regarding the performance of state-of-the-art model atmospheres. The release of the homogeneous IUE final archive and the availability of the high-accuracy Hipparcos parallaxes provide an opportunity to revisit this issue, as accurate stellar distances make it possible to compare observed absolute fluxes with the predictions of model atmospheres. The near-UV continuum is highly sensitive to Teff and [Fe/H], and once the gravity is constrained from the parallax, these parameters may be derived from the analysis of low-dispersion "long-wavelength" (2000-3000 A) IUE spectra for stars previously studied by Alonso et al. (1996; A&AS 117, 227) using the Infrared Flux Method (IRFM). A second comparison is carried out against the stars spectroscopically investigated by Gratton et al. (1996; A&A 314, 191). It is shown that there is a good agreement between Teffs obtained from the IRFM and from the near-UV continuum,...

  6. Circumstellar carbonaceous material associated with late-type dusty WC Wolf-Rayet stars

    NARCIS (Netherlands)

    Chiar, JE; Tielens, AGGM

    2001-01-01

    We have studied the 5-8.5 mum infrared spectra of the late-type Wolf-Rayet stars WR 118, WR 112, and WR 104, the WN star WR 147, the B5 hypergiant Cygnus OB2 No. 12, and the Galactic center luminous blue variable Pistol Star using the Short Wavelength Spectrometer on the Infrared Space Observatory.

  7. CO fundamental bands in late-type stars. II - Spectrum simulations for F-K stars

    Science.gov (United States)

    Wiedemann, Guenter; Ayres, Thomas R.

    1991-01-01

    The procedure of Ayres and Wiedemann (1989) was applied to a range of stellar-atmosphere models to study the CO Delta-v = 1 spectrum and to establish its use as a remote sensor of thermal conditions in late-type stars. Spectra were computed to examine the sensitivity of the CO Delta-v = 1 to fundamental stellar parameters and to assess the errors introduced into the spectrum intepretation by uncertain input parameters and non-LTE effects. Results of the sensitivity study demonstrate that CO fundamental spectra are useful probes for the temperature structure of the outer layers of cool stellar atmospheres, but that their value is limited by the uncertainties introduced by non-LTE effects. However, in stars with surface gravities of log g of about 1.5 and greater, the values of these uncertainties are reasonably small.

  8. EUV Flare Activity in Late-Type Stars

    CERN Document Server

    Audard, M; Drake, J J; Kashyap, V L; Audard, Marc; Guedel, Manuel; Drake, Jeremy J.

    2000-01-01

    \\textit{Extreme Ultraviolet Explorer} Deep Survey observations of cool stars (spectral type F to M) have been used to investigate the distribution of coronal flare rates in energy and its relation to activity indicators and rotation parameters. Cumulative and differential flare rate distributions were constructed and fitted with different methods. Power laws are found to approximately describe the distributions. A trend toward flatter distributions for later-type stars is suggested in our sample. Assuming that the power laws continue below the detection limit, we have estimated that the superposition of flares with radiated energies of about $10^{29}-10^{31}$ergs could explain the observed radiative power loss of these coronae, while the detected flares are contributing only $\\approx 10$%. While the power-law index is not correlated with rotation parameters (rotation period, projected rotational velocity, Rossby number) and only marginally with the X-ray luminosity, the flare occurrence rate is correlated wit...

  9. Stellar populations and star formation histories in late-type dwarfs

    CERN Document Server

    Tosi, M P

    2003-01-01

    Studies of the resolved stellar populations in nearby systems are crucial to understand galaxy evolution. Here, we summarize how the interpretation of the colour-magnitude diagrams of field stars in late-type dwarfs inside and outside the Local Group has allowed us to infer their star formation histories and put useful constraints on the evolution of this type of galaxies.

  10. Distribution of Late-type Stars around IC 4665

    Science.gov (United States)

    Fronto, A.; Balazs, L. G.; Paparo, M.

    1990-01-01

    We have investigated 424 stars of F8 spectral types and later in a 19.5 sq. degree field around IC 4665. The main purpose of our study in this low latitude field (b = +16.5 in our case) was the testing of the plane-parallel hypothesis of the density distribution, i.e. the hypothesis that the spatial density of the Population I stars observed at great angular distance from the galactic caps is well approximated by the z = r sin (b) scaling of the distributions obtained in the polar regions. We used the factor analysis of multivariate mathematical statistics in order to extract the effect of absorption from the photometric data. To identify the factor component describing the interstellar reddening we invoked the corresponding IRAS Sky Flux Data. We computed the spatial densities for the F8 - G5 dwarfs and the K giants separately. We used a maximum likelihood algorithm for oblating the space densities. We arrived at the following main conclusions in our paper: The absorbing material concentrates closer than 150 pc in our area. There is a weak but still significant correlation between the optical measures of absorption and the IRAS 100 micron Sky Flux Maps data. The spatial densities of F8 - G5 dwarfs essentially reflect the densities obtained in the galactic plane. The distribution of distance moduli of K giants in our sample can be well modelled by the z = sin (b) scaling of Upgren's data from the North Polar region. The actual form of the space density curve of the K giants can be satisfactorily fitted both by an isothermal model and an exponential model.

  11. Spectroscopic properties of nearby late-type stars, members of stellar kinematic groups

    CERN Document Server

    Maldonado, J; Eiroa, C; Montes, D; Montesinos, B

    2010-01-01

    Nearby late-type stars are excellent targets to look for young objects in stellar associations and moving groups. The study of these groups goes back more than one century ago however, their origin is still misunderstood. Although their existence have been confirmed by statistical studies of large sample of stars, the identification of a group of stars as member of moving groups, is not an easy task, list of members often change with time and most members have been identified by means of kinematics criteria which is not sufficient since many old stars can share the same spatial motion of those stars in moving groups. In this contribution we attempt to identify unambiguous moving groups members, among a sample of nearby-late type stars. High resolution echelle spectra is used to i) derive accurate radial velocities which allow us to study the stars' kinematics and make a first selection of moving groups members; and ii) analyze several age-related properties for young late-type stars (i.e., lithium LiI 6707.8 ...

  12. Principal component analysis-based inversion of effective temperatures for late-type stars

    CERN Document Server

    Paletou, F; Houdebine, E R; Watson, V

    2015-01-01

    We show how the range of application of the principal component analysis-based inversion method of Paletou et al. (2015) can be extended to late-type stars data. Besides being an extension of its original application domain, for FGK stars, we also used synthetic spectra for our learning database. We discuss our results on effective temperatures against previous evaluations made available from Vizier and Simbad services at CDS.

  13. Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series

    CERN Document Server

    Mascareño, A Suárez; Hernández, J I González

    2016-01-01

    We investigate the photometric modulation induced by magnetic activity cycles and study the relationship between rotation period and activity cycle(s) in late-type (FGKM) stars. We analyse light-curves spanning up to 9 years of 125 nearby stars provided by the ASAS survey. The sample is mainly conformed by low-activity main sequence late A to mid M-type stars. A search is performed for short (days) and long-term (years) periodic variations in the photometry. We modelled with combinations of sinusoids the light-curves to measure the properties of these periodic signals. To provide a better statistical interpretation of our results we complement them with the results from previous similar works. We have been able to measure long-term photometric cycles of 47 stars. Rotational modulation was also detected and rotational periods measured in 36 stars. For 28 stars we have simultaneous measurements of both, activity cycles and rotational periods, being 17 of them M-type stars. From sinusoidal fits we measured both ...

  14. Detection of Neutral Phosphorus in the Near Ultraviolet Spectra of Late-Type Stars

    CERN Document Server

    Roederer, Ian U; Thanathibodee, Thanawuth; Frebel, Anna; Toller, Elizabeth

    2014-01-01

    We report the detection of several absorption lines of neutral phosphorus (P, Z=15) in archival near ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We derive phosphorus abundances or interesting upper limits in 14 late-type stars with metallicities spanning -3.8-1.0, the [P/Fe] ratio decreases toward the solar value with increasing metallicity, in agreement with previous observational studies. In stars with [Fe/H]=+0.04+/-0.10, which overlaps with the [P/Fe] ratios found in several high-redshift damped Lyman-alpha systems. This behavior hints at a primary origin in massive stars.

  15. A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups

    CERN Document Server

    Maldonado, J; Eiroa, C; Montes, D; Montesinos, B; 10.1051/0004-6361/201014948

    2010-01-01

    Nearby late-type stars are excellent targets for seeking young objects in stellar associations and moving groups. The origin of these structures is still misunderstood, and lists of moving group members often change with time and also from author to author. Most members of these groups have been identified by means of kinematic criteria, leading to an important contamination of previous lists by old field stars. We attempt to identify unambiguous moving group members among a sample of nearby-late type stars by studying their kinematics, lithium abundance, chromospheric activity, and other age-related properties. High-resolution echelle spectra ($R \\sim 57000$) of a sample of nearby late-type stars are used to derive accurate radial velocities that are combined with the precise Hipparcos parallaxes and proper motions to compute galactic-spatial velocity components. Stars are classified as possible members of the classical moving groups according to their kinematics. The spectra are also used to study several a...

  16. The Wolf-Rayet stars in M31: I. Analysis of the late-type WN stars

    CERN Document Server

    Sander, Andreas; Hainich, Rainer; Hamann, Wolf-Rainer

    2014-01-01

    Context: Comprehensive studies of Wolf-Rayet stars were performed in the past for the Galactic and the LMC population. The results revealed significant differences, but also unexpected similarities between the WR populations of these different galaxies. Analyzing the WR stars in M31 will extend our understanding of these objects in different galactic environments. Aims: The present study aims at the late-type WN stars in M31. The stellar and wind parameters will tell about the formation of WR stars in other galaxies with different metallicity and star formation histories. The obtained parameters will provide constraints to the evolution of massive stars in the environment of M31. Methods: We used the latest version of the Potsdam Wolf-Rayet model atmosphere code to analyze the stars via fitting optical spectra and photometric data. To account for the relatively low temperatures of the late WN10 and WN11 subtypes, our WN models have been extended into this temperature regime. Results: Stellar and atmospheric p...

  17. Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit

    CERN Document Server

    Graefener, G

    2008-01-01

    The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to the formation of long-duration Gamma Ray Bursts (GRBs) and the yields from early stellar generations. However, the mechanism of formation of WR-type stellar winds is still under debate. We present the first fully self-consistent atmosphere/wind models for late-type WN stars. We investigate the mechanisms leading to their strong mass loss, and examine the dependence on stellar parameters, in particular on the metallicity Z. We identify WNL stars as very massive stars close to the Eddington limit, potentially still in the phase of central H-burning. Due to their high L/M ratios, these stars develop optically thick, radiatively driven winds. These winds show qualitatively different properties than the thin winds of OB stars. The resultant mass loss depends strongly on Z, but also on the Eddington factor, and the stellar temperature. We c...

  18. KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars

    Science.gov (United States)

    Feldmeier-Krause, A.; Kerzendorf, W.; Neumayer, N.; Schödel, R.; Nogueras-Lara, F.; Do, T.; de Zeeuw, P. T.; Kuntschner, H.

    2017-01-01

    Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4 pc2 of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the Göttingen spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H] > +0.3 dex to metal-poor [M/H] 0 dex), a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4 pc2 of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.

  19. KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars

    CERN Document Server

    Feldmeier-Krause, A; Neumayer, N; Schödel, R; Nogueras-Lara, F; Do, T; de Zeeuw, P T; Kuntschner, H

    2016-01-01

    Knowing the metallicity distribution of stars in the Galactic Centre has important implications for the formation history of the Milky Way nuclear star cluster. However, this distribution is not well known, and is currently based on a small sample of fewer than 100 stars. We obtained near-infrared K-band spectra of more than 700 late-type stars in the central 4 pc^2 of the Milky Way nuclear star cluster with the integral-field spectrograph KMOS (VLT). We analyse the medium-resolution spectra using a full-spectral fitting method employing the G\\"ottingen Spectral library of synthetic PHOENIX spectra. The derived stellar metallicities range from metal-rich [M/H]>+0.3 dex to metal-poor [M/H]0 dex) a globular cluster origin can be ruled out. As there is only a very low fraction of metal-poor stars in the central 4 pc^2 of the Galactic Centre, we believe that our data can discard a scenario in which the Milky Way nuclear star cluster is purely formed from infalling globular clusters.

  20. The chemical abundance analysis of normal early A- and late B-type stars

    CERN Document Server

    Fossati, L; Bagnulo, S; Alecian, E; Grunhut, J; Kochukhov, O; Wade, G

    2009-01-01

    Modern spectroscopy of early-type stars often aims at studying complex physical phenomena. Comparatively less attention is paid to identifying and studying the "normal" A- and B-type stars and testing how the basic atomic parameters and standard spectral analysis allow one to fit the observations. We wish to stablish whether the chemical composition of the solar photosphere can be regarded as a reference for early A- and late B-type stars. We have obtained optical high-resolution, high signal-to-noise ratio spectra of three slowly rotating early-type stars (HD 145788, 21 Peg and pi Cet) that show no obvious sign of chemical peculiarity, and performed a very accurate LTE abundance analysis of up to 38 ions of 26 elements (for 21 Peg), using a vast amount of spectral lines visible in the spectral region covered by our spectra. We provide an exhaustive description of the abundance characteristics of the three analysed stars with a critical review of the line parameters used to derive the abundances. We compiled ...

  1. BUILDING LATE-TYPE SPIRAL GALAXIES BY IN-SITU AND EX-SITU STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Pillepich, Annalisa [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Madau, Piero [Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High St., Santa Cruz, CA 95064 (United States); Mayer, Lucio [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-9057 Zurich (Switzerland)

    2015-02-01

    We analyze the formation and evolution of the stellar components in ''Eris'', a 120 pc resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of ''in-situ'' (within the main host) and ''ex-situ'' (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: (1) approximately 70% of today's stars formed in-situ; (2) more than two thirds of the ex-situ stars formed within satellites after infall; (3) the majority of ex-situ stars are found today in the disk and in the bulge; (4) the stellar halo is dominated by ex-situ stars, whereas in-situ stars dominate the mass profile at distances ≲ 5 kpc from the center at high latitudes; and (5) approximately 25% of the inner, r ≲ 20 kpc, halo is composed of in-situ stars that have been displaced from their original birth sites during Eris' early assembly history.

  2. A Consistency Test of Spectroscopic Gravities for Late-Type Stars

    CERN Document Server

    Allende-Prieto, C; Lambert, D L; Gustafsson, B; Prieto, Carlos Allende; Lopez, Ramon J. Garcia; Lambert, David L.; Gustafsson, Bengt

    1999-01-01

    Chemical analyses of late-type stars are usually carried out following the classical recipe: LTE line formation and homogeneous, plane-parallel, flux-constant, and LTE model atmospheres. We review different results in the literature that have suggested significant inconsistencies in the spectroscopic analyses, pointing out the difficulties in deriving independent estimates of the stellar fundamental parameters and hence,detecting systematic errors. The trigonometric parallaxes measured by the HIPPARCOS mission provide accurate appraisals of the stellar surface gravity for nearby stars, which are used here to check the gravities obtained from the photospheric iron ionization balance. We find an approximate agreement for stars in the metallicity range -1 <= [Fe/H] <= 0, but the comparison shows that the differences between the spectroscopic and trigonometric gravities decrease towards lower metallicities for more metal-deficient dwarfs (-2.5 <= [Fe/H] <= -1.0), which casts a shadow upon the abundanc...

  3. Magnetic fields around late-type stars using water maser observations

    CERN Document Server

    Vlemmings, W H T; Diamond, P J

    2005-01-01

    We present the analysis of the circular polarization, due to Zeeman splitting, of the water masers around a sample of late-type stars to determine the magnetic fields in their circumstellar envelopes. The magnetic field strengths in the water maser regions around the Mira variable stars U Ori and U Her are shown to be several Gauss while those of the supergiants S Per, NML Cyg and VY CMa are several hundred mG. We also show that large scale magnetic fields permeate the CSE of an evolved star; the polarization of the water masers around VX Sgr reveals a dipole field structure. We shortly discuss the coupling of the magnetic field with the stellar outflow, as such fields could possibly be the cause of distinctly aspherical mass-loss and the resulting aspherical planetary nebulae.

  4. Building Late-Type Spiral Galaxies by In-Situ and Ex-Situ Star Formation

    CERN Document Server

    Pillepich, Annalisa; Mayer, Lucio

    2014-01-01

    We analyze the formation and evolution of the stellar components in "Eris", a 120 pc-resolution cosmological hydrodynamic simulation of a late-type spiral galaxy. The simulation includes the effects of a uniform UV background, a delayed-radiative-cooling scheme for supernova feedback, and a star formation recipe based on a high gas density threshold. It allows a detailed study of the relative contributions of "in-situ" (within the main host) and "ex-situ" (within satellite galaxies) star formation to each major Galactic component in a close Milky Way analog. We investigate these two star-formation channels as a function of galactocentric distance, along different lines of sight above and along the disk plane, and as a function of cosmic time. We find that: 1) approximately 70 percent of today's stars formed in-situ; 2) more than two thirds of the ex-situ stars formed within satellites after infall; 3) the majority of ex-situ stars are found today in the disk and in the bulge; 4) the stellar halo is dominated ...

  5. A Copernicus survey of Mg II emission in late-type stars

    Science.gov (United States)

    Weiler, E. J.; Oegerle, W. R.

    1979-01-01

    The behavior of Mg II emission in late-type stars is examined using scan data obtained with the Copernicus satellite. The luminosity in the Mg II k emission line was found to be closely related to stellar absolute magnitude, leading to the suggestion that such correlation may be very useful for future UV observations. The stellar surface flux in the k line was observed to be roughly constant or to decrease slowly with later spectral type, a finding which is then used to show that the pressure at the top of the chromosphere decreases with later spectral type, in agreement with the conclusions by McClintock et al. (1975). An asymmetry in the Mg II k line was noticed to be present in the available data for the stars later than K2-K5.

  6. The NaI D resonance lines in main-sequence late-type stars

    Science.gov (United States)

    Díaz, Rodrigo F.; Cincunegui, Carolina; Mauas, Pablo J. D.

    2007-07-01

    We study the sodium D lines (D1: 5895.92Å D2: 5889.95Å) in late-type dwarf stars. The stars have spectral types between F6 and M5.5 (B - V between 0.457 and 1.807) and metallicity between [Fe/H] = -0.82 and 0.6. We obtained medium-resolution echelle spectra using the 2.15-m telescope at the Argentinian observatory Complejo Astronómico El Leoncito (CASLEO). The observations have been performed periodically since 1999. The spectra were calibrated in wavelength and in flux. A definition of the pseudo-continuum level is found for all our observations. We also define a continuum level for calibration purposes. The equivalent width of the D lines is computed in detail for all our spectra and related to the colour index (B - V) of the stars. When possible, we perform a careful comparison with previous studies. Finally, we construct a spectral index (R'D) as the ratio between the flux in the D lines and the bolometric flux. We find that, once corrected for the photospheric contribution, this index can be used as a chromospheric activity indicator in stars with a high level of activity. Additionally, we find that combining some of our results, we obtain a method to calibrate in flux stars of unknown colour.

  7. Is there a compact companion orbiting the late O-type binary star HD 164816?

    Science.gov (United States)

    Trepl, L.; Hambaryan, V. V.; Pribulla, T.; Tetzlaff, N.; Chini, R.; Neuhäuser, R.; Popov, S. B.; Stahl, O.; Walter, F. M.; Hohle, M. M.

    2012-12-01

    We present a multi-wavelength (X-ray, γ-ray, optical and radio) study of HD 164816, a late O-type X-ray detected spectroscopic binary. X-ray spectra are analysed and the X-ray photon arrival times are checked for pulsation. In addition, newly obtained optical spectroscopic monitoring data on HD 164816 are presented. They are complemented by available radio data from several large-scale surveys as well as the Fermi γ-ray data from its Large Area Telescope. We report the detection of a low energy excess in the X-ray spectrum that can be described by a simple absorbed blackbody model with a temperature of ˜50 eV as well as a 9.78 s pulsation of the X-ray source. The soft X-ray excess, the X-ray pulsation and the kinematical age would all be consistent with a compact object like a neutron star as companion to HD 164816. The size of the soft X-ray excess emitting area is consistent with a circular region with a radius of about 7 km, typical for neutron stars, while the emission measure (EM) of the remaining harder emission is typical for late O-type single or binary stars. If HD 164816 includes a neutron star born in a supernova, this supernova should have been very recent and should have given the system a kick, which is consistent with the observation that the star HD 164816 has a significantly different radial velocity than the cluster mean. In addition we confirm the binarity of HD 164816 itself by obtaining an orbital period of 3.82 d, projected masses m1sin3i = 2.355(69) M⊙, m2sin3i = 2.103(62) M⊙ apparently seen at low inclination angle, determined from high-resolution optical spectra.

  8. A spectroscopic orbit for the late-type Be star β CMi

    Science.gov (United States)

    Dulaney, Nick; Richardson, Noel; Gerhartz, Cody; Bjorkman, Jon Eric; Bjorkman, Karen S.; Carciofi, Alex C.; Wang, Luqian; Morrison, Nancy D.; Klement, Robert; Ritter Observing Team

    2017-01-01

    The late-type Be star beta CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. (2015) These results showed that the disk is likely truncated at a finite radius from the star, which is easily accomplished by a binary companion in orbit. We report on an analysis of the Ritter Observatory spectroscopic archive of beta CMi in hopes of discovering evidence of the elusive companion. We detect orbital motion caused by a companion from small shifts in the H-alpha emission line. We then compared the small changes in the violet-to-red peak height changes (V/R) with the orbital motion. While some V/R variability seems to be present in the H-alpha profile, there is only weak evidence that it follows the orbital motion, as suggested by recent Be binary models by Panoglou et al. (2016). We also analyze several epochs of near-infrared moderate resolution spectra from the InfraRed Telescope Facility with the SpeX spectrograph. Near-infrared spectra show variations of the Pa-beta and Br-gamma lines, suggesting structure could be present in the inner parts of the Be disk. These results suggest that beta CMi is similar to several other Be stars, and is a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no sign of this star is found in the very limited archive of International Ultraviolet Explorer spectra, so future UV studies of the system are necessary.We are grateful for support of the NSF REU program at the University of Toledo through NSF grant 1262810 and addtional support from the NSF under grant AST-1412135.

  9. The nature of the late B-type stars HD 67044 and HD 42035

    CERN Document Server

    Monier, R; Royer, F

    2016-01-01

    While monitoring a sample of apparently slowly rotating superficially normal bright late B and early A stars in the northern hemisphere, we have discovered that HD 67044 and HD 42035, hitherto classified as normal late B-type stars, are actually respectively a new chemically peculiar star and a new spectroscopic binary containing a very slow rotator HD 42035 S with ultra-sharp lines (vsini = 3.7 km/s) and a fast rotator HD 42035 B with broad lines. The lines of Ti, Cr, Mn, Sr, Y, Zr and Ba are conspicuous features in the high resolution SOPHIE spectrum of HD 67044. The HgII line at 3983.93 A is also present as a weak feature. The composite spectrum of HD 42035 is characterised by very sharp lines formed in HD 42035 S superimposed onto the shallow and broad lines of HD 42035 B. These very sharp lines are mostly due to light elements from C to Ni, the only heavy species definitely present are Sr and Ba. Selected lines of 21 chemical elements from He up to Hg have been synthesized using model atmospheres compute...

  10. Observations and theory of mass loss in late-type stars

    Science.gov (United States)

    Hartmann, L.

    1981-01-01

    The presented review is mainly concerned with the ubiquitous mass loss which occurs during most of a star's existence as a cool giant or supergiant. Observations of mass loss are considered, taking into account wind components and kinematics, and the temperature structure of cool winds. Theories of mass loss are examined, giving attention to radiation pressure on dust, radiation pressure in Lyman alpha, and magnetic wave-driven winds. It is pointed out that the study of mass loss from late-type stars appears to be entering a promising new phase. In this phase, the behavior of cool giants and supergiants is considered from a solar perspective, a perspective which contains important implications concerning the nature of solar activity.

  11. Hydrodynamical model atmospheres: Their impact on stellar spectroscopy and asteroseismology of late-type stars

    CERN Document Server

    Ludwig, Hans-G

    2016-01-01

    Hydrodynamical, i.e. multi-dimensional and time-dependent, model atmospheres of late-type stars have reached a high level of realism. They are commonly applied in high-fidelity work on stellar abundances but also allow the study of processes that are not modelled in standard, one-dimensional hydrostatic model atmospheres. Here, we discuss two observational aspects that emerge from such processes, the photometric granulation background and the spectroscopic microturbulence. We use CO5BOLD hydrodynamical model atmospheres to characterize the total granular brightness fluctuations and characteristic time scale for FGK stars. Emphasis is put on the diagnostic potential of the granulation background for constraining the fundamental atmospheric parameters. We find a clear metallicity dependence of the granulation background. The comparison between the model predictions and available observational constraints at solar metallicity shows significant differences, that need further clarification. Concerning microturbule...

  12. The magnetic field around late-type stars revealed by the circumstellar H2O masers

    CERN Document Server

    Vlemmings, W H T; Diamond, P J

    2005-01-01

    Through polarization observations, circumstellar masers are excellent probes of the magnetic field in the envelopes of late-type stars. Whereas observations of the polarization of the SiO masers close to the star and on the OH masers much further out were fairly commonplace, observations of the magnetic field strength in the intermediate density and temperature region where the 22 GHz water masers occur have only recently become possible. Here we present the analysis of the circular polarization, due to Zeeman splitting, of the water masers around the Mira variable stars U Her and U Ori and the supergiant VX Sgr. We present an upper limit of the field around U Her that is lower but consistent with previous measurements, reflecting possible changes in the circumstellar envelope. The field strengths around U Ori and VX Sgr are shown to be of the order of several Gauss. Moreover, we show for the first time that large scale magnetic fields permeate the circumstellar envelopes of an evolved star; the polarization ...

  13. A grid of MARCS model atmospheres for late-type stars. II. S stars and their properties

    Science.gov (United States)

    Van Eck, Sophie; Neyskens, Pieter; Jorissen, Alain; Plez, Bertrand; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt; Jørgensen, Uffe Gråe; Nordlund, Åke

    2017-05-01

    S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing asymptotic giant branch. A grid of MARCS model atmospheres has been computed for S stars, covering the range 2700 ≤ Teff(K) ≤ 4000, 0.50 ≤ C/O ≤ 0.99, 0 ≤ log g ≤ 5, [Fe/H] = 0., -0.5 dex, and [s/Fe] = 0, 1, and 2 dex (where the latter quantity refers to the global overabundance of s-process elements). The MARCS models make use of a new ZrO line list. Synthetic spectra computed from these models are used to derive photometric indices in the Johnson and Geneva systems, as well as TiO and ZrO band strengths. A method is proposed to select the model best matching any given S star, a non-trivial operation since the grid contains more than 3500 models covering a five-dimensional parameter space. The method is based on the comparison between observed and synthetic photometric indices and spectral band strengths, and has been applied on a vast subsample of the Henize sample of S stars. Our results confirm the old claim by Piccirillo (1980, MNRAS, 190, 441) that ZrO bands in warm S stars (Teff>3200 K) are not caused by the C/O ratio being close to unity, as traditionally believed, but rather by some Zr overabundance. The TiO and ZrO band strengths, combined with V-K and J-K photometric indices, are used to select Teff, C/O, [Fe/H] and [s/Fe]. The Geneva U-B1 and B2-V1 indices (or any equivalent) are good at selecting the gravity. The defining spectral features of dwarf S stars are outlined, but none is found among the Henize S stars. More generally, it is found that, at Teff = 3200 K, a change of C/O from 0.5 to 0.99 has a strong impact on V-K (2 mag). Conversely, a range of 2 mag in V-K corresponds to a 200 K shift along the (Teff, V-K) relationship (for a fixed C/O value). Hence, the use of a (Teff, V-K) calibration established for M

  14. Age-rotation relationship for late-type main-sequence stars

    Science.gov (United States)

    Rengarajan, T. N.

    1984-01-01

    With advancing spectral type and increasing age, late main-sequence stars exhibit monotonic decrease in rotational velocity. It is of great interest to extend the rotation-age relationship to stars of later spectral type. In recent times it has become possible to measure directly the rotational periods from the photometric modulation by Ca II H and K line emission. There have also been successful attempts to relate the chromospheric activity as manifested through Ca II H and K lines to the rotation period, and it was shown that the fraction of total stellar luminosity in Ca II H and K lines, corrected for photospheric contribution, is a function of a single parameter related to P and B-V. In the present investigation, this rotation-activity relation is utilized to infer the rotation periods as a function of spectral type. The period versus B-V plot is employed as a basis to infer that the rotational period of main-sequence stars is a single-valued function of mass (B-V color) and age.

  15. The Na I D resonance lines in main sequence late-type stars

    CERN Document Server

    Díaz, Rodrigo F; Mauas, Pablo J D

    2007-01-01

    We study the sodium D lines (D1: 5895.92 \\AA; D2: 5889.95 \\AA) in late-type dwarf stars. The stars have spectral types between F6 and M5.5 (B-V between 0.457 and 1.807) and metallicity between [Fe/H] = -0.82 and 0.6. We obtained medium resolution echelle spectra using the 2.15-m telescope at the argentinian observatory CASLEO. The observations have been performed periodically since 1999. The spectra were calibrated in wavelength and in flux. A definition of the pseudo-continuum level is found for all our observations. We also define a continuum level for calibration purposes. The equivalent width of the D lines is computed in detail for all our spectra and related to the colour index (B-V) of the stars. When possible, we perform a careful comparison with previous studies. Finally, we construct a spectral index (R_D') as the ratio between the flux in the D lines, and the bolometric flux. We find that, once corrected for the photospheric contribution, this index can be used as a chromospheric activity indicator...

  16. Looking for activity cycles in late-type Kepler stars using time-frequency analysis

    CERN Document Server

    Vida, K; Szabó, R

    2014-01-01

    We analyse light curves covering four years of 39 fast-rotating ($P_\\mathrm{rot}< 1d$) late-type active stars from the Kepler database. Using time-frequency analysis (Short-Term Fourier-Transform), we find hints for activity cycles of 300-900 days at 9 targets from the changing typical latitude of the starspots, which, with the differential rotation of the stellar surface change the observed rotation period over the activity cycle. We also give a lowest estimation for the shear parameter of the differential rotation, which is ~0.001 for the cycling targets. These results populate the less studied, short period end of the rotation-cycle length relation.

  17. The delta upsilon = 1 fundamental bands of carbon monoxide in late-type stars

    Science.gov (United States)

    Wiedemann, G.; Ayres, T.; Saar, S.; Jennings, D.

    1987-01-01

    A program was begun to develop the fundamental vibration-rotation bands of CO near 4.7 micron, as a tool to investigate the properties of late type stellar atmospheres. The strong delta v = 1 lines are sensitive probes of the thermal structure of the outer layers, which can be strongly affected by the CO, itself: cooling in the fundamental lines can depress the surface temperature to low values that are in sharp contrast with those derived from chromospheric diagnostics like Ca II K and Mg II k. Cool atmospheric models are being constructed to reproduce observed high resolution CO spectra of several late-type stars. The sensitivity is illustrated of CO LTE spectra to variations in T sub eff, log g, (Fe/H), and isotopic abundances of C and O for a grid of such models. In parallel, the assumptions of LTE line formation are tested using newly available cross sections for translational-to-vibrational energy exchange in collisions of atomic H on CO. In addition, spectra of CO and Ca II K calculated from semi-empirical UV based hot chromospheric models are used to estimate geometrical filling factors for the CO dominated and chromospheric regions on the stellar surface, in the spirit of Ayres' thermal bifurcation scenario.

  18. X ray observations of late-type stars using the ROSAT all-sky survey

    Science.gov (United States)

    Linsky, Jeffrey L.; Fleming, Thomas A.

    1992-03-01

    The ROSAT mission made the first x ray survey of the entire sky using an imaging detector. Although ROSAT is a joint NASA/German project and involves direct American participation during its second phase of pointed observations, the all-sky survey remains the sole property of the German investigators. NASA grant represented the first use of ROSAT data analysis funds to support direct American participation in the ROSAT all-sky survey. The project involved a collaborative agreement between the Joint Institute for Laboratory Astrophysics (JILA) and the Max-Planck-Institut fur Extraterrestrische Physik (MPE) where JILA supplied MPE with a post-doctoral research associate with experience in the field of stellar (coronal) x ray emission to work within their ROSAT group. In return, members of the cool star research group at JILA were given the opportunity to collaborate on projects involving ROSAT all-sky survey data. Both sides have benefitted (and still benefit) from this arrangement since MPE suffers from a shortage of researchers who are interested in x ray emission from 'normal' stars and white dwarfs. MPE has also drawn upon experience in optical identification of x ray sources from the Einstein Extended Medium Sensitivity Survey in planning their own identification strategies for the ROSAT all-sky survey. The JILA cool stars group has benefitted since access to all-sky survey data has expanded the scope of their already extensive research programs involving multiwavelength observations of late-type stars. ROSAT was successfully launched on 1 June 1990 and conducted the bulk of the survey from 30 July 1990 to 25 January 1991. Data gaps in the survey have subsequently been made up. At the time of this writing (February 1992), the survey data have been processed once with the Standard Analysis Software System (SASS). A second processing will soon begin with improvements made to the SASS to correct errors and bugs found while carrying out scientific projects with data

  19. 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 ...

  20. Ionization balance of Ti in the photospheres of the Sun and four late-type stars

    CERN Document Server

    Bergemann, Maria

    2011-01-01

    In this paper we investigate statistical equilibrium of Ti in the atmospheres of late-type stars. The Ti I/Ti II level populations are computed with available experimental atomic data, except for photoionization and collision induced transition rates, for which we have to rely on theoretical approximations. For the Sun, the NLTE line formation with adjusted H I inelastic collision rates and MAFAGS-OS model atmosphere solve the long-standing discrepancy between Ti I and Ti II lines. The NLTE abundances determined from both ionization stages agree within $0.01$ dex with each other and with the Ti abundance in C I meteorites. The Ti NLTE model does not perform similarly well for the metal-poor stars, overestimating NLTE effects in the atmospheres of dwarfs, but underestimating overionization for giants. Investigating different sources of errors, we find that only [Ti/Fe] ratios based on Ti II and Fe II lines can be safely used in studies of Galactic chemical evolution. To avoid spurious abundance trends with met...

  1. The initial period function of late-type binary stars and its variation

    CERN Document Server

    Kroupa, Pavel

    2011-01-01

    The variation of the period distribution function of late-type binaries is studied. It is shown that the Taurus--Auriga pre-main sequence population and the main sequence G dwarf sample do not stem from the same parent period distribution with better than 95 per cent confidence probability. The Lupus, Upper Scorpius A and Taurus--Auriga populations are shown to be compatible with being drawn from the same initial period function (IPF), which is inconsistent with the main sequence data. Two possible IPF forms are used to find parent distributions to various permutations of the available data which include Upper Scorpius B (UScB), Chameleon and Orion Nebula Cluster pre-main sequence samples. All the pre-main sequence samples studied here are consistent with the hypothesis that there exists a universal IPF which is modified through binary-star disruption if it forms in an embedded star cluster leading to a general decline of the observed period function with increasing period. The pre-main sequence data admit a ...

  2. Is there a compact companion orbiting the late O-type binary star HD 164816?

    CERN Document Server

    Trepl, L; Pribulla, T; Tetzlaff, N; Chini, R; Neuhäuser, R; Popov, S B; Stahl, O; Walter, F M; Hohle, M M

    2012-01-01

    We present a multi-wavelength (X-ray, $\\gamma$-ray, optical and radio) study of HD 194816, a late O-type X-ray detected spectroscopic binary. X-ray spectra are analyzed and the X-ray photon arrival times are checked for pulsation. In addition, newly obtained optical spectroscopic monitoring data on HD 164816 are presented. They are complemented by available radio data from several large scale surveys as well as the \\emph{FERMI} $\\gamma$-ray data from its \\emph{Large Area Telescope}. We report the detection of a low energy excess in the X-ray spectrum that can be described by a simple absorbed blackbody model with a temperature of $\\sim$ 50 eV as well as a 9.78 s pulsation of the X-ray source. The soft X-ray excess, the X-ray pulsation, and the kinematical age would all be consistent with a compact object like a neutron star as companion to HD 164816. The size of the soft X-ray excess emitting area is consistent with a circular region with a radius of about 7 km, typical for neutron stars, while the emission m...

  3. 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.

  4. 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.

  5. The centimeter radio continuum from IRC + 10216 and other late-type stars with mass-loss envelopes

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, R. (Chalmers Univ. of Tech., Goeteborg (SE). Inst. of Theoretical Physics); Claussen, M.J. (Hulburt (E.O.) Center for Space Research, Washington, DC (US)); Sahai, R.; Claussen, M.J.; Masson, C.R. (California Inst. of Tech., Pasadena CA (US). Owens Valley Radio Observatory)

    1989-08-01

    We report the discovery of continuum emission at 1.5 and 2 cm from the late-type carbon star IRC + 10216 (CW Leo). We discuss various mechanisms for the production of the centimeter continuum emission from IRC + 10216. We find that the combination of emission from circumstellar dust (with a constant emissivity index) and a stellar black-body cannot account for the observed radio fluxes, given current estimates of the long-wavelength dust emissivity index. This leads to possible implications for the centimeter dust emissivity or the evolutionary status of this object. The results of a survey of 1.5 cm emission from a list of late-type stars (and proto-planetary nebulae) with extensive mass-loss envelopes, are reported.

  6. On the new late B- and early A-type periodic variable stars

    CERN Document Server

    Mowlavi, Nami; Barblan, Fabio; Eyer, Laurent

    2013-01-01

    We summarize the properties of the new periodic, small amplitude, variable stars recently discovered in the open cluster NGC 3766. They are located in the region of the Hertzsprung-Russell diagram between \\delta\\ Sct and slowly pulsating B stars, a region where no sustained pulsation is predicted by standard models. The origin of their periodic variability is currently unknown. We also discuss how the Gaia mission, to be launched at the end of 2013, can contribute to our knowledge of those stars.

  7. A grid of MARCS model atmospheres for late-type stars I. Methods and general properties

    CERN Document Server

    Gustafsson, Bengt; Eriksson, Kjell; Jorgensen, Uffe Graae; Nordlund, Aake; Plez, Bertrand

    2008-01-01

    We have constructed a grid of about 10,000 spherically symmetric and plane-parallel models with the MARCS program, and make it available for public use. Parameter ranges are: Teff=2500 to 8000 K, log g =log(GM/R2)= -1 to 5 (cgs) with various masses and radii, [Me/H]=-5 to +1, with [Alpha/Fe] = 0.0 and 0.4 and different choices of C and N abundances to also represent stars of types R, S and N, and with microturbulence parameters from 1 to 5 km/s. We also list fluxes in approximately 108,000 wavelength points. Underlying assumptions in addition to 1D stratification include hydrostatic equilibrium, MLT convection and LTE. A number of general properties of the models are discussed, in relation to the effects of changing blanketing and sphericity. Models are compared with other available grids and excellent agreement is found with plane-parallel models of Castelli and Kurucz within the overlapping parameter range. Although there are departures from the spherically symmetric NextGen models, the agreement with more ...

  8. SPECTRAL TYPING OF LATE-TYPE STELLAR COMPANIONS TO YOUNG STARS FROM LOW-DISPERSION NEAR-INFRARED INTEGRAL FIELD UNIT DATA

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Lewis C.; Beichman, Charles A.; Burruss, Rick; Ligon, E. Robert; Lockhart, Thomas G.; Roberts, Jennifer E.; Shao, Michael [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Rice, Emily L.; Brenner, Douglas; Oppenheimer, Ben R. [American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Crepp, Justin R.; Dekany, Richard G.; Hillenbrand, Lynne A.; Hinkley, Sasha [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); King, David; Parry, Ian R. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Metchev, Stanimir [Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794-3800 (United States); Pueyo, Laurent; Sivaramakrishnan, Anand; Soummer, Remi, E-mail: lewis.c.roberts@jpl.nasa.gov [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2012-07-15

    We used the Project 1640 near-infrared coronagraph and integral field spectrograph to observe 19 young solar-type stars. Five of these stars are known binary stars and we detected the late-type secondaries and were able to measure their JH spectra with a resolution of R {approx} 30. The reduced, extracted, and calibrated spectra were compared to template spectra from the IRTF spectral library. With this comparison, we test the accuracy and consistency of spectral-type determination with the low-resolution near-infrared spectra from P1640. Additionally, we determine effective temperature and surface gravity of the companions by fitting synthetic spectra calculated with the PHOENIX model atmosphere code. We also present several new epochs of astrometry of each of the systems. Together, these data increase our knowledge and understanding of the stellar make up of these systems. In addition to the astronomical results, the analysis presented helps validate the Project 1640 data reduction and spectral extraction processes and the utility of low-resolution, near-infrared spectra for characterizing late-type companions in multiple systems.

  9. Atomic and molecular hydrogen in the circumstellar envelopes of late-type stars

    Science.gov (United States)

    Glassgold, A. E.; Huggins, P. J.

    1983-01-01

    The distribution of atomic and molecular hydrogen in the expanding circumstellar envelopes of cool evolved stars is discussed. The main concern is to evaluate the effects of photodestruction of H2 by galactic UV radiation, including shielding of the radiation by H2 itself and by dust in the envelope. One of the most important parameters is the H/H2 ratio which is frozen out in the upper atmosphere of the star. For stars with photospheric temperatures greater than about 2500 K, atmospheric models suggest that the outflowing hydrogen is mainly atomic, whereas cooler stars should be substantially molecular. In the latter case, photodissociation of H2 and heavy molecules contribute to the atomic hydrogen content of the outer envelope. The presented estimates indicate that atomic hydrogen is almost at the limit of detection in the C-rich star IRC + 10216, and may be detectable in warmer stars. Failure to detect it would have important implications for the general understanding of circumstellar envelopes.

  10. VizieR Online Data Catalog: Spectroscopic orbits for 15 late-type stars (Willmarth+, 2016)

    Science.gov (United States)

    Willmarth, D. W.; Fekel, F. C.; Abt, H. A.; Pourbaix, D.

    2016-09-01

    The radial velocities used here are mainly from four sources: those obtained during the aforementioned work of Abt & Willmarth 2006 (Cat. J/ApJS/162/207), an earlier survey of solar-type stars (1986-1990, Julian Days 2546708-2550885) reported in Abt & Willmarth (1992ASPC...32...82A), subsequent observations by the first author (DW) using the same spectrograph, and observations by the second author (FF) that were acquired at Fairborn Observatory (Fekel et al. 2009AJ....137.3900F). The observations of Abt & Willmarth 2006 (Cat. J/ApJS/162/207) were obtained with the Kitt Peak National Observatory (KPNO) 0.9m auxillary coude feed telescope and the coude spectrograph, which was originally built for the KPNO 2.1m telescope. The observations reported in Abt & Willmarth (1992ASPC...32...82A) employed the same equipment, except the "B" grating was used yielding approximately half the resolution used in Abt & Willmarth 2006 (Cat. J/ApJS/162/207). Subsequent observations obtained by DW used either the "A" grating as in Abt & Willmarth 2006 (Cat. J/ApJS/162/207) or a 31.6grooves/mm echelle grating cross-dispersed by grisms. The latter combination yields a resolving power λ/Δλ=72000 for 2 pixels. Spectroscopic observations with the 2m Tennessee State University telescope and fiber-fed echelle spectrograph at Fairborn Observatory in southeast Arizona were described in detail in Fekel et al. 2015 (Cat. J/AJ/149/63), and provide the majority of the more recent radial velocities. (3 data files).

  11. A grid of NLTE corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia

    CERN Document Server

    Merle, Thibault; Pichon, Bernard; Bigot, Lionel

    2011-01-01

    We investigate NLTE effects for magnesium and calcium in the atmospheres of late-type giant and supergiant stars. The aim of this paper is to provide a grid of NLTE/LTE equivalent width ratios W/W* of Mg and Ca lines for the following range of stellar parameters: Teff in [3500, 5250] K, log g in [0.5, 2.0] dex and [Fe/H] in [-4.0, 0.5] dex. We use realistic model atoms with the best physics available and taking into account the fine structure. The Mg and Ca lines of interest are in optical and near IR ranges. A special interest concerns the lines in the Gaia spectrograph (RVS) wavelength domain [8470, 8740] A. The NLTE corrections are provided as function of stellar parameters in an electronic table as well as in a polynomial form for the Gaia/RVS lines.

  12. Know the Star, Know the Planet. III. Discovery of Late-Type Companions to Two Exoplanet Host Stars

    CERN Document Server

    Roberts,, Lewis C; Mason, Brian D; Riddle, Reed L; Hartkopf, William I; Law, Nicholas M; Baranec, Christoph

    2015-01-01

    We discuss two multiple star systems that host known exoplanets: HD 2638 and 30 Ari B. Adaptive optics imagery revealed an additional stellar companion to both stars. We collected multi-epoch images of the systems with Robo-AO and the PALM-3000 adaptive optics systems at Palomar Observatory and provide relative photometry and astrometry. The astrometry indicates that the companions share common proper motion with their respective primaries. Both of the new companions have projected separations less than 30 AU from the exoplanet host star. Using the projected separations to compute orbital periods of the new stellar companions, HD 2638 has a period of 130 yrs and 30 Ari B has a period of 80 years. Previous studies have shown that the true period is most likely within a factor of three of these estimated values. The additional component to the 30 Ari makes it the second confirmed quadruple system known to host an exoplanet. HD 2638 hosts a hot Jupiter and the discovery of a new companion strengthens the connect...

  13. Rotation periods of late-type stars in the young open cluster IC 2602

    CERN Document Server

    Barnes, S A; Prosser, C F; Stauffer, J R; Barnes, Sydney A.; Sofia, Sabatino; Prosser, Charles F.; Stauffer, John R.

    1999-01-01

    We present the results of a monitoring campaign aimed at deriving rotation periods for a representative sample of stars in the young (30 Myr) open cluster IC 2602. Rotation periods were derived for 29 of 33 stars monitored. The periods derived range from 0.2d (one of the shortest known rotation periods of any single open cluster star) to about 10d (which is almost twice as long as the longest period previously known for a cluster of this age). We are able to confirm 8 previously known periods and derive 21 new ones, delineating the long period end of the distribution. Despite our sensitivity to longer periods, we do not detect any variables with periods longer than about 10d. The combination of these data with those for IC 2391, an almost identical cluster, leads to the following conclusions: 1) The fast rotators in a 30 Myr cluster are distributed across the entire 0.5 < B-V < 1.6 color range. 2) 6 stars in our sample are slow rotators, with periods longer than 6d. 3) The amplitude of variability depen...

  14. A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden Lines in Late-Type Stars

    CERN Document Server

    Redfield, S; Linsky, J L; Ake, T B; Dupree, A K; Robinson, R D; Young, P R; Redfield, Seth; Ayres, Thomas R.; Linsky, Jeffrey L.; Ake, Thomas B.; Robinson, Richard D.; Young, Peter R.

    2002-01-01

    We present a survey of coronal forbidden lines detected in Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of nearby stars. Two strong coronal features, Fe XVIII 974 A and Fe XIX 1118 A, are observed in 10 of the 26 stars in our sample. Various other coronal forbidden lines, observed in solar flares, also were sought but not detected. The Fe XVIII feature, formed at log T (K) = 6.8, appears to be free of blends, whereas the Fe XIX line can be corrupted by a C I multiplet. FUSE observations of these forbidden iron lines at spectral resolution R ~ 15,000 provides the opportunity to study dynamics of hot coronal plasmas. We find that the velocity centroid of the Fe XVIII feature deviates little from the stellar rest frame, confirming that the hot coronal plasma is confined. The observed line widths generally are consistent with thermal broadening at the high temperatures of formation and show little indication of additional turbulent broadening. The fastest rotating stars, 31 Com, alpha Aur Ab, and AB Dor,...

  15. High resolution spectroscopy of two young active late type stars within 20 parsecs of the Sun

    Institute of Scientific and Technical Information of China (English)

    Hui-Juan Wang; Jian-Yan Wei

    2009-01-01

    We present high-resolution optical echell spectroscopy of HIP 544 and HIP 46843, two nearby solar like stars. The discovery of these young stars at such a close distance to the Sun is really a surprising phenomenon. It will help us to have a better understanding of the structure and evolutionary history of the Milky Way. The radial ve-locities (RV) of HIP 544 and HIP 46843 are measured to be -6.88±0.13km s-1 and 8.30±0.16km s-1, respectively, which are more accurate than before. The equivalent widths (EW) of the Li I 6707.8 A absorption line of HIP 544 and HIP 46843 are mea-sured to be 110±5mA and 195±5mA respectively. Based on these properties, HIP 544 is estimated to be 100-800Myr old and HIP 46843 30-100Myr old using three relatively creditable methods.

  16. Non-LTE modeling of the near UV band of late-type stars

    CERN Document Server

    Short, C Ian

    2008-01-01

    We investigate the ability of both LTE and Non-LTE models to fit the near UV band absolute flux distribution and individual spectral line profiles of three standard stars for which high quality spectrophotometry and high resolution spectroscopy are available: The Sun (G2 V), Arcturus (K2 III), and Procyon (F5 IV-V). We investigate 1) the effect of the choice of atomic line list on the ability of NLTE models to fit the near UV band flux level, 2) the amount of a hypothesized continuous thermal absorption extinction source required to allow NLTE models to fit the observations, and 3) the semi-empirical temperature structure required to fit the observations with NLTE models and standard continuous near UV extinction. We find that all models that are computed with high quality atomic line lists predict too much flux in the near UV band for Arcturus, but fit the warmer stars well. The variance among independent measurements of the solar irradiance in the near UV is sufficiently large that we cannot definitely conc...

  17. Doppler Imaging of Young Late-Type Stars: HII 686, HII 3163, and P1724

    Science.gov (United States)

    Stout-Batalha, Natalie Marie

    Maximum entropy image reconstruction (Doppler imaging) is applied to HII 686 (K4V, v sin i=64 km s-1) and HII 3163 (K0, v sin i=70 km s-1), two zero-age main sequence stars of the Pleiades cluster, and the weak-lined T Tauri star Parenago 1724 (K0, v sin i=71 km s-1). Their surface temperature distributions are determined in order to study the nature of magnetic activity in young ultra-fast rotators. Specific intensity line profiles used in the DI algorithm are synthesized. The sensitivity of the reconstructions to the choice of input stellar and atomic data is investigated. The quality of the fit to the average disk integrated line profile is found to be more important to DI analysis than the exact parameters used to generate the fit when the shape of the disk integrated line profile is dominated by rotational broadening. Fifteen absorption lines are used to generate fifteen individual reconstructions of each Pleiades target. Averaging reduces noise in the reconstructions. However, spurious features can persist at sub-observer longitudes. Such 'phase-ghosting' can largely be eliminated by including broad-band photometric observations in the analysis. Using the large number of reconstructions for a given star, uncertainties in the images are estimated. HII 686 shows one predominant feature at 77o latitude which is 700 K cooler than the surrounding photosphere. HII 3163 also shows one predominant feature centered at approximately 70o latitude. A spot temperature 1000 K cooler than the photosphere best reproduces the observations. P1724 shows a predominant feature (or features) centered at 30o latitude which is 800 K cooler than its photosphere. These results are discussed in light of recent theoretical observations and existing image reconstructions of similar objects. No correlations are found among reconstructions which could be attributed to line characteristics: equivalent width, excitation potential or depth of formation. This is also true for the LiI and KI

  18. On the interpretation of new late B- and early A-type periodic variable stars in NGC 3766

    CERN Document Server

    Mowlavi, N; Barblan, F; Eyer, L

    2013-01-01

    We investigate possible interpretations of the new periodic B- and A-type variable stars discovered in NGC 3766. They lie in the region of the Hertzsprung-Russell diagram between slowly pulsating B and delta Sct stars, a region where no pulsation is predicted by standard models of pulsating stars. We show that the two other possible causes of periodic light curve variations, rotational modulation and binarity, cannot provide a satisfactory explanation for all the properties observed in those stars either. The question of their origin is thus currently an open issue.

  19. Effects of Scattering on the Temperature Stratification in 3D Model Atmospheres of Late-Type Stars

    Science.gov (United States)

    Collet, R.; Hayek, W.; Asplund, M.

    2011-12-01

    Three-dimensional (3D) radiative hydrodynamic model atmospheres of metal-poor late-type stars predict cooler upper photospheric stratifications than their one-dimensional (1D) counterparts. This property of 3D model atmospheres affects the determination of elemental abundances from temperature-sensitive spectral features, with important consequences for galactic chemical evolution studies. In this contribution, we investigate the impact of different approximations of scattering in the solution of the radiative transfer equation on the temperature stratification of 3D model atmospheres of metal-poor red giants. We use the BIFROST code to construct 3D model atmospheres of metal-poor red giants using three different approximations of scattering. First, we self-consistently solve the radiative transfer equation for the general case of a source function with a coherent scattering term; second, we solve the radiative transfer equation assuming a Planckian source function and neglecting altogether the contribution of continuum scattering to extinction in the optically thin layers; third, we assume a Planckian source function and treat continuum scattering as pure absorption everywhere in the simulation's domain. We find that the second approach produces very similar temperature structures with cool upper photospheric layers as when treating scattering correctly, and at a much lower computational cost. In contrast, treating scattering as pure absorption leads to significantly hotter and shallower temperature stratifications.

  20. WASP-39b: a highly inflated Saturn-mass planet orbiting a late G-type star

    CERN Document Server

    Faedi, F; Anderson, D R; Brown, D J A; Cameron, A Collier; Pollacco, D; Boisse, I; Hebrard, G; Lendl, M; Lister, T A; Smalley, B; Street, R A; Triaud, A H M J; Bento, J; Butters, O W; Enoch, B; Bouchy, F; Haswell, C A; Hellier, C; Keenan, F P; Miller, G R M; Moulds, V; Moutou, C; Norton, A J; Queloz, D; Santerne, A; Simpson, E K; Skillen, I; Smith, A M S; Udry, S; Watson, C A; West, R G; Wheatley, P J

    2011-01-01

    We present the discovery of WASP-39b, a highly inflated transiting Saturn-mass planet orbiting a late G-type dwarf star with a period of 4.055259$\\pm0.000008$~d, Transit Epoch T$_{0}=2455342.9688\\pm0.0002$(HJD), of duration 0.1168$\\pm0.0008$~d. A combined analysis of the WASP photometry, high-precision follow up transit photometry and radial velocities yield a planetary mass of $\\mpl=0.28\\pm0.03$~\\mj\\ and a radius of $\\rpl=1.27\\pm0.04$~\\rj, resulting in a mean density of 0.14$\\pm0.02$~\\rhoj. The stellar parameters are mass $\\mstar = 0.93\\pm0.03\\msun$, radius $\\rstar = 0.895\\pm0.23\\rsun$, and age $9^{+3}_{-4}$~Gyr. Only WASP-17b and WASP-31b have lower densities than WASP-39b, although they are slightly more massive and highly irradiated planets. We measure, from our spectral analysis, the metallicity of WASP-39 to be [Fe/H]= $-0.12\\pm0.01$ dex, and we find the planet to have an equilibrium temperature of $1116^{+33}_{-32}$~K; both values strengthen the observed empirical correlation between these parameters a...

  1. A close look at the Centaurus A group of galaxies III. Recent star formation histories of late-type dwarfs around M83

    CERN Document Server

    Crnojević, D; Cole, A A

    2011-01-01

    We study the resolved stellar populations of dwarf galaxies in the nearby Centaurus A/M83 group of galaxies. Our goal is to characterize their evolutionary history and to investigate eventual similarities or differences with the dwarf population in other group environments. This work presents the analysis of five late-type (irregular) dwarfs found in the vicinity of the giant spiral M83. Using archival HST/ACS data, we perform synthetic color-magnitude diagram modeling to derive the star formation histories of these late-type dwarfs. The target objects show heterogeneous star formation histories, with average star formation rates of 0.08 to 0.70x10^{-2} M_odot/yr. Some of them present prolonged, global bursts of star formation (~300-500 Myr). The studied galaxies are all metal-poor ([Fe/H] ~-1.4). We further investigate the spatial extent of different stellar populations, finding that the young stars show a clumpy distribution, as opposed to the smooth, broad extent of the old ones. The actively star forming ...

  2. Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\\beta$ CMi

    CERN Document Server

    Klement, R; Rivinius, T; Panoglou, D; Vieira, R G; Bjorkman, J E; Štefl, S; Tycner, C; Faes, D M; Korčáková, D; Müller, A; Zavala, R T; Curé, M

    2015-01-01

    The viscous decretion disk (VDD) model is able to explain most of the currently observable properties of the circumstellar disks of Be stars. However, more stringent tests, focusing on reproducing multitechnique observations of individual targets via physical modeling, are needed to study the predictions of the VDD model under specific circumstances. In the case of nearby, bright Be star $\\beta$ CMi, these circumstances are a very stable low-density disk and a late-type (B8Ve) central star. The aim is to test the VDD model thoroughly, exploiting the full diagnostic potential of individual types of observations, in particular, to constrain the poorly known structure of the outer disk if possible, and to test truncation effects caused by a possible binary companion using radio observations. We use the Monte Carlo radiative transfer code HDUST to produce model observables, which we compare with a very large set of multitechnique and multiwavelength observations that include ultraviolet and optical spectra, photo...

  3. Direct Imaging Discovery of a "Super-Jupiter" around the Late B-type Star κ And

    NARCIS (Netherlands)

    Carson, J.; et al., [Unknown; Thalmann, C.

    2013-01-01

    We present the direct imaging discovery of an extrasolar planet, or possible low-mass brown dwarf, at a projected separation of 55 ± 2 AU (1.''058 ± 0.''007) from the B9-type star κ And. The planet was detected with Subaru/HiCIAO during the SEEDS survey and confirmed as a bound companion via common

  4. DIRECT IMAGING DISCOVERY OF A 'SUPER-JUPITER' AROUND THE LATE B-TYPE STAR {kappa} And

    Energy Technology Data Exchange (ETDEWEB)

    Carson, J.; Kozakis, T.; Stevens, L.; Wong, P.; Gainey, K. [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); Thalmann, C.; Bonnefoy, M.; Biller, B.; Schlieder, J.; Henning, T.; Brandner, W.; Feldt, M. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Janson, M. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Currie, T.; McElwain, M. [ExoPlanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Goto, M. [Young Stars and Star Formation Universitaets-Sternwarte Muenchen, Ludwig-Maximilians-Universitaet, D-81679 Muenchen (Germany); Kandori, R.; Kuzuhara, M. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Fukagawa, M.; Kuwada, Y. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); and others

    2013-02-01

    We present the direct imaging discovery of an extrasolar planet, or possible low-mass brown dwarf, at a projected separation of 55 {+-} 2 AU (1.''058 {+-} 0.''007) from the B9-type star {kappa} And. The planet was detected with Subaru/HiCIAO during the SEEDS survey and confirmed as a bound companion via common proper motion measurements. Observed near-infrared magnitudes of J = 16.3 {+-} 0.3, H = 15.2 {+-} 0.2, K{sub s} = 14.6 {+-} 0.4, and L' = 13.12 {+-} 0.09 indicate a temperature of {approx}1700 K. The galactic kinematics of the host star are consistent with membership in the Columba Association, implying a corresponding age of 30{sup +20}{sub -10} Myr. The system's age, combined with the companion photometry, points to a model-dependent companion mass {approx}12.8 M{sub Jup}. The host star's estimated mass of 2.4-2.5 M{sub Sun} places it among the most massive stars ever known to harbor an extrasolar planet or low-mass brown dwarf. While the mass of the companion is close to the deuterium burning limit, its mass ratio, orbital separation, and likely planet-like formation scenario imply that it may be best defined as a 'super-Jupiter' with properties similar to other recently discovered companions to massive stars.

  5. The Green Valley is a Red Herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies

    CERN Document Server

    Schawinski, Kevin; Simmons, Brooke D; Fortson, Lucy; Kaviraj, Sugata; Keel, William C; Lintott, Chris J; Masters, Karen L; Nichol, Robert C; Sarzi, Marc; Ramin,; Skibba,; Treister, Ezequiel; Willett, Kyle W; Wong, O Ivy; Yi, Sukyoung K

    2014-01-01

    We use SDSS+\\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disk to spheroid and star formation is quenched rapidly. In contrast, the majority of blue star-forming galaxies have significant disks, and they retain their late-type morphologies as their star formation rates decline very slowly. We summarize a range of observations that lead to these conclusions, including UV-optical colours and halo masses, which both show a striking dependence on morphological type. We interpret these results in terms of the evolution of co...

  6. Direct Imaging Discovery of a `Super-Jupiter' Around the late B-Type Star Kappa And

    CERN Document Server

    Carson, J; Janson, M; Kozakis, T; Bonnefoy, M; Biller, B; Schlieder, J; Currie, T; McElwain, M; Goto, M; Henning, T; Brandner, W; Feldt, M; Kandori, R; Kuzuhara, M; Stevens, L; Wong, P; Gainey, K; Fukagawa, M; Kuwada, Y; Brandt, T; Kwon, J; Abe, L; Egner, S; Grady, C; Guyon, O; Hashimoto, J; Hayano, Y; Hayashi, M; Hayashi, S; Hodapp, K; Ishii, M; Iye, M; Knapp, G; Kudo, T; Kusakabe, N; Matsuo, T; Miyama, S; Morino, J; Moro-Martin, A; Nishimura, T; Pyo, T; Serabyn, E; Suto, H; Suzuki, R; Takami, M; Takato, N; Terada, H; Turner, E; Watanabe, M; Wisniewski, J; Yamada, T; Takami, H; Usuda, T; Tamura, M

    2012-01-01

    We present the direct imaging discovery of an extrasolar planet, or possible low-mass brown dwarf, at a projected separation of 55 +/- 2 AU (1.058 +/- 0.007 arcsec) from the B9-type star Kappa And. The planet was detected with Subaru/HiCIAO during the SEEDS survey, and confirmed as a bound companion via common proper motion measurements. Observed near-infrared magnitudes of J = 16.3 +/- 0.3, H = 15.2 +/- 0.2, Ks = 14.6 +/- 0.4, and L' = 13.12 +/- 0.09 indicate a temperature of ~1700 K. The galactic kinematics of the host star are consistent with membership in the Columba association, implying a corresponding age of 30 +20 -10 Myr. The system age, combined with the companion photometry, points to a model-dependent companion mass ~12.8 MJup. The host star's estimated mass of 2.4-2.5 Msun places it among the most massive stars ever known to harbor an extrasolar planet or low-mass brown dwarf. While the mass of the companion is close to the deuterium burning limit, its mass ratio, orbital separation, and likely p...

  7. Progress report on the monitoring active late-type stars in 2005/2006 and the analysis of V523 Cas

    Directory of Open Access Journals (Sweden)

    Zboril M.

    2006-01-01

    Full Text Available We present the light curve analysis of late-type binary V523 Cas for the season 2005. The spot has been revealed on the secondary. According to theoretical considerations, the spot appeared to be hotter than the surrounding photosphere and located at middle latitudes (the radius 40º and latitude 48º. The light curves for other stars in the observational list (many of them again with O'Connell effect, for the same season, have been made electronically available. These objects are SV Cam, IV Dra, BI Vul, DD Com, 12 Cam and II Peg.

  8. A Super-Jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406

    CERN Document Server

    Tsapras, Y; Street, R A; Han, C; Bozza, V; Gould, A; Dominik, M; Beaulieu, J -P; Udalski, A; Jørgensen, U G; Sumi, T; Bramich, D M; Browne, P; Horne, K; Hundertmark, M; Ipatov, S; Kains, N; Snodgrass, C; Steele, I A; Alsubai, K A; Andersen, J M; Novati, S Calchi; Damerdji, Y; Diehl, C; Elyiv, A; Giannini, E; Hardis, S; Harpsøe, K; Hinse, T C; Juncher, D; Kerins, E; Korhonen, H; Liebig, C; Mancini, L; Mathiasen, M; Penny, M T; Rabus, M; Rahvar, S; Scarpetta, G; Skottfelt, J; Southworth, J; Surdej, J; Tregloan-Reed, J; Vilela, C; Kozłowski, J Wambsganss S; Kubiak, M; Pietrukowicz, P; Pietrzyński, G; Poleski, R; Skowron, J; Soszyński, I; Szymański, M K; Ulaczyk, K; Albrow, Łukasz Wyrzykowski M D; Bachelet, E; Barry, R; Batista, V; Bhattacharya, A; Brillant, S; Caldwell, J A R; Cassan, A; Cole, A; Corrales, E; Coutures, Ch; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Greenhill, J; Kane, S R; Kubas, D; Marquette, J -B; Martin, R; Menzies, J; Pollard, K R; Williams, A; Wouters, D; Christie, G; DePoy, D L; Dong, S; Drummond, J; Gaudi, B S; Henderson, C B; Hwang, K H; Jung, Y K; Kavka, A; Koo, J -R; Lee, C -U; Maoz, D; Monard, L A G; Natusch, T; Ngan, H; Park, H; Pogge, R W; Porritt, I; Shin, I -G; Shvartzvald, Y; Tan, T G; Yee, J C; Abe, F; Bennett, D P; Bond, I A; Botzler, C S; Freeman, M; Fukui, A; Fukunaga, D; Itow, Y; Koshimoto, N; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Namba, S; Ohnishi, K; Rattenbury, N J; Saito, To; Sullivan, D J; Sweatman, W L; Suzuki, D; Tristram, P J; Tsurumi, N; Wada, K; Yamai, N; Yonehara, P C M Yock A

    2013-01-01

    We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a $2.73\\pm 0.43\\ M_{\\rm J}$ planet orbiting a $0.44\\pm 0.07\\ M_{\\odot}$ early M-type star. The distance to the lens is $4.97\\pm 0.29$\\ kpc and the projected separation between the host star and its planet at the time of the event is $3.45\\pm 0.26$ AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens.

  9. A super-jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406

    Energy Technology Data Exchange (ETDEWEB)

    Tsapras, Y.; Street, R. A. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Choi, J.-Y.; Han, C. [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Bozza, V. [Dipartimento di Fisica " E. R. Caianiello," Università di Salerno, Via Giovanni Paolo II n. 132, I-84084 Fisciano (Italy); Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Dominik, M.; Browne, P.; Horne, K.; Hundertmark, M. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Beaulieu, J.-P. [UPMC-CNRS, UMR7095, Institut d' Astrophysique de Paris, 98bis boulevard Arago, F-75014 Paris (France); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Jørgensen, U. G. [Niels Bohr Institute, Astronomical Observatory, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Bramich, D. M.; Kains, N. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany); Ipatov, S.; Alsubai, K. A. [Qatar Foundation, P.O. Box 5825, Doha (Qatar); Snodgrass, C. [Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany); Steele, I. A. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool CH41 1LD (United Kingdom); Collaboration: RoboNet Collaboration; MiNDSTEp Collaboration; OGLE Collaboration; PLANET Collaboration; μFUN Collaboration; MOA Collaboration; and others

    2014-02-10

    We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the light curve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a 2.73 ± 0.43 M {sub J} planet orbiting a 0.44 ± 0.07 M {sub ☉} early M-type star. The distance to the lens is 4.97 ± 0.29 kpc and the projected separation between the host star and its planet at the time of the event is 3.45 ± 0.26 AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens.

  10. Photometric and spectroscopic observations of three rapidly rotating late-type stars: EY Dra, V374 Peg and GSC 02038-00293

    CERN Document Server

    Korhonen, H; Husarik, M; Mahajan, S; Szczygiel, D; Olah, K

    2010-01-01

    Here, BV(RI)c broad band photometry and intermediate resolution spectroscopy in Halpha region are presented for two rapidly rotating late-type stars: EY Dra and V374 Peg. For a third rapid rotator, GSC 02038-00293, intermediate resolution Halpha spectroscopy and low resolution spectroscopy are used for spectral classification and stellar parameter investigation of this poorly known object. The low resolution spectrum of GSC 02038-00293 clearly indicates that it is a K-type star. Its intermediate resolution spectrum can be best fitted with a model with Teff=4750K and vsini=90km/s, indicating a very rapidly rotating mid-K star. The Halpha line strength is variable, indicating changing chromospheric emission on GSC 02038-00293. In the case of EY Dra and V374 Peg, the stellar activity in the photosphere is investigated from the photometric observations, and in the chromosphere from the Halpha line. The enhanced chromospheric emission in EY Dra correlates well with the location of the photospheric active regions, ...

  11. A non-LTE study of neutral and singly-ionized calcium in late-type stars

    Science.gov (United States)

    Mashonkina, L.; Korn, A. J.; Przybilla, N.

    2007-01-01

    Aims:Non-local thermodynamical equilibrium (NLTE) line formation for neutral and singly-ionized calcium is considered through a range of spectral types when the Ca abundance varies from the solar value down to [Ca/H] = -5. We evaluate the influence of departures from LTE on Ca abundance determinations and inspect the possibility of using Ca I / Ca II line-strength ratios as indicators of surface gravity for extremely metal-poor stars. Methods: A comprehensive model atom for Ca I and Ca II is presented. Accurate radiative and electron collisional atomic data are incorporated. The role of inelastic collisions with hydrogen atoms in the statistical equilibrium of Ca I/II is estimated empirically from inspection of their different influences on the Ca I and Ca II lines in selected stars with well determined stellar parameters and high-quality observed spectra. Results: The dependence of NLTE effects on the atmospheric parameters is discussed. Departures from LTE significantly affect the profiles of Ca I lines over the whole range of stellar parameters being considered. However, at [Ca/H] ≥ -2, NLTE abundance correction of individual lines have a low absolute value due to the different influence of NLTE effects on line wings and the line core. At lower Ca abundances, NLTE leads to systematically depleted total absorption in the line and positive abundance corrections, exceeding +0.5 dex for Ca I λ 4226 at [Ca/H] = -4.9. In contrast, the NLTE effects strengthen the Ca II lines and lead to negative abundance corrections. NLTE corrections are small, ≤0.02 dex, for the Ca II resonance lines, and they grow in absolute value with decreasing Ca abundance for the IR lines of multiplet 3d-4p, exceeding 0.4 dex in the metal-poor models with [Fe/H] ≤ -3. As a test and first application of the Ca I/II model atom, Ca abundances are determined on the basis of plane-parallel LTE model atmospheres for the Sun, Procyon (F IV-V), and seven metal-poor stars, using high S/N and high

  12. NLTE analysis of Sr lines in spectra of late-type stars with new R-matrix atomic data

    CERN Document Server

    Bergemann, M; Bautista, M; Ruchti, G

    2012-01-01

    We investigate statistical equilibrium of neutral and singly-ionized strontium in late-type stellar atmospheres. Particular attention is given to the completeness of the model atom, which includes new energy levels, transition probabilities, photoionization and electron-impact excitation cross-sections computed with the R-matrix method. The NLTE model is applied to the analysis of Sr I and Sr II lines in the spectra of the Sun, Procyon, Arcturus, and HD 122563, showing a significant improvement in the ionization balance compared to LTE line formation calculations, which predict abundance discrepancies of up to 0.5 dex. The solar Sr abundance is log A = 2.93 \\pm 0.04 dex, in agreement with the meteorites. A grid of NLTE abundance corrections for Sr I and Sr II lines covering a large range of stellar parameters is presented.

  13. A non-LTE study of neutral and singly-ionized calcium in late-type stars

    CERN Document Server

    Mashonkina, L I; Przybilla, N

    2006-01-01

    Non-local thermodynamical equilibrium (NLTE) line formation for neutral and singly-ionized calcium is considered through a range of spectral types when the Ca abundance varies from the solar value down to [Ca/H] = -5. Departures from LTE significantly affect the profiles of Ca I lines over the whole range of stellar parameters considered. However, at [Ca/H] >= -2, NLTE abundance correction of individual lines may be small in absolute value due to the different influence of NLTE effects on line wings and the line core. At lower Ca abundances, NLTE leads to systematically depleted total absorption in the line and positive abundance corrections, exceeding +0.5 dex for Ca I 4226 at [Ca/H] = -4.9. In contrast, NLTE effects strengthen the Ca II lines and lead to negative abundance corrections. NLTE corrections are small, <= 0.02 dex, for the Ca II resonance lines. For the IR lines of multiplet 3d - 4p, they grow in absolute value with decreasing Ca abundance exceeding 0.4 dex in metal-poor stars with [Fe/H] <...

  14. BANYAN. V. A SYSTEMATIC ALL-SKY SURVEY FOR NEW VERY LATE-TYPE LOW-MASS STARS AND BROWN DWARFS IN NEARBY YOUNG MOVING GROUPS

    Energy Technology Data Exchange (ETDEWEB)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Malo, Lison; Artigau, Étienne [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada)

    2015-01-10

    We present the BANYAN All-Sky Survey (BASS) catalog, consisting of 228 new late-type (M4-L6) candidate members of nearby young moving groups (YMGs) with an expected false-positive rate of ∼13%. This sample includes 79 new candidate young brown dwarfs and 22 planetary-mass objects. These candidates were identified through the first systematic all-sky survey for late-type low-mass stars and brown dwarfs in YMGs. We cross-matched the Two Micron All Sky Survey and AllWISE catalogs outside of the galactic plane to build a sample of 98,970 potential ≥M5 dwarfs in the solar neighborhood and calculated their proper motions with typical precisions of 5-15 mas yr{sup –1}. We selected highly probable candidate members of several YMGs from this sample using the Bayesian Analysis for Nearby Young AssociatioNs II tool (BANYAN II). We used the most probable statistical distances inferred from BANYAN II to estimate the spectral type and mass of these candidate YMG members. We used this unique sample to show tentative signs of mass segregation in the AB Doradus moving group and the Tucana-Horologium and Columba associations. The BASS sample has already been successful in identifying several new young brown dwarfs in earlier publications, and will be of great interest in studying the initial mass function of YMGs and for the search of exoplanets by direct imaging; the input sample of potential close-by ≥M5 dwarfs will be useful to study the kinematics of low-mass stars and brown dwarfs and search for new proper motion pairs.

  15. AO Vel: The role of multiplicity in the development of chemical peculiarities in late B-type stars

    CERN Document Server

    González, J F; Castelli, F; 10.1111/j.1365-2966.2009.16061.x

    2010-01-01

    We present high-resolution, high signal-to-noise UVES spectra of AO Vel, a quadruple system containing an eclipsing BpSi star. From these observations we reconstruct the spectra of the individual components and perform an abundance analysis of all four stellar members. We found that all components are chemically peculiar with different abundances patters. In particular, the two less massive stars show typical characteristics of HgMn stars. The two most massive stars in the system show variable line profiles indicating the presence of chemical spots. Given the youth of the system and the notable chemical peculiarities of their components, this system could give important insights in the origin of chemical anomalies.

  16. The UVJ Selection of Quiescent and Star Forming Galaxies: Separating Early and Late-Type Galaxies and Isolating Edge-on Spirals

    CERN Document Server

    Patel, Shannon G; Kelson, Daniel D; Franx, Marijn; van der Wel, Arjen; Illingworth, Garth D

    2011-01-01

    We utilize for the first time HST ACS imaging to examine the structural properties of galaxies in the rest-frame U-V versus V-J diagram (i.e., the UVJ diagram) using a sample at 0.610.25). The use of the UVJ diagram as a tool to distinguish quiescent galaxies from star forming galaxies (SFGs) is becoming more common due to its ability to separate red quiescent galaxies from reddened SFGs. Quiescent galaxies occupy a small and distinct region of UVJ color space and we find most of them to have concentrated profiles with high Sersic indices (n>2.5) and smooth structure characteristic of early-type systems. SFGs populate a broad, but well-defined sequence of UVJ colors and are comprised of objects with a mix of Sersic indices. Interestingly, most UVJ-selected SFGs with high Sersic indices also display structure due to dust and star formation typical of the n<2.5 SFGs and late-type systems. Finally, we find that the position of a SFG on the sequence of UVJ colors is determined to a large degree by the mass of ...

  17. The Structure of Nuclear Star Clusters in Nearby Late-type Spiral Galaxies from Hubble Space Telescope Wide Field Camera 3 Imaging

    CERN Document Server

    Carson, Daniel J; Seth, Anil C; Brok, Mark den; Cappelari, Michele; Greene, Jenny E; Ho, Luis C; Neumayer, Nadine

    2015-01-01

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters residing in late-type spiral galaxies, in seven bands that span the near-ultraviolet to the near-infrared. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties. For six of the ten clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population which is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer waveleng...

  18. A search for line intensity enhancements in the far-UV spectra of active late-type stars arising from opacity

    CERN Document Server

    Keenan, F P; Rose, S J; Mathioudakis, M

    2011-01-01

    Radiative transfer calculations have predicted intensity enhancements for optically thick emission lines, as opposed to the normal intensity reductions, for astrophysical plasmas under certain conditions. In particular, the results are predicted to be dependent both on the geometry of the emitting plasma and the orientation of the observer. Hence in principle the detection of intensity enhancement may provide a way of determining the geometry of an unresolved astronomical source. To investigate such enhancements we have analyzed a sample of active late-type stars observed in the far ultraviolet spectral region. Emission lines of O VI in the FUSE satellite spectra of epsilon Eri, II Peg and Prox Cen were searched for intensity enhancements due to opacity. We have found strong evidence for line intensity enhancements due to opacity during active or flare-like activity for all three stars. The O VI 1032/1038 line intensity ratios, predicted to have a value of 2.0 in the optically thin case, are found to be up to...

  19. Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies using X-ray Emission: Results from the CHANDRA Deep Fields

    Science.gov (United States)

    Lehmer, B.D; Brandt, W.N.; Schneider, D.P.; Steffen, A.T.; Alexander, D.M.; Bell, E.F.; Hornschemeier, A.E.; McIntosh, D.H.; Bauer, F.E.; Gilli, R.; Mainieri, V.; Silverman, J.D.; Tozzi, P.; Wolf, C.

    2008-01-01

    We report on the X-ray evolution over the last approx.9 Gyr of cosmic history (i.e., since z = 1.4) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S. respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies. which were identified using rest-frame optical colors and HST morphologies. We utilized X-ray stacking analyses to investigate the X-ray emission from these galaxies, emphasizing the contributions from normal galaxies that are not dominated by active galactic nuclei (AGNs). Over this redshift range, we find significant increases (factors of approx. 5-10) in the X-ray-to-optical mean luminosity ratio (L(sub x)/L(sub B)) and the X-ray-to-stellar-mass mean ratio (L(sub x)/M(sub *)) for galaxy populations selected by L(sub B) and M(sub *), respectively. When analyzing galaxy samples selected via SFR, we find that the mean X-ray-to-SFR ratio (L(sub x)/SFR) is consistent with being constant over the entire redshift range for galaxies with SFR = 1-100 Solar Mass/yr, thus demonstrating that X-ray emission can be used as a robust indicator of star-formation activity out to z approx. 1.4. We find that the star-formation activity (as traced by X-ray luminosity) per unit stellar mass in a given redshift bin increases with decreasing stellar mass over the redshift range z = 0.2-1, which is consistent with previous studies of how star-formation activity depends on stellar mass. Finally, we extend our X-ray analyses to Lyman break galaxies at z approx. 3 and estimate that L(sub x)/L(sub B) at z approx. 3 is similar to its value at z = 1.4.

  20. A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age

    CERN Document Server

    Lopez-Santiago, J; Galvez-Ortiz, M C; Crespo-Chacon, I; Martinez-Arnaiz, R M; Fernandez-Figueroa, M J; De Castro, E; Cornide, M

    2010-01-01

    Aims: We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood which may be used to investigate different aspects of the formation and evolution of the solar neighborhood in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. Methods: We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral range simultaneously. Standard data reduction was performed with the IRAF ECHELLE package. We applied the spectral subtraction technique to reveal chromospheric emission in the stars of the sample. The equivalent width of chromospheric emission lines was measured in the subtracted spectra and then converted to fluxes using equivalent width-flux relationships. Radial and rotational velocities were determined by the cross-co...

  1. Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

    DEFF Research Database (Denmark)

    Amarsi, A. M.; Lind, K.; Asplund, M.;

    2016-01-01

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D...

  2. THE STRUCTURE OF NUCLEAR STAR CLUSTERS IN NEARBY LATE-TYPE SPIRAL GALAXIES FROM HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Carson, Daniel J.; Barth, Aaron J. [Department of Physics and Astronomy, University of California Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Seth, Anil C.; Brok, Mark den [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Cappellari, Michele [Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Peyton Hall—Ivy Lane, Princeton, NJ 08544 (United States); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Neumayer, Nadine [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2015-05-15

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters (NCs) residing in late-type spiral galaxies, in seven bands that span the near-UV to the near-IR. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties, with F814W absolute magnitudes that range from −11.2 to −15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc. For 6 of the 10 clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population that is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer wavelengths, as well as a correlation between the axis ratios of the NCs and their host galaxies. These observations indicate that blue disks aligned with the host galaxy plane are a common feature of NCs in late-type galaxies, but are difficult to detect in galaxies that are close to face-on. In color–color diagrams spanning the near-UV through the near-IR, most of the clusters lie far from single-burst evolutionary tracks, showing evidence for multi-age populations. Most of the clusters have integrated colors consistent with a mix of an old population (>1 Gyr) and a young population (∼100–300 Myr). The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only. The surface brightness profiles presented in this work will be used for future

  3. Chemical surface inhomogeneities in late B-type stars with Hg and Mn peculiarity I Spot evolution in HD 11753 on short and long time scales

    CERN Document Server

    Korhonen, H; Briquet, M; Soriano, M Flores; Hubrig, S; Savanov, I; Hackman, T; Ilyin, I V; Eulaers, E; Pessemier, W

    2013-01-01

    Aims: Time series of high-resolution spectra of the late B-type star HD 11753 exhibiting HgMn chemical peculiarity are used to study the surface distribution of different chemical elements and their temporal evolution. Methods: High-resolution and high signal-to-noise ratio spectra were obtained using the CORALIE spectrograph at La Silla in 2000, 2009, and 2010. Surface maps of YII, SrII, TiII, and CrII were calculated using the Doppler imaging technique. The results were also compared to equivalent width measurements. The evolution of chemical spots both on short and long time scales were investigated. Results: We determine the binary orbit of HD 11753 and fine-tune the rotation period of the primary. The earlier discovered fast evolution of the chemical spots is confirmed by an analysis using both the chemical spot maps and equivalent width measurements. In addition, a long-term decrease in the overall YII and SrII abundances is discovered. A detailed analysis of the chemical spot configurations reveals som...

  4. A Late-Type Star Spectra Outlier Data Mining System%一种晚型天体光谱离群数据挖掘系统

    Institute of Scientific and Technical Information of China (English)

    蔡江辉; 杨海峰; 赵旭俊; 张继福

    2014-01-01

    探索海量的M型恒星中具有磁活动、巨星等较特殊、稀有的天体,对于后续观测、银河系结构、演化等科学研究具有重要的意义,针对M型恒星光谱特征线出现在子空间中的局部偏离,设计并实现了晚型恒星离群数据挖掘系统。首先采用稀疏因子和稀疏度系数度量样本在属性空间上的分布特征,并在此基础上对M型恒星光谱特征线进行离散化、降维等预处理,获得光谱子空间;然后采用微粒群算法搜索离群子空间,并证认子空间内光谱是否离群;此外,选择SDSS M型光谱特征线指数集为样本,实验分析了稀疏因子和稀疏度系数的设置对离群结果的影响,并将离群挖掘结果与SDSS提供光谱型等参数对照,表明利用该系统实现晚型恒星光谱特征线局部离群数据挖掘是可行并有价值的。%In M star population ,some special objects ,which may be of magnetic activity ,may be giant stars ,or may be of other rare properties ,are very important for the follow-up observation and the scientific research on galactic structure and evolution . For local bias of M-type star spectral characteristic lines contained in subspace ,a late-type star spectra outlier data mining system is given in the present paper .Firstly ,for the sample of M stellar spectral characteristic lines indices ,its distribution characteris-tics in attribute spaces are measured by using the sparse factor and sparsity coefficient ,and then this sample is discretized and di-mension-reduced to the spectral subspace .Secondly ,local outlier subspaces are extracted by PSO (particle swarm optimization ) algorithm and identified .Additionally ,the effects of sparse coefficient and sparse factor on the number of outliers are discussed by experiments on the sample of SDSS M stellar spectral line index set ,and the outliers are compared with spectral type provided by SDSS .In this way ,the feasibility and value of this

  5. Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

    Science.gov (United States)

    Amarsi, A. M.; Lind, K.; Asplund, M.; Barklem, P. S.; Collet, R.

    2016-08-01

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves.We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally- and temporally-averaged 3D STAGGER model atmospheres.

  6. Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

    Science.gov (United States)

    Amarsi, A. M.; Lind, K.; Asplund, M.; Barklem, P. S.; Collet, R.

    2016-12-01

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves. We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally and temporally averaged 3D STAGGER model atmospheres.

  7. Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

    CERN Document Server

    Amarsi, A M; Asplund, M; Barklem, P S; Collet, R

    2016-01-01

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic Stagger model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe i/Fe ii excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is over-estimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmos...

  8. Late stages of the evolution of A-type stars on the main sequence: comparison between observed chemical abundances and diffusion models for 8 Am stars of the Praesepe cluster

    CERN Document Server

    Fossati, L; Monier, R; Khan, S A; Kochukhov, O; Landstreet, J; Wade, G; Weiss, W

    2007-01-01

    Aims. We aim to provide observational constraints on diffusion models that predict peculiar chemical abundances in the atmospheres of Am stars. We also intend to check if chemical peculiarities and slow rotation can be explained by the presence of a weak magnetic field. Methods. We have obtained high resolution, high signal-to-noise ratio spectra of eight previously-classified Am stars, two normal A-type stars and one Blue Straggler, considered to be members of the Praesepe cluster. For all of these stars we have determined fundamental parameters and photospheric abundances for a large number of chemical elements, with a higher precision than was ever obtained before for this cluster. For seven of these stars we also obtained spectra in circular polarization and applied the LSD technique to constrain the longitudinal magnetic field. Results. No magnetic field was detected in any of the analysed stars. HD 73666, a Blue Straggler previously considered as an Ap (Si) star, turns out to have the abundances of a no...

  9. The Late-Type Extension to MoVeRS (LaTE-MoVeRS): Proper Motion Verified Low-mass Stars and Brown Dwarfs from SDSS, 2MASS, and WISE

    Science.gov (United States)

    Theissen, Christopher A.; West, Andrew A.; Shippee, Guillaume; Burgasser, Adam J.; Schmidt, Sarah J.

    2017-03-01

    We present the Late-Type Extension to the Motion Verified Red Stars (LaTE-MoVeRS) catalog, containing 46,463 photometric late-type (>M5) dwarfs within the Sloan Digital Sky Survey (SDSS) footprint. Proper motions were computed for objects combining astrometry from the SDSS Data Release 12 (DR12), the Two-micron All-Sky Survey (2MASS) Point Source Catalog, and the Wide-field Infrared Survey Explorer (WISE) AllWISE data sets. LaTE-MoVeRS objects were required to have significant proper motion ({μ }{tot}≥slant 2{σ }{μ {tot}}). Using the LaTE-MoVeRS sample and Gaia Data Release 1, we estimate Gaia will be ∼64% complete for very low-mass objects (>M5) in comparison to the combined SDSS+2MASS+WISE data set (iSDSS CasJobs and VizieR.

  10. Spectroscopic Binaries Among λ Bootis-type Stars

    NARCIS (Netherlands)

    Paunzen, Ernst; Fraga, Luciano; Heiter, Ulrike; Iliev, Ilian Kh.; Kamp, Inga; Pintado, Olga

    2012-01-01

    The small group of λ Bootis stars comprises late B to early F-type stars, with moderate to extreme (up to a factor 100) surface under-abundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). The main mechanisms responsible for this phenomenon are atmospheric dif

  11. Cool dwarfs in wide multiple systems. Paper 3: Two common-proper-motion, late-type stars separated by over 11 arcmin

    CERN Document Server

    Caballero, J A; Miret, F X; Tobal, T; Cairol, J

    2012-01-01

    LP 209-28 and LP 209-27 have similar proper motions as tabulated by several catalogues. Using seven astrometric epochs spanning 59 years, we confirm a common tangential velocity by measuring a constant angular separation of rho = 666.62+/-0.09 arcsec. Accurate SDSS and 2MASS photometry indicates that they are normal dwarfs of approximate spectral types K7 V and M3 V. However, from their apparent magnitudes, both LP 209-28 and LP 209-27 are located at 200-250 pc, from where one can deduce an astonishing projected physical separation of 0.6-0.8 pc. The system Koenigstuhl 6 AB represents another world record among the least-bound systems with low-mass star components.

  12. Influence of inelastic collisions with hydrogen atoms on the non-LTE modelling of Ca i and Ca ii lines in late-type stars

    Science.gov (United States)

    Mashonkina, L.; Sitnova, T.; Belyaev, A. K.

    2017-09-01

    equilibrium method can successfully be applied to determine surface gravities of [Ca/H] ≾ -5 stars. We provide the NLTE abundance corrections for 28 lines of Ca i in a grid of model atmospheres with 5000 K ≤ Teff ≤ 6500 K, 2.5 ≤ log g ≤ 4.5, -4 ≤ [Fe/H] ≤ 0, which is suitable for abundance analysis of FGK-type dwarfs and subgiants.

  13. A close look at the Centaurus A group of galaxies IV. Recent star formation histories of late-type dwarfs around CenA

    CERN Document Server

    Crnojević, D; Cole, A A

    2012-01-01

    We study a sample of 5 dwarf irregular galaxies in the CenA/M83 group, which are companions to the giant elliptical CenA. We aim at deriving their physical properties over their lifetime and compare them to those of dwarfs located in different environments. We use archival HST/ACS data and apply synthetic color-magnitude diagram fitting in order to reconstruct the past star formation activity of the target galaxies. The average star formation rate for the studied galaxies ranges from 10^{-3} up to \\sim 7x10^{-2} M_odot/yr, and their mean metallicities correlate with their luminosities (from [Fe/H]\\sim -1.4 up to \\sim -1.0). The form of the star formation histories varies across the sample, with quiescent periods alternating with intermittent enhancements in the star formation (from a few up to several times the average lifetime value). The dwarfs in this sample formed ~35% to ~60% of their stellar content prior to ~5 Gyr ago. The resulting star formation histories for the CenA companions are similar to those ...

  14. A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars

    CERN Document Server

    Mashonkina, L; Shi, J -R; Korn, A J; Grupp, F

    2011-01-01

    A comprehensive model atom for Fe with more than 3000 energy levels is presented. As a test and first application of this model atom, Fe abundances are determined for the Sun and five stars with well determined stellar parameters and high-quality observed spectra. Non-LTE leads to systematically depleted total absorption in the Fe I lines and to positive abundance corrections in agreement with the previous studies, however, the magnitude of non-LTE effect is smaller compared to the earlier results. Non-LTE corrections do not exceed 0.1 dex for the solar metallicity and mildly metal-deficient stars, and they vary within 0.21 dex and 0.35 dex in the very metal-poor stars HD 84937 and HD 122563, respectively, depending on the assumed efficiency of collisions with hydrogen atoms. Based on the analysis of the Fe I/Fe II ionization equilibrium in these two stars, we recommend to apply the Drawin formalism in non-LTE studies of Fe with a scaling factor of 0.1. For the Fe II lines, non-LTE corrections do not exceed 0...

  15. 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.

  16. The Atmospheric Dynamics of Alpha Tau (K5 III) - Clues to Understanding the Magnetic Dynamo in Late-Type Giant Stars

    Science.gov (United States)

    Carpenter, Kenneth G.; Airapetian, Vladimir

    2008-01-01

    Using HST/GHRS, HST/STIS and FUSE archival data for a Tau and the CHIANTI spectroscopic code, we have derived line shifts, volumetric emission measures, and plasma density estimates, and calculated filling factors for a number of UV lines forming between 10,000 K and 300,000 K in the outer atmosphere of this red giant star. The data suggest the presence of low-temperature extended regions and high-temperature compact regions, associated with magnetically open and closed structures in the stellar atmosphere, respectively. The signatures of UV lines from a Tau can be consistently understood via a model of upward-traveling Alfv6n waves in a gravitationally stratified atmosphere. These waves cause nonthermal broadening in UV lines due to unresolved wave motions and downward plasma motions in compact magnetic loops heated by resonant Alfven wave heating.

  17. Environmental Effects on Late-Type Galaxies in Nearby Clusters

    CERN Document Server

    Boselli, A

    2006-01-01

    The transformations taking place in late-type galaxies in the environment of rich clusters of galaxies at z=0 are reviewed. From the handful of late-type galaxies that inhabit local clusters, whether they were formed in-situ and survived as such, avoiding transformation or even destruction or if they are newcomers that recently infall from outside, we can learn an important lesson on the latest stages of galaxy evolution. We start by reviewing the observational scenario, covering the broadest possible stretch of the electromagnetic spectrum, from the gas tracers, the star formation tracers, the old star tracers and the dust. Strong emphasis is given to the three nearby, well studied clusters Virgo, A1367 and Coma, representative of different evolutionary stages, from unrelaxed, spiral rich (Virgo) to relaxed, spiral poor clusters (Coma). We continue by providing a review of models of galaxy interactions relevant to clusters of galaxies. Prototypes of various mechanisms and processes are discussed and their ty...

  18. A self-consistent determination of the temperature profile and the magnetic field geometry in winds of late-type stars

    CERN Document Server

    Vidotto, A A

    2006-01-01

    Cool giant and supergiant stars generally present low velocity winds with high mass loss rates. Several models have been proposed to explain the acceleration process of these winds. Although dust is known to be present in these objects, the radiation pressure on these particles is uneffective in reproducing the observed physical parameters of the wind. The most promising acceleration mechanism cited in the literature is the transference of momentum and energy from Alfven waves to the gas. Usually, these models consider the wind to be isothermal. We present a stellar wind model in which the Alfven waves are used as the main acceleration mechanism, and determine the temperature profile by solving the energy equation taking into account both the radiative losses and the wave heating. We also determine self-consistently the magnetic field geometry as the result of the competition between the magnetic field and the thermal pressures gradient. As main result, we show that the magnetic geometry present a super-radia...

  19. The decay of debris disks around solar-type stars

    Energy Technology Data Exchange (ETDEWEB)

    Sierchio, J. M.; Rieke, G. H.; Su, K. Y. L.; Gáspár, Andras, E-mail: sierchio@mit.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

    2014-04-10

    We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 μm for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral type range, at 24 μm, 13.6% ± 2.8% of the stars younger than 1 Gyr have excesses at the 3σ level or more, whereas none of the older stars do, confirming previous work. At 70 μm, 22.5% ± 3.6% of the younger stars have excesses at ≥3σ significance, whereas only 4.7{sub −2.2}{sup +3.7}% of the older stars do. To characterize the far-infrared behavior of debris disks more robustly, we doubled the sample by including stars from the DEBRIS and DUNES surveys. For the F4-K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far-infrared excess with spectral type (detected fractions of 21.9{sub −4.3}{sup +4.8}%, late F; 16.5{sub −3.3}{sup +3.9}%, G; and 16.9{sub −5.0}{sup +6.3}%, early K). Taking this spectral type range together, there is a significant decline between 3 and 4.5 Gyr in the incidence of excesses, with fractional luminosities just under 10{sup –5}. There is an indication that the timescale for decay of infrared excesses varies roughly inversely with the fractional luminosity. This behavior is consistent with theoretical expectations for passive evolution. However, more excesses are detected around the oldest stars than are expected from passive evolution, suggesting that there is late-phase dynamical activity around these stars.

  20. The Decay of Debris Disks around Solar-type Stars

    Science.gov (United States)

    Sierchio, J. M.; Rieke, G. H.; Su, K. Y. L.; Gáspár, Andras

    2014-04-01

    We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 μm for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral type range, at 24 μm, 13.6% ± 2.8% of the stars younger than 1 Gyr have excesses at the 3σ level or more, whereas none of the older stars do, confirming previous work. At 70 μm, 22.5% ± 3.6% of the younger stars have excesses at >=3σ significance, whereas only 4.7^{+3.7}_{-2.2}% of the older stars do. To characterize the far-infrared behavior of debris disks more robustly, we doubled the sample by including stars from the DEBRIS and DUNES surveys. For the F4-K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far-infrared excess with spectral type (detected fractions of 21.9^{+4.8}_{-4.3}%, late F; 16.5^{+3.9}_{-3.3}%, G; and 16.9^{+6.3}_{-5.0}%, early K). Taking this spectral type range together, there is a significant decline between 3 and 4.5 Gyr in the incidence of excesses, with fractional luminosities just under 10-5. There is an indication that the timescale for decay of infrared excesses varies roughly inversely with the fractional luminosity. This behavior is consistent with theoretical expectations for passive evolution. However, more excesses are detected around the oldest stars than are expected from passive evolution, suggesting that there is late-phase dynamical activity around these stars.

  1. Superflares on solar-type stars.

    Science.gov (United States)

    Maehara, Hiroyuki; Shibayama, Takuya; Notsu, Shota; Notsu, Yuta; Nagao, Takashi; Kusaba, Satoshi; Honda, Satoshi; Nogami, Daisaku; Shibata, Kazunari

    2012-05-16

    Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10(29) to 10(32) ergs of energy on a timescale of hours. Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars, some of which are rapidly rotating and some of which are of ordinary solar type. The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars, but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.

  2. The Decay of Debris Disks around Solar-Type Stars

    CERN Document Server

    Sierchio, J M; Su, K Y L; Gaspar, Andras

    2014-01-01

    We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 $\\mu$m for 255 stars of types F4 - K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the HR diagram, to assign accurate stellar ages. Within this spectral type range, at 24 $\\mu$m, $13.6 \\pm 2.8 \\%$ of the stars younger than 5 Gyr have excesses at the 3$\\sigma$ level or more, while none of the older stars do, confirming previous work. At 70 $\\mu$m, $22.5 \\pm 3.6\\%$ of the younger stars have excesses at $ \\ge$ 3 $\\sigma$ significance, while only $4.7^{+3.7}_{-2.2}$% of the older stars do. To characterize the far infrared behavior of debris disks more robustly, we double the sample by including stars from the DEBRIS and DUNES surveys. For the F4 - K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far infrared excess with spectral type (detected fractions of 21.9$^{+4.8}_{-4.3}\\%$, late F; 16.5$^{+3.9}_{-3.3...

  3. Asteroseismic Inference for Solar-Type Stars

    CERN Document Server

    Monteiro, M J P F G; Thompson, M J

    2001-01-01

    The oscillation spectra of solar-type stars may in the not-too- distant future be used to constrain certain properties of the stars. The CD diagram of large versus small frequency separations is one of the powerful tools available to infer the properties - including perhaps masses and ages - of stars which display a detectable spectrum of oscillation. Also, the border of a convective region in a solar-type star gives rise to a characteristic periodic signal in the star's low-degree p-mode frequencies. Such a signature contains information about the location and nature of the transition between convective and non-convective regions in the star. In this work we address some of the uncertainties associated with the direct use of the CD diagram to evaluate the mass and age of the star due to the unknown contributions that make the stars different from the evolutionary models used to construct our reference grid. We also explore the possibility of combining an amplitude versus period diagram with the CD diagram to...

  4. On the late spectral types of cataclysmic variable secondaries

    CERN Document Server

    Baraffe, I

    2000-01-01

    We investigate why the spectral type of most cataclysmic variable (CV) secondaries is significantly later than that of a ZAMS star with the same mean density. Using improved stellar input physics, tested against observations of low-mass stars at the bottom of the main sequence, we calculate the secular evolution of CVs with low-mass donors. We consider sequences with different mass transfer rates and with a different degree of nuclear evolution of the donor prior to mass transfer. Systems near the upper edge of the gap ($P \\sim 3 - 6$ h) can be reproduced by models with a wide range of mass transfer rates from $1.5 \\times 10^{-9} \\msolyr$ to $10^{-8} \\msolyr$. Evolutionary sequences with a small transfer rate and donors that are substantially evolved off the ZAMS (central hydrogen content $0.05-0.5$) reproduce CVs with late spectral types above $P \\simgr$ 6 h. Systems with the most discrepant (late) spectral type should have the smallest donor mass at any given $P$. Consistency with the period gap suggests th...

  5. On laminar convection in solar type stars

    CERN Document Server

    Bruevich, E A

    2010-01-01

    We present a new model of large-scale multilayer convection in solar type stars. This model allows us to understand such self-similar structures observed at solar surface as granulation, supergranulation and giant cells. We study the slow-rotated hydrogen star without magnetic field with the spherically-symmetric convective zone. The photon's flux comes to the convective zone from the central thermonuclear zone of the star. The interaction of these photons with the fully ionized hydrogen plasma with $T>10^5K$ is carried out by the Tomson scattering of photon flux on protons and electrons. Under these conditions plasma is optically thick relative to the Tomson scattering. This fact is the fundamental one for the multilayer convection formation. We find the stationary solution of the convective zone structure. This solution describes the convective layers responsible to the formation of the structures on the star's surface.

  6. Photometric Variations In The Sun And Solar-Type Stars

    Science.gov (United States)

    Giampapa, Mark

    The rich array of solar magnetic field-related phenomena we see occurs not only on stellar counterparts of our Sun but in stars that represent significant departures in their fundamental parameters from those of the Sun. Though these phenomena appear energetically negligible when compared to the total luminosity of stars, they nevertheless govern the angular momentum evolution and modulate the radiative and particle output of the Sun and late-type stars. The term "The Solar-Stellar Connection" has been coined to describe the solar-stellar synergisms in the investigation of the generation, emergence and coupling of magnetic fields with the outer solar-stellar atmosphere to produce what we broadly refer to as magnetic activity. With the discovery of literally thousands of planets beyond our solar system, the Solar-Stellar-Planet Connection is quickly emerging as a new area of investigation of the impacts of magnetic activity on exoplanet atmospheres. In parallel with this rapid evolution in our perspectives is the advent of transformative facilities for the study of the Sun and the dynamic Universe. The primary focus of this invited talk will be on photometric variations in solar-type stars and the Sun. These brightness variations are associated with thermal homogeneities typically defined by magnetic structures that are also spatially coincident with key radiative proxies. Photometric variability in solar-type stars and the Sun includes transient brightening, rotational modulation by cool spots and cycle-related variability, each with a characteristic signature in time and wavelength. The emphasis of this presentation will be on the relationship between broadband photometric variations and magnetic field-related activity in solar-type stars and the Sun. Facets of this topic will be discussed both retrospectively and prospectively as we enter a revolutionary, new era for astronomy.

  7. Dust origin in late-type dwarf galaxies: ISM growth vs. type II supernovae

    CERN Document Server

    Zhukovska, Svitlana

    2014-01-01

    We re-evaluate the roles of different dust sources in dust production as a function of metallicity in late-type dwarf galaxies, with the goal of understanding the relation between dust content and metallicity. The dust content ol late-type dwarf galaxies with episodic star formation is studied with a multicomponent model of dust evolution, which includes dust input from AGB stars, type II SNe and dust growth by accretion of atoms in the ISM. Dust growth in the ISM becomes an important dust source in dwarf galaxies, on the timescale of 0.1 - a few Gyrs. It increases the dust-to-gas ratio (DGR) during post-burst evolution, unlike type II SNe, which eject grains to the ISM only during starbursts. Before the dust growth in the ISM overtakes the dust production, AGB stars can be major sources of dust in metal-poor dwarf galaxies. Our models reproduce the relation between the DGR and oxygen abundance, derived from observations of a large sample of dwarf galaxies. The steep decrease in the DGR at low O values is exp...

  8. B-type stars in eclipsing binaries

    Science.gov (United States)

    Ratajczak, Milena; Pigulski, Andrzej

    2016-07-01

    B-type stars in eclipsing binary systems are unique astrophysical tools to test several aspects of stellar evolution. Such objects can be used e.g. to determine the masses of Beta Cephei variable stars, as well as help to place tighter constraints on the value of the convective core overshooting parameter α. Both precise photometry and high-resolution spectroscopy with high SNR are required to achieve these goals, but since many of the targets are bright enough, the challenge is fair. Following this assumption, we shall explain how we plan to examine both the aforementioned aspects of stellar evolution using observations of B-type stars obtained with a wide range of spectrographs, as well as BRITE-Constellation satellites.

  9. Magnetic fields in early-type stars

    CERN Document Server

    Grunhut, Jason H

    2015-01-01

    For several decades we have been cognizant of the presence of magnetic fields in early-type stars, but our understanding of their magnetic properties has recently (over the last decade) expanded due to the new generation of high-resolution spectropolarimeters (ESPaDOnS at CFHT, Narval at TBL, HARPSpol at ESO). The most detailed surface magnetic field maps of intermediate-mass stars have been obtained through Doppler imaging techniques, allowing us to probe the small-scale structure of these stars. Thanks to the effort of large programmes (e.g. the MiMeS project), we have, for the first time, addressed key issues regarding our understanding of the magnetic properties of massive (M > 8 M_sun) stars, whose magnetic fields were only first detected about fifteen years ago. In this proceedings article we review the spectropolarimetric observations and statistics derived in recent years that have formed our general understanding of stellar magnetism in early-type stars. We also discuss how these observations have fu...

  10. Characterization of the radial velocity signal induced by rotation in late-type dwarfs

    Science.gov (United States)

    Suárez Mascareño, A.; Rebolo, R.; González Hernández, J. I.; Esposito, M.

    2017-07-01

    We investigate the activity-induced signals related to rotation and magnetic cycles in late-type stars (FGKM) and analyse the Ca II H&K, the H α and the radial velocity time series of 55 stars using the spectra from the HARPS public data base and the light curves provided by the All Sky Automated Survey. We search for short-term and long-term periodic signals in the time series of activity indicators as well as in the photometric light curves. Radial velocity data sets are then analysed to determine the presence of activity-induced signals. We measure a radial velocity signal induced by rotational modulation of stellar surface features in 37 stars, from late-F-type to mid-M-type stars. We report an empirical relationship, with some degree of spectral type dependency, between the mean level of chromospheric emission measured by the log _{10}(R^' }_{HK}) and the measured radial velocity semi-amplitude. We also report a relationship between the semi-amplitude of the chromospheric measured signal and the semi-amplitude of the radial velocity-induced signal, which strongly depends on the spectral type. We find that for a given strength of chromospheric activity (i.e. a given rotation period), M-type stars tend to induce larger rotation-related radial velocity signals than G- and K-type stars.

  11. Further Results from the Galactic O-Star Spectroscopic Survey: Rapidly Rotating Late ON Giants

    CERN Document Server

    Walborn, Nolan R; Sota, Alfredo; Alfaro, Emilio J; Morrell, Nidia I; Barba, Rodolfo H; Arias, Julia I; Gamen, Roberto C

    2011-01-01

    With new data from the Galactic O-Star Spectroscopic Survey, we confirm and expand the ONn category of late-O, nitrogen-enriched (N), rapidly rotating (n) giants. In particular, we have discovered two "clones" (HD 102415 and HD 117490) of one of the most rapidly rotating O stars previously known (HD 191423, "Howarth's Star"). We compare the locations of these objects in the theoretical HR Diagram to those of slowly rotating ON dwarfs and supergiants. All ON giants known to date are rapid rotators, whereas no ON dwarf or supergiant is; but all ON stars are small fractions of their respective spectral-type/luminosity-class/rotational subcategories. The ONn giants, displaying both substantial processed material and high rotation at an intermediate evolutionary stage, may provide significant information about the development of those properties. They may have preserved high initial rotational velocities or been spun up by TAMS core contraction; but alternatively and perhaps more likely, they may be products of bi...

  12. Challenges to Understand Stellar Chromospheres and Stellar Activity: The Limit Case of Late-A and Early-F Stars

    Science.gov (United States)

    Freire Ferrero, R.; Gouttebroze, P.

    The onset of chromospheric activity appears at late-A and early-F stars where theories predict atmospheres in radiative equilibrium and shallow or non-existent convective zones. The detection of Ly-α emission cores in several A and F stars, first with the IUE satellite and then with the HST, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0. ^m19 (Catalano et al. [CITE]). Semiempirical chromospheric models for Altair allowed us (Freire et al. [CITE]) to explain the observed emission profiles taking into account normal HI IS absorption. However, due to the very high rotational velocity we analyzed alternative hypotheses like the formation of Ly-α emissions into a corotating expanding wind, but we ruled out this alternative because we obtained inconsistent results. In addition, X-ray emission (originated surely in a corona) strengthen the presence of a chromosphere. Here we place the problem of chromospheric activity of late-A and early-F stars in the general context of the formation of over-photospheric stellar layers, comparing them with late-type star and solar cases.

  13. Star Clusters as Type Ia Supernova Factories

    CERN Document Server

    Shara, M M; Shara, Michael M.; Hurley, Jarrod R.

    2002-01-01

    We find a remarkably enhanced production rate in star clusters (relative to the field) of very short period, massive double-white-dwarf stars and of giant-white dwarf binaries. These results are based on N-body simulations performed with the new GRAPE-6 special purpose hardware and are important in identifying and characterizing the progenitors of type Ia supernovae. The high incidence of very close double-white-dwarf systems is the result of dynamical encounters between (mostly) primordial binaries and other cluster stars. Orbital hardening rapidly drives these degenerate binaries to periods under ~10 hours. Gravitational radiation emission and mergers producing supra-Chandrasekhar objects follow in less than a Hubble time. If most stars are born in clusters then estimates of the double white dwarf merger rates in galaxies (due to cluster dynamical interaction) must be increased more than tenfold. A majority of the Roche lobe overflow giant-white dwarf binaries are not primordial; they are produced in exchan...

  14. Change in activity character of coronae of low-mass stars of various spectral types

    CERN Document Server

    Nizamov, B A; Livshits, M A

    2016-01-01

    We study the dependence of the coronal activity index on the star's rotation rate. This question was considered earlier for 824 late-type stars on the basis of a consolidated catalogue of the soft X-ray fluxes. We carry out a more refined analysis separately for G, K and M dwarfs. They distinctively exhibit two modes of activity. The first one is the saturation mode, it is characteristic of young stars and is practically not related to their rotation. The second one refers to the solar-type activity the level of which strongly depends on the rotation period. We show that the transition from one mode to another takes place at the rotation periods of 1.1, 3.3 and 7.2 days for the stars of spectral types G2, K4 and M3 respectively. In the light of the discovery of superflares on G and K stars on the Kepler spacecraft there arises a question of how these objects differ from other active late-type stars. We analyse the location of superflare stars relative to the stars observed by Kepler on the "amplitude of rotat...

  15. Kepler observations of the variability in B-type stars

    DEFF Research Database (Denmark)

    Balona, Luis A.; Pigulski, A.; De Cat, P.

    2011-01-01

    The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies, characteristic of slowly pulsating B (SPB) stars. Seven of these stars also show a few weak, isolated high frequencies and they could be cons...

  16. Zeeman-Doppler imaging of active young solar type stars

    CERN Document Server

    Hackman, Thomas; Rosén, Lisa; Kochukhov, Oleg; Käpylä, Maarit J

    2015-01-01

    By studying young magnetically active late-type stars, i.e. analogues to the young Sun, one can draw conclusions on the evolution of the solar dynamo. We determine the topology of the surface magnetic field and study the relation between the magnetic field and cool photospheric spots in three young late-type stars. High-resolution spectropolarimetry of the targets were obtained with the HARPSpol instrument mounted at the ESO 3.6 m telescope. The signal-to-noise ratio of the Stokes IV measurements were boosted by combining the signal from a large number of spectroscopic absorption lines through the least squares deconvolution technique. Surface brightness and magnetic field maps were calculated using the Zeeman-Doppler imaging technique. All the three targets show clear signs of both magnetic fields and cool spots. Only one of the targets, namely V1358 Ori, shows evidence of the dominance of non-axisymmetric modes. In two of the targets, the poloidal field is significantly stronger than the toroidal one, indic...

  17. Convection in Oblate Solar-Type Stars

    CERN Document Server

    Wang, Junfeng; Liang, Chunlei

    2016-01-01

    We present the first global 3D simulations of thermal convection in the oblate envelopes of rapidly-rotating solar-type stars. This has been achieved by exploiting the capabilities of the new Compressible High-ORder Unstructured Spectral difference (CHORUS) code. We consider rotation rates up to 85\\% of the critical (breakup) rotation rate, which yields an equatorial radius that is up to 17\\% larger than the polar radius. This substantial oblateness enhances the disparity between polar and equatorial modes of convection. We find that the convection redistributes the heat flux emitted from the outer surface, leading to an enhancement of the heat flux in the polar and equatorial regions. This finding implies that lower-mass stars with convective envelopes may not have darker equators as predicted by classical gravity darkening arguments. The vigorous high-latitude convection also establishes elongated axisymmetric circulation cells and zonal jets in the polar regions. Though the overall amplitude of the surface...

  18. Photometric and period investigation of the late F-type overcontact binary II UMa

    CERN Document Server

    Zhou, X; Zhang, J; Zhang, B; Kreiner, J

    2016-01-01

    II UMa is a late F-type (F5) contact binary with a close-in tertiary and a distant visual companion. According to the four-color ($B$ $V$ $R_c$ $I_c$) light curves' solutions of II UMa, it is a high fill-out (f=$86.6\\,\\%$) and low mass ratio ($q = 0.172$) contact binary system, which indicate that it is at the late evolutionary stage of late-type tidal-locked binary stars. The mass of the primary star and secondary one are calculated to be $M_1 = 1.99M_\\odot$, $M_2 = 0.34M_\\odot$. The primary star has evolved from ZAMS, but it is still before TAMS, and the secondary star is even more evolved. Considering the mass ratio ($M_3/M_1 = 0.67$) obtained by spectroscopic observations, the mass of the close-in tertiary is estimated to be $M_3 = 1.34M_\\odot$. The period variations of the binary system is investigated for the first time. According to the observed-calculated ($O$-$C$) curve analysis, a continuous period increase at a rate of $dP/dt=4.88\\times{10^{-7}}day\\cdot year^{-1}$ is determined. It may be just a pa...

  19. B- and A-Type Stars in the Taurus-Auriga Star-Forming Region

    Science.gov (United States)

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), t Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  20. Origin of the Galactic Center S-Stars: Gravitational Torques from Lin-Shu-Type Spiral Density Waves

    Science.gov (United States)

    Griv, Evgeny

    2010-02-01

    The supermassive ~4 × 106 M sun black hole at the Galactic center is surrounded by a parsec-scale star disk, with several thousands of dynamically relaxed, evolved, late-type CO absorption line stars and a small ~100 population of luminous O and Wolf-Rayet stars which move in approximately circular Keplerian orbits. These bluish in color massive O and Wolf-Rayet stars are very young with an estimated age of 6 ± 2 Myr. Another small group of roughly 20 young (blue B stars with the orbital periods as short as 15 years ("S-stars") follow eccentric, randomly oriented orbits well inside the disk stars. A model is proposed to explain the S-stars. Accordingly, the stars formed originally in the parsec-scale disk through Jeans' gravitational fragmentation of gas. The newly formed S-stars then migrated inward to the Galactic center via the torques exerted by Lin-Shu-type spiral density waves on the stars at an inner Lindblad resonance. The model explains both the number of observed S-stars orbiting the Galactic black hole within the nuclear (<0.05 pc) star cluster and the key property of the S-star orbits, namely, their high eccentricities.

  1. Carbon-rich RR Lyr type stars

    CERN Document Server

    Wallerstein, George; Andrievsky, S M

    2009-01-01

    We have derived CNO abundances in 12 RR Lyrae stars. Four stars show [C/Fe] near 0.0 and two stars show [C/Fe] = 0.52 and 0.65. Red giant branch stars, which are known to be the predecessors of RR Lyrae stars, generally show a deficiency of carbon due to proton captures during their evolution from the main sequence up the giant branch. We suggest that the enhancement of carbon is due to production during the helium flash combined with mixing to the surface by vigorous convection induced by the flash itself.

  2. Stellar Populations and Chemical Evolution of Late--Type Dwarf Galaxies

    CERN Document Server

    Tosi, M P

    2001-01-01

    Some aspects of the chemical evolution of late-type dwarf galaxies are reviewed, together with their implications on three issues of cosmological relevance: similarity to primeval galaxies, derivation of the primordial helium abundance, contribution to the excess of faint blue galaxies. A more detailed approach to model their evolution is suggested. The importance of deriving the star formation history in these systems by studying their resolved stellar populations is emphasized.

  3. Two types of glitches in a solid quark star model

    CERN Document Server

    Lu, Jiguang

    2015-01-01

    The glitch of anomalous X-ray pulsars \\& soft gamma repeaters (AXP/SGRs) usually accompanied with detectable energy releases manifesting as X-ray bursts or outbursts, while the glitch of some pulsars like Vela release negligible energy. We find that these two types of glitch can naturally correspond to two types of starquake of solid stars. So far only quark star and quark cluster star model develop a solid star model. Then the two types of glitch may be an implication that the pulsar is composed by quark matter or quark cluster matter.

  4. Late Pop III Star Formation During the Epoch of Reionization: Results from the Renaissance Simulations

    Science.gov (United States)

    Xu, Hao; Norman, Michael L.; O'Shea, Brian W.; Wise, John H.

    2016-06-01

    We present results on the formation of Population III (Pop III) stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high-redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc3, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in (“not so”) small primordial halos with mass less than ˜3 × 107 M ⊙. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogs to the recently discovered luminous Ly α emitter CR7, which has been interpreted as a Pop III star cluster within or near a metal-enriched star-forming galaxy. We find and discuss a system similar to this in some respects, however, the Pop III star cluster is far less massive and luminous than CR7 is inferred to be.

  5. B- and A-Type Stars in the Taurus-Auriga Star Forming Region

    CERN Document Server

    Mooley, Kunal P; Rebull, Luisa M; Padgett, Deborah L; Knapp, Gillian R

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral type B. The second group consists of early-type stars compiled from (i) literature listings in SIMBAD; (ii) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud; (iii) magnitude- and color-selected point sources from the 2MASS; and (iv) spectroscopically identified early-type stars from the SDSS coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emiss...

  6. Multiplicity of A-type and related stars

    CERN Document Server

    North, Pierre L

    2013-01-01

    The origin of chemically peculiar stars remains enigmatic, especially regarding their frequency among their "normal" peers. In addition to magnetic fields and rotation, multiplicity may shed light on the question. We mention the main surveys of the three kinds performed so far of intermediate mass stars, either normal or chemically peculiar, magnetic or not: imaging, spectroscopic, and photometric. We also consider the mulitiplicity of red giant stars, since many of them are descendants of A-type stars, through Mermilliod's radial velocity monitoring of open cluster members. We briefly review the orbital properties of binary systems hosting chemically peculiar stars. Some specific objects of special interest are mentioned as deserving further study. Finally, we recall that some binary systems composed of A-type stars are progenitors of Type Ia supernovae, and evoke the potentialities of future surveys like Gaia.

  7. Rotation Periods of Nine ROSAT Selected Solar-Type Stars

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magnitude in nine of the objects. Using the method of Phase Dispersion Minimization (PDM) and Fourier analysis (software PERIOD04), the rotation periods of these stars were determined from the photometric data. The rotation periods of all nine stars are shorter than about 3 days.It is suggested that, as with the Pleiades cluster, small amplitude light variations are quite common among young solar-type stars with rotation periods around 3 days or less. This gives further evidence for the spin up of solar-type stars predicted by models of angular momentum evolution of pre-main sequence stars.

  8. Modelling of W UMa-type variable stars

    Directory of Open Access Journals (Sweden)

    P. L. Skelton

    2010-01-01

    Full Text Available W Ursae Majoris (W UMa-type variable stars are over-contact eclipsing binary stars. To understand how these systems form and evolve requires observations spanning many years, followed by detailed models of as many of them as possible. The All Sky Automated Survey (ASAS has an extensive database of these stars. Using the ASAS V band photometric data, models of W UMatype stars are being created to determine the parameters of these stars. This paper discusses the classification of eclipsing binary stars, the methods used to model them as well as the results of the modelling of ASAS 120036–3915.6, an over-contact eclipsing binary star that appears to be changing its period.

  9. Kepler observations of variability in B-type stars

    CERN Document Server

    Balona, L A; De Cat, P; Handler, G; Gutierrez-Soto, J; Engelbrecht, C A; Frescura, F; Briquet, M; Cuypers, J; Daszynska-Daszkiewicz, J; Degroote, P; Dukes, R J; Garcia, R A; Green, E M; Heber, U; Kawaler, S D; Ostensen, R; Pricopi, D; Roxburgh, I; Salmon, S; Smith, M A; Suarez, J C; Suran, M; Szabo, R; Uytterhoeven, K; Christensen-Dalsgaard,; Kjeldsen, H; Caldwell, D A; Girouard, F R; Sanderfer, D T

    2011-01-01

    The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies characteristic of SPB stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/beta Cep hybrids. In all cases the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the beta Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence fo...

  10. Lithium Abundance Of The Solar-Type Superflare Stars

    Science.gov (United States)

    Honda, Satoshi; Notsu, Yuta; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2016-07-01

    We performed the high dispersion spectroscopy of solar-type superflare stars by Subaru/HDS, and estimate the stellar parameters and lithium abundance of the stars to compare with the Sun. Our spectroscopic analysis of superflare stars show more than half of targets have no evidence of binary system and the stellar parameters are in the range of solar-type stars (Notsu et al. 2015a&b). We also investigate the correlations of Lithium abundance with stellar atmospheric parameters, rotational velocity, and superflare activities to understand the nature of superflare stars and the possibility of the nucleosynthesis of lithium by superflares. The derived lithium abundance in superflare stars do not show the correlation with stellar parameters. As compared with the lithium abundance in Hyades cluster which is younger than the sun, it is suggested that half of observed stars are young. However, there are some objects which show the low lithium and slowly rotate from the estimated v sin(i) and period of brightness variation. These results indicate that the superflare stars are not only young stars but also old stars like our sun. In our observations, we could not find the any evidence of lithium productions by superflare.

  11. Abundance analysis of 5 early-type stars in the young open cluster IC2391

    CERN Document Server

    Stuetz, C; Jehin, E; Ledoux, C; Cabanac, R A; Melo, C; Smoker, J V; Stuetz, Ch.

    2006-01-01

    It is unclear whether chemically peculiar stars of the upper main sequence represent a class completely distinct from normal A-type stars, or whether there exists a continuous transition from the normal to the most peculiar late F- to early B-type stars. A systematic abundance analysis of open cluster early-type stars would help to relate the observed differences of the chemical abundances of the photospheres to other stellar characteristics, without being concerned by possible different original chemical composition. Furthermore, if a continuous transition region from the very peculiar to the so called normal A-F stars exists, it should be possible to detect objects with mild peculiarities. As a first step of a larger project, an abundance analysis of 5 F-A type stars in the young cluster IC2391 was performed using high resolution spectra obtained with the UVES instrument of the ESO VLT. Our targets seem to follow a general abundance pattern: close to solar abundance of the light elements and iron peak eleme...

  12. Coronal thermal structure and abundances of supermetal-rich solar-type stars

    Science.gov (United States)

    Brickhouse, Nancy S. (Principal Investigator); Mushotzky, Richard F. (Technical Monitor)

    2005-01-01

    This observation is for grating spectroscopy of Tau Boo, a late-type star with very high metallicity (about twice solar). Despite the extreme condition of high metallicity in the photosphere, the abundance ratios of the corona appear consistent with the general picture of a coronal abundance/activity relation. The target was obtained by XMM-Newton on 24 June 2003 for 71900 sec. The European PI Antonio Maggio is responsible for data reduction. Members of our team presented at the Cool Stars Workshop 13 held in Hamburg, Germany in July 2004 and conferred at that time on the publication of results. This project is complete except for the final publication.

  13. L'-band AGPM vector vortex coronagraph's first light on VLT/NACO: Discovery of a late-type companion at two beamwidths from an F0V star

    CERN Document Server

    Mawet, D; Delacroix, C; Girard, J H; Milli, J; O'Neil, J; Baudoz, P; Boccaletti, A; Bourget, P; Christiaens, V; Forsberg, P; Gonte, F; Habraken, S; Hanot, C; Karlsson, M; Kasper, M; Lizon, J -L; Muzic, K; Pena, E; Olivier, R; Slusarenko, N; Tacconi-Garman, L E; Surdej, J

    2013-01-01

    Context. High contrast imaging has thoroughly combed through the limited search space accessible with first-generation ground-based adaptive optics instruments and the Hubble Space Telescope. Only a few objects were discovered, and many non-detections reported and statistically interpreted. The field is now in need of a technological breakthrough. Aim. Our aim is to open a new search space with first-generation systems such as NACO at the Very Large Telescope, by providing ground-breaking inner working angle (IWA) capabilities in the L' band. The L' band is a sweet spot for high contrast coronagraphy since the planet-to-star brightness ratio is favorable, while the Strehl ratio is naturally higher. Methods. An annular groove phase mask (AGPM) vector vortex coronagraph optimized for the L' band, made from diamond subwavelength gratings was manufactured and qualified in the lab. The AGPM enables high contrast imaging at very small IWA, potentially being the key to unexplored discovery space. Results. Here we pr...

  14. Late time cooling of neutron star transients and the physics of the inner crust

    CERN Document Server

    Deibel, Alex; Brown, Edward F; Reddy, Sanjay

    2016-01-01

    An accretion outburst onto a neutron star transient heats the neutron star's crust out of thermal equilibrium with the core. After the outburst the crust thermally relaxes toward equilibrium with the neutron star core and the surface thermal emission powers the quiescent X-ray light curve. Crust cooling models predict that thermal equilibrium of the crust will be established $\\approx 1000 \\, \\mathrm{d}$ into quiescence. Recent observations of the cooling neutron star transient MXB 1659-29, however, suggest that the crust did not reach thermal equilibrium with the core on the predicted timescale and continued to cool after $\\approx 2500 \\, \\mathrm{d}$ into quiescence. Because the quiescent light curve reveals successively deeper layers of the crust, the observed late time cooling of MXB 1659-29 depends on the thermal transport in the inner crust. In particular, the observed late time cooling is consistent with a low thermal conductivity layer near the depth predicted for nuclear pasta that maintains a temperat...

  15. Anomalous Spectral Types and Intrinsic Colors of Young Stars

    CERN Document Server

    Pecaut, Mark J

    2016-01-01

    We highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions ...

  16. Anomalous Spectral Types and Intrinsic Colors of Young Stars

    Science.gov (United States)

    Pecaut, Mark J.

    2016-01-01

    We highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.

  17. AN ACTIVITY–ROTATION RELATIONSHIP AND KINEMATIC ANALYSIS OF NEARBY MID-TO-LATE-TYPE M DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    West, Andrew A.; Weisenburger, Kolby L. [Department of Astronomy, Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States); Irwin, Jonathan; Charbonneau, David; Dittmann, Jason [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Berta-Thompson, Zachory K. [MIT, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Ave., Bldg. 37, Cambridge, MA 02139 (United States); Pineda, J. Sebastian, E-mail: aawest@bu.edu [California Institute of Technology, Department of Astronomy, 1200 E. California Ave, Pasadena, CA 91125 (United States)

    2015-10-10

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by Hα emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that v sin i measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, late-type, slowly rotating stars present in our sample. Additionally, we find that all M dwarfs with rotation periods shorter than 26 days (early-type; M1–M4) and 86 days (late-type; M5–M8) are magnetically active. This potential mismatch suggests that the physical mechanisms that connect stellar rotation to chromospheric heating may be different in fully convective stars. A kinematic analysis suggests that the magnetically active, rapidly rotating stars are consistent with a kinematically young population, while slow-rotators are less active or inactive and appear to belong to an older, dynamically heated stellar population.

  18. Two types of glitches in a solid quark star model

    OpenAIRE

    Lu, Jiguang; Zhou, Enping

    2015-01-01

    TThe glitch of anomalous X-ray pulsars \\& soft gamma repeaters (AXP/SGRs) usually accompanied with detectable energy releases manifesting as X-ray bursts or outbursts, while the glitch of some pulsars like Vela release negligible energy. We find that these two types of glitches can naturally correspond to two types of starquake of solid strange stars. By applying the EoS of quark cluster star and some realistic pulsar parameters, we can reproduce consistent results compared with previous cons...

  19. Late Pop III Star Formation During the Epoch of Reionization: Results from the Renaissance Simulations

    CERN Document Server

    Xu, Hao; O'Shea, Brian W; Wise, John H

    2016-01-01

    We present results on the formation of Pop III stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc$^3$, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in ("not so") small primordial halos with mass less than $\\sim$ 3 $\\times$ 10$^7$ M$_\\odot$. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogues to the recently discovered luminous Ly $\\alpha$ emitter CR7 ...

  20. On Helium-Dominated Stellar Evolution: The Mysterious Role of the O(He)-Type Stars

    Science.gov (United States)

    Reindl, N.; Rauch, T.; Werner, K.; Kruk, J. W.; Todt, H.

    2014-01-01

    Context. About a quarter of all post-asymptotic giant branch (AGB) stars are hydrogen-deficient. Stellar evolutionary models explain the carbon-dominated H-deficient stars by a (very) late thermal pulse scenario where the hydrogen-rich envelope is mixed with the helium-rich intershell layer. Depending on the particular time at which the final flash occurs, the entire hydrogen envelope may be burned. In contrast, helium-dominated post-AGB stars and their evolution are not yet understood. Aims. A small group of very hot, helium-dominated stars is formed by O(He)-type stars. A precise analysis of their photospheric abundances will establish constraints to their evolution. Methods. We performed a detailed spectral analysis of ultraviolet and optical spectra of four O(He) stars by means of state-of-the-art non-LTE model-atmosphere techniques. Results. We determined effective temperatures, surface gravities, and the abundances of H, He, C, N, O, F, Ne, Si, P, S, Ar, and Fe. By deriving upper limits for the mass-loss rates of the O(He) stars, we found that they do not exhibit enhanced mass-loss. The comparison with evolutionary models shows that the status of the O(He) stars remains uncertain. Their abundances match predictions of a double helium white dwarf (WD) merger scenario, suggesting that they might be the progeny of the compact and of the luminous helium-rich sdO-type stars. The existence of planetary nebulae that do not show helium enrichment around every other O(He) star precludes a merger origin for these stars. These stars must have formed in a different way, for instance via enhanced mass-loss during their post-AGB evolution or a merger within a common-envelope (CE) of a CO-WD and a red giant or AGB star. Conclusions. A helium-dominated stellar evolutionary sequence exists that may be fed by different types of mergers or CE scenarios. It appears likely that all these pass through the O(He) phase just before they become WDs.

  1. Late-time spectroscopy of Type Iax Supernovae

    Science.gov (United States)

    Foley, Ryan J.; Jha, Saurabh W.; Pan, Yen-Chen; Zheng, Wei Kang; Bildsten, Lars; Filippenko, Alexei V.; Kasen, Daniel

    2016-09-01

    We examine the late-time (t ≳ 200 d after peak brightness) spectra of Type Iax supernovae (SNe Iax), a low-luminosity, low-energy class of thermonuclear stellar explosions observationally similar to, but distinct from, Type Ia supernovae. We present new spectra of SN 2014dt, resulting in the most complete late-time spectral sequence of an SN Iax. At late times, SNe Iax have generally similar spectra, all with a similar continuum shape and strong forbidden-line emission. However, there is also significant diversity where some SN Iax spectra display narrow P-Cygni features from permitted lines and a continuum indicative of a photosphere at late times in addition to strong narrow (FWHM 6000 km s-1) forbidden lines, and weak narrow forbidden lines, and some SNe Iax have spectra intermediate to these two varieties. We find that SNe Iax with strong broad forbidden lines are more luminous and have higher velocity ejecta at peak brightness. We estimate blackbody and kinematic radii of the late-time photosphere, finding the latter significantly larger than the former. We propose a two-component model that solves this discrepancy and explains the diversity of the late-time spectra of SNe Iax. In this model, the broad forbidden lines originate from the SN ejecta, while the photosphere, P-Cygni lines, and narrow forbidden lines originate from a wind launched from the remnant of the progenitor white dwarf and is driven by the radioactive decay of newly synthesized material left in the remnant. The relative strength of the two components accounts for the diversity of late-time SN Iax spectra. This model also solves the puzzle of a long-lived photosphere and the slow late-time decline of SNe Iax.

  2. A Bcool magnetic snapshot survey of solar-type stars

    CERN Document Server

    Marsden, S C; Jeffers, S V; Morin, J; Fares, R; Reiners, A; Nascimento, J D do; Auriere, M; Bouvier, J; Carter, B D; Catala, C; Dintrans, B; Donati, J -F; Gastine, T; Jardine, M; Konstantinova-Antova, R; Lanoux, J; Lignieres, F; Morgenthaler, A; Ramirez-Velez, J C; Theado, S; Van Grootel, V

    2013-01-01

    Stellar magnetic field measurements obtained from spectropolarimetry offer key data for activity and dynamo studies, and we present the results of a major high-resolution spectropolarimetric Bcool project magnetic snapshot survey of 170 solar-type stars from observations with the Telescope Bernard Lyot and the Canada-France-Hawaii Telescope. For each target star a high signal-to-noise circularly polarised Stokes V profile has been obtained using Least-Squares Deconvolution, and used to detect surface magnetic fields and measure the corresponding mean surface longitudinal magnetic field ($B_{l}$). Chromospheric activity indicators were also measured. Surface magnetic fields were detected for 67 stars, with 21 of these stars classified as mature solar-type stars, a result that increases by a factor of four the number of mature solar-type stars on which magnetic fields have been observed. In addition, a magnetic field was detected for 3 out of 18 of the subgiant stars surveyed. For the population of K-dwarfs the...

  3. Large HI structures linked to southern O-type stars

    CERN Document Server

    Martín, M C; Romero, G A

    2008-01-01

    In our search for interstellar bubbles around massive stars we analyze the environs of the O-type stars HD 38666, HD 124979, HD 163758, and HD 171589. The location of the stars, which are placed far from the galactic plane, favors the formation of large wind bubbles. We investigate the distribution of the neutral and ionized gas based on HI, CO, and radio continuum data, and that of the interstellar dust based on far infrared IRIS images. Here we report the discovery of neutral gas cavities and slowly expanding shells associated with the four massive stars. IR and optical counterparts were also detected for some of the stars. We discuss the probability that the features have originated in the action of the stellar winds on the surrounding gas.

  4. Late-type dwarf galaxies in the Virgo cluster; 1, the samples

    CERN Document Server

    Almoznino, E; Almoznino, Elchanan; Brosch, Noah

    1996-01-01

    We selected complete samples of late-type dwarf galaxies in the Virgo cluster with HI information. The galaxies were observed at the Wise-Observatory using several broad-band and H\\alpha bandpasses. UV measurements were carried out with the IUE Observatory from VILSPA, and use was made of images from the FAUST shuttle-borne UV telescope. We describe our observations in detail, paying particular attention to the determination of measurement errors, and present the observational results together with published data and far-infrared information from IRAS. The sample will be analyzed in subsequent papers, in order to study star formation mechanisms.

  5. Observations of Type I Bursts from Neutron Stars

    CERN Document Server

    Swank, J H

    2000-01-01

    Observations of Type I X-ray bursts have long been taken as evidence that the sources are neutron stars. Black body models approximate the spectral data and imply a suddenly heated neutron star cooling over characteristic times of seconds to minutes. The phenomena are convincingly explained in terms of nuclear burning of accreted gas on neutron stars with low mass companion stars. Prospects are promising that detailed theory and data from RXTE and future missions will lead to better determinations of important physical parameters (neutron star mass and radius, composition of the accreting gas, distance of the source). Among the variety of bursts observed, there are probably representatives of different kinds of explosive burning. RXTE's discovery of a 2.5 ms persistent coherent period from one Type I burster has now linked bursters indisputably to the epitome of a neutron star, a fast spinning magnetic compact object. Oscillations in some bursts had already been thought to arise from the neutron stars' rotati...

  6. A Be-type star with a black hole companion

    CERN Document Server

    Casares, J; Ribo, M; Ribas, I; Paredes, J M; Herrero, A; Simon-Diaz, S

    2014-01-01

    Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the ~80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (also known as HD 215227), although that was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of the Be star. This, together with an improved radial velocity curve of ...

  7. Automated Asteroseismic Analysis of Solar-type Stars

    DEFF Research Database (Denmark)

    Karoff, Christoffer; Campante, T.L.; Chaplin, W.J.

    2010-01-01

    The rapidly increasing volume of asteroseismic observations on solar-type stars has revealed a need for automated analysis tools. The reason for this is not only that individual analyses of single stars are rather time consuming, but more importantly that these large volumes of observations open...... the possibility to do population studies on large samples of stars and such population studies demand a consistent analysis. By consistent analysis we understand an analysis that can be performed without the need to make any subjective choices on e.g. mode identification and an analysis where the uncertainties...

  8. Measurability of the tidal polarizability of neutron stars in late-inspiral gravitational-wave signals

    CERN Document Server

    Damour, Thibault; Villain, Loic

    2012-01-01

    The gravitational wave signal from a binary neutron star inspiral contains information on the nuclear equation of state. This information is contained in a combination of the tidal polarizability parameters of the two neutron stars and is clearest in the late inspiral, just before merger. We use the recently defined tidal extension of the effective one-body formalism to construct a controlled analytical description of the frequency-domain phasing of neutron star inspirals up to merger. Exploiting this analytical description we find that the tidal polarizability parameters of neutron stars can be measured by the advanced LIGO-Virgo detector network from gravitational wave signals having a reasonable signal-to-noise ratio of $\\rho=16$. This measurability result seems to hold for all the nuclear equations of state leading to a maximum mass larger than $1.97M_\\odot$. We also propose a promising new way of extracting information on the nuclear equation of state from a coherent analysis of an ensemble of gravitatio...

  9. Late-time Spectroscopy of Type Iax Supernovae

    CERN Document Server

    Foley, Ryan J; Pan, Yen-Chen; Zheng, WeiKang; Bildsten, Lars; Filippenko, Alexei V; Kasen, Daniel

    2016-01-01

    We examine the late-time (t > 200 days after peak brightness) spectra of Type Iax supernovae (SNe Iax), a low-luminosity, low-energy class of thermonuclear stellar explosions observationally similar to, but distinct from, Type Ia supernovae. We present new spectra of SN 2014dt, resulting in the most complete published late-time spectral sequence of a SN Iax. At late times, SNe Iax have generally similar spectra, all with a similar continuum shape and strong forbidden-line emission. However, there is also significant diversity where some late-time SN Iax spectra display narrow P-Cygni features and a continuum indicative of a photosphere in addition to strong narrow forbidden lines, while others have no obvious P-Cygni features, strong broad forbidden lines, and weak narrow forbidden lines. Finally, some SNe Iax have spectra intermediate to these two varieties with weak P-Cygni features and broad/narrow forbidden lines of similar strength. We find that SNe Iax with strong broad forbidden lines also tend to be m...

  10. Mid-infrared observations of O-type stars: spectral morphology

    Science.gov (United States)

    Marcolino, W. L. F.; Bouret, J.-C.; Lanz, T.; Maia, D. S.; Audard, M.

    2017-09-01

    We present mid-infrared (mid-IR) observations for a sample of 16 O-type stars. The data were acquired with the NASA Spitzer Space Telescope, using the IRS instrument at moderate resolution (R ∼ 600), covering the range of ∼10-37 μm. Our sample includes early, mid and late O supergiants and dwarfs. We explore for the first time their mid-IR spectral morphology in a quantitative way. We use NLTE expanding atmosphere models to help with line identifications, analyse profile contributions and line-formation regions. The O supergiants present a rich emission line spectra. The most intense features are from hydrogen - 6 α, 7 α and 8 α - that have non-negligible contributions of He i or He ii lines, depending on the spectral type. The spectrum of early O supergiants is a composite of H i and He ii lines, He i lines being absent. On the other hand, late O supergiants present features composed mainly by H i and He i lines. All emission lines are formed throughout the stellar wind. We found that O dwarfs exhibit a featureless mid-IR spectrum. Two stars of our sample exhibit very similar mid-IR features, despite having a very different optical spectral classification. The analysis of O-type stars based on mid-IR spectra alone to infer spectral classes or to estimate physical parameters may thus be prone to substantial errors. Our results may therefore inform spectroscopic observations of massive stars located in heavily obscured regions and help establish an initial framework for observations of massive stars using the Mid-Infrared Instrument on the James Webb Space Telescope.

  11. Understanding Activity Cycles of Solar Type Stars with Kepler

    Science.gov (United States)

    Tovar, Guadalupe; Montet, Benjamin; Johnson, John A.

    2017-01-01

    As the era of exploring new worlds and systems advances we seek to answer the question: How common is our Sun? There is considerable evidence about the recurring activity cycles of our Sun but very little is known about the activity cycles of other stars. By calibrating the full frame images from the original Kepler mission that were taken once a month over the course of four years, we are able to do relative photometry on roughly 5 million stars. By building a model of the pixel response function we were able to achieve 0.8% precision photometry. We identify 50,000 solar type stars based on magnitude, surface gravity, and temperature cuts. We observe the relative increase and decrease in brightness of the stars indicating signs of activity cycles similar to our Sun. We continue to explore how a data driven pixel response function model could improve our precision to 0.1% photometry measurements.

  12. Metallicity calibration for solar type stars based on red spectra

    Institute of Scientific and Technical Information of China (English)

    Jing-Kun Zhao; Gang Zhao; Yu-Qin Chen; A-Li Luo

    2011-01-01

    Based on a high resolution and high signal-to-noise ratio (S/N) spectral analysis of 90 solar-type stars, we have established several new metallicity calibrations in the Teff range [5600, 6500] K based on red spectra with the wavelength range of 560-880 nm. The new metallicity calibrations are applied to determine the metallicity of solar analogs selected from Sloan Digital Sky Survey (SDSS) spectra. There is a good consistent result with the adopted value presented in SDSS-DR7 and a small scatter of 0.26 dex for stars with S/N > 50 being obtained. This study provides a new reliable way to derive the metallicity for solar-like stars with low resolution spectra.In particular, our calibrations are useful for finding metal-rich stars, which are missing in the SEGUE Stellar Parameter Pipeline.

  13. Quantifying Star Formation in Early-Type Galaxies using Spatially-Resolved UV-Optical Photometry

    Science.gov (United States)

    Kaviraj, Sugata

    2013-01-01

    Our understanding of star formation in nearby early-type galaxies (ETGs) has evolved rapidly in recent years, due to new UV data from GALEX and HST. Contrary to the classical notion of them being old, passively-evolving systems, recent work has demonstrated widespread late-epoch star formation in ETGs, which builds ~20% of their stellar mass after 1, via minor mergers between ETGs and gas-rich dwarfs. While survey data from GALEX has indicated the average properties of star formation in the ETG population as a whole, I demonstrate how spatially-resolved UV studies can offer detailed insights into the star formation histories of individual galaxies, using an HST-WFC3 case study of NGC 4150. Using a pixel-by-pixel analysis in 5 WFC3 filters, spanning UV to i-band, reveals a central 0.9 Gyr old young stellar population, with a median metallicity of 0.5 solar, that contributes around 3% of the stellar mass and coincides spatially with a small, kinematically-decoupled core (indicating a recent minor merger). Assuming that the metallicity of the young stars traces the gas-phase metallicity of the satellite that fuels the star formation, we use the mass-metallicity relation to estimate the mass ratio of the merger to be ~1:20. An WFC3 study of globular clusters reveals a substantial population of young star clusters coincident with the central region of star formation and indicates that the bulk of the stellar mass in this galaxy probably formed 6-8 Gyrs in the past. This study demonstrates the utility of high-resolution imaging from future instruments such as the extremely large telescopes. (Based on Early Release Science observations by the WFC3 Scientific Oversight Committee. We are grateful to the Director of the Space Telescope Science Institute for awarding Director's Discretionary time for this program.)

  14. Mid-UV HST Imaging of Nearby Late-Type, Irregular, and Peculiar Galaxies

    Science.gov (United States)

    Taylor, V. A.; Windhorst, R. A.; Chiarenza, C. A. T.; Odewahn, S. C.; Conselice, C. J.; MacKenty, J.; de Jong, R. S.; de Grijs, R.; Eskridge, P. B.; Frogel, J. A.; Gallagher, J. S.; Kobulnicky, H.; Hibbard, J. E.; Matthews, L. D.; O'Connell, R. W.

    2000-12-01

    Distant galaxies observed by HST appear to have primarily late-type, irregular, or peculiar morphologies. However, because of their high redshift they are observed in their restframe mid-UV. Nearby galaxies can look dramatically different in the rest-frame mid- and far-UV. We must therefore ask if these high redshift morphologies are due to real evolutionary effects or band-pass shifting and surface brightness dimming at high redshift. To address this, we have conducted a survey with HST of 37 nearby galaxies of various Hubble types and inclinations in two mid-UV bands. Most of these galaxies have supporting ground based data in UBVRJHK. A comparison of the photometric properties of these galaxies in these different band-passes will lead to a better ability to separate true evolutionary effects from the morphological K-correction. We will present and discuss preliminary results from the HST survey and ground-based observations in UBVR. Our preliminary results suggest that the late-types imaged so far are a heterogeneous mixture. More than half of the few irregulars/peculiars/mergers show a mid-UV F300W morphology that is similar to I-band F814W, but with important differences due to recognizable dust-lanes blocking out UV light, star-formation ``ridges,'' and hot stars or star-clusters that are mostly visible in F300W but not in F814W. Others yield significantly different classifications in F300W and F814W. We acknowledge NASA grant GO-8645.01-99A from STScI and the NASA Space Grant. This project is based on observations with the VATT: the Alice P. Lennon Telescope and the Thomas J. Bannan Astrophysics Facility.

  15. New Insights on Late-A and Early-F Star Activity

    Science.gov (United States)

    Freire Ferrero, R.; Catalano, S.; Marilli, E.; Gouttebroze, P.; Talavera, A.; Bruhweiler, F.

    The onset of chromospheric activity in late-A and early-F stars is here discussed. The detection of Ly- emission core in several A and F atars with the IUE satellite, gives evidence for the presence of chromospheric layers in these stars up to B - V = 0m.19 (Marilli et al., 1996). Semiempirical chromospheric models for Altair allowed us (Freire Ferrero et al., 1995) to explain the observed emission profiles taking into account normal H I interstellar (IS) absorption. However, due to the very high rotational velocity, we analysed alternative hypotheses to explain the observed emissions: (1) circumstellar or shell matter; (2) co-rotating expanding optically thin wind. We ruled out these hypotheses because their effects are negligible and as a consequence, this result reinforces the chromospheric origin of the observed Ly- core in Altair. The stars of our sample, having observed Ly- profilies similar to Altair's and similar stellar and IS properties, should reproduce similar chromospheric behaviour. Here we discuss several important questions that are raised by these results.

  16. 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.

  17. Four types of neoplasms in Asian sea bass (Lates calcarifer)

    Institute of Scientific and Technical Information of China (English)

    Ramalingam Vijayakumar; Kuzhanthaivel Raja; Vijayapoopathi Singaravel; Ayyaru Gopalakrishnan

    2015-01-01

    Objective:To describe and observe four types of neoplasms on different parts (external and internal organs) of an Asian sea bass (Lates calcarifer). Methods:The sample was collected from local fish landing center (south east coast of India). Histopathology of normal and tumour tissues were analyzed. Results:A total of 83 tumour masses (neoplasm) were recorded on the fish skin, also the neoplasms were recorded in internal organs of fish such as liver, stomach and ovary. Conclusions:Aetiology of such neoplasm’s are unknown, further more researches need to confirm the causative agent for this type of neoplasm.

  18. Peculiar early-type galaxies with central star formation

    Institute of Scientific and Technical Information of China (English)

    Chong Ge; Qiu-Sheng Gu

    2012-01-01

    Early-type galaxies (ETGs) are very important for understanding the formation and evolution of galaxies.Recent observations suggest that ETGs are not simply old stellar spheroids as we previously thought.Widespread recent star formation,cool gas and dust have been detected in a substantial fraction of ETGs.We make use of the radial profiles of g - r color and the concentration index from the Sloan Digital Sky Survey database to pick out 31 peculiar ETGs with central blue cores.By analyzing the photometric and spectroscopic data,we suggest that the blue cores are caused by star formation activities rather than the central weak active galactic nucleus.From the results of stellar population synthesis,we find that the stellar population of the blue cores is relatively young,spreading from several Myr to less than one Gyr.In 14 galaxies with H I observations,we find that the average gas fraction of these galaxies is about 0.55.The bluer galaxies show a higher gas fraction,and the total star formation rate (SFR) correlates very well with the H l gas mass.The star formation history of these ETGs is affected by the environment,e.g.in the denser environment the H 1 gas is less and the total SFR is lower.We also discuss the origin of the central star formation of these early-type galaxies.

  19. Acoustic glitches in solar-type stars from Kepler

    DEFF Research Database (Denmark)

    Mazumdar, A.; Monteiro, M. J. P. F. G.; Ballot, J

    2012-01-01

    We report the measurement of the acoustic locations of layers of sharp variation in sound speed in the interiors of 19 solar-type stars observed by the Kepler mission. The oscillatory signal in the frequencies arising due to the acoustic glitches at the base of the convection zone and the second...

  20. The Spitzer Spectroscopic Survey of S-type Stars

    CERN Document Server

    Smolders, K; Blommaert, J A D L; Hony, S; Van Winckel, H; Decin, L; Van Eck, S; Sloan, G C; Cami, J; Uttenthaler, S; Degroote, P; Barry, D; Feast, M; Groenewegen, M A T; Matsuura, M; Menzies, J; Sahai, R; van Loon, J Th; Zijlstra, A A; Acke, B; Bloemen, S; Cox, N; de Cat, P; Desmet, M; Exter, K; Ladjal, D; Ostensen, R; Saesen, S; van Wyk, F; Verhoest, T; Zima, W

    2012-01-01

    S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because of their peculiar chemical composition, one may expect a strong influence of the stellar C/O ratio on the molecular chemistry and the mineralogy of the circumstellar dust. In this paper, we present a large sample of 87 intrinsic galactic S-type AGB stars, observed at infrared wavelengths with the Spitzer Space Telescope, and supplemented with ground-based optical data. On the one hand, we derive the stellar parameters from the optical spectroscopy and photometry, using a grid of model atmospheres. On the other, we decompose the infrared spectra to quantify the flux-contributions from the different dust species. Finally, we compare the independently determined stellar parameters and dust properties. For the stars without significant dust emission, we detect a strict relation between the presence of SiS absorption in the Spitzer spectra and the C/O ratio of the stellar atmosphere. These absorption bands can...

  1. Automated Asteroseismic Analysis of Solar-type Stars

    DEFF Research Database (Denmark)

    Karoff, Christoffer; Campante, T.L.; Chaplin, W.J.

    2010-01-01

    The rapidly increasing volume of asteroseismic observations on solar-type stars has revealed a need for automated analysis tools. The reason for this is not only that individual analyses of single stars are rather time consuming, but more importantly that these large volumes of observations open...... are calculated in a consistent way. Here we present a set of automated asterosesimic analysis tools. The main engine of these set of tools is an algorithm for modelling the autocovariance spectra of the stellar acoustic spectra allowing us to measure not only the frequency of maximum power and the large...

  2. Neon and Chemical Fractionation Trends in Late-type Stellar Atmospheres

    CERN Document Server

    García-Álvarez, D; Testa, P

    2008-01-01

    A survey of Ne, O and Fe coronal abundances culled from the recent literature for about 60 late-type stars confirms that the Ne/O ratio of stellar outer atmospheres is about two times the value recently recommended by Asplund et al. The mean Ne/O remains flat from the most active stars down to at least intermediate activity levels (-5L_X/L_bol<-2), with some evidence for a decline toward the lowest activity levels sampled. The abundances surveyed are all based on emission measure distribution analyses and the mean Ne/O is about 0.1 dex lower than that found from line ratios in the seminal study of mostly active stars by Drake & Testa (2005), but is within the systematic uncertainties of that study. We also confirm a pattern of strongly decreasing Fe/O with increasing stellar activity. The observed abundance patterns are reminiscent of the recent finding of a dependence of the solar Ne/O and Fe/O ratios on active region plasma temperature and indicate a universal fractionation process is at work. The fi...

  3. The Young Stellar Population of the Nearby Late-Type Galaxy NGC 1311

    CERN Document Server

    Eskridge, Paul B; Mager, Violet A; Jansen, Rolf A

    2010-01-01

    We have extracted PSF-fitted stellar photometry from near-ultraviolet, optical and near-infrared images, obtained with the Hubble Space Telescope, of the nearby (D ~ 5.5 Mpc) SBm galaxy NGC 1311. The ultraviolet and optical data reveal a population of hot main sequence stars with ages of 2-10 Myr. We also find populations of blue supergiants with ages between 10 and 40 Myr and red supergiants with ages between 10 and 100 Myr. Our near-infrared data shows evidence of star formation going back ~1 Gyr, in agreement with previous work. Fits to isochrones indicate a metallicity of Z ~ 0.004. The ratio of blue to red supergiants is consistent with this metallicity. This indicates that NGC 1311 follows the well-known luminosity-metallicity relation for late-type dwarf galaxies. About half of the hot main sequence stars and blue supergiants are found in two regions in the inner part of NGC 1311. These two regions are each about 200 pc across, and thus have crossing times roughly equal to the 10 Myr age we find for th...

  4. StarBench: The D-type expansion of an HII region

    CERN Document Server

    Bisbas, T G; Williams, R J R; Mackey, J; Tremblin, P; Raga, A C; Arthur, S J; Baczynski, C; Dale, J E; Frostholm, T; Geen, S; Haugboelle, T; Hubber, D; Iliev, I T; Kuiper, R; Rosdahl, J; Sullivan, D; Walch, S; Wuensch, R

    2015-01-01

    StarBench is a project focused on benchmarking and validating different star-formation and stellar feedback codes. In this first StarBench paper we perform a comparison study of the D-type expansion of an HII region. The aim of this work is to understand the differences observed between the twelve participating numerical codes against the various analytical expressions examining the D-type phase of HII region expansion. To do this, we propose two well-defined tests which are tackled by 1D and 3D grid- and SPH- based codes. The first test examines the `early phase' D-type scenario during which the mechanical pressure driving the expansion is significantly larger than the thermal pressure of the neutral medium. The second test examines the `late phase' D-type scenario during which the system relaxes to pressure equilibrium with the external medium. Although they are mutually in excellent agreement, all twelve participating codes follow a modified expansion law that deviates significantly from the classical Spit...

  5. Central stars of planetary nebulae. II. New OB-type and emission-line stars

    Science.gov (United States)

    Weidmann, W. A.; Gamen, R.

    2011-07-01

    Context. There are more than 3000 confirmed and probably known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. Aims: We have undertaken a spectroscopic survey of the central stars in PNe to identify their spectral types. Methods: We performed spectroscopic observations at low resolution with the 2-m telescope at CASLEO, Argentina. Results: We present the spectra of 46 central stars of PNe, most of them are OB-type and emission-line stars. Based on data collected at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina y Universidades Nacionales de La Plata, Córdoba y San Juan, Argentina.The reduced spectra (FITS files) are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A172

  6. Beryllium, Lithium and Oxygen Abundances in F-type Stars

    CERN Document Server

    García-López, R J; Pérez de Taoro, M R; Casares, C; Rasilla, J L; Rebolo, R; Allende-Prieto, C

    1997-01-01

    Beryllium and oxygen abundances have been derived in a sample of F-type field stars for which lithium abundances had been measured previously, with the aim of obtaining observational constraints to discriminate between the different mixing mechanisms proposed. Mixing associated with the transport of angular momentum in the stellar interior and internal gravity waves within the framework of rotating evolutionary models, appear to be promising ways to explain the observations.

  7. Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem

    CERN Document Server

    Marcolino, W L F; Martins, F; Hillier, D J; Lanz, T; Escolano, C

    2009-01-01

    We have investigated the stellar and wind properties of a sample of five late-type O dwarfs in order to address the weak wind problem. A grid of TLUSTY models was used to obtain the stellar parameters, and the wind parameters were determined by using the CMFGEN code. We found that the spectra have mainly a photospheric origin. A weak wind signature is seen in CIV 1549, from where mass-loss rates consistent with previous CMFGEN results regarding O8-9V stars were obtained. A discrepancy of roughly 2 orders of magnitude is found between these mass-loss rates and the values predicted by theory (Mdot(Vink)), confirming a breakdown or a steepening of the modified wind momentum-luminosity relation at log L/Lsun -3.5) (abridged).

  8. Rotation and surface abundance peculiarities in A-type stars

    CERN Document Server

    Takeda, Yoichi; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min

    2008-01-01

    In an attempt of clarifying the connection between the photospheric abundance anomalies and the stellar rotation as well as of exploring the nature of "normal A" stars, the abundances of seven elements (C, O, Si, Ca, Ti, Fe, and Ba) and the projected rotational velocity for 46 A-type field stars were determined by applying the spectrum-fitting method to the high-dispersion spectral data obtained with BOES at BOAO. We found that the peculiarities (underabundances of C, O, and Ca; an overabundance of Ba) seen in slow rotators efficiently decrease with an increase of rotation, which almost disappear at v_e sin i > 100 km s^-1. This further suggests that stars with sufficiently large rotational velocity may retain the original composition at the surface without being altered. Considering the subsolar tendency (by several tenths dex below) exhibited by the elemental abundances of such rapidly-rotating (supposedly normal) A stars, we suspect that the gas metallicity may have decreased since our Sun was born, contra...

  9. Evolution of Cold Circumstellar Dust Around Solar-Type Stars

    CERN Document Server

    Carpenter, J M; Schreyer, K; Launhardt, R; Henning, T; Carpenter, John M.; Wolf, Sebastian; Schreyer, Katharina; Launhardt, Ralf; Henning, Th.

    2004-01-01

    We present submillimeter (CSO 350um) and millimeter (SEST 1.2 mm, OVRO 3 mm) photometry for 125 solar-type stars from the FEPS Spitzer Legacy program that have masses between ~0.5 and 2.0 Msun and ages from 3 Myr to 3 Gyr. Continuum emission was detected toward four stars with a signal to noise ratio >= 3$: the classical T Tauri stars RX J1842.9-3532, RX J1852.3-3700, and PDS 66 with SEST, and the debris disk system HD 107146 with OVRO. RXJ1842.9-3532 and RXJ1852.3-3700 are located in projection nearby the R CrA molecular cloud with estimated ages of ~10 Myr, while PDS66 is a probable member of the 20 Myr old Lower Centaurus-Crux subgroup of the Sco-Cen OB association. The continuum emission toward these three sources is unresolved at the 24'' SEST resolution and likely originates from circumstellar accretion disks, each with estimated dust masses of ~5x10**-5 Msun. Analysis of the visibility data toward HD107146 (age 80-200 Myr) indicates that the 3 mm continuum emission is centered on the star within the as...

  10. V4046 Sgr: Touchstone to Investigate Spectral Type Discrepancies for Pre-main Sequence Stars

    CERN Document Server

    Kastner, Joel H; Sargent, Benjamin; Smith, C T; Rayner, John

    2014-01-01

    Determinations of the fundamental properties (e.g., masses and ages) of late-type, pre-main sequence (pre-MS) stars are complicated by the potential for significant discrepancies between the spectral types of such stars as ascertained via optical vs. near-infrared observations. To address this problem, we have obtained near-IR spectroscopy of the nearby, close binary T Tauri system V4046 Sgr AB with the NASA Infrared Telescope Facility (IRTF) SPEX spectrometer. The V4046 Sgr close binary (and circumbinary disk) system provides an important test case for spectral type determination thanks to the stringent observational constraints on its component stellar masses (i.e., ~0.9 Msun each) as well as on its age (12-21 Myr) and distance (73 pc). Analysis of the IRTF data indicates that the composite near-IR spectral type for V4046 Sgr AB lies in the range M0-M1, i.e., significantly later than the K5+K7 composite type previously determined from optical spectroscopy. However, the K5+K7 composite type is in better agre...

  11. Zeeman-Doppler imaging of active young solar-type stars

    Science.gov (United States)

    Hackman, T.; Lehtinen, J.; Rosén, L.; Kochukhov, O.; Käpylä, M. J.

    2016-03-01

    Context. By studying young magnetically active late-type stars, i.e. analogues to the young Sun, we can draw conclusions on the evolution of the solar dynamo. Aims: We determine the topology of the surface magnetic field and study the relation between the magnetic field and cool photospheric spots in three young late-type stars. Methods: High-resolution spectropolarimetry of the targets was obtained with the HARPSpol instrument mounted at the ESO 3.6 m telescope. The signal-to-noise ratios of the Stokes IV measurements were boosted by combining the signal from a large number of spectroscopic absorption lines through the least squares deconvolution technique. Surface brightness and magnetic field maps were calculated using the Zeeman-Doppler imaging technique. Results: All three targets show clear signs of magnetic fields and cool spots. Only one of the targets, V1358 Ori, shows evidence of the dominance of non-axisymmetric modes. In two of the targets, the poloidal field is significantly stronger than the toroidal one, indicative of an α2-type dynamo, in which convective turbulence effects dominate over the weak differential rotation. In two of the cases there is a slight anti-correlation between the cool spots and the strength of the radial magnetic field. However, even in these cases the correlation is much weaker than in the case of sunspots. Conclusions: The weak correlation between the measured radial magnetic field and cool spots may indicate a more complex magnetic field structure in the spots or spot groups involving mixed magnetic polarities. Comparison with a previously published magnetic field map shows that on one of the stars, HD 29615, the underlying magnetic field changed its polarity between 2009 and 2013. Based on observations made with the HARPSpol instrument on the ESO 3.6 m telescope at La Silla (Chile), under the program ID 091.D-0836.

  12. Fundamental properties of nearby single early B-type stars

    Science.gov (United States)

    Nieva, María-Fernanda; Przybilla, Norbert

    2014-06-01

    Aims: Fundamental parameters of a sample of 26 apparently slowly-rotating single early B-type stars in OB associations and in the field within a distance of ≲400 pc from the Sun are presented and compared to high-precision data from detached eclipsing binaries (DEBs). Together with surface abundances for light elements the data are used to discuss the evolutionary status of the stars in context of the most recent Geneva grid of models for core hydrogen-burning stars in the mass-range ~6 to 18 M⊙ at metallicity Z = 0.014. Methods: The fundamental parameters are derived on the basis of accurate and precise atmospheric parameters determined earlier by us from non-LTE analyses of high-quality spectra of the sample stars, utilising the new Geneva stellar evolution models. Results: Evolutionary masses plus radii and luminosities are determined to better than typically 5%, 10%, and 20% uncertainty, respectively, facilitating the mass-radius and mass-luminosity relationships to be recovered for single core hydrogen-burning objects with a similar precision as derived from DEBs. Good agreement between evolutionary and spectroscopic masses is found. Absolute visual and bolometric magnitudes are derived to typically ~0.15-0.20 mag uncertainty. Metallicities are constrained to better than 15-20% uncertainty and tight constraints on evolutionary ages of the stars are provided. Overall, the spectroscopic distances and ages of individual sample stars agree with independently derived values for the host OB associations. Signatures of mixing with CN-cycled material are found in 1/3 of the sample stars. Typically, these are consistent with the amount predicted by the new Geneva models with rotation. The presence of magnetic fields appears to augment the mixing efficiency. In addition, a few objects are possibly the product of binary evolution. In particular, the unusual characteristics of τ Sco point to a blue straggler nature, due to a binary merger. Conclusions: The accuracy

  13. H-alpha as a Luminosity Class Diagnostic for K- and M-type Stars

    CERN Document Server

    Jennings, Jeff

    2016-01-01

    We have identified the H-alpha absorption feature as a new spectroscopic diagnostic of luminosity class in K- and M-type stars. From high-resolution spectra of 19 stars with well-determined physical properties (including effective temperatures and stellar radii), we measured equivalent widths for H-alpha and the Ca II triplet and examined their dependence on both luminosity class and stellar radius. H-alpha shows a strong relation with both luminosity class and radius that extends down to late M spectral types. This behavior in H-alpha has been predicted as a result of the density-dependent overpopulation of the metastable 2S level in hydrogen, an effect that should become dominant for Balmer line formation in non-LTE conditions. We conclude that this new metallicity-insensitive diagnostic of luminosity class in cool stars could serve as an effective means of discerning between populations such as Milky Way giants and supergiant members of background galaxies.

  14. Pre-explosion companion stars in Type Iax supernovae

    CERN Document Server

    Liu, Zheng-Wei; Abate, Carlo; Wang, Bo

    2015-01-01

    Type Iax supernovae (SNe Iax) are proposed as one new sub-class of SNe Ia since they present sufficiently distinct observational properties from the bulk of SNe Ia. SNe Iax are the most common of all types of peculiar SNe by both number and rate, with an estimated rate of occurrence of about 5-30% of the total SN Ia rate. However, the progenitor systems of SNe Iax are still uncertain. Analyzing pre-explosion images at SN Iax positions provides a direct way to place strong constraints on the nature of progenitor systems of SNe Iax. In this work, we predict pre-explosion properties of binary companion stars in a variety of potential progenitor systems by performing detailed binary evolution calculations with the one-dimensional stellar evolution code STARS. This will be helpful for constraining progenitor systems of SNe Iax from their pre-explosion observations. With our binary evolution calculations, it is found that the non-degenerate helium (He) companion star to both a massive C/O WD (> 1.1 solar mass) and ...

  15. The Kepler characterization of the variability amongst A- and F-type stars. I. General overview

    CERN Document Server

    Uytterhoeven, K; Grigahcene, A; Guzik, J A; Gutierrez-Soto, J; Smalley, B; Handler, G; Balona, L A; Niemczura, E; Machado, L Fox; Benatti, S; Chapellier, E; Tkachenko, A; Szabo, R; Suarez, J C; Ripepi, V; Pascual, J; Mathias, P; Martin-Ruiz, S; Lehmann, H; Jackiewicz, J; Hekker, S; Gruberbauer, M; Garcia, R A; Dumusque, X; Diaz-Fraile, D; Bradley, P; Antoci, V; Roth, M; Leroy, B; Murphy, S J; De Cat, P; Cuypers, J; Kjeldsen, H; Christensen-Dalsgaard, J; Breger, M; Pigulski, A; Kiss, L L; Still, M; Thompson, S E; Van Cleve, J

    2011-01-01

    The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars. We propose three main groups to describe the observed variety in pulsating A-F type stars: gamma Dor, delta Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much larger fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities...

  16. Signatures of A Companion Star in Type Ia Supernovae

    CERN Document Server

    Maeda, Keiichi; Shigeyama, Toshikazu

    2014-01-01

    While type Ia Supernovae (SNe Ia) have been used as precise cosmological distance indicators, their progenitor systems remain unresolved. One of the key questions is if there is a non-degenerate companion star at the time of a thermonuclear explosion of a white dwarf (WD). In this paper, we investigate if an interaction between the SN ejecta and the companion star may result in observable footprints around the maximum brightness and thereafter, by performing multi-dimensional radiation transfer simulations based on hydrodynamic simulations of the interaction. We find that such systems result in variations in various observational characteristics due to different viewing directions, while the predicted behaviors (redder and fainter for the companion direction) are opposite to what were suggested by the previous study. The variations are generally modest and within observed scatters. However, the model predicts trends between some observables different from observationally derived, thus a large sample of SNe Ia...

  17. Asteroseismology of solar-type stars with K2

    CERN Document Server

    Chaplin, W J; Handberg, R; Basu, S; Buchhave, L A; Campante, T L; Davies, G R; Huber, D; Latham, D W; Latham, C A; Serenelli, A; Antia, H M; Appourchaux, T; Ball, W H; Benomar, O; Casagrande, L; Christensen-Dalsgaard, J; Coelho, H R; Creevey, O L; Elsworth, Y; Garc, R A; Gaulme, P; Hekker, S; Kallinger, T; Karoff, C; Kawaler, S D; Kjeldsen, H; Lundkvist, M S; Marcadon, F; Mathur, S; Miglio, A; Mosser, B; R, C; Roxburgh, I W; Aguirre, V Silva; Stello, D; Verma, K; White, T R; Bedding, T R; Barclay, T; Buzasi, D L; Deheuvels, S; Gizon, L; Houdek, G; Howell, S B; Salabert, D; Soderblom, D R

    2015-01-01

    We present the first detections by the NASA K2 Mission of oscillations in solar-type stars, using short-cadence data collected during K2 Campaign\\,1 (C1). We understand the asteroseismic detection thresholds for C1-like levels of photometric performance, and we can detect oscillations in subgiants having dominant oscillation frequencies around $1000\\,\\rm \\mu Hz$. Changes to the operation of the fine-guidance sensors are expected to give significant improvements in the high-frequency performance from C3 onwards. A reduction in the excess high-frequency noise by a factor of two-and-a-half in amplitude would bring main-sequence stars with dominant oscillation frequencies as high as ${\\simeq 2500}\\,\\rm \\mu Hz$ into play as potential asteroseismic targets for K2.

  18. Activity trends in young solar-type stars

    CERN Document Server

    Lehtinen, Jyri; Hackman, Thomas; Kajatkari, Perttu; Henry, Gregory W

    2015-01-01

    We apply the Continuous Period Search (CPS) time series analysis method on Johnson B and V band photometry of 21 young and active solar-type, collected over 16 to 27 years and characterize the behaviour of their activity. Using the CPS method, differential rotation could be estimated from the observed variations of the photometric rotation period. Active longitudes were retrieved by applying a non-parametric period search on the light curve minimum epochs, and activity cycles by applying a secondary period search on the modelled light curve mean and amplitude values. We supplemented the time series results by calculating new $\\log{R'_{\\rm HK}}$ emission indices for the stars from high resolution spectroscopy. The measurements of the photometric rotation period variations point to a trend of increasing differential rotation coefficients towards longer rotation periods but do not reveal any dependence from the effective temperature of the stars. The secondary period searches revealed activity cycles in 18 of th...

  19. The VLT-FLAMES Tarantula Survey. XII. Rotational velocities of the single O-type stars

    Science.gov (United States)

    Ramírez-Agudelo, O. H.; Simón-Díaz, S.; Sana, H.; de Koter, A.; Sabín-Sanjulían, C.; de Mink, S. E.; Dufton, P. L.; Gräfener, G.; Evans, C. J.; Herrero, A.; Langer, N.; Lennon, D. J.; Maíz Apellániz, J.; Markova, N.; Najarro, F.; Puls, J.; Taylor, W. D.; Vink, J. S.

    2013-12-01

    Context. The 30 Doradus (30 Dor) region of the Large Magellanic Cloud, also known as the Tarantula nebula, is the nearest starburst region. It contains the richest population of massive stars in the Local Group, and it is thus the best possible laboratory to investigate open questions on the formation and evolution of massive stars. Aims: Using ground-based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Dor. The sample is large enough to obtain statistically significant information and to search for variations among subpopulations - in terms of spectral type, luminosity class, and spatial location - in the field of view. Methods: We measured projected rotational velocities, νesini, by means of a Fourier transform method and a profile fitting method applied to a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, P(νe), of the equatorial rotational velocity, νe. Results: The distribution of νesini shows a two-component structure: a peak around 80 kms-1 and a high-velocity tail extending up to ~600 kms-1. This structure is also present in the inferred distribution P(νe) with around 80% of the sample having 0 low-velocity peak is consistent with what has been found in other studies for late O- and early B-type stars. Conclusions: Most of the stars in our sample rotate with a rate less than 20% of their break-up velocity. For the bulk of the sample, mass loss in a stellar wind and/or envelope expansion is not efficient enough to significantly spin down these stars within the first few Myr of evolution. If massive-star formation results in stars rotating at birth with a large portion of their break-up velocities, an alternative braking mechanism, possibly magnetic fields, is thus required to explain the present

  20. Dynamo Action and Magnetic Cycles in F-type Stars

    Science.gov (United States)

    Augustson, Kyle C.; Brun, Allan Sacha; Toomre, Juri

    2013-11-01

    Magnetic activity and differential rotation are commonly observed features on main-sequence F-type stars. We seek to make contact with such observations and to provide a self-consistent picture of how differential rotation and magnetic fields arise in the interiors of these stars. The three-dimensional magnetohydrodynamic anelastic spherical harmonic code is employed to simulate global-scale convection and dynamo processes in a 1.2 M ⊙ F-type star at two rotation rates. The simulations are carried out in spherical shells that encompass most of the convection zone and a portion of the stably stratified radiative zone below it, allowing us to explore the effects a stable zone has upon the morphology of the global-scale magnetic fields. We find that dynamo action with a high degree of time variation occurs in the star rotating more rapidly at 20 Ω⊙, with the polarity of the mean field reversing on a timescale of about 1600 days. Between reversals, the magnetic energy rises and falls with a fairly regular period, with three magnetic energy cycles required to complete a reversal. The magnetic energy cycles and polarity reversals arise due to a linking of the polar-slip instability in the stable region and dynamo action present in the convection zone. For the more slowly rotating case (10 Ω⊙), persistent wreaths of magnetism are established and maintained by dynamo action. Compared to their hydrodynamic progenitors, the dynamo states here involve a marked reduction in the exhibited latitudinal differential rotation, which also vary during the course of a cycle.

  1. Mg line formation in late-type stellar atmospheres: I. The model atom

    CERN Document Server

    Osorio, Y; Lind, K; Belyaev, A K; Spielfiedel, A; Guitou, M; Feautrier, N

    2015-01-01

    Mg is often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from LTE. The astrophysical importance of Mg as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. For the low-lying states of Mg i, electron collision data were calculated using the R-matrix method. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed. The modelled spectra agree well with observed spectra. The line-to-line scatter in the derived abundances shows improve...

  2. After the Fall: Late-Time Spectroscopy of Type IIP Supernovae

    Science.gov (United States)

    Silverman, Jeffrey M.; Pickett, Stephanie; Craig Wheeler, J.; Filippenko, Alexei V.; Vinkó, József; Marion, G. H.; Bradley Cenko, S.; Chornock, Ryan; Clubb, Kelsey I.; Foley, Ryan J.; Graham, Melissa L.; Kelly, Patrick L.; Matheson, Thomas; Shields, Joseph C.

    2017-01-01

    Herein we analyse late-time (post-plateau; 103 stars have ejecta with a more physically extended oxygen layer that is well-mixed with the hydrogen layer. In addition, we find a subset of objects with evidence for asymmetric 56Ni ejection, likely bipolar in shape. We also compare our observations to theoretical late-time spectral models of SNe IIP from two separate groups and find moderate-to-good agreement with both sets of models. Our SNe IIP spectra are consistent with models of 12-15 M⊙ progenitor stars having relatively low metallicity (Z ≤ 0.01).

  3. The dustier early-type galaxies deviate from late-type galaxies' scaling relations

    CERN Document Server

    Lianou, Sophia; Madden, Suzanne; Barmby, Pauline

    2016-01-01

    Several dedicated surveys focusing on early-type galaxies (ETGs) reveal that significant fractions of them are detectable in all interstellar medium phases studied to date. We select ETGs from the Herschel Reference Survey that have both far-infrared Herschel and either HI or CO detection (or both). We derive their star formation rates (SFR), stellar masses and dust masses via modelling their spectral energy distributions. We combine these with literature information on their atomic and molecular gas properties, in order to relate their star formation, total gas mass and dust mass on global scales. The ETGs deviate from the dust mass-SFR relation and the Schmidt-Kennicutt relation that SDSS star forming galaxies define: compared to SDSS galaxies, ETGs have more dust at the same SFR, or less SFR at the same dust mass. When placing them in the M*-SFR plane, ETGs show a much lower specific SFR as compared to normal star-forming galaxies. ETGs show a large scatter compared to the Schmidt-Kennicutt relation found ...

  4. Forming Realistic Late-type Spirals in a ΛCDM Universe: The Eris Simulation

    Science.gov (United States)

    Guedes, Javiera; Callegari, Simone; Madau, Piero; Mayer, Lucio

    2011-12-01

    Simulations of the formation of late-type spiral galaxies in a cold dark matter (ΛCDM) universe have traditionally failed to yield realistic candidates. Here we report a new cosmological N-body/smooth particle hydrodynamic simulation of extreme dynamic range in which a close analog of a Milky Way disk galaxy arises naturally. Named "Eris," the simulation follows the assembly of a galaxy halo of mass M vir = 7.9 × 1011 M ⊙ with a total of N = 18.6 million particles (gas + dark matter + stars) within the final virial radius, and a force resolution of 120 pc. It includes radiative cooling, heating from a cosmic UV field and supernova explosions (blastwave feedback), a star formation recipe based on a high gas density threshold (n SF = 5 atoms cm-3 rather than the canonical n SF = 0.1 atoms cm-3), and neglects any feedback from an active galactic nucleus. Artificial images are generated to correctly compare simulations with observations. At the present epoch, the simulated galaxy has an extended rotationally supported disk with a radial scale length Rd = 2.5 kpc, a gently falling rotation curve with circular velocity at 2.2 disk scale lengths of V 2.2 = 214 km s-1, an i-band bulge-to-disk ratio B/D = 0.35, and a baryonic mass fraction within the virial radius that is 30% below the cosmic value. The disk is thin, has a typical H I-to-stellar mass ratio, is forming stars in the region of the ΣSFR-ΣH I plane occupied by spiral galaxies, and falls on the photometric Tully-Fisher and the stellar-mass-halo-virial-mass relations. Hot (T > 3 × 105 K) X-ray luminous halo gas makes up only 26% of the universal baryon fraction and follows a "flattened" density profile vpropr -1.13 out to r = 100 kpc. Eris appears then to be the first cosmological hydrodynamic simulation in which the galaxy structural properties, the mass budget in the various components, and the scaling relations between mass and luminosity are all consistent with a host of observational constraints. A

  5. FORMING REALISTIC LATE-TYPE SPIRALS IN A {Lambda}CDM UNIVERSE: THE ERIS SIMULATION

    Energy Technology Data Exchange (ETDEWEB)

    Guedes, Javiera; Madau, Piero [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Callegari, Simone [Institute for Theoretical Physics, University of Zuerich, Winterthurerstrasse 190, CH-9057 Zuerich (Switzerland); Mayer, Lucio [Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, 8093 Zuerich (Switzerland)

    2011-12-01

    Simulations of the formation of late-type spiral galaxies in a cold dark matter ({Lambda}CDM) universe have traditionally failed to yield realistic candidates. Here we report a new cosmological N-body/smooth particle hydrodynamic simulation of extreme dynamic range in which a close analog of a Milky Way disk galaxy arises naturally. Named 'Eris', the simulation follows the assembly of a galaxy halo of mass M{sub vir} = 7.9 Multiplication-Sign 10{sup 11} M{sub Sun} with a total of N = 18.6 million particles (gas + dark matter + stars) within the final virial radius, and a force resolution of 120 pc. It includes radiative cooling, heating from a cosmic UV field and supernova explosions (blastwave feedback), a star formation recipe based on a high gas density threshold (n{sub SF} = 5 atoms cm{sup -3} rather than the canonical n{sub SF} = 0.1 atoms cm{sup -3}), and neglects any feedback from an active galactic nucleus. Artificial images are generated to correctly compare simulations with observations. At the present epoch, the simulated galaxy has an extended rotationally supported disk with a radial scale length R{sub d} = 2.5 kpc, a gently falling rotation curve with circular velocity at 2.2 disk scale lengths of V{sub 2.2} = 214 km s{sup -1}, an i-band bulge-to-disk ratio B/D = 0.35, and a baryonic mass fraction within the virial radius that is 30% below the cosmic value. The disk is thin, has a typical H I-to-stellar mass ratio, is forming stars in the region of the {Sigma}{sub SFR}-{Sigma}{sub HI} plane occupied by spiral galaxies, and falls on the photometric Tully-Fisher and the stellar-mass-halo-virial-mass relations. Hot (T > 3 Multiplication-Sign 10{sup 5} K) X-ray luminous halo gas makes up only 26% of the universal baryon fraction and follows a 'flattened' density profile {proportional_to}r{sup -1.13} out to r = 100 kpc. Eris appears then to be the first cosmological hydrodynamic simulation in which the galaxy structural properties, the

  6. Pure Testicular Seminoma Relapsing Late with Somatic Type Malignancy

    Directory of Open Access Journals (Sweden)

    Klaus-Peter Dieckmann

    2017-01-01

    Full Text Available Background. Somatic type malignancy (STM occurs in 2% of all germ cell tumours (GCTs. The prognosis is unfavourable and the origin is poorly understood. Pathogenetic hypotheses involve direct transformation of teratoma, origin from totipotent cancer cells, or derivation from yolk sac tumour elements. Case Presentation. A 31-year-old patient was cured from testicular seminoma clinical stage IIc by orchiectomy and cisplatin-based chemotherapy. Nine years later, he experienced a late relapse with a mass sized 5×6 cm located at the former metastatic site. As no remission occurred after chemotherapy with three cycles of cisplatin, ifosfamide and etoposide, the mass was surgically resected. Histologically, the specimen consisted of neurofibroma with areas of malignant peripheral nerve sheath tumour and spots with mature bone formation. FISH analysis disclosed isochromosome 12p in the majority of evaluated cells suggesting somatic type malignancy (STM of GCT. The patient is well 1 year after surgery. Conclusion. The pathogenesis of this STM remains enigmatic. The origin from GCT was evidenced by documentation of isochromosome 12p. Unrecognized teratomatous elements in the primary and totipotent cancer cells surviving the first chemotherapy could be hypothesized to represent the origin. STM developing from seminoma cells would be another novel hypothesis.

  7. Investigating the possible connection between lambda Bootis stars and intermediate Population II type stars

    CERN Document Server

    Paunzen, E; Fossati, L; Heiter, U; Weiss, W W

    2014-01-01

    The lambda Bootis (LB) stars are located at the upper main sequence of the H-R diagram and exhibit a peculiar abundance pattern. The light elements (C, N, O, and S) present solar abundances whereas all other elements are moderately to strongly underabundant. It has not yet been determined whether that abundance pattern is intrinsic, or is restricted to the stellar surface. If we follow the hypothesis that the LB stars are intrinsically metal-weak, then there should be a connection with the intermediate Population II and F-weak objects. Such a possible affinity has not been previously investigated. We present detailed elemental abundances, including those of the light elements carbon and oxygen, for 38 bright intermediate Population II and F-weak objects. In addition, we investigate the kinematic characteristics of the groups. From photometric, spectroscopic, and kinematic data, there is no distinction between the intermediate Population II and F-weak type stars. We therefore conclude that the two groups are i...

  8. Kinematics of gas and stars in circumnuclear star-forming regions of early type spirals

    CERN Document Server

    Hagele, Guillermo F; Cardaci, Monica V; Terlevich, Elena; Terlevich, Roberto

    2008-01-01

    (Abbr.) We present high resolution (R~20000) spectra in the blue and the far red of cicumnuclear star-forming regions (CNSFRs) in three early type spirals (NGC3351, NGC2903 and NGC3310) which have allowed the study of the kinematics of stars and ionized gas in these structures and, for the first time, the derivation of their dynamical masses for the first two. In some cases these regions, about 100 to 150 pc in size, are seen to be composed of several individual star clusters with sizes between 1.5 and 4.9 pc estimated from Hubble Space Telescope (HST) images. The stellar dispersions have been obtained from the Calcium triplet (CaT) lines at $\\lambda\\lambda$ 8494,8542,8662 \\AA, while the gas velocity dispersions have been measured by Gaussian fits to the H$\\beta$ and [OIII] $\\lambda\\lambda$ 5007 \\AA lines on the high dispersion spectra. Values of the stellar velocity dispersions are between 30 and 68 km/s. We apply the virial theorem to estimate dynamical masses of the clusters, assuming that systems are grav...

  9. Magnetic field measurements and wind-line variability of OB-type stars

    NARCIS (Netherlands)

    Schnerr, R.S.; Henrichs, H.F.; Neiner, C.; Verdugo, E.; de Jong, J.; Geers, V.C.; Wiersema, K.; van Dalen, B.; Tijani, A.; Plaggenborg, B.; Rygl, K.L.J.

    2008-01-01

    Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely to be related to such magnetic fields. Aims. We attempt to

  10. Forming an Early O-type Star Through Gas Accretion?

    CERN Document Server

    Zapata, Luis A; HO, Paul; Schilke, Peter; Garrod, Robin T; Rodriguez, Luis F; Menten, Karl

    2007-01-01

    We present high angular resolution ($\\sim$ 3$''$) and sensitive 1.3 mm continuum, cyanogen (CN) and vinyl cyanide (C$_2$H$_3$CN) line observations made with the Submillimeter Array (SMA) toward one of most highly obscured objects of the W51 IRS2 region, W51 North. We find that the CN line exhibits a pronounced inverse P-Cygni profile indicating that the molecular gas is infalling inwards this object with a mass accretion rate between 4 and 7 $\\times$ 10$^{-2}$ M$_\\odot$ yr$^{-1}$. The C$_2$H$_3$CN traces an east-west rotating molecular envelope that surrounds either a single obscured (proto)star with a kinematic mass of 40 M$_{\\odot}$ or a small central cluster of B-type stars and that is associated with a compact high velocity bipolar outflow traced by H$_2$O masers and SiO molecular emission. We thus confirm that the W51 North region is part of the growing list of young massive star forming regions that have been associated with infalling motions and with large mass accretion rates ($\\sim$ 10$^{-2}$ -- 10$^...

  11. Starspot Activity and Superflares on Solar-type Stars

    Science.gov (United States)

    Maehara, Hiroyuki

    2017-10-01

    Recent high-precision photometry from space (e.g., Kepler) enables us to investigate the nature of ``superflares'' on solar-type stars. The bolometric energy of superflares detected by Kepler ranges from 1033 erg to 1036 erg which is 10-10,000 times larger than that released by a typical X10 class solar flare. The occurrence frequency (dN/dE) of superflares as a function of flare energy (E) shows the power-law distribution with the power-law index of ~-1.8 for 1034 < E < 1036 erg. Most of superflare stars show quasi-periodic light variations which suggest the presence of large starspots. The bolometric energy released by flares is consistent with the magnetic energy stored near the starspots. The occurrence frequency of superflares increases as the rotation period decreases. However, the energy of the largest flares observed in a given period bin does not show any clear correlation with the rotation period. These results suggest that superflares would occur on the slowly-rotating stars.

  12. Star Product and Invariant Integration for Lie type Noncommutative Spacetimes

    CERN Document Server

    Chryssomalakos, Chryssomalis

    2007-01-01

    We present a star product for noncommutative spaces of Lie type, including the so called ``canonical'' case by introducing a central generator, which is compatible with translations and admits a simple, manageable definition of an invariant integral. A quasi-cyclicity property for the latter is shown to hold, which reduces to exact cyclicity when the adjoint representation of the underlying Lie algebra is traceless. Several explicit examples illuminate the formalism, dealing with kappa-Minkowski spacetime and the Heisenberg algebra (``canonical'' noncommutative 2-plane).

  13. Non-thermal emission from early-type stars

    CERN Document Server

    Benaglia, P

    2006-01-01

    Massive, early-type stars deposit energy and momentum in the interstellar medium through dense, supersonic winds. These objects are one of the most important sources of ionising radiation and chemical enrichment in the Galaxy. The physical conditions in the winds give rise to thermal and non-thermal emission, detectable from radio to gamma rays. In this report the relevant radiation processes will be described and studies on particular systems will be presented, discussing the information provided by multifrequency observations. Future steps aiming at understanding the stellar wind phenomenon as a whole will be outlined.

  14. Galactic membership of BL Her type variable stars

    Science.gov (United States)

    Jurkovic, M. I.; Stojanovic, M.; Ninkovic, S.

    2016-05-01

    As the RR Lyrae stars evolve on the Hertzsprung-Russell diagram they are believed to become short period Type II Cepheids, known as BL Her type (with a pulsation period from 1 to 3-8 days). Assuming that their mass is around 0.5-0.6M_Sol, and that they are low metallicity objects, they were thought to belong to the halo of the Milky Way. We investigated seven Galactic short period Type II Cepheids (BL Her, SW Tau, V553 Cen, DQ And, BD Cas, V383 Cyg, and KT Com) in order to establish their membership within the Galactic structure using the kinematic approach. Gaia should provide us with more data needed to conduct the study of the whole sample.

  15. Galactic membership of BL Her type variable stars

    CERN Document Server

    Jurkovic, Monika I; Ninković, Slobodan

    2016-01-01

    As the RR Lyrae stars evolve on the Hertzsprung-Russell diagram they are believed to become short period Type II Cepheids, known as BL Her type (with a pulsation period from $1$ to $3-8$ days). Assuming that their mass is around $0.5 - 0.6 {\\rm M}_{\\odot}$, and that they are low metallicity objects, they were thought to belong to the halo of the Milky Way. We investigated seven Galactic short period Type II Cepheids (BL Her, SW Tau, V553 Cen, DQ And, BD Cas, V383 Cyg, and KT Com) in order to establish their membership within the Galactic structure using the kinematic approach. $Gaia$ should provide us with more data needed to conduct the study of the whole sample.

  16. Spectroscopic survey of Kepler stars - II. FIES/NOT observations of A- and F-type stars

    Science.gov (United States)

    Niemczura, E.; Polińska, M.; Murphy, S. J.; Smalley, B.; Kołaczkowski, Z.; Jessen-Hansen, J.; Uytterhoeven, K.; Lykke, J. M.; Triviño Hage, A.; Michalska, G.

    2017-09-01

    We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed using the Fibre-Fed Échelle Spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50 stars. Balmer, Fe i and Fe ii lines were used to derive effective temperatures, surface gravities and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. Effective temperatures calculated by spectral energy distribution fitting are in good agreement with those determined from the spectral line analysis. The stars analysed include chemically peculiar stars of the Am and λ Boo types, as well as stars with approximately solar chemical abundances. The wide distribution of projected rotational velocity, vsin i, is typical for A and F stars. The microturbulence velocities obtained are typical for stars in the observed temperature and surface gravity ranges. Moreover, we affirm the results of Niemczura et al. that Am stars do not have systematically higher microturbulent velocities than normal stars of the same temperature.

  17. A Bake-Off Between CMFGEN and FASTWIND: Modeling the Physical Properties of SMC and LMC O-type Stars

    CERN Document Server

    Massey, Philip; Hillier, D John; Puls, Joachim

    2013-01-01

    The model atmosphere programs FASTWIND and CMFGEN are both elegantly designed to perform non-LTE analyses of the spectra of hot massive stars, and include sphericity and mass-loss. The two codes differ primarily in their approach towards line blanketing, with CMFGEN treating all of the lines in the co-moving frame and FASTWIND taking an approximate approach which speeds up execution times considerably. Although both have been extensively used to model the spectra of O-type stars, no studies have used the codes to independently model the same spectra of the same stars and compare the derived physical properties. We perform this task on ten O-type stars in the Magellanic Clouds. For the late-type O supergiants, both CMFGEN and FASTWIND have trouble fitting some of the He I lines, and we discuss causes and cures. We find that there is no difference in the average effective temperatures found by the two codes for the stars in our sample, although the dispersion is large, due primarily to the various difficulties ...

  18. An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-type M Dwarfs

    CERN Document Server

    West, Andrew A; Irwin, Jonathan; Berta-Thompson, Zachory K; Charbonneau, David; Dittmann, Jason; Pineda, J Sebastian

    2015-01-01

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H-alpha emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that vsini measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, lat...

  19. Surveying the Bright Stars by Optical Interferometry I: A Search for Multiplicity Among Stars of Spectral Types F - K

    CERN Document Server

    Hutter, Donald; Tycner, Christopher; Benson, James; Hummel, Christian; Sanborn, Jason; Franz, Otto G; Johnston, Kenneth

    2016-01-01

    We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of $\\beta$ Scuti with precise relative astrometry, to illustrate the instrument's detection sensitivity for binaries at magnitude differences $\\Delta$$m$ $\\lessapprox$ 3 over the range of angular separation 3 - 860 milliarcseconds (mas). A limiting $\\Delta$$m_{700}$ $\\sim$ 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, $\\sigma$ Her. We then discuss early results of the survey of bright stars at $\\delta$ $\\geq$ -20$\\deg$. This survey, which complements previous surveys of the bright stars by speckle interferometry, initially emphasizes bright stars of spectral types F...

  20. Dynamical Model for Spindown of Solar-type Stars

    Science.gov (United States)

    Sood, Aditi; Kim, Eun-jin; Hollerbach, Rainer

    2016-12-01

    After their formation, stars slow down their rotation rates by the removal of angular momentum from their surfaces, e.g., via stellar winds. Explaining how this rotation of solar-type stars evolves in time is currently an interesting but difficult problem in astrophysics. Despite the complexity of the processes involved, a traditional model, where the removal of angular momentum by magnetic fields is prescribed, has provided a useful framework to understand observational relations between stellar rotation, age, and magnetic field strength. Here, for the first time, a spindown model is proposed where loss of angular momentum by magnetic fields evolves dynamically, instead of being prescibed kinematically. To this end, we evolve the stellar rotation and magnetic field simultaneously over stellar evolution time by extending our previous work on a dynamo model which incorporates nonlinear feedback mechanisms on rotation and magnetic fields. We show that our extended model reproduces key observations and is capable of explaining the presence of the two branches of (fast and slow rotating) stars which have different relations between rotation rate Ω versus time (age), magnetic field strength | B| versus rotation rate, and frequency of magnetic field {ω }{cyc} versus rotation rate. For fast rotating stars we find that: (i) there is an exponential spindown {{Ω }}\\propto {e}-1.35t, with t measured in Gyr; (ii) magnetic activity saturates for higher rotation rate; (iii) {ω }{cyc}\\propto {{{Ω }}}0.83. For slow rotating stars we find: (i) a power-law spindown {{Ω }}\\propto {t}-0.52; (ii) that magnetic activity scales roughly linearly with rotation rate; (iii) {ω }{cyc}\\propto {{{Ω }}}1.16. The results obtained from our investigations are in good agreement with observations. The Vaughan-Preston gap is consistently explained in our model by the shortest spindown timescale in this transition from fast to slow rotators. Our results highlight the importance of self

  1. A close hidden stellar companion to the SX Phe-type variable star DW Psc

    Energy Technology Data Exchange (ETDEWEB)

    Qian, S.-B.; Li, L.-J.; Wang, S.-M.; He, J.-J.; Zhou, X.; Jiang, L.-Q., E-mail: qsb@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China)

    2015-01-01

    DW Psc is a high-amplitude SX Phe-type variable with a period of pulsation of 0.05875 days. Using a few newly determined times of maximum light together with those collected from the literature, the changes in the observed-calculated (O-C) diagram are analyzed. It is discovered that the O-C curve of DW Psc shows a cyclic variation with a period of 6.08 years and a semi-amplitude of 0.0066 days. The periodic variation is analyzed for the light travel time effect, which is due to the presence of a stellar companion (M{sub 2}sini∼0.45(±0.03) M{sub ⊙}). The two-component stars in the binary system are orbiting each other in an eccentric orbit (e ∼ 0.4) at an orbital separation of about 2.7(±0.3) AU. The detection of a close stellar companion to an SX Phe-type star supports the idea that SX Phe-type pulsating stars are blue stragglers that were formed from the merging of close binaries. The stellar companion has played an important role in the merging of the original binary by removing angular momentum from the central binary during early dynamical interaction or/and late dynamical evolution. After the more massive component in DW Psc evolves into a red giant, the cool close companion should help to remove the giant envelope via possible critical Roche-lobe overflow, and the system may be a progenitor of a cataclysmic variable. The detection of a close stellar companion to DW Psc makes it a very interesting system to study in the future.

  2. High dispersion spectroscopy of solar-type superflare stars with Subaru/HDS

    CERN Document Server

    Notsu, Yuta; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2015-01-01

    We carried out spectroscopic observations with Subaru/HDS of 50 solar-type superflare stars found from Kepler data. More than half (34 stars) of the target stars show no evidence of the binary system, and we confirmed atmospheric parameters of these stars are roughly in the range of solar-type stars. We then conducted the detailed analyses for these 34 stars. First, the value of the "$v\\sin i$" (projected rotational velocity) measured from spectroscopic results is consistent with the rotational velocity estimated from the brightness variation. Second, there is a correlation between the amplitude of the brightness variation and the intensity of Ca II IR triplet line. All the targets expected to have large starspots because of their large amplitude of the brightness variation show high chromospheric activities compared with the Sun. These results support that the brightness variation of superflare stars is explained by the rotation of a star with large starspots.

  3. {High dispersion spectroscopy of solar-type superflare stars with Subaru/HDS†

    Science.gov (United States)

    Notsu, Yuta; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    We carried out spectroscopic observations with Subaru/HDS of 50 solar-type superflare stars found from Kepler data. More than half (34 stars) of the target stars show no evidence of the binary system, and we confirmed atmospheric parameters of these stars are roughly in the range of solar-type stars. We then conducted the detailed analyses for these 34 stars. First, the value of the ``v sin i'' (projected rotational velocity) measured from spectroscopic results is consistent with the rotational velocity estimated from the brightness variation. Second, there is a correlation between the amplitude of the brightness variation and the intensity of Ca II IR triplet line. All the targets expected to have large starspots because of their large amplitude of the brightness variation show high chromospheric activities compared with the Sun. These results support that the brightness variation of superflare stars is explained by the rotation of a star with large starspots.

  4. Star Formation in Nearby Early-Type Galaxies: The Radio Continuum Perspective

    CERN Document Server

    Nyland, Kristina; Wrobel, Joan M; Davis, Timothy A; Bureau, Martin; Alatalo, Katherine; Morganti, Raffaella; Duc, Pierre-Alain; de Zeeuw, P T; McDermid, Richard M; Crocker, Alison F; Oosterloo, Tom

    2016-01-01

    We present a 1.4 GHz Karl G. Jansky Very Large Array (VLA) study of a sample of early-type galaxies (ETGs) from the volume- and magnitude-limited ATLAS-3D survey. The radio morphologies of these ETGs at a resolution of 5" are diverse and include sources that are compact on sub-kpc scales, resolved structures similar to those seen in star-forming spiral galaxies, and kpc-scale radio jets/lobes associated with active nuclei. We compare the 1.4 GHz, molecular gas, and infrared (IR) properties of these ETGs. The most CO-rich ATLAS-3D ETGs have radio luminosities consistent with extrapolations from H_2-mass-derived star formation rates from studies of late-type galaxies. These ETGs also follow the radio-IR correlation. However, ETGs with lower molecular gas masses tend to have less radio emission relative to their CO and IR emission compared to spirals. The fraction of galaxies in our sample with high IR-radio ratios is much higher than in previous studies, and cannot be explained by a systematic underestimation o...

  5. uvbybeta photometry of early type open cluster and field stars

    CERN Document Server

    Handler, G

    2011-01-01

    The beta Cephei stars and slowly pulsating B (SPB) stars are massive main sequence variables. The strength of their pulsational driving strongly depends on the opacity of iron-group elements. As many of those stars naturally occur in young open clusters, whose metallicities can be determined in several fundamental ways, it is logical to study the incidence of pulsation in several young open clusters. To provide the foundation for such an investigation, Str\\"omgren-Crawford uvbybeta photometry of open cluster target stars was carried out to determine effective temperatures, luminosities, and therefore cluster memberships. In the course of three observing runs, uvbybeta photometry for 168 target stars was acquired and transformed into the standard system by measurements of 117 standard stars. The list of target stars also included some known cluster and field beta Cephei stars, as well as beta Cephei and SPB candidates that are targets of the asteroseismic part of the Kepler satellite mission. The uvbybeta phot...

  6. Flares on A-type Stars: Evidence for Heating of Solar Corona by Nanoflares?

    Science.gov (United States)

    Švanda, Michal; Karlický, Marian

    2016-11-01

    We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted toward a high-energy tail for A-type stars compared to stars of cooler spectral types. We extrapolated the fitted power laws toward flares with smaller energies (nanoflares) and made estimates for total energy flux to stellar atmospheres by flares. We found that, for A-type stars, the total energy flux density was at least four-times smaller than for G stars. We speculate that this deficit in energy supply may explain the lack of hot coronae on A-type stars. Our results indicate the importance of nanoflares for heating and formation of the solar corona.

  7. Flares on A-type stars: Evidence for heating of solar corona by nanoflares?

    CERN Document Server

    Svanda, M

    2016-01-01

    We analyzed the occurrence rates of flares on stars of spectral types K, G, F, and A, observed by Kepler. We found that the histogram of occurrence frequencies of stellar flares is systematically shifted towards a high-energy tail for A-type stars compared to stars of cooler spectral types. We extrapolated the fitted power laws towards flares with smaller energies (nanoflares) and made estimates for total energy flux to stellar atmospheres by flares. We found that for A-type stars the total energy flux density was at least 4-times smaller than for G-stars. We speculate that this deficit in energy supply may explain the lack of hot coronae on A-type stars. Our results indicate an importance of nanoflares for heating and formation of the solar corona.

  8. THE RUNAWAYS AND ISOLATED O-TYPE STAR SPECTROSCOPIC SURVEY OF THE SMC (RIOTS4)

    Energy Technology Data Exchange (ETDEWEB)

    Lamb, J. B.; Oey, M. S.; Segura-Cox, D. M.; Graus, A. S.; Golden-Marx, J. B. [Astronomy Department, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109-1107 (United States); Kiminki, D. C. [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Parker, J. Wm., E-mail: joellamb@umich.edu [Southwest Research Institute, Department of Space Studies, Suite 300, 1050 Walnut Street, Boulder, CO 80302-5150 (United States)

    2016-02-01

    We present the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4), a spatially complete survey of uniformly selected field OB stars that covers the entire star-forming body of the Small Magellanic Cloud (SMC). Using the IMACS (Inamori-Magellan Areal Camera and Spectrograph) multislit spectrograph and MIKE (Magellan Inamori Kyocera Echelle) echelle spectrograph on the Magellan telescopes, we obtained spectra of 374 early-type field stars that are at least 28 pc from any other OB candidates. We also obtained spectra of an additional 23 field stars in the SMC bar identified from slightly different photometric criteria. Here, we present the observational catalog of stars in the RIOTS4 survey, including spectral classifications and radial velocities. For three multi-slit fields covering 8% of our sample, we carried out monitoring observations over 9–16 epochs to study binarity, finding a spectroscopic, massive binary frequency of at least ∼60% in this subsample. Classical Oe/Be stars represent a large fraction of RIOTS4 (42%), occurring at much higher frequency than in the Galaxy, consistent with expectation at low metallicity. RIOTS4 confirmed a steep upper initial mass function in the field, apparently caused by the inability of the most massive stars to form in the smallest clusters. Our survey also yields evidence for in situ field OB star formation, and properties of field emission-line star populations, including sgB[e] stars and classical Oe/Be stars. We also discuss the radial velocity distribution and its relation to SMC kinematics and runaway stars. RIOTS4 presents a first quantitative characterization of field OB stars in an external galaxy, including the contributions of sparse, but normal, star formation; runaway stars; and candidate isolated star formation.

  9. A survey for pulsations in A-type stars using SuperWASP

    Science.gov (United States)

    Holdsworth, Daniel L.

    2015-12-01

    "It is sound judgement to hope that in the not too distant future we shall be competent to understand so simple a thing as a star." - Sir Arthur Stanley Eddington, The Internal Constitution of Stars, 1926 A survey of A-type stars is conducted with the SuperWASP archive in the search for pulsationally variable stars. Over 1.5 million stars are selected based on their (J-H) colour. Periodograms are calculated for light curves which have been extracted from the archive and cleaned of spurious points. Peaks which have amplitudes greater than 0.5 millimagnitude are identified in the periodograms. In total, 202 656 stars are identified to show variability in the range 5-300 c/d. Spectroscopic follow-up was obtained for 38 stars which showed high-frequency pulsations between 60 and 235 c/d, and a further object with variability at 636 c/d. In this sample, 13 were identified to be normal A-type δ Sct stars, 14 to be pulsating metallic-lined Am stars, 11 to be rapidly oscillating Ap (roAp) stars, and one to be a subdwarf B variable star. The spectra were used not only to classify the stars, but to determine an effective temperature through Balmer line fitting. Hybrid stars have been identified in this study, which show pulsations in both the high- and low-overtone domains; an observation not predicted by theory. These stars are prime targets to perform follow-up observations, as a confirmed detection of this phenomenon will have significant impact on the theory of pulsations in A-type stars. The detected number of roAp stars has expanded the known number of this pulsator class by 22 per cent. Within these results both the hottest and coolest roAp star have been identified. Further to this, one object, KIC 7582608, was observed by the Kepler telescope for 4 yr, enabling a detailed frequency analysis. This analysis has identified significant frequency variations in this star, leading to the hypothesis that this is the first close binary star of its type. The observational

  10. A search for nearby young stars among the flare stars

    CERN Document Server

    König, B; Hambaryan, V; Neuh\\"auser, Ralph; Hambaryan, Valeri

    2001-01-01

    Flare stars were discovered in the late 1940s in the solar vicinity and were named UV Cet-type variables (classical FSs). Among the FSs within 100 pc we search for young stars. For the search we take spectra with sufficient resolution to resolve Lithium at 6707 \\AA and Calcium at 6718 \\AA of all the stars. The real young stars are prime targets for the search of extra-solar planets by direct imaging.

  11. Exploring Photometric Methods for Identifying Emission-Line B-Type Stars

    Science.gov (United States)

    Glazier, Amy; Whelan, David

    2017-06-01

    Emission-line B-type stars, or Be stars, are a mysterious class of stars defined by their unique behavior: These stars eject material from their surfaces, forming a disc of gas that surrounds them. Furthermore, the gaseous disc is not necessarily a permanent feature of its host star. Some Be stars’ discs vary in structure over time, and may even disappear only to be regenerated later. Other Be stars may never show appreciable changes in the natures of their discs once they have been formed. The disc’s existence causes the appearance of characteristic emission lines in Be stars’ spectra, making spectroscopy the traditional method for identifying Be stars. However, spectroscopy is an inefficient and time-consuming method of finding Be stars, because it allows for only a single star to be observed in each exposure, and each star may require multiple exposures for durations of many minutes. Photometry, on the other hand, can be used to observe many stars simultaneously, but at the cost of the greater detail afforded by spectroscopy. While photometry has been used to identify Be stars, its success has been limited. In this work, we present a novel photometric technique that enables efficient identification of Be stars.

  12. Quantifying the Faint Structure of Galaxies: The Late-type Spiral NGC 2403

    CERN Document Server

    Barker, Mike K; Irwin, Mike J; Arimoto, Nobuo; Jablonka, Pascale

    2011-01-01

    Ground-based surveys have mapped the stellar outskirts of Local Group galaxies in unprecedented detail, but extending this work to other galaxies is necessary to overcome stochastic variations in evolutionary history and provide more stringent constraints on cosmological galaxy formation models. As part of our continuing program of ultra-deep imagery of galaxies beyond the Local Group, we present a wide-field analysis of the isolated late-type spiral NGC2403 using data obtained with Suprime-Cam on Subaru. The survey reaches a maximum projected radius of 30 kpc or deprojected radius of R_dp~60 kpc. The colour-magnitude diagram reaches 1.5 mag below the tip of the metal-poor red giant branch (RGB) at a completeness rate > 50% for R_dp >12 kpc. Using the combination of diffuse light photometry and resolved star counts, we are able to trace the radial surface brightness (SB) profile over a much larger range of radii and surface brightness than is possible with either technique alone. The exponential disc as trace...

  13. Long time-scale variability of X-ray binaries with late type giant companions

    CERN Document Server

    Filippova, E; Parkin, E R

    2013-01-01

    In this paper we propose and examine a physical mechanism which can lead to the generation of noise in the mass accretion rate of low mass X-ray binaries on time-scales comparable to the orbital period of the system. We consider modulations of mass captured by the compact object from the companion star's stellar wind in binaries with late type giants, systems which usually have long orbital periods. We show that a hydrodynamical interaction of the wind matter within a binary system even without eccentricity results in variability of the mass accretion rate with characteristic time-scales close to the orbital period. The cause of the variability is an undeveloped turbulent motion (perturbed motion without significant vorticity) of wind matter near the compact object. Our conclusions are supported by 3D simulations with two different hydrodynamic codes based on Lagrangian and Eulerian approaches -- the SPH code GADGET and the Eulerian code PLUTO. In this work we assume that the wind mass loss rate of the second...

  14. The MiMeS survey of Magnetism in Massive Stars: magnetic analysis of the O-type stars

    Science.gov (United States)

    Grunhut, J. H.; Wade, G. A.; Neiner, C.; Oksala, M. E.; Petit, V.; Alecian, E.; Bohlender, D. A.; Bouret, J.-C.; Henrichs, H. F.; Hussain, G. A. J.; Kochukhov, O.; MiMeS Collaboration

    2017-02-01

    We present the analysis performed on spectropolarimetric data of 97 O-type targets included in the framework of the Magnetism in Massive Stars (MiMeS) Survey. Mean least-squares deconvolved Stokes I and V line profiles were extracted for each observation, from which we measured the radial velocity, rotational and non-rotational broadening velocities, and longitudinal magnetic field Bℓ. The investigation of the Stokes I profiles led to the discovery of two new multiline spectroscopic systems (HD 46106, HD 204827) and confirmed the presence of a suspected companion in HD 37041. We present a modified strategy of the least-squares deconvolution technique aimed at optimizing the detection of magnetic signatures while minimizing the detection of spurious signatures in Stokes V. Using this analysis, we confirm the detection of a magnetic field in six targets previously reported as magnetic by the MiMeS collaboration (HD 108, HD 47129A2, HD 57682, HD 148937, CPD-28 2561, and NGC 1624-2), as well as report the presence of signal in Stokes V in three new magnetic candidates (HD 36486, HD 162978, and HD 199579). Overall, we find a magnetic incidence rate of 7 ± 3 per cent, for 108 individual O stars (including all O-type components part of multiline systems), with a median uncertainty of the Bℓ measurements of about 50 G. An inspection of the data reveals no obvious biases affecting the incidence rate or the preference for detecting magnetic signatures in the magnetic stars. Similar to A- and B-type stars, we find no link between the stars' physical properties (e.g. Teff, mass, and age) and the presence of a magnetic field. However, the Of?p stars represent a distinct class of magnetic O-type stars.

  15. Physical characterization of Galactic O-type stars targeted by the IACOB and OWN surveys

    Science.gov (United States)

    Holgado, G.; Simón-Díaz, S.; Barbá, R.

    2017-03-01

    We present first results from the quantitative spectroscopic analysis of ˜ 270 Galactic O-type stars targeted by the IACOB and OWN surveys (implying the largest sample of stars of this type analyzed homogeneously). We also evaluate what is the present situation regarding available information about distances, as provided by the Hipparcos and Gaia missions

  16. Physical characterization of Galactic O-type stars targeted by the IACOB and OWN surveys

    CERN Document Server

    Holgado, G; Barbá, R H

    2016-01-01

    We present first results from the quantitative spectroscopic analysis of 266 Galactic O-type stars targeted by the IACOB and OWN surveys (implying the largest sample of stars of this type analyzed homogeneously). We also evaluate what is the present situation regarding available information about distances, as provided by the Hipparcos and Gaia missions.

  17. Revealing the nature of star forming blue early-type galaxies at low redshift

    CERN Document Server

    George, Koshy

    2015-01-01

    Context: Star forming early-type galaxies with blue optical colours at low redshift can be used to test our current understanding of galaxy formation and evolution. Aims: We want to reveal the fuel and triggering mechanism for star formation in these otherwise passively evolving red and dead stellar systems. Methods: We undertook an optical and ultraviolet study of 55 star forming blue early-type galaxies, searching for signatures of recent interactions that could be driving the molecular gas into the galaxy and potentially triggering the star formation. Results: We report here our results on star forming blue early-type galaxies with tidal trails and in close proximity to neighbouring galaxies that are evidence of ongoing or recent interactions between galaxies. There are 12 galaxies with close companions with similar redshifts, among which two galaxies are having ongoing interactions that potentially trigger the star formation. Two galaxies show a jet feature that could be due to the complete tidal disrupti...

  18. Searching for swept-up Hydrogen and Helium in the late-time spectra of 11 nearby Type Ia supernovae

    CERN Document Server

    Maguire, Kate; Sullivan, Mark; Mazzali, Paolo A

    2015-01-01

    The direct detection of a stellar system that explodes as a Type Ia supernova (SN Ia) has not yet been successful. Various indirect methods have been used to investigate SN Ia progenitor systems but none have produced conclusive results. A prediction of single-degenerate models is that H- (or He-) rich material from the envelope of the companion star should be swept up by the SN ejecta in the explosion. Seven SNe Ia have been analysed to date looking for signs of H-rich material in their late-time spectra and none were detected. We present results from new late-time spectra of 11 SNe Ia obtained at the VLT using XShooter and FORS2. We present the tentative detection of H-alpha emission for SN 2013ct, corresponding to ~0.007 Msun of stripped/ablated companion star material (under the assumptions of the spectral modelling). This mass is significantly lower than expected for single-degenerate scenarios, suggesting that >0.1 Msun of H-rich is present but not observed. We do not detect H-alpha emission in the othe...

  19. Multi-Mode Oscillations in Classical Cepheids and RR Lyrae-Type Stars

    CERN Document Server

    Moskalik, Paweł

    2014-01-01

    I review different types of multi-mode pulsations observed in classical Cepheids and in RR Lyrae-type star. The presentation concentrates on the newest results, with special emphasis on recently detected nonradial oscillations.

  20. Origin of the Lyman excess in early-type stars

    CERN Document Server

    Cesaroni, R; Beltrán, M T; Molinari, S; Olmi, L; Treviño-Morales, S P

    2016-01-01

    Ionized regions around early-type stars are believed to be well-known objects, but until recently, our knowledge of the relation between the free-free radio emission and the IR emission has been observationally hindered by the limited angular resolution in the far-IR. The advent of Herschel has now made it possible to obtain a more precise comparison between the two regimes, and it has been found that about a third of the young HII regions emit more Lyman continuum photons than expected, thus presenting a Lyman excess. With the present study we wish to distinguish between two scenarios that have been proposed to explain the existence of the Lyman excess: (i) underestimation of the bolometric luminosity, or (ii) additional emission of Lyman-continuum photons from an accretion shock. We observed an outflow (SiO) and an infall (HCO+) tracer toward a complete sample of 200 HII regions, 67 of which present the Lyman excess. Our goal was to search for any systematic difference between sources with Lyman excess and ...

  1. The IACOB project . III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars

    Science.gov (United States)

    Simón-Díaz, S.; Godart, M.; Castro, N.; Herrero, A.; Aerts, C.; Puls, J.; Telting, J.; Grassitelli, L.

    2017-01-01

    late-B dwarfs and giants, which present a mixture of cases in terms of line-profile shape and variability, the whole O-type and B supergiant domain (or, roughly speaking, stars with MZAMS ≳ 15 M⊙) is fully dominated by stars with a remarkable non-rotational broadening component and very similar profiles (including type of variability). We provide some examples illustrating how this observational dataset can be used to evaluate scenarios aimed at explaining the existence of sources of non-rotational broadening in massive stars. Full Table 1 is 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/597/A22

  2. Spectroscopic survey of Kepler stars. I. HERMES/Mercator observations of A- and F-type stars

    CERN Document Server

    Niemczura, E; Smalley, B; Uytterhoeven, K; Pigulski, A; Lehmann, H; Bowman, D M; Catanzaro, G; van Aarle, E; Bloemen, S; Briquet, M; De Cat, P; Drobek, D; Eyer, L; Gameiro, J F S; Gorlova, N; Kaminski, K; Lampens, P; Marcos-Arenal, P; Papics, P I; Vandenbussche, B; Van Winckel, H; Steslicki, M; Fagas, M

    2015-01-01

    The Kepler space mission provided near-continuous and high-precision photometry of about 207,000 stars, which can be used for asteroseismology. However, for successful seismic modelling it is equally important to have accurate stellar physical parameters. Therefore, supplementary ground-based data are needed. We report the results of the analysis of high-resolution spectroscopic data of A- and F-type stars from the Kepler field, which were obtained with the HERMES spectrograph on the Mercator telescope. We determined spectral types, atmospheric parameters and chemical abundances for a sample of 117 stars. Hydrogen Balmer, Fe I, and Fe II lines were used to derive effective temperatures, surface gravities, and microturbulent velocities. We determined chemical abundances and projected rotational velocities using a spectrum synthesis technique. The atmospheric parameters obtained were compared with those from the Kepler Input Catalogue (KIC), confirming that the KIC effective temperatures are underestimated for ...

  3. Circumnuclear Regions of Star Formation in Early Type Galaxies

    CERN Document Server

    Diaz, Angeles I; Hagele, Guillermo F; Castellanos, Marcelo

    2008-01-01

    Circumnuclear star forming regions, also called hotspots, are often found in the inner regions of some spiral galaxies where intense processes of star formation are taking place. In the UV, massive stars dominate the observed circumnuclear emission even in the presence of an active nucleus, contributing between 30 and 50% to the H$\\beta$ total emission of the nuclear zone. Spectrophotometric data of moderate resolution (3000 < R < 11000) are presented from which the physical properties of the ionized gas: electron density, oxygen abundances, ionization structure etc. have been derived.

  4. A nova re-accretion model for J-type carbon stars

    CERN Document Server

    Sengupta, S; Lau, H H B

    2013-01-01

    The J-type carbon (J)-stars constitute 10-15% of the observed carbon stars in both our Galaxy and the Large Magellanic Cloud (LMC). They are characterized by strong 13C absorption bands with low 12C/13C ratios along with other chemical signatures peculiar for typical carbon stars, e.g. a lack of s-process enhancement. Most of the J-stars are dimmer than the N-type carbon stars some of which, by hot-bottom burning, make 13C only in a narrow range of masses. We investigate a binary-star formation channel for J-stars involving re-accretion of carbon-rich nova ejecta on main-sequence companions to low-mass carbon-oxygen white-dwarfs. The subsequent evolution of the companion stars in such systems is studied with a rapid binary evolutionary code to predict chemical signatures of nova pollution in systems which merge into giant single stars. A detailed population synthesis study is performed to estimate the number of these mergers and compare their properties with observed J-stars. Our results predict that such nov...

  5. Synthetic spectra for O and B type subdwarf stars

    CERN Document Server

    Nemeth, Peter; Tremblay, Pier-Emmanuel; Hubeny, Ivan

    2013-01-01

    We present a grid of optical (3200--7200 \\AA) synthetic spectra calculated with Tlusty/Synspec. The new NLTE model atmospheres include the most recent hydrogen Stark broadening profiles; were calculated in opacity sampling and limited to pure H/He composition. The grid covers the observed parameter space of (He-)sdB and (He-)sdO stars, therefore it is suitable for the homogeneous spectral analyses of such evolved stars.

  6. Copernicus observations of the N v resonance doublet in 53 early-type stars

    Science.gov (United States)

    Abbott, D. C.; Bohlin, R. C.; Savage, B. D.

    1982-01-01

    UV spectra in the wavelength interval 1170-1270 A are presented for 53 early-type stars ranging in spectral type from O6.5 V to B2.5 IV. The sample includes four Wolf-Rayet stars, seven known Oe-Be stars, and six galactic halo OB stars. A qualitative analysis of the stellar N v doublet reveals that: (1) N v is present in all stars hotter and more luminous than type B0 for the main sequence, B1 for giants, and B2 for supergiants; (2) shell components of N v and an unidentified absorption feature at 1230 A are present in about half of the stars; (3) the column density of N v is well correlated with bolometric luminosity over the spectral range O6 to B2; and (4) the ratio of emission to absorption equivalent width is a factor of 2 smaller in the main sequence stars than in supergiants, which suggests that the wind structure changes as a star evolves. For several stars, this ratio is too small to be explained by traditional wind models.

  7. Steady-state evolution of debris disks around solar-type stars

    CERN Document Server

    Kains, N; Greaves, J S

    2011-01-01

    We present an analysis of debris disk data around Solar-type stars (spectral types F0-K5) using the steady-state analytical model of Wyatt et al. (2007). Models are fitted to published data from the FEPS (Meyer et al. 2006) project and various GTO programs obtained with MIPS on the Spitzer Space Telescope at 24 micron and 70 micron, and compared to a previously published analysis of debris disks around A stars using the same evolutionary model. We find that the model reproduces most features found in the data sets, noting that the model disk parameters for solar-type stars are different to those of A stars. Although this could mean that disks around Solar-type stars have different properties from their counterparts around earlier-type stars, it is also possible that the properties of disks around stars of different spectral types appear more different than they are because the blackbody disk radius underestimates the true disk radius by a factor $X_r$ which varies with spectral type. We use results from reali...

  8. Late Type 3b Endoleak with an Endurant Endograft

    Directory of Open Access Journals (Sweden)

    Mehmet Barburoglu

    2015-01-01

    Full Text Available Endovascular stent grafting with different commercially available stent graft systems is widely applied for the treatment of abdominal aortic aneurysms with high success rates in the current era. Various types of endoleaks are potential complications of the procedure. They usually occur in the early period. In this report, we present type 3b endoleak occurring 14 months after a successful endovascular abdominal aortic aneurysm repair with a Medtronic Endurant stent graft.

  9. CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. II. P-TYPE BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Kaltenegger, Lisa [MPIA, Koenigstuhl 17, Heidelberg, D-69117 (Germany)

    2013-11-10

    We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results.

  10. Discovery of a magnetic field in the early B-type star σ Lupi

    NARCIS (Netherlands)

    Henrichs, H.F.; Kolenberg, K.; Plaggenborg, B.; Marsden, S.C.; Waite, I.A.; Landstreet, J.D.; Wade, G.A.; Grunhut, J.H.; Oksala, M.E.

    2012-01-01

    Context. Magnetic early B-type stars are rare. Indirect indicators are needed to identify them before investing in time-intensive spectropolarimetric observations. Aims. We use the strongest indirect indicator of a magnetic field in B stars, which is periodic variability of ultraviolet (UV) stellar

  11. Observations of non-solar-type dynamo processes in stars with shallow convective zones

    NARCIS (Netherlands)

    Jeffers, S.V.; Donati, J.F.; Alecian, E.; Marsden, S.C.

    2010-01-01

    The magnetic field topology and differential rotation are fundamental signatures of the dynamo processes that generate the magnetic activity observed in the Sun and solar-type stars. To investigate how these dynamo processes evolve in stars with shallow convective zones, we present high-resolution s

  12. Deep infrared imaging of close companions to austral A- and F-type stars

    CERN Document Server

    Ehrenreich, David; Montagnier, Guillaume; Chauvin, Gaël; Galland, Franck; Beuzit, Jean-Luc; Rameau, Julien

    2010-01-01

    The search for substellar companions around stars with different masses along the main sequence is critical to understand the different processes leading to the formation of low-mass stars, brown dwarfs, and planets. In particular, the existence of a large population of low-mass stars and brown dwarfs physically bound to early-type main-sequence stars could imply that the massive planets recently imaged at wide separations (10-100 AU) around A-type stars are disc-born objects in the low-mass tail of the binary distribution. Our aim is to characterize the environment of early-type main-sequence stars by detecting brown dwarf or low-mass star companions between 10 and 500 AU. High contrast and high angular resolution near-infrared images of a sample of 38 southern A- and F-type stars have been obtained between 2005 and 2009 with the instruments VLT/NaCo and CFHT/PUEO. Multi-epoch observations were performed to discriminate comoving companions from background contaminants. About 41 companion candidates were imag...

  13. Asteroseismology of solar-type stars with Kepler: II. Stellar modeling

    DEFF Research Database (Denmark)

    Metcalfe , T.S.; Karoff, Christoffer

    2010-01-01

    Observations from the Kepler satellite were recently published for three bright G-type stars, which were monitored during the first 33.5 days of science operations. One of these stars, KIC 11026764, exhibits a characteristic pattern of oscillation frequencies suggesting that the star has evolved...... significantly. We have derived initial estimates of the properties of KIC 11026764 from the oscillation frequencies observed by Kepler, combined with ground-based spectroscopic data. We present preliminary results from detailed modeling of this star, employing a variety of independent codes and analyses...

  14. Weak magnetic fields in early-type stars: failed fossils

    CERN Document Server

    Braithwaite, Jonathan

    2012-01-01

    Weak magnetic fields have recently been detected in Vega and Sirius. Here, we explore the possibility that these fields are the remnants of some field inherited or created during or shortly after star formation and, unlike true fossil fields, are still evolving as we observe them. The timescale of this evolution is given in terms of the Alfven timescale and the rotation frequency by tau_evol ~ tau_A^2 Omega, which would be comparable to the age of the star. It is shown that it is likely that all intermediate- and high-mass stars contain fields of at least the order of the strength found so far in Vega and Sirius. Faster rotators are expected to have stronger magnetic fields. Stars may experience an increase in field strength during their early main-sequence, but for most of their lives field strength will decrease slowly. The length scale of the magnetic structure on the surface may be small in very young stars but should quickly increase to at least very approximately a fifth of the stellar radius.

  15. Late-Onset Glioma with Neurofibromatosis Type 1

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2002-10-01

    Full Text Available The frequency of symptomatic nonoptic pathway brain tumors in adolescents and adults known to have neurofibromatosis type 1 (NF1 was determined from the National Neurofibromatosis Foundation International Database (NNFFID in a study at Washington University School of Medicine, St Louis, MO.

  16. Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra

    Science.gov (United States)

    Becker, Juliette C.; Johnson, John Asher; Vanderburg, Andrew; Morton, Timothy D.

    2015-04-01

    We present a technique to extract radial velocity (RV) measurements from echelle spectrograph observations of rapidly rotating stars (V sin i≳ 50 km s-1). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the RV shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract RV measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute RVs with a precision ranging from 0.5-2.0 km s-1 per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with RV scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly rotating stars.

  17. A BCool survey of the magnetic fields of planet-hosting solar-type stars

    Science.gov (United States)

    Mengel, M. W.; Marsden, S. C.; Carter, B. D.; Horner, J.; King, R.; Fares, R.; Jeffers, S. V.; Petit, P.; Vidotto, A. A.; Morin, J.; BCool Collaboration

    2017-03-01

    We present a spectropolarimetric snapshot survey of solar-type planet-hosting stars. In addition to 14 planet-hosting stars observed as part of the BCool magnetic snapshot survey, we obtained magnetic observations of a further 19 planet-hosting solar-type stars in order to see if the presence of close-in planets had an effect on the measured surface magnetic field (|Bℓ|). Our results indicate that the magnetic activity of this sample is congruent with that of the overall BCool sample. The effects of the planetary systems on the magnetic activity of the parent star, if any, are too subtle to detect compared to the intrinsic dispersion and correlations with rotation, age and stellar activity proxies in our sample. Four of the 19 newly observed stars, two of which are subgiants, have unambiguously detected magnetic fields and are future targets for Zeeman-Doppler mapping.

  18. A BCool survey of the magnetic fields of planet-hosting solar-type stars

    CERN Document Server

    Mengel, M W; Carter, B D; Horner, J; King, R; Fares, R; Jeffers, S V; Petit, P; Vidotto, A A; Morin, J

    2016-01-01

    We present a spectropolarimetric snapshot survey of solar-type planet hosting stars. In addition to 14 planet-hosting stars observed as part of the BCool magnetic snapshot survey, we obtained magnetic observations of a further 19 planet-hosting solar-type stars in order to see if the presence of close-in planets had an effect on the measured surface magnetic field (|B$_{\\ell}$|). Our results indicate that the magnetic activity of this sample is congruent with that of the overall BCool sample. The effects of the planetary systems on the magnetic activity of the parent star, if any, are too subtle to detect compared to the intrinsic dispersion and correlations with rotation, age and stellar activity proxies in our sample. Four of the 19 newly observed stars, two of which are subgiants, have unambiguously detected magnetic fields and are future targets for Zeeman Doppler Mapping.

  19. PROJECTED ROTATIONAL VELOCITIES OF 136 EARLY B-TYPE STARS IN THE OUTER GALACTIC DISK

    Energy Technology Data Exchange (ETDEWEB)

    Garmany, C. D.; Glaspey, J. W. [National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719 (United States); Bragança, G. A.; Daflon, S.; Fernandes, M. Borges; Cunha, K. [Observatório Nacional-MCTI, Rua José Cristino, 77. CEP: 20921-400, Rio de Janeiro, RJ (Brazil); Oey, M. S. [University of Michigan, Department of Astronomy, 311 West Hall, 1085 S. University Ave., Ann Arbor, MI: 48109-1107 (United States); Bensby, T., E-mail: garmany@noao.edu [Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-22100, Lund (Sweden)

    2015-08-15

    We have determined projected rotational velocities, v sin i, from Magellan/MIKE echelle spectra for a sample of 136 early B-type stars having large Galactocentric distances. The target selection was done independently of their possible membership in clusters, associations or field stars. We subsequently examined the literature and assigned each star as Field, Association, or Cluster. Our v sin i results are consistent with a difference in aggregate v sin i with stellar density. We fit bimodal Maxwellian distributions to the Field, Association, and Cluster subsamples representing sharp-lined and broad-lined components. The first two distributions, in particular, for the Field and Association are consistent with strong bimodality in v sin i. Radial velocities are also presented, which are useful for further studies of binarity in B-type stars, and we also identify a sample of possible new double-lined spectroscopic binaries. In addition, we find 18 candidate Be stars showing emission at Hα.

  20. Exploring the origin of magnetic fields in massive stars: A survey of O-type stars in clusters and in the field

    CERN Document Server

    Hubrig, S; Kharchenko, N V; Langer, N; de Wit, W J; Ilyin, I; Kholtygin, A F; Piskunov, A E; Przybilla, N

    2011-01-01

    To investigate statistically whether magnetic fields in massive stars are ubiquitous or appear in stars with specific spectral classification, certain ages, or in a special environment, we acquired 41 new spectropolarimetric observations for 36 stars. Among the observed sample roughly half of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association. Spectropolarimetric observations were obtained during three different nights using the low-resolution spectropolarimetric mode of FORS2 (FOcal Reducer low dispersion Spectrograph) mounted on the 8-m Antu telescope of the VLT. To assess the membership in open clusters and associations, we used astrometric catalogues with the best currently available kinematic and photometric data. A field at a significance level of 3sigma was detected in ten O-type stars. Importantly, the largest longitudinal magnetic fields were measured in two Of?p stars: =-381+-122G for CPD-282561 ...

  1. PNP-Pincer-Type Phosphaalkene Complexes of Late Transition Metals.

    Science.gov (United States)

    Ozawa, Fumiyuki; Nakajima, Yumiko

    2016-10-01

    This account summarizes our recent studies on PNP-pincer-type phosphaalkene complexes. Phosphaalkenes with a P=C bond possess an extremely low-lying π* orbital and have a marked tendency to engage in strong π back-bonding with transition metals. This particular ligand property provides PNP-pincer complexes with unique structures and reactivities. 2,6-Bis(phosphaethenyl)pyridine leads to the isolation of coordinatively unsaturated complexes of Fe(I) and Cu(I); the former adopts a trigonal monopyramidal configuration, whereas the latter has a strong affinity for PF6- and SbF6- as non-coordinating anions. Unsymmetrical PNP-pincer-type phosphaalkene complexes of Ir(I) bearing a dearomatized pyridine unit instantly cleave the N-H bond of NH3 and the C-H bond of MeCN at room temperature. The dearomatized iridium complexes catalyze the dehydrative coupling of amines with alcohols to afford N-alkylated amines and imines in high yields.

  2. The multiplicity of O-type stars in NGC 2244

    NARCIS (Netherlands)

    Mahy, L.; Rauw, G.; Martins, F.; Gosset, E.; Nazé, Y.; Godart, M.; Sana, H.A.A.; De Becker, M.; Eenens, P.

    2011-01-01

    The investigation of the multiplicity of massive stars is crucial to determine a robust binary fraction but also for understanding the physical properties of these objects. In this contribution, we will present the main results from our long-term spectroscopic survey devoted to the young open cluste

  3. A new type of compact stellar population: dark star clusters

    CERN Document Server

    Banerjee, Sambaran; 10.1088/2041-8205/741/1/L12

    2011-01-01

    Among the most explored directions in the study of dense stellar systems is the investigation of the effects of the retention of supernova remnants, especially that of the massive stellar remnant black holes (BHs), in star clusters. By virtue of their eventual high central concentration, these stellar mass BHs potentially invoke a wide variety of physical phenomena, the most important ones being emission of gravitational waves (GWs), formation of X-ray binaries, and modification of the dynamical evolution of the cluster. Here we propose, for the first time, that rapid removal of stars from the outer parts of a cluster by the strong tidal field in the inner region of our Galaxy can unveil its BH sub-cluster, which appears as a star cluster that is gravitationally bound by an invisible mass. We study the formation and properties of such systems through direct N-body computations and estimate that they can be present in significant numbers in the inner region of the Milky Way. We call such objects "dark star clu...

  4. A rare early-type star revealed in the Wing of the Small Magellanic Cloud

    CERN Document Server

    Evans, C J; Oskinova, L M; Gallagher, J S; Chu, Y -H; Gruendl, R A; Hamann, W -R; Hénault-Brunet, V; Todt, H

    2012-01-01

    Sk 183 is the visually-brightest star in the N90 nebula, a young star-forming region in the Wing of the Small Magellanic Cloud (SMC). We present new optical spectroscopy from the Very Large Telescope which reveals Sk 183 to be one of the most massive O-type stars in the SMC. Classified as an O3-type dwarf on the basis of its nitrogen spectrum, the star also displays broadened He I absorption which suggests a later type. We propose that Sk 183 has a composite spectrum and that it is similar to another star in the SMC, MPG 324. This brings the number of rare O2- and O3-type stars known in the whole of the SMC to a mere three. We estimate physical parameters for Sk 183 from analysis of its spectrum. For a single-star model, we estimate an effective temperature of 46+/-2 kK, a low mass-loss rate of ~10^-7 Msun yr^-1, and a spectroscopic mass of 46^+9_-8 Msun (for an adopted distance modulus of 18.7 mag to the young population in the SMC Wing). An illustrative binary model requires a slightly hotter temperature (~...

  5. Magnetic field measurements and wind-line variability of OB-type stars

    CERN Document Server

    Schnerr, R S; Neiner, C; Verdugo, E; de Jong, J; Geers, V C; Wiersema, K; van Dalen, B; Tijani, A; Plaggenborg, B; Rygl, K L J

    2010-01-01

    Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely to be related to such magnetic fields. Aims. We attempt to improve our understanding of massive-star magnetic fields, and observe twenty-five carefully-selected, OB-type stars. Methods. Of these stars we obtain 136 magnetic field strength measurements. We present the UV wind-line variability of all selected targets and summarise spectropolarimetric observations acquired using the MUSICOS spectropolarimeter, mounted at the TBL, Pic du Midi, between December 1998 and November 2004. From the average Stokes I and V line profiles, derived using the LSD method, we measure the magnetic field strengths, radial velocities, and first moment of the line profiles. Results. No significant magnetic field is detected in any OB-type star that we observed. Typical 1{\\sigma} errors are betwee...

  6. High Dispersion Spectroscopy of Solar-type Superflare Stars. II. Stellar Rotation, Starspots, and Chromospheric Activities

    CERN Document Server

    Notsu, Yuta; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2014-01-01

    We conducted high dispersion spectroscopic observations of 50 superflare stars with Subaru/HDS. These 50 stars were selected from the solar-type superflare stars that we had discovered from the Kepler data. More than half (34 stars) of these 50 target superflare stars show no evidence of binarity, and we estimated stellar parameters of these 34 stars in our previous study (Notsu et al. 2015, hereafter called Paper I). According to our previous studies using Kepler data, superflare stars show quasi-periodic brightness variations whose amplitude (0.1-10\\%) is much larger than that of the solar brightness variations (0.01-0.1\\%) caused by the existence of sunspots on the rotating solar surface. In this study, we investigated whether these quasi-periodic brightness variations of superflare stars are explained by the rotation of a star with fairly large starspots, by using stellar parameters derived in Paper I. First, we confirmed that the value of the projected rotational velocity $v \\sin i$ is consistent with th...

  7. Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79

    CERN Document Server

    Austin, S J; Tycner, C; Campbell, T; Honeycutt, R K

    2007-01-01

    The secondary photometric standard star #79 for the FS Aur field (Henden & Honeycutt 1997) designated as [HH97] FS Aur-79 (GSC 1874 399) is a short period (0.2508 days) eclipsing binary whose light curve is a combination of the $\\beta$ Lyr and BY Dra type variables. High signal-to-noise multi-color photometry were obtained using the USNO 1-m telescope. These light curves show asymmetry at quadrature phases (O'Connell effect), which can be modeled with the presence of star spots. A low resolution spectrum obtained with the 3.5-m WIYN telescope at orbital phase 0.76 is consistent with a spectral type of dK7e and dM3e. A radial velocity curve for the primary star was constructed using twenty-four high resolution spectra from the 9.2 m HET. Spectra show H-alpha and H-beta in emission confirming chromospheric activity and possibly the presence of circumstellar material. Binary star models that simultaneously fit the U, B, V, R and RV curves are those with a primary star of mass 0.59+-0.02 Msun, temperature 410...

  8. The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 Additional O-type Systems.

    Science.gov (United States)

    Maíz Apellániz, J.; Sota, A.; Arias, J. I.; Barbá, R. H.; Walborn, N. R.; Simón-Díaz, S.; Negueruela, I.; Marco, A.; Leão, J. R. S.; Herrero, A.; Gamen, R. C.; Alfaro, E. J.

    2016-05-01

    This is the third installment of the Galactic O-Star Spectroscopic Survey (GOSSS), a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ˜ 2500 digital observations selected from the Galactic O-Star Catalog. In this paper, we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects, there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries, 6 of which are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al. The GOSSS spectroscopic data in this article were gathered with five facilities: the 1.5 m Telescope at the Observatorio de Sierra Nevada (OSN), the 2.5 m du Pont Telescope at Las Campanas Observatory (LCO), the 3.5 m Telescope at Calar Alto Observatory (CAHA), and the 4.2 m William Herschel Telescope (WHT) and 10.4 m Gran Telescopio Canarias (GTC) at Observatorio del Roque de los Muchachos (ORM).

  9. SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies as a function of galaxy mass and type

    Science.gov (United States)

    Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo-Fernández, M.; Lian, J.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Storchi-Bergmann, T.; Schneider, D. P.

    2016-12-01

    We study the internal gradients of stellar population properties within 1.5 Re for a representative sample of 721 galaxies with stellar masses ranging between 109 M⊙ to 1011.5 M⊙ from the SDSS-IV MaNGA IFU survey. Through the use of our full spectral fitting code FIREFLY, we derive light and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quanfify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties, and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types are positive (˜0.09 dex/Re) pointing to "outside-in" progression of star formation, while late-type galaxies have negative light-weighted age gradients (˜-0.11 dex/Re), suggesting an "inside-out" formation of discs. We detect negative metallicity gradients in both early and late-type galaxies, but these are significantly steeper in late-types, suggesting that radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(∇[Z/H])/d(log M) ˜ -0.2 ± 0.05 , compared to d(∇[Z/H])/d(log M) ˜ -0.05 ± 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.

  10. SDSS-IV MaNGA: Spatially resolved star formation histories in galaxies as a function of galaxy mass and type

    Science.gov (United States)

    Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo-Fernández, M.; Lian, J.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Storchi-Bergmann, T.; Schneider, D. P.

    2017-04-01

    We study the internal gradients of stellar population properties within 1.5 Re for a representative sample of 721 galaxies, with stellar masses ranging between 109 M⊙ and 1011.5 M⊙ from the SDSS-IV MaNGA Integral-Field-Unit survey. Through the use of our full spectral fitting code firefly, we derive light- and mass-weighted stellar population properties and their radial gradients, as well as full star formation and metal enrichment histories. We also quantify the impact that different stellar population models and full spectral fitting routines have on the derived stellar population properties and the radial gradient measurements. In our analysis, we find that age gradients tend to be shallow for both early-type and late-type galaxies. Mass-weighted age gradients of early-types arepositive (˜0.09 dex/Re) pointing to 'outside-in' progression of star formation, while late-type galaxies have negative light-weighted age gradients (˜-0.11 dex/Re), suggesting an 'inside-out' formation of discs. We detect negative metallicity gradients in both early- and late-type galaxies, but these are significantly steeper in late-types, suggesting that the radial dependence of chemical enrichment processes and the effect of gas inflow and metal transport are far more pronounced in discs. Metallicity gradients of both morphological classes correlate with galaxy mass, with negative metallicity gradients becoming steeper with increasing galaxy mass. The correlation with mass is stronger for late-type galaxies, with a slope of d(∇[Z/H])/d(log M) ˜ -0.2 ± 0.05 , compared to d(∇[Z/H])/d(log M) ˜ -0.05 ± 0.05 for early-types. This result suggests that the merger history plays a relatively small role in shaping metallicity gradients of galaxies.

  11. Statistical studies of superflares on G-, K-, M- type stars from Kepler data

    Science.gov (United States)

    Notsu, Yuta; Maehara, Hiroyuki; Honda, Satoshi; Notsu, Shota; Namekata, Kosuke; Ikuta, Kai; Nogami, Daisaku; Shibata, Kazunari

    2017-05-01

    Flares are thought to be sudden releases of magnetic energy stored around starspots. Recent space high-precision photometry shows “superflares”, 10-104 times more energetic than the largest solar flares, occur on many G, K, M-type stars (e.g., Maehara+2012 Nature). Harmful UV/X-ray radiation and high-energy particles such as protons are caused by such superflares. This may suggest that exoplanet host stars have severe effects on the physical and chemical evolution of exoplanetary atmospheres (cf. Segura+2010 Astrobiology, Takahashi+2016 ApJL).We here present statistical properties of superflares on G, K, M-type stars on the basis of our analyses of Kepler photometric data (Maehara+2012 Nature, Shibayama+2013 ApJS, Notsu+2013 ApJ, Canderaresi+2014 ApJ, Maehara+2015 EPS, Maehara+2017 PASJ). We found more than 5000 superflares on 800 G, K, M-type main-sequence stars, and the occurrence frequency (dN/dE) of superflares as a function of flare energy (E) shows the power-law distribution with the index of -1.8 -1.9. This power-law distribution is consistent with that of solar flares.Flare frequency increases as stellar temperature decreases. As for M-type stars, energy of the largest flares is smaller compared with G,K-type stars, but more frequent “hazardous” flares for the habitable planets since the habitable zone around M-type stars is much smaller compared with G, K-type stars.Rotation period and starspot coverage can be estimated from the quasi-periodic brightness variation of the superflare stars. The intensity of Ca II 8542 line of superflare stars, which is measured from spectroscopic observations with Subaru Telescope, has a well correlation with the brightness variation amplitude (Notsu+2015a&b PASJ).Flare frequency has a correlation with rotation period, and this suggests young rapidly-rotating stars (like “young Sun”) have more severe impacts of flares on the planetary atmosphere (cf. Airapetian+2016 ApJL). Flare energy and frequency also depends

  12. High Dispersion Spectroscopy of Solar-Type Superflare Stars With Subaru/HDS

    Science.gov (United States)

    Notsu, Yuta; Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Namekata, Kosuke; Nogami, Daisaku; Shibata, Kazunari

    2016-07-01

    Superflares are flares that release total energy 10-104times greater than that of the biggest solar flares ( 1032 erg). Recent Kepler-space-telescope observations found more than 1000superflares on a few hundred solar-type stars (Maehara et al. 2012, Nature; Shibayama et al. 2013, ApJS, Maehara et al. 2015 EPS).Suchsuperflare stars show quasi-periodicbrightnessvariations with the typical period of from one to a few tens of days. Such variations are thought to be caused by the rotation of the star with large starspots (Notsu et al. 2013, ApJ). However, spectroscopic observations are needed in order to confirm whether the variation is really due to the rotation and whether superflares can occur on ordinary single stars similar to our Sun.Then we have carried out spectroscopic observations for 50 solar-type superflare stars with Subaru/HDS (Notsu et al. 2015a&b, PASJ). As a result, more than half (34 stars) of the targetstars show no evidence of binarity, and the atmospheric parameters of these stars are in the range of solar-type stars.The detailed analyses for these 34 stars show that (1) the projected rotational velocities (v sin i) are consistent with the rotational velocities estimated from the brightness variations, (2)there is a correlation between the brightness variation amplitude and the intensity of Ca II IR triplet line. These results support that the brightness variation discussed above is explained bythe rotation of a star with large starspots. (The contents of this poster were already summarized in the proceeding of IAU Symposium S320 (Notsu et al. 2016 IAUS in press, arXiv:1510.08143))

  13. DUst around NEarby Stars (DUNES): searching for Kuiper-belt analogues around solar-type stars

    Science.gov (United States)

    Montesinos, B.; Dunes Consortium

    2011-11-01

    In this paper we summarize some of the results of the Herschel Open Time Key Programme DUNES (DUst around NEarby Stars). This project aims at detecting and studying cold dust discs, i.e. Edgeworth-Kuiper-belt analogues, around FGK stars of the solar neighbourhood, in a volume-limited sample. The sensitivity and wavelengths of the two instruments used, namely PACS (70, 100 and 160 micron) and SPIRE (250, 350 and 500 micron) are the appropriate ones for these tasks. Despite of the fact that, at the time of writing these proceedings, only about half of the sample has been observed, new results and increased statistics with respect to previous surveys and observations have emerged. Some new, unexpected results, in the form of very cold discs, pose some challenges to the current modelling paradigms. Note that at the time this paper is published, the results given and some of the conclusions will be obviously out of date.

  14. Rotating models of young solar-type stars : Exploring braking laws and angular momentum transport processes

    CERN Document Server

    Amard, Louis; Charbonnel, Corinne; Gallet, Florian; Bouvier, Jérôme

    2016-01-01

    We study the predicted rotational evolution of solar-type stars from the pre-main sequence to the solar age with 1D rotating evolutionary models including physical ingredients. We computed rotating evolution models of solar-type stars including an external stellar wind torque and internal transport of angular momentum following the method of Maeder and Zahn with the code STAREVOL. We explored different formalisms and prescriptions available from the literature. We tested the predictions of the models against recent rotational period data from extensive photometric surveys, lithium abundances of solar-mass stars in young clusters, and the helioseismic rotation profile of the Sun. We find a best-matching combination of prescriptions for both internal transport and surface extraction of angular momentum. This combination provides a very good fit to the observed evolution of rotational periods for solar-type stars from early evolution to the age of the Sun. Additionally, we show that fast rotators experience a st...

  15. Dynamical model for spindown of solar-type stars

    CERN Document Server

    Sood, Aditi; Hollerbach, Rainer

    2016-01-01

    Since their formation, stars slow down their rotation rates by the removal of angular momentum from their surfaces, e.g. via stellar winds. Despite the complexity of the processes involved, a traditional model, where the removal of angular momentum loss by magnetic fields is prescribed, has provided a useful framework to understand observational relations between stellar rotation and age and magnetic field strength. Here, a spindown model is proposed where loss of angular momentum by magnetic fields is evolved dynamically, instead of being kinematically prescribed. To this end, we evolve the stellar rotation and magnetic field simultaneously over stellar evolution time by extending our previous work on a dynamo model which incorporates the nonlinear feedback mechanisms on rotation and magnetic fields. Our extended model reproduces key observations and explains the presence of the two branches of (fast and slow rotating) stars which have different relations between rotation rate $\\Omega$ vs. time (age), magnet...

  16. Direct multi-wavelength limb-darkening measurements of three late-type giants with the Navy Prototype Optical Interferometer

    CERN Document Server

    Wittkowski, M; Johnston, K J; Mozurkewich, D; Hajian, A R; White, N M

    2001-01-01

    We present direct measurements of the limb-darkened intensity profiles of the late-type giant stars HR5299, HR7635, and HR8621 obtained with the Navy Prototype Optical Interferometer (NPOI) at the Lowell Observatory. A triangle of baselines with lengths of 18.9 m, 22.2 m, and 37.5 m was used. We utilized squared visibility amplitudes beyond the first minimum, as well as triple amplitudes and phases in up to 10 spectral channels covering a wavelength range of ~650 nm to ~850 nm. We find that our data can best be described by featureless symmetric limb-darkened disk models while uniform disk and fully darkened disk models can be rejected. We derive high-precision angular limb-darkened diameters for the three stars of 7.44 mas +/- 0.11 mas, 6.18 mas +/- 0.07 mas, and 6.94 mas +/- 0.12 mas, respectively. Using the HIPPARCOS parallaxes, we determine linear limb-darkened radii of 114 R$_\\odot \\pm $13 R$_\\odot$, 56 R$_\\odot \\pm $4 R$_\\odot$, and 98 R$_\\odot \\pm $9 R$_\\odot$, respectively. We compare our data to a gr...

  17. Solar-type dynamo behaviour in fully convective stars without a tachocline.

    Science.gov (United States)

    Wright, Nicholas J; Drake, Jeremy J

    2016-07-28

    In solar-type stars (with radiative cores and convective envelopes like our Sun), the magnetic field powers star spots, flares and other solar phenomena, as well as chromospheric and coronal emission at ultraviolet to X-ray wavelengths. The dynamo responsible for generating the field depends on the shearing of internal magnetic fields by differential rotation. The shearing has long been thought to take place in a boundary layer known as the tachocline between the radiative core and the convective envelope. Fully convective stars do not have a tachocline and their dynamo mechanism is expected to be very different, although its exact form and physical dependencies are not known. Here we report observations of four fully convective stars whose X-ray emission correlates with their rotation periods in the same way as in solar-type stars. As the X-ray activity-rotation relationship is a well-established proxy for the behaviour of the magnetic dynamo, these results imply that fully convective stars also operate a solar-type dynamo. The lack of a tachocline in fully convective stars therefore suggests that this is not a critical ingredient in the solar dynamo and supports models in which the dynamo originates throughout the convection zone.

  18. Solar-type dynamo behaviour in fully convective stars without a tachocline

    Science.gov (United States)

    Wright, Nicholas J.; Drake, Jeremy J.

    2016-07-01

    In solar-type stars (with radiative cores and convective envelopes like our Sun), the magnetic field powers star spots, flares and other solar phenomena, as well as chromospheric and coronal emission at ultraviolet to X-ray wavelengths. The dynamo responsible for generating the field depends on the shearing of internal magnetic fields by differential rotation. The shearing has long been thought to take place in a boundary layer known as the tachocline between the radiative core and the convective envelope. Fully convective stars do not have a tachocline and their dynamo mechanism is expected to be very different, although its exact form and physical dependencies are not known. Here we report observations of four fully convective stars whose X-ray emission correlates with their rotation periods in the same way as in solar-type stars. As the X-ray activity-rotation relationship is a well-established proxy for the behaviour of the magnetic dynamo, these results imply that fully convective stars also operate a solar-type dynamo. The lack of a tachocline in fully convective stars therefore suggests that this is not a critical ingredient in the solar dynamo and supports models in which the dynamo originates throughout the convection zone.

  19. A New Type of Extremely Metal Poor Star

    CERN Document Server

    Cohen, J G; Christlieb, N; Shectman, S; Thompson, I; Melendez, J; Reimers, L W D; Cohen, Judith G.; William, Andrew Mc; Christlieb, Norbert; Shectman, Stephen; Thompson, Ian; Melendez, Jorge; Reimers, Lutz Wisotzki & Dieter

    2007-01-01

    We present an abundance analysis for the extremely metal poor star HE1424-0241 based on high dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ~ -4.0 dex. Relative to Fe, HE1424-0241 has normal Mg, but it shows a very large deficiency of Si, with epsilon(Si)/epsilon(Fe) ~ 1/10 and epsilon(Si)/epsilon(Mg) ~ 1/25 that of all previously known extremely metal poor giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNII contributing to the chemical inventory of HE1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE1424-0241 shows a deficiency of the explosive alpha-burning elements Si, Ca and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic...

  20. Binary star detectability in $Kepler$ data from phase modulation of different types of oscillations

    CERN Document Server

    Compton, Douglas L; Murphy, Simon J; Stello, Dennis

    2016-01-01

    Detecting binary stars in photometric time series is traditionally done by measuring eclipses. This requires the orbital plane to be aligned with the observer. A new method without that requirement uses stellar oscillations to measure delays in the light arrival time and has been successfully applied to $\\delta$ Scuti stars. However, application to other types of stars has not been explored. To investigate this we simulated light curves with a range of input parameters. We find a correlation between the signal-to-noise of the pulsation modes and the time delay required to detect binary motion. The detectability of the binarity in the simulations and in real $Kepler$ data shows strong agreement, hence, we describe the factors that have prevented this method from discovering binary companions to stars belonging to various classes of pulsating stars.

  1. On the rarity of FK Com stars

    Science.gov (United States)

    Hagen, W.; Stencel, R. E.

    1985-01-01

    Very high-dispersion spectra (2.5 A/mm) were obtained of 31 southern late-type stars, predominantly early G giants, in an effort to find new rapidly rotating, active stars which would be FK Com-like. Measurements of linewidths and the strength of chromospheric Ca II K-line emission are presented, but no new star could be added to the class of 'rapid rotators'. Space densities and evolutionary lifetimes for FK Com stars are discussed.

  2. Pulsating B-type stars in the open cluster NGC 884: frequencies, mode identification and asteroseismology

    CERN Document Server

    Saesen, S; Aerts, C; Miglio, A; Carrier, F

    2013-01-01

    Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. We present an observational asteroseismology study based on the discovery of numerous multi-periodic and mono-periodic B-stars in the open cluster NGC 884. We describe a thorough investigation of the pulsational properties of all B-type stars in the cluster. Overall, our detailed frequency analysis resulted in 115 detected frequencies in 65 stars. We found 36 mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic stars and one star with 9 independent frequencies. We also derived the amplitudes and phases of all detected frequencies in the U, B, V and I filter, if available. We achieved unambiguous identifications of the mode degree for twelve of the de...

  3. Ruptured Aortic Aneurysm From Late Type II Endoleak Treated by Transarterial Embolization

    Energy Technology Data Exchange (ETDEWEB)

    Gunasekaran, Senthil, E-mail: sgunasekaran@lumc.edu [Loyola University Medical Center Chicago (United States); Funaki, Brian, E-mail: bfunaki@radiology.bsd.uchicago.edu; Lorenz, Jonathan, E-mail: jlorenz@radiology.bsd.uchicago.edu [University of Chicago Medical Center (United States)

    2013-02-15

    Endoleak is the most common complication after endovascular aneurysm repair. The most common type of endoleak, a type II endoleak, typically follows a benign course and is only treated when associated with increasing aneurysm size. In this case report, we describe a ruptured abdominal aortic aneurysm due to a late, type II endoleak occurring 10 years after endovascular aneurysm repair that was successfully treated by transarterial embolization.

  4. High Dispersion Spectroscopy of Solar-type Superflare Stars. III. Lithium Abundances

    CERN Document Server

    Honda, Satoshi; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2015-01-01

    We report on the abundance analysis of Li in solar-type (G-type main sequence) superflare stars which were found by the analysis of Kepler photometric data. Li is a key element to understand the evolution of the stellar convection zone which reflects the age of solar-type stars. We performed the high dispersion spectroscopy of solar-type superflare stars with Subaru/HDS, and confirmed that 34 stars show no evidence of binarity in our previous study. In this study, we derived the Li abundances of these 34 objects. We investigate correlations of Li abundance with stellar atmospheric parameters, rotational velocity, and superflare activities to understand the nature of superflare stars and the possibility of the nucleosynthesis of Li by superflares. We confirm the large dispersion in the Li abundance, and the correlation with stellar parameters is not seen. As compared with the Li abundance in Hyades cluster which is younger than the Sun, it is suggested that half of the observed stars are younger than Hyades cl...

  5. Age dependence of wind properties for solar type stars: a 3d study

    CERN Document Server

    Réville, Victor; Strugarek, Antoine; Brun, Allan Sacha

    2016-01-01

    Young and rapidly rotating stars are known for intense, dynamo generated magnetic fields. Spectropolarimetric observations of those stars in precisely aged clusters are key input for gyrochronology and magnetochronology. We use ZDI maps of several young K-type stars of similar mass and radius but with various ages and rotational periods, to perform 3D numerical MHD simulations of their coronae and follow the evolution of their magnetic properties with age. Those simulations yield the coronal structure as well as the instant torque exerted by the magnetized, rotating wind on the star. As stars get older, we find that the angular momentum loss decreases with $\\Omega^3$, which is the reason for the convergence on the Skumanich law. For the youngest stars of our sample, the angular momentum loss show signs of saturation around $8\\Omega_{\\odot}$, which is a common value used in spin evolution models for K-type stars. We compare these results to semi-analytical models and existing braking laws. We observe a complex...

  6. The Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4)

    CERN Document Server

    Lamb, J B; Segura-Cox, D M; Graus, A S; Kiminki, D C; Golden-Marx, J B; Parker, J Wm

    2015-01-01

    We present the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4), a spatially complete survey of uniformly selected field OB stars that covers the entire star-forming body of the SMC. Using the IMACS multislit spectrograph and MIKE echelle spectrograph on the Magellan telescopes, we obtained spectra of 374 early-type field stars that are at least 28 pc from any other OB candidates. We also obtained spectra of an additional 23 field stars in the SMC bar identified from slightly different photometric criteria. Here, we present the observational catalog of stars in the RIOTS4 survey, including spectral classifications and radial velocities. For three multi-slit fields covering 8% of our sample, we carried out monitoring observations over 9-16 epochs to study binarity, finding a spectroscopic, massive binary frequency of at least $\\sim$60% in this subsample. Classical Oe/Be stars represent a large fraction of RIOTS4 (42%), occurring at much higher frequency than in the Galaxy, consistent ...

  7. Rotational velocities of single and binary O-type stars in the Tarantula Nebula

    CERN Document Server

    Ramírez-Agudelo, O H; de Koter, A; Simón-Díaz, S; de Mink, S E; Tramper, F; Dufton, P L; Evans, C J; Gräfener, G; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2014-01-01

    Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, $v_e\\sin i$, of $\\sim$330 O-type objects, i.e. $\\sim$210 spectroscopic single stars and $\\sim$110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30\\,Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the $v_e\\sin i$ distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100\\,$\\rm{km s^{-1}}$. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tai...

  8. Emission from the Centrifugal Magnetospheres of Magnetic B-type Stars

    Science.gov (United States)

    Shultz, M.; Wade, G.; Rivinius, T.; Townsend, R.; MiMeS Collaboration

    2016-11-01

    Approximately 10% of B-type stars possess strong magnetic fields, and of these, 25% host centrifugal magnetospheres in which the radiative wind, magnetic field, and rotational support interact to form a dense circumstellar plasma visible in a variety of diagnostic lines. In this article we review the basic theory behind CMs, outline current theoretical and observational problems, compare the observational properties of CM host stars to those of classical Be stars, and finally present preliminary results of a population study aimed at clarifying the characteristics of this growing sub-class.

  9. Emission from the Centrifugal Magnetospheres of Magnetic B-type Stars

    CERN Document Server

    Shultz, Matt; Rivinius, Thomas; Townsend, Richard

    2014-01-01

    Approximately 10% of B-type stars possess strong magnetic fields, and of these, 25% host centrifugal magnetospheres (CMs) in which the radiative wind, magnetic field, and rotational support interact to form a dense circumstellar plasma visible in a variety of diagnostic lines. In this article we review the basic theory behind CMs, outline current theoretical and observational problems, compare the observational properties of CM host stars to those of classical Be stars, and finally present preliminary results of a population study aimed at clarifying the characteristics of this growing sub-class.

  10. WASP-26b: A 1-Jupiter-mass planet around an early-G-type star

    CERN Document Server

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

    2010-01-01

    We report the discovery of WASP-26b, a moderately over-sized Jupiter-mass exoplanet transiting its 11.3-magnitude early-G-type host star (1SWASP J001824.70-151602.3; TYC 5839-876-1) every 2.7566 days. A simultaneous fit to transit photometry and radial-velocity measurements yields a planetary mass of 1.02 +/- 0.03 M_Jup and radius of 1.32 +/- 0.08 R_Jup. The host star, WASP-26, has a mass of 1.12 +/- 0.03 M_sun and a radius of 1.34 +/- 0.06 R_sun and is in a visual double with a fainter K-type star. The two stars are at least a common-proper motion pair with a common distance of around 250 +/- 15 pc and an age of 6 +/- 2 Gy.

  11. The Galactic O-Star Spectroscopic Survey (GOSSS). III. 142 additional O-type systems

    CERN Document Server

    Apellániz, J Maíz; Arias, J I; Barbá, R H; Walborn, N R; Simón-Díaz, S; Negueruela, I; Marco, A; Leão, J R S; Herrero, A; Gamen, R C; Alfaro, E J

    2016-01-01

    This is the third installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R~2500 digital observations selected from the Galactic O-Star Catalog (GOSC). In this paper we present 142 additional stellar systems with O stars from both hemispheres, bringing the total of O-type systems published within the project to 590. Among the new objects there are 20 new O stars. We also identify 11 new double-lined spectroscopic binaries (SB2s), of which 6 are of O+O type and 5 of O+B type, and an additional new tripled-lined spectroscopic binary (SB3) of O+O+B type. We also revise some of the previous GOSSS classifications, present some egregious examples of stars erroneously classified as O-type in the past, introduce the use of luminosity class IV at spectral types O4-O5.5, and adapt the classification scheme to the work of Arias et al. (2016).

  12. SUPERFLARES ON SOLAR-TYPE STARS OBSERVED WITH KEPLER. I. STATISTICAL PROPERTIES OF SUPERFLARES

    Energy Technology Data Exchange (ETDEWEB)

    Shibayama, Takuya; Notsu, Shota; Notsu, Yuta; Nagao, Takashi [Department of Astronomy, Kyoto University, Sakyo, Kyoto 606-8502 (Japan); Maehara, Hiroyuki; Honda, Satoshi; Ishii, Takako T.; Nogami, Daisaku; Shibata, Kazunari, E-mail: shibayama@kwasan.kyoto-u.ac.jp [Kwasan and Hida Observatory, Kyoto University, Yamashina, Kyoto 607-8471 (Japan)

    2013-11-01

    By extending our previous study by Maehara et al., we searched for superflares on G-type dwarfs (solar-type stars) using Kepler data for a longer period (500 days) than that (120 days) in our previous study. As a result, we found 1547 superflares on 279 G-type dwarfs, which is much more than the previous 365 superflares on 148 stars. Using these new data, we studied the statistical properties of the occurrence rate of superflares, and confirmed the previous results, i.e., the occurrence rate (dN/dE) of superflares versus flare energy (E) shows a power-law distribution with dN/dE∝E {sup –α}, where α ∼ 2. It is interesting that this distribution is roughly similar to that for solar flares. In the case of the Sun-like stars (with surface temperature 5600-6000 K and slowly rotating with a period longer than 10 days), the occurrence rate of superflares with an energy of 10{sup 34}-10{sup 35} erg is once in 800-5000 yr. We also studied long-term (500 days) stellar brightness variation of these superflare stars and found that in some G-type dwarfs the occurrence rate of superflares was extremely high, ∼57 superflares in 500 days (i.e., once in 10 days). In the case of Sun-like stars, the most active stars show a frequency of one superflare (with 10{sup 34} erg) in 100 days. There is evidence that these superflare stars have extremely large starspots with a size about 10 times larger than that of the largest sunspot. We argue that the physical origin of the extremely high occurrence rate of superflares in these stars may be attributed to the existence of extremely large starspots.

  13. Granulation in K-type Dwarf Stars. I. Spectroscopic observations

    CERN Document Server

    Ramírez, I; Lambert, D L

    2008-01-01

    Very high resolution (R~160,000-210,000), high signal-to-noise ratio (S/N>300) spectra of nine bright K-dwarfs were obtained with the 2dcoude spectrograph on the 2.7m Telescope at McDonald Observatory to determine wavelength shifts and asymmetries of Fe I lines. The observed shapes and positions of Fe I lines reveal asymmetries and wavelength shifts that indicate the presence of granulation. In particular, line bisectors show characteristic C-shapes while line core wavelengths are blueshifted by an amount that increases with decreasing equivalent width (EW). On average, Fe I line bisectors have a span that ranges from nearly 0 for the weakest lines (residual core flux > 0.7) to about 75 m/s for the strongest lines (residual core flux ~ 0.3) while wavelength shifts range from about -150 m/s in the weakest (EW ~ 10 mA) lines to 0 in the strongest (EW > 100 mA) features. A more detailed inspection of the bisectors and wavelength shifts reveals star-to-star differences that are likely associated with differences ...

  14. Improving the surface-brightness color relation for early-type stars using optical interferometry

    CERN Document Server

    Challouf, M; Mourard, D; Graczyk, D; Aroui, H; Chesneau, O; Delaa, O; Pietrzyński, G; Gieren, W; Ligi, R; Meilland, A; Perraut, K; Tallon-Bosc, I; McAlister, H; Brummelaar, T ten; Sturmann, J; Sturmann, L; Turner, N; Farrington, C; Vargas, N; Scott, N

    2014-01-01

    The aim of this work is to improve the SBC relation for early-type stars in the $-1 \\leq V-K \\leq 0$ color domain, using optical interferometry. Observations of eight B- and A-type stars were secured with the VEGA/CHARA instrument in the visible. The derived uniform disc angular diameters were converted into limb darkened angular diameters and included in a larger sample of twenty four stars, already observed by interferometry, in order to derive a revised empirical relation for O, B, A spectral type stars with a V-K color index ranging from -1 to 0. We also take the opportunity to check the consistency of the SBC relation up to $V-K \\simeq 4$ using 100 additional measurements. We determined the uniform disc angular diameter for the eight following stars: $\\gamma$ Ori, $\\zeta$ Per, $8$ Cyg, $\\iota$ Her, $\\lambda$ Aql, $\\zeta$ Peg, $\\gamma$ Lyr and $\\delta$ Cyg with V-K color ranging from -0.70 to 0.02 and typical precision of about $1.5\\%$. Using our total sample of 132 stars with $V-K$ colors index ranging f...

  15. A catalog of M-type star candidates in the LAMOST data release 1

    Science.gov (United States)

    Zhong, Jing; Lépine, Sébastien; Li, Jing; Chen, Li; Hou, Jinliang

    2016-08-01

    In this work, we present a set of M-type star candidates selected from the LAMOST DR1. A discrimination method with the spectral index diagram is used to separate M giants and M dwarfs. Then, we have successfully assembled a set of M giants templates from M0 to M6, using the spectra identified from the LAMOST spectral database. After combining the M dwarf templates in Zhong et al. (2015a) and the new created M giant templates, we use the M-type spectral library to perform the template-fit method to classify and identify M-type stars in the LAMOST DR1. A catalog of M-type star candidates including 8639 M giants and 101690 M dwarfs/subdwarfs is provided. As an additional results, we also present other fundamental parameters like proper motion, photometry, radial velocity and spectroscopic distance.

  16. Late phase contrast enhanced-CT analysis of thrombosed type aortic dissection

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Hiromitsu; Kawamata, Hiroshi; Takagi, Ryo; Kumazaki, Tatsuo [Nippon Medical School, Tokyo (Japan)

    1995-10-01

    Seven patients with thrombosed type aortic dissection who underwent both early- and late-phase contrast enhanced (CE)-CT scans were analyzed. The image acquisition of early-phase CE-CT began 30 seconds after the intravenous administration of contrast material at an injection rate of 1.5 ml per second. Late-phase CE-CT began 6 minutes after contrast material injection. The thrombosed false lumens were not enhanced on early-phase CE-CTs in any of the cases. In five of seven cases, on the other hand, false lumens of the descending aorta were enhanced on late-phase images. Late enhancement in the false lumen was roughly divided into two patterns; a crescentic enhancement of the sub-adventitial region (3 cases), and a vague enhancement around the ulcer-like projection (2 cases). The mechanism of late enhancement in the false lumen was not fully elucidated. Although the clinical significance of late enhancement has not yet been established, it will be useful to demonstrate an unstable status of the thrombosed false lumens before organization. (author).

  17. Absorption-line strengths of 18 late-type spiral galaxies observed with SAURON

    NARCIS (Netherlands)

    Ganda, Katia; Peletier, Reynier F.; McDermid, Richard M.; Falcon-Barroso, Jesus; de Zeeuw, P. T.; Bacon, Roland; Cappellari, Michele; Davies, Roger L.; Emsellem, Eric; Krajnovic, Davor; Kuntschner, Harald; Sarzi, Marc; van de Ven, Glenn

    2007-01-01

    We present absorption line strength maps for a sample of 18 Sb-Sd galaxies observed using the integral-field spectrograph SAURON operating at the William Herschel Telescope on La Palma, as part of a project devoted to the investigation of the kinematics and stellar populations of late-type spirals,

  18. Postprandial chylomicron clearance rate in late teenagers with diabetes mellitus type 1

    NARCIS (Netherlands)

    van Waarde, WM; Odink, RJ; Rouwe, C; Stellaard, F; Westers, M; Vonk, RJ; Sauer, PJJ; Verkade, HJ

    2001-01-01

    A delayed chylomicron (CM) clearance rate, a known risk factor for atherosclerosis, has been described in adults with diabetes type I (DMI). We determined the CM clearance rate in late teenagers with DM1, and the relationship between CM clearance rate and elevated plasma lipid concentrations in DMI

  19. Synthetic activity indicators for M-type dwarf stars

    CERN Document Server

    Wedemeyer, Sven

    2015-01-01

    Here, we present a set of time-dependent 3D RMHD simulations of a M-dwarf star representative of AD Leo, which extend from the upper convection zone into the chromosphere. The 3D model atmospheres are characterized by a very dynamic and intermittent structure on small spatial and temporal scales and a wealth of physical processes, which by nature cannot be described by means of 1D static model atmospheres. Artificial observations of these models imply that a combination of complementary diagnostics such as Ca II lines and the continuum intensity from UV to millimeter wavelengths, probe various properties of the dynamics, thermal and magnetic structure of the photosphere and the chromosphere and thus provide measures of stellar activity, which can be compared to observations. The complicated magnetic field structure and its imprint in synthetic diagnostics may have important implications for the understanding and characterization of stellar activity and with it possibly for the evaluation of planetary habitabi...

  20. Supernova enrichment and dynamical histories of solar-type stars in clusters

    CERN Document Server

    Parker, Richard J; Davies, Melvyn B; Meyer, Michael R

    2013-01-01

    We use N-body simulations of star cluster evolution to explore the hypothesis that short-lived radioactive isotopes found in meteorites, such as 26-Al, were delivered to the Sun's protoplanetary disc from a supernova at the epoch of Solar System formation. We cover a range of star cluster formation parameter space and model both clusters with primordial substructure, and those with smooth profiles. We also adopt different initial virial ratios - from cool, collapsing clusters to warm, expanding associations. In each cluster we place the same stellar population; the clusters each have 2100 stars, and contain one massive 25M_Sun star which is expected to explode as a supernova at about 6.6Myr. We determine the number of Solar (G)-type stars that are within 0.1 - 0.3pc of the 25M_Sun star at the time of the supernova, which is the distance required to enrich the protoplanetary disc with the 26-Al abundances found in meteorites. We then determine how many of these G-dwarfs are unperturbed `singletons'; stars whic...

  1. Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79

    Science.gov (United States)

    Austin, S. J.; Robertson, J. W.; Tycner, C.; Campbell, T.; Honeycutt, R. K.

    2007-05-01

    The secondary photometric standard star number 79 for the FS Aur field (Henden & Honeycutt 1997), designated as [HH97] FS Aur-79 (GSC 1874-399), is a short-period (0.2508 days) eclipsing binary whose light curve is a combination of the β Lyr and BY Dra type variables. High signal-to-noise ratio multicolor photometry was obtained using the US Naval Observatory 1 m telescope. These light curves show asymmetry at quadrature phases (the O'Connell effect), which can be modeled with the presence of starspots. A low-resolution spectrum obtained with the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope at orbital phase 0.76 is consistent with a spectral type of dK7e and dM3e. A radial velocity curve for the primary star was constructed using 24 high-resolution spectra from the 9.2 m Hobby-Eberly Telescope. Spectra show Hα and Hβ in emission confirming chromospheric activity and possibly the presence of circumstellar material. Binary star models that simultaneously fit the U, B, V, R, and radial velocity curves are those with a primary star of mass 0.59+/-0.02 Msolar, temperature 4100+/-25 K, and mean radius 0.67 Rsolar, just filling its Roche lobe, and a secondary star of mass 0.31+/-0.09 Msolar, temperature 3425+/-25 K, and mean radius 0.48 Rsolar, just within its Roche lobe. An inclination angle of 83deg+/-2deg with a center-of-mass separation of 1.62 Rsolar is also derived. Starspots, expected for a rotation period of less than 1 day, had to be included in the modeling to fit the O'Connell effect.

  2. L-alanine supplementation in late infantile glycogen storage disease type II.

    Science.gov (United States)

    Bodamer, Olaf A; Haas, Dorothea; Hermans, Monique M; Reuser, Arnold J; Hoffmann, Georg F

    2002-08-01

    We report a male with late infantile glycogen storage disease type II (Pompe's disease) who presented at 12 months of age with muscular hypotonia and developmental delay. Oral supplementation with L-alanine has been administered for 5 years. Progression of skeletal myopathy was slow, and cardiomyopathy resolved almost completely. L-alanine may be a valuable supplement for infants with glycogen storage disease type II.

  3. Exploring the origin of magnetic fields in massive stars: a survey of O-type stars in clusters and in the field

    NARCIS (Netherlands)

    Hubrig, S.; Schöller, M.; Kharchenko, N.V.; Langer, N.; de Wit, W.J.M.; Ilyin, I.; Kholtygin, A.F.; Piskunov, A.E.; Przybilla, N.

    2011-01-01

    Context. Although the effects of magnetic fields in massive stars have been found to be substantial by recent models and observations, the magnetic fields of only a small number of massive O-type stars have so far been investigated. Additional observations are of the utmost importance to constrainin

  4. Investigation of the binary fraction among candidate A-F type hybrid stars detected by Kepler

    Directory of Open Access Journals (Sweden)

    Lampens P.

    2015-01-01

    Full Text Available We are currently monitoring up to 40 Kepler candidate δ Scuti-γ Doradus (resp. γ Doradus-δ Scuti hybrid stars in radial velocity in order to identify the physical cause behind the low frequencies observed in the periodograms based on the ultra-high accuracy Kepler space photometry. The presence of low frequency variability in unevolved or slightly evolved oscillating A/F-type stars can generally be explained in three ways: either 1 the star is an (undetected binary or multiple system, or 2 the star is a g-mode pulsator (i.e. a genuine hybrid, or 3 the star’s atmosphere displays an asymmetric intensity distribution (caused by spots, i.e. chemical anomalies, or by (very high rotation, which is detected through rotational modulation. Our targets were selected from the globally characterized variable A/F-type stars of the Kepler mission [7]. We observe each star at least 4 times unevenly spread over a time lapse up to 2 months with the HERMES spectrograph [6]. In the case of composite, multiple-lined spectra, these observations also provide the atmospheric properties of each component. Our principal goal is to estimate the fraction of short-period, spectroscopic systems in the sample.

  5. Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample

    CERN Document Server

    Borgniet, Simon; Meunier, Nadège; Galland, Franck

    2016-01-01

    Massive, Main-Sequence AF-type stars have so far remained unexplored in past radial velocity surveys, due to their small number of spectral lines and their high rotational velocities that prevent the classic RV computation method. Our aim was to search for giant planets around AF MS stars, to get first statistical information on their occurrence rate and to compare the results with evolved stars and lower-mass MS stars. We used the HARPS spectrograph located on the 3.6m telescope at ESO La Silla Observatory to observe 108 AF MS stars with B-V in the -0.04 to 0.58 range and masses in the range 1.1-3.6 Msun. We used our SAFIR software specifically developed to compute the radial velocities of these early-type stars. We report the new detection of a mpsini = 4.51 Mjup companion with a ~826-day period to the F6V dwarf HD111998. We present new data on the 2-planet system around the F6IV-V dwarf HD60532. We also report the detection of 14 binaries with long-term RV trends. 70% of our targets show detection limits b...

  6. Solar-type dynamo behaviour in fully convective stars without a tachocline

    CERN Document Server

    Wright, Nicholas J

    2016-01-01

    In solar-type stars (with radiative cores and convective envelopes), the magnetic field powers star spots, flares and other solar phenomena, as well as chromospheric and coronal emission at ultraviolet to X-ray wavelengths. The dynamo responsible for generating the field depends on the shearing of internal magnetic fields by differential rotation. The shearing has long been thought to take place in a boundary layer known as the tachocline between the radiative core and the convective envelope. Fully convective stars do not have a tachocline and their dynamo mechanism is expected to be very different, although its exact form and physical dependencies are not known. Here we report observations of four fully convective stars whose X-ray emission correlates with their rotation periods in the same way as in Sun-like stars. As the X-ray activity - rotation relationship is a well-established proxy for the behaviour of the magnetic dynamo, these results imply that fully convective stars also operate a solar-type dyna...

  7. Statistical properties of superflares on solar-type stars with Kepler data

    CERN Document Server

    Notsu, Yuta; Shibayama, Takuya; Honda, Satoshi; Notsu, Shota; Namekata, Kosuke; Nogami, Daisaku; Shibata, Kazunari

    2016-01-01

    Superflares are flares that release total energy 10$\\sim$10$^{4}$ times greater than that of the biggest solar flares with energy of $\\sim$10$^{32}$ erg. We searched superflares on solar-type stars (G-type main sequence stars) using the Kepler 30-min (long) and 1-min (short) cadence data. We found more than 1500 superflares on 279 stars from 30-min cadence data (Q0-6) and 187 superflares on 23 stars from 1-min cadence data (Q0-17). The bolometric energy of detected superflares ranges from the order of 10$^{32}$ erg to 10$^{36}$ erg. Using these data, we found that the occurrence frequency ($dN/dE$) of superflares is expressed as a power-law function of flare energy ($E$) with the index of -1.5 for $10^{33}$ Most of the superflare stars show quasi-periodic light variations with the amplitude of a few percent, which can be explained by the rotation of the star with large starspots. The bolometric energy released by flares is consistent with the magnetic energy stored around such large starspots. Furthermore, ou...

  8. An Einstein Observatory SAO-based catalog of B-type stars

    Science.gov (United States)

    Grillo, F.; Sciortino, S.; Micela, G.; Vaiana, G. S.; Harnden, F. R., Jr.

    1992-01-01

    About 4000 X-ray images obtained with the Einstein Observatory are used to measure the 0.16-4.0 keV emission from 1545 B-type SAO stars falling in the about 10 percent of the sky surveyed with the IPC. Seventy-four detected X-ray sources with B-type stars are identified, and it is estimated that no more than 15 can be misidentified. Upper limits to the X-ray emission of the remaining stars are presented. In addition to summarizing the X-ray measurements and giving other relevant optical data, the present extensive catalog discusses the reduction process and analyzes selection effects associated with both SAO catalog completeness and IPC target selection procedures. It is concluded that X-ray emission, at the level of Lx not less than 10 exp 30 ergs/s, is quite common in B stars of early spectral types (B0-B3), regardless of luminosity class, but that emission, at the same level, becomes less common, or nonexistent, in later B-type stars.

  9. Models of rotating boson stars and geodesics around them: New type of orbits

    Science.gov (United States)

    Grandclément, Philippe; Somé, Claire; Gourgoulhon, Eric

    2014-07-01

    We have developed a highly accurate numerical code capable of solving the coupled Einstein-Klein-Gordon system, in order to construct rotating boson stars in general relativity. Free fields and self-interacting fields, with quartic and sextic potentials, are considered. In particular, we present the first numerical solutions of rotating boson stars with rotational quantum number k=3 and k=4, as well as the first determination of the maximum mass of free-field boson stars with k=2. We have also investigated timelike geodesics in the spacetime generated by a rotating boson star for k=1, 2 and 3. A numerical integration of the geodesic equation has enabled us to identify a peculiar type of orbit: the zero-angular-momentum ones. These orbits pass very close to the center and are qualitatively different from orbits around a Kerr black hole. Should such orbits be observed, they would put stringent constraints on astrophysical compact objects like the Galactic center.

  10. A Bcool spectropolarimetric survey of over 150 solar-type stars

    CERN Document Server

    Marsden, Stephen; Jeffers, Sandra; Nascimento, Jose-Dias do; Carter, Bradley; Brown, Carolyn

    2013-01-01

    As part of the Bcool project, over 150 solar-type stars chosen mainly from planet search databases have been observed between 2006 and 2013 using the NARVAL and ESPaDOnS spectropolarimeters on the Telescope Bernard Lyot (Pic du Midi, France) and the Canada France Hawaii Telescope (Mauna Kea, USA), respectively. These single 'snapshot' observations have been used to detect the presence of magnetic fields on 40% of our sample, with the highest detection rates occurring for the youngest stars. From our observations we have determined the mean surface longitudinal field (or an upper limit for stars without detections) and the chromospheric surface fluxes, and find that the upper envelope of the absolute value of the mean surface longitudinal field is directly correlated to the chromospheric emission from the star and increases with rotation rate and decreases with age.

  11. Models of rotating boson stars and geodesics around them: new type of orbits

    CERN Document Server

    Grandclement, Philippe; Gourgoulhon, Eric

    2014-01-01

    We have developed a highly accurate numerical code capable of solving the coupled Einstein-Klein-Gordon system, in order to construct rotating boson stars in general relativity. Free fields and self-interacting fields, with quartic and sextic potentials, are considered. In particular, we present the first numerical solutions of rotating boson stars with rotational quantum number $k=3$ and $k=4$, as well as the first determination of the maximum mass of free-field boson stars with $k=2$. We have also investigated timelike geodesics in the spacetime generated by a rotating boson star for $k=1$, $2$ and $3$. A numerical integration of the geodesic equation has enabled us to identify a peculiar type of orbits: the zero-angular-momentum ones. These orbits pass very close to the center and are qualitatively different from orbits around a Kerr black hole. Should such orbits be observed, they would put stringent constraints on astrophysical compact objects like the Galactic center.

  12. Probing Spin-Orbit Misalignment Processes Around Early-Type Stars

    Science.gov (United States)

    Ahlers, Johnathon; Barnes, Jason W.

    2016-10-01

    Planets in early-type systems seem to frequently misalign from their host star's spin axis. These spin-orbit misaligned systems challenge conventional planet-formation theories because planets probably do not form with initially misaligned orbits -- their angular momenta must be conserved with the stellar nursery in which they formed. In such a case, planets must migrate to their misaligned positions. However, very few transiting exoplanets have had their spin-orbit alignment angles measured. Our model constrains spin-orbit alignment angles via photometry and asteroseismology while accounting for the brightness effects of stellar variability and rapid rotation that commonly occur in early-type stars, making the analysis of hundreds of Kepler transit light curves possible for the first time. We will employ these techniques to probe spin-orbit misalignment theories by empirically testing the spin-orbit state of exoplanets orbiting early-type stars.

  13. NuSTAR Reveals Extreme Absorption in z <0.5 Type 2 Quasars

    DEFF Research Database (Denmark)

    Lansbury, G. B.; Gandhi, P.; Alexander, D. M.

    2015-01-01

    The intrinsic column density (N-H) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z ...-ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (N-H > 1.5 x 10(24) cm(-2)) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously......STAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the N-H distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of f(CT) = 36(-12)(+14)%, although higher...

  14. A Be-type star with a black-hole companion.

    Science.gov (United States)

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

    2014-01-16

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

  15. A JVLA survey of the high-frequency radio emission of the massive magnetic B- and O-type stars

    Science.gov (United States)

    Kurapati, Sushma; Chandra, Poonam; Wade, Gregg; Cohen, David H.; David-Uraz, Alexandre; Gagne, Marc; Grunhut, Jason; Oksala, Mary E.; Petit, Veronique; Shultz, Matt; Sundqvist, Jon; Townsend, Richard H. D.; ud-Doula, Asif

    2017-02-01

    We conducted a survey of seven magnetic O-type stars and eleven B-type stars with masses above 8 M⊙ using the Very Large Array in the 1, 3 and 13 cm bands. The survey resulted in a detection of two O- and two B-type stars. While the detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries. All four stars were detected at 3 cm, whereas three were detected at 1 cm and only one star was detected at 13 cm. The detected B-type stars are significantly more radio luminous than the non-detected ones, which is not the case for O-type stars. The non-detections at 13 cm are interpreted as due to thermal free-free absorption. Mass-loss rates were estimated using 3 cm flux densities and were compared with theoretical mass-loss rates, which assume free-free emission. For HD 37742, the two values of the mass-loss rates were in good agreement, possibly suggesting that the radio emission for this star is mainly thermal. For the other three stars, the estimated mass-loss rates from radio observations were much higher than those expected from theory, suggesting either a possible contribution from non-thermal emission from the magnetic star or thermal or non-thermal emission due to interacting winds of the binary system, especially for HD 47129. All the detected stars are predicted to host centrifugal magnetospheres except HD 37742, which is likely to host a dynamical magnetosphere. This suggests that non-thermal radio emission is favoured in stars with centrifugal magnetospheres.

  16. Brightness variations of the FUor-type eruptive star V346 Normae

    Science.gov (United States)

    Kóspál, Á.; Ábrahám, P.; Westhues, Ch.; Haas, M.

    2017-01-01

    Decades after the beginning of its FU Orionis-type outburst, V346 Nor unexpectedly underwent a fading event of ΔK = 4.6 mag around 2010. We obtained near-infrared observations and re-analyzed data from the VISTA/VVV survey to outline the brightness evolution. In our VLT/NaCO images, we discovered a halo of scattered light around V346 Nor with a size of about 0".04 (30 au). The VISTA data outlined a well-defined minimum in the light curve in late 2010/early 2011, and tentatively revealed a small-amplitude periodic modulation of 58 days. Our latest data points from 2016 demonstrate that the source is still brightening but has not yet reached the 2008 level. We used a simple accretion disk model with varying accretion rate and line-of-sight extinction to reproduce the observed near-infrared magnitudes and colors. We found that the flux changes of V346 Nor before 2008 were caused by a correlated change of extinction and accretion rate, while the minimum around 2010 was mostly due to decreasing accretion. The source reached a highest accretion rate of ≈ 10-4M⊙ yr-1 in 1992. A combination of accretion and extinction changes has been invoked in the literature to interpret the flux variations of certain embedded young eruptive stars. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 71.C-0526(A), 179.B-2002, and 381.C-0241(A).

  17. Asteroseismic modelling of the solar-type subgiant star β Hydri

    DEFF Research Database (Denmark)

    Brandão, I.M.; Dogan, Gülnur; Christensen-Dalsgaard, Jørgen;

    2011-01-01

    the surface layers of stars. Because β Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims: The goal of the present work is to search for a representative model of the solar-type star β Hydri, based on up-to-date non...... and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of β Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed...

  18. Determining element abundances of [WC]-type Central Stars for probing stellar evolution and nucleosynthesis

    CERN Document Server

    Todt, H; Hamann, W -R; Gräfener, G

    2007-01-01

    [WC]-type CSPNs are hydrogen-deficient Central Stars of Planetary Nebulae showing strong stellar winds and a carbon-rich chemistry. We have analyzed new high-resolution spectra of [WC]-type CSPNs with the Potsdam Wolf-Rayet (PoWR) non-LTE expanding atmosphere models, using upgraded model atoms and atomic data. Previous analyses are repeated on the basis of the current models which account for iron-line blanketing. We especially focus on determining the chemical composition, including some trace elements like nitrogen which are of key importance for understanding the evolutionary origin of the hydrogen-deficient Central Stars.

  19. Atmospheric Parameters of 169 F, G, K and M-type Stars in the Kepler Field

    CERN Document Server

    Molenda-Zakowicz, J; Frasca, A; Uytterhoeven, K; Briquet, M; Van Winckel, H; Drobek, D; Niemczura, E; Lampens, P; Lykke, J; Bloemen, S; Gameiro, J F; Jean, C; Volpi, D; Gorlova, N; Mortier, A; Tsantaki, M; Raskin, G

    2013-01-01

    The asteroseismic and planetary studies, like all research related to stars, need precise and accurate stellar atmospheric parameters as input. We aim at deriving the effective temperature (Teff), the surface gravity (log g), the metallicity ([Fe/H]), the projected rotational velocity (v sin i) and the MK type for 169 F, G, K, and M-type Kepler targets which were observed spectroscopically from the ground with five different instruments. We use two different spectroscopic methods to analyse 189 high-resolution, high-signal-to-noise spectra acquired for the 169 stars. For 67 stars, the spectroscopic atmospheric parameters are derived for the ?first time. KIC 9693187 and 11179629 are discovered to be double-lined spectroscopic binary systems. The results obtained for those stars for which independent determinations of the atmospheric parameters are available in the literature are used for a comparative analysis. As a result, we show that for solar-type stars the accuracy of present determinations of atmospheric...

  20. Two Wide Planetary-Mass Companions to Solar-Type Stars in Upper Scorpius

    CERN Document Server

    Ireland, Michael J; Martinache, Frantz; Law, Nicholas M; Hillenbrand, Lynne A

    2010-01-01

    At wide separations, planetary-mass and brown dwarf companions to solar type stars occupy a curious region of parameters space not obviously linked to binary star formation or solar-system scale planet formation. These companions provide insight into the extreme case of companion formation (either binary or planetary), and due to their relative ease of observation when compared to close companions, they offer a useful template for our expectations of more typical planets. We present the results from an adaptive optics imaging survey for wide (50-500 AU) companions to solar type stars in Upper Scorpius. We report one new discovery of a ~14 M_J companion around GSC 06214-00210, and confirm that the candidate planetary mass companion 1RXS J160929.1-210524 detected by Lafreniere et al (2008) is in fact co-moving with its primary star. In our survey, these two detections correspond to ~4% of solar type stars having companions in the 6-20 M_J mass and 200-500 AU separation range. This figure is higher than would be...

  1. Activity Of T Tauri Type Stars And Objects Similar To Them

    Science.gov (United States)

    Ibryamov, Sunay

    2016-06-01

    The main purpose of the dissertation is on the basis of long-term light curves, to be classified the variability of 28 PMS stars and to be draw conclusions about the physical mechanisms initiating observed changes in their brightness. 22 of the investigated stars are located in the dense molecular cloud L935, known as 'Gulf of Mexico' (NGC 7000/IC 5070), and 6 stars are located in the vicinity of the reflection nebula NGC 7129. The multicolour photometric observations that we present were performed from 1993 to 2015 with the 2-m RCC, the 50/70-cm Schmidt and the 60-cm Cassegrain telescopes of the Rozhen NAO (Bulgaria) and the 1.3-m RC telescope of the Skinakas Observatory (Greece). All frames were taken through a standard Johnson-Cousins set of filters. The studied stars were classified as follows: V752 Cyg, V1539 Cyg, V1716 Cyg, FHO 26, FHO 29, LkHα 186, LkHα 187, LkHα 191, [KW97] 53-17, [KW97] 53-22, [KW97] 53-23, V391 Cep, NGC 7129 S V2 and 2MASS J21403576+6635000 show characteristics for classical T Tauri stars; V1538 Cyg, V1929 Cyg, [KW97] 53-20 and NGC 7129 S V1 are probably weak-line T Tauri stars; LkHα 189 and [KW97] 53-11 show characteristics for both type T Tauri stars and spectral observations are needed for their exact classification; V350 Cep shows indications for EXor and/or FUor-type variability; V521 Cyg, FHO 27, FHO 28 and NGC 7129 S V3 show characteristics for UXor-type variability; V1957 Cyg, V2051 Cyg and [KW97] 53-36 likely are evolved PMS stars or post-T Tauri stars. Periodicity was discovered for 3 of the investigated stars. V1716 Cyg indicates 4.15-day period, V1929 Cyg indicates 0.43-day period and LkHα 189 indicates 2.45-day period.

  2. Type C Semiregulars and Irregulars: the Forgotten Pulsating Luminous Stars (Abstract)

    Science.gov (United States)

    Turner, D. G.

    2016-12-01

    (Abstract only) Variable M supergiants, comprising the SRC and LC classes of semiregular and irregular variables, represent late stages of evolution for stars of about 20-25 solar masses, and the likely progenitors for many core collapse supernovae. Most have escaped dedicated study, either long-term photometry or detailed spectroscopy, primarily because of lengthy pulsation periods of 100-1000 days. Yet they appear to share many of the characteristics of classical Cepheids, and their high luminosities make them just as valuable, if not more so, for calibrating the extragalactic distance scale. Many are double-mode, and possibly triple-mode, pulsators, much like Cepheids, which complicates estimates for their periods of variability. Demonstrated here are some of the techniques used for studying such stars, and what has been learned so far about their characteristics. AAVSO observers have a wonderful opportunity to contribute to the field through observations of the forthcoming 2016 maximum of m Cephei.

  3. Characterizing the atmospheres of transiting rocky planets around late type dwarfs

    CERN Document Server

    Pallé, E; Muñoz, A García

    2011-01-01

    Visible and near-infrared spectra of transiting hot Jupiter planets have recently been observed, revealing some of the atmospheric constituents of their atmospheres. In the near future, it is probable that primary and secondary eclipse observations of Earth-like rocky planets will also be achieved. The characterization of the Earth's transmission spectrum has shown that both major and trace atmospheric constituents may present strong absorption features, including important bio-markers such as water, oxygen and methane. Our simulations using a recently published empirical Earth's transmission spectrum, and the stellar spectra for a variety of stellar types, indicate that the new generation of extremely large telescopes, such as the proposed 42-meter European Extremely Large Telescope(E-ELT), could be capable of retrieving the transmission spectrum of an Earth-like planet around very cool stars and brown dwarfs (Teff < 3100 K). For a twin of Earth around a star with Teff around 3100 K (M4), for example, the...

  4. The Peculiar Type Ib Supernova 2006jc: A WC Star Explosion

    CERN Document Server

    Tominaga, N; Suzuki, T; Tanaka, M; Nomoto, K; Maeda, K; Chieffi, A; Tornambé, A; Minezaki, T; Yoshii, Y; Sakon, I; Wada, T; Ohyama, Y; Tanabé, T; Kaneda, H; Onaka, T; Nozawa, T; Kozasa, T; Kawabata, K S; Anupama, G C; Sahu, D K; Gurugubelli, U K; Prabhu, T P; Deng, J

    2007-01-01

    We present a theoretical model for Type Ib supernova (SN) 2006jc associated with a luminous blue variable (LBV)-like event. We calculate the presupernova evolution of the progenitor star, hydrodynamics and nucleosynthesis of the SN explosion, and the SN bolometric light curve (LC). The observed bolometic LC is constructed by integrating the UV, optical, near-infrared (NIR), and mid-infrared (MIR) fluxes. The progenitor is assumed to be as massive as $40\\Msun$ on the zero-age. The star undergoes extensive mass loss to reduce its mass down to as small as $6.9\\Msun$, thus becoming a WC Wolf-Rayet star at the presupernova stage. The WC star model has a thick carbon-rich layer, in which amorphous carbon grains can be formed during the explosion. This could explain the brightening in the NIR flux and the observed dust feature in MIR. The typical main-sequence mass of a WC Wolf-Rayet star and thus the progenitor of SN 2006jc is more massive than $40\\Msun$. We suggest that the explosions of stars more massive than $4...

  5. Discovery of a magnetic field in the early B-type star sigma Lupi

    CERN Document Server

    Henrichs, H F; Plaggenborg, B; Marsden, S C; Waite, I A; Landstreet, J D; Wade, G A; Grunhut, J H; Oksala, M E

    2012-01-01

    Magnetic early B-type stars are rare. To identify them, we use the strongest indirect indicator of a magnetic field in B stars, which is periodic variability of UV stellar wind lines occurring symmetric about the approximate rest wavelength. Probable magnetic candidates are targets for follow-up spectropolarimetry to search for a magnetic field. From the UV wind line variability the B1/B2V star sigma Lupi emerged as a new magnetic candidate star. AAT spectropolarimetric measurements with SEMPOL were obtained. The longitudinal component of the magnetic field integrated over the visible surface of the star was determined with the Least-Squares Deconvolution method. The UV line variations of sigma Lupi are similar to what is known in magnetic B stars, but no periodicity could be determined. We detected a varying longitudinal magnetic field with amplitude of about 100 G with error bars of typically 20 G, which supports an oblique magnetic-rotator configuration. The EW variations of the UV lines, the magnetic and ...

  6. X-ray Emission from Nitrogen-Type Wolf-Rayet Stars

    CERN Document Server

    Skinner, S L; Guedel, M; Schmutz, W; Sokal, K R

    2009-01-01

    We summarize new X-ray detections of four nitrogen-type Wolf-Rayet (WR) stars obtained in a limited survey aimed at establishing the X-ray properties of WN stars across their full range of spectral subtypes. None of the detected stars is so far known to be a close binary. We report Chandra detections of WR 2 (WN2), WR 18 (WN4), and WR 134 (WN6), and an XMM-Newton detection of WR79a (WN9ha). These observations clearly demonstrate that both WNE and WNL stars are X-ray sources. We also discuss Chandra archive detections of the WN6h stars WR 20b, WR 24, and WR 136 and ROSAT non-detections of WR 16 (WN8h) and WR 78 (WN7h). The X-ray spectra of all WN detections show prominent emission lines and an admixture of cool (kT 2 keV) plasma. The hotter plasma is not predicted by radiative wind shock models and other as yet unidentified mechanisms are at work. Most stars show X-ray absorption in excess of that expected from visual extinction (Av), likely due to their strong winds or cold circumstellar gas. Existing data s...

  7. Abundances of Refractory Elements for G-type Stars with Extrasolar Planets

    CERN Document Server

    Kang, Wonseok; Kim, Kang-Min

    2011-01-01

    We confirm the difference of chemical abundance between stars with and without exoplanet, as well as present the relation between chemical abundances and the physical properties of exoplanets such as planetary mass and semi-major axis of planetary orbit. We have obtained the spectra of 52 G-type stars with BOES (BOAO Echelle Spectrograph) and carried out the abundance analysis for 12 elements of Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni. We first have found that the [Mn/Fe] ratios of planet-host stars are higher than those of comparisons in the whole metallicity range, and in metal-poor stars of [Fe/H] $<$ -0.4, the abundance difference have been larger than in metal-rich samples, especially for the elements of Mg, Al, Sc, Ti, V, and Co. When examined the relation between planet properties and metallicities of planet-host stars, we have observed that planet-host stars with low-metallicity tend to bear several low-mass planets ($< M_J$) instead of a massive gas-giant planet.

  8. Transport Phenomena and Light Element Abundances in the Sun and Solar Type Stars

    CERN Document Server

    Vauclair, S

    2000-01-01

    The observations of light elements in the Sun and Solar type stars givespecial clues for understanding the hydrodynamical processes at work in stellarinteriors. In the Sun 7Li is depleted by 140 while 3He has not increased bymore than 10 0n 3 Gyrs. Meanwhile the inversion of helioseismic modes lead toa precision on the sound velocity of about .1The mixing processes below thesolar convection zone are constrained by these observations. Lithium isdepleted in most Pop I solar type stars. In halo stars however, the lithiumabundance seems constant in the "spite plateau" with no observed dispersion,which is difficult to reconcile with the theory of diffusion processes. In thepresent paper, the various relevant observations will be discussed. It will beshown that the mu-gradients induced by element settling may help solving the"lithium paradox".

  9. Early-type massive stars in Carina Nebula within the Gaia-ESO Survey.

    Science.gov (United States)

    Berlanas, S. R.; Herrero, A.; Martins, F.; Simón-Díaz, S.; Mahy, L.; Blomme, R.; GES WG-13

    2017-03-01

    The Gaia-ESO Survey (GES) is obtaining high quality spectra of ˜ 10^5 stars in our Galaxy, providing an homogeneous and unique overview of all the main components of the Milky Way, its formation history and the evolution of young, mature and ancient Galactic populations. Our group is in charge of the early-type massive stars that define the youngest population in the survey. In this contribution, we present the results of the quantitative spectroscopic analysis of O-type stars in the Carina Nebula within the Gaia-ESO Survey. For this aim, we have used FASTWIND and CMFGEN stellar atmosphere codes, providing stellar parameters for the current sample (GES data release iDR4).

  10. On Iron Enrichment, Star Formation, and Type Ia Supernovae in Galaxy Clusters

    Science.gov (United States)

    Loewenstein, Michael

    2006-01-01

    The nature of star formation and Type Ia supernovae (SNIa) in galaxies in the field and in rich galaxy clusters are contrasted by juxtaposing the buildup of heavy metals in the universe inferred from observed star formation and supernovae rate histories with data on the evolution of Fe abundances in the intracluster medium (ICM). Models for the chemical evolution of Fe in these environments are constructed, subject to observational constraints, for this purpose. While models with a mean delay for SNIa of 3 Gyr and standard initial mass function (IMF) are fully consistent with observations in the field, cluster Fe enrichment immediately tracked a rapid, top-heavy phase of star formation - although transport of Fe into the ICM may have been more prolonged and star formation likely continued beyond redshift 1. The means of this prompt enrichment consisted of SNII yielding greater than or equal to 0.1 solar mass per explosion (if the SNIa rate normalization is scaled down from its value in the field according to the relative number of candidate progenitor stars in the 3 - 8 solar mass range) and/or SNIa with short delay times originating during the rapid star formation epoch. Star formation is greater than 3 times more efficient in rich clusters than in the field, mitigating the overcooling problem in numerical cluster simulations. Both the fraction of baryons cycled through stars, and the fraction of the total present-day stellar mass in the form of stellar remnants, are substantially greater in clusters than in the field.

  11. BESO échelle spectroscopy of solar-type stars at Cerro Armazones

    Science.gov (United States)

    Fuhrmann, K.; Chini, R.; Hoffmeister, V. H.; Lemke, R.; Murphy, M.; Seifert, W.; Stahl, O.

    2011-03-01

    The Bochum Échelle Spectroscopic Observer BESO is a fibre-fed high-resolution spectrograph for the 1.5-m Hexapod Telescope at the Cerro Armazones Observatory in the Atacama desert in Chile. Here we report on the first BESO observations and model atmosphere analyses of solar-type stars secured in 2010 April. The quality of the data is first tested with a reflected sunlight spectrum as well as the standard G-type subgiant 70 Vir. We then investigate the bright and supposedly single F-type star ξ Gem and present the spectroscopic evidence that instead favours an equal-mass binary. We present also the first composite synthetic modelling of the G-type visual binary HR 3430 and discuss the spectroscopic observations that identify this as a triple system. We conclude with another triple, the famous and very nearby α Cen, and the basic stellar parameters of its inner, solar-type visual binary.

  12. Do AGN suppress star formation in early-type galaxies?

    OpenAIRE

    Schawinski, Kevin

    2010-01-01

    The observation that AGN host galaxies preferentially inhabit the "green valley" between the blue cloud and the red sequence has significant consequences for our understanding of the co-evolution of galaxies and black holes via accretion events. I discuss the interpretation of green valley AGN host galaxy colours with particular focus on early-type galaxies.

  13. The late-type stellar density profile in the Galactic Center: A statistical approach

    CERN Document Server

    Chappell, Samantha N; Do, Tuan; Martinez, Gregory D; Yelda, Sylvana; Sitarski, Breann N; Lu, Jessica R; Morris, Mark R

    2016-01-01

    The late-type stellar population in the Galactic Center was first predicted to reside in a dynamically relaxed cusp (power law slope ranging from 3/2 to 7/4). However, observations - which rely on models to correct for projection effects - have suggested a flat distribution instead. The need for this correction is due to the lack of information regarding the line-of-sight distances. With a two decade long baseline in astrometric measurements, we are now able to measure significant projected radial accelerations, six of which are newly reported here, that directly constrain line-of-sight distances. Here we present a statistical approach to take advantage of this information and more accurately constrain the shape of the radial density profile of the late-type stellar population in the Galactic Center.

  14. Superflares on the slowly rotating solar-type stars KIC10524994 and KIC07133671?

    CERN Document Server

    Kitze, M; Hambaryan, V; Ginski, C

    2014-01-01

    An investigation of the G-type stellar population with Kepler (as done by Maehara et al.) shows that less than 1 per cent of those stars show superflares. Due to the large pixel scale of Kepler ($\\sim4 arcsec \\: px^{-1}$), it is still not clear whether the detected superflares really occur on the G-type stars. Knowing the origin of such large brightenings is important to study their frequency statistics, which are uncertain due to the low number of sun-like stars ($T_{eff} = 5600-6000 \\:K$ and $P_{rot} > 10 \\:d$) which are currently considered to exhibit superflares. We present a complete Kepler data analysis of the sun-like stars KIC10524994 and KIC07133671 (the only two stars within this subsample of solar twins with flare energies larger than $10^{35}$ erg; Maehara et al.), regarding superflare properties and a study about their origin. We could detect four new superflares within the epoch Maehara et al. investigated and found 14 superflares in the remaining light curve for KIC10524994. Astrometric Kepler ...

  15. Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars

    OpenAIRE

    Meunier, N.; Lagrange, A. -M.; Kabuiku, L. Mbemba; Alex, M; Mignon, L.; Borgniet, S.

    2016-01-01

    In solar-type stars, the attenuation of convective blueshift by stellar magnetic activity dominates the RV variations over the low amplitude signal induced by low mass planets. Models of stars that differ from the Sun will require a good knowledge of the attenuation of the convective blueshift to estimate its impact on the variations. It is therefore crucial to precisely determine not only the amplitude of the convective blueshift for different types of stars, but also the dependence of this ...

  16. Strömgren and Hß photometry of O and B type stars in star-forming regions. II. Moneceros OB2, Canis Major OB1 and Collinder 121

    DEFF Research Database (Denmark)

    Kaltcheva, N.T.; Olsen, Erik Heyn; Clausen, J.V.

    1999-01-01

    Stars: Early-type - Galaxy: Open clusters and associations: Individual: Mon OB2, CMa OB1, Col 121......Stars: Early-type - Galaxy: Open clusters and associations: Individual: Mon OB2, CMa OB1, Col 121...

  17. NLTE analysis of spectra I : Departures from LTE for A-type stars

    NARCIS (Netherlands)

    Kamp, I.; Monier, R.; Smalley, B.; Wahlgren, G.; Stee, Ph.

    2010-01-01

    A-type stars with their shallow convection zones serve as ideal physics laboratories for stellar atmosphere research. In the absence of large scale mixing, processes such as diffusion, mass loss and accretion leave their characteristic imprint on the chemical composition of the photosphere. This cha

  18. NLTE analysis of spectra i: Departures from LTE for A-type stars

    NARCIS (Netherlands)

    Kamp, I.

    2010-01-01

    A-type stars with their shallow convection zones serve as ideal physics laboratories for stellar atmosphere research. In the absence of large scale mixing, processes such as diffusion, mass loss and accretion leave their characteristic imprint on the chemical composition of the photosphere. This cha

  19. Ensemble asteroseismology of solar-type stars with the NASA Kepler mission

    NARCIS (Netherlands)

    Chaplin, W.J.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Basu, S.; Miglio, A.; Appourchaux, T.; Bedding, T.R.; Elsworth, Y.; Garcia, R.A.; Gilliland, R.L.; Girardi, L.; Houdek, G.; Karoff, C.; Kawaler, S.D.; Metcalfe, T.S.; Molenda-Zakowicz, J.; Monteiro, M.J.P.F.G.; Thompson, M.J.; Verner, G.A.; Ballot, J.; Bonanno, A.; Brandao, I.M.; Broomhall, A.M.; Bruntt, H.; Campante, T.L.; Corsaro, E.; Creevey, O.L.; Esch, L.; Gai, N.; Gaulme, P.; Hale, S.J.; Handberg, R.; Hekker, S.; Huber, D.; Jimenez, A.; Mathur, S.; Mazumdar, A.; Mosser, B.; New, R.; Pinsonneault, M.H.; Pricopi, D.; Quirion, P.O.; Regulo, C.; Salabert, D.; Serenelli, A.M.; Silva Aguirre, V.; Sousa, S.G.; Stello, D.; Stevens, I.R.; Suran, M.D.; Uytterhoeven, K.; White, T.R.; Borucki, W.J.; Brown, T.M.; Jenkins, J.M.; Kinemuchi, K.; Van Cleve, J.; Klaus, T.C.

    2011-01-01

    In addition to its search for extrasolar planets, the NASA Kepler mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solar-type stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar

  20. The VLT-FLAMES Tarantula Survey. XXII. Multiplicity properties of the B-type stars

    NARCIS (Netherlands)

    Dunstall, P.R.; Dufton, P.L.; Sana, H.; Evans, C.J.; Howarth, I.D.; Simón-Díaz, S.; de Mink, S.E.; Langer, N.; Maíz Apellániz, J.; Taylor, W.D.

    2015-01-01

    We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal

  1. Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission

    DEFF Research Database (Denmark)

    Chaplin, William J.; Kjeldsen, Hans; Christensen-Dalsgaard, Jørgen

    2011-01-01

    In addition to its search for extrasolar planets, the NASA Kepler mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solar-type stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar...

  2. Verification of the Kepler Input Catalog from asteroseismology of solar-type stars

    NARCIS (Netherlands)

    G.A. Verner; W.J. Chaplin; S. Basu; T.M. Brown; S. Hekker; D. Huber; C. Karoff; S. Mathur; T.S. Metcalfe; B. Mosser; P.O. Quirion; T. Appourchaux; T.R. Bedding; H. Bruntt; T.L. Campante; Y. Elsworth; R.A. Garcia; R. Handberg; C. Regulo; I.W. Roxburgh; D. Stello; J. Christensen-Dalsgaard; R.L. Gilliland; S.D. Kawaler; H. Kjeldsen; C. Allen; B.D. Clarke; F.R. Girouard

    2011-01-01

    We calculate precise stellar radii and surface gravities from the asteroseismic analysis of over 500 solar-type pulsating stars observed by the Kepler space telescope. These physical stellar properties are compared with those given in the Kepler Input Catalog (KIC), determined from ground-based mult

  3. Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler

    DEFF Research Database (Denmark)

    Howard, Andrew W.; Marcy, Geoffrey W.; Bryson, Stephen T.

    2012-01-01

    We report the distribution of planets as a function of planet radius, orbital period, and stellar effective temperature for orbital periods less than 50 days around solar-type (GK) stars. These results are based on the 1235 planets (formally "planet candidates") from the Kepler mission that inclu...

  4. Physical parameters of late M-type members of Chamaleon I and TW Hydrae Association: Dust settling, age dispersion and activity

    CERN Document Server

    Bayo, A; Allard, F; Henning, T; Comeron, F; Morales-Calderon, M; Rajpurohit, A S; Ramırez, K Pena; Beamın, J C

    2016-01-01

    Although mid-to-late type M dwarfs are the most common stars in our stellar neighborhood, our knowledge of these objects is still limited. Open questions include the evolution of their angular momentum, internal structures, dust settling in their atmospheres, age dispersion within populations. In addition, at young ages, late-type Ms have masses below the hydrogen burning limit and therefore are key objects in the debate on the brown dwarf mechanism of formation. In this work we determine and study in detail the physical parameters of two samples of young, late M-type sources belonging to either the Chamaeleon I Dark Cloud or the TW Hydrae Association and compare them with the results obtained in the literature for other young clusters and also for older, field, dwarfs. We used multi-wavelength photometry to construct and analyze SEDs to determine general properties of the photosphere and disk presence. We also used low resolution optical and near-infrared spectroscopy to study activity, accretion, gravity an...

  5. The Carbon Star Phenomenon

    Science.gov (United States)

    Wing, Robert F.

    2000-06-01

    The atmospheres of many stars have chemical compositions that are significantly different from that of the interstellar medium from which they are formed. This symposium considered all kinds of late-type stars showing altered compositions, the carbon stars being simply the best-known of these. All stages of stellar evolution from the main sequence to the ejection of a planetary nebula were considered, with emphasis on the changes that occur on the asymptotic giant branch. The spectroscopic properties of the photospheres and circumstellar envelopes of chemically-peculiar red giant stars, their origins via single-star evolution or mass transfer in binary systems, and the methods currently used to study them were all discussed in detail. This volume includes the full texts of papers given orally at the symposium and abstracts of the posters. Link: http://www.wkap.nl/book.htm/0-7923-6347-7

  6. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.; Peimbert, A. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, A.P. 70-264, 04510 Mexico D.F. (Mexico); Velazquez, H. M., E-mail: barbara@astroscu.unam.mx [Observatorio Astronomico Nacional, Universidad Nacional Autonoma de Mexico, Apdo. Postal 877, 22800 Ensenada (Mexico)

    2012-01-20

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10 Degree-Sign to 60 Degree-Sign . Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately {approx}20 Degree-Sign , the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than {approx}20 Degree-Sign would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than {approx}50 Degree-Sign , chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is {approx}50 Degree-Sign .

  7. A JVLA survey of the high frequency radio emission of the massive magnetic B- and O-type stars

    CERN Document Server

    Kurapati, Sushma; Wade, Gregg; Cohen, David H; David-Uraz, Alexandre; Gagne, Marc; Grunhut, Jason; Oksala, Mary E; Petit, Veronique; Shultz, Matt; Sundqvist, Jon; Townsend, Richard H D; ud-Doula, Asif

    2016-01-01

    We conducted a survey of seven magnetic O and eleven B-type stars with masses above $8M_{\\odot}$ using the Very Large Array in the 1cm, 3cm and 13cm bands. The survey resulted in a detection of two O and two B-type stars. While the detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries. All four stars were detected at 3cm, whereas three were detected at 1cm and only one star was detected at 13cm. The detected B-type stars are significantly more radio luminous than the non-detected ones, which is not the case for O-type stars. The non-detections at 13cm are interpreted as due to thermal free-free absorption. Mass-loss rates were estimated using 3cm flux densities and were compared with theoretical mass-loss rates, which assume free-free emission. For HD 37742, the two values of the mass-loss rates were in good agreement, possibly suggesting that the radio emission for this star is mainly thermal. For the other th...

  8. NLTE carbon abundance determination in selected A- and B-type stars and the interpretation of C I emission lines

    Science.gov (United States)

    Alexeeva, S. A.; Ryabchikova, T. A.; Mashonkina, L. I.

    2016-10-01

    We constructed a comprehensive model atom for C I-C II using the most up-to-date atomic data available and evaluated the non-local thermodynamic equilibrium (NLTE) line formation for C I and C II in classical 1D models representing the atmospheres of A- and late B-type stars. Our NLTE calculations predict the emission that appears at effective temperature of 9250 to 10 500 K depending on log g in the C I 8335, 9405 Å singlet lines and at Teff> 15 000 K (log g = 4) in the C I 9061-9111 Å, 9603-9658 Å triplet lines. A pre-requisite of the emission phenomenon is the overionization-recombination mechanism resulting in a depopulation of the lower levels of C I to a greater extent than the upper levels. Extra depopulation of the lower levels of the transitions corresponding to the near-infrared lines, is caused by photon loss in the UV lines C I 2479, 1930, and 1657 Å. We analysed the lines of C I and C II in Vega, HD 73666, Sirius, 21 Peg, π Cet, HD 22136, and ι Her taking advantage of their observed high-resolution spectra. The C I emission lines were detected in the four hottest stars, and they were well reproduced in our NLTE calculations. For each star, the mean NLTE abundances from lines of the two ionization stages, C I and C II, including the C I emission lines, were found to be consistent. We show that the predicted C I emission phenomenon depends strongly on whether accurate or approximate electron-impact excitation rates are applied.

  9. Early-type stars in the young open cluster NGC 2244 and in the Mon OB2 association I. The multiplicity of O-type stars

    CERN Document Server

    Mahy, L; Rauw, G; Gosset, E; De Becker, M; Sana, H; Eenens, P

    2009-01-01

    Aims. We present the results obtained from a long-term spectroscopic campaign devoted to the multiplicity of O-type stars in the young open cluster NGC2244 and in the Mon OB2 association. Methods. Our spectroscopic monitoring was performed over several years, allowing us to probe different time-scales. For each star, several spectral diagnostic tools are applied, in order to search for line shifts and profile variations. We also measure the projected rotational velocity and revisit the spectral classification. Results. In our sample, several stars were previously considered as spectroscopic binaries, though only a few scattered observations were available. Our results now reveal a more complex situation. Our study identifies two new spectroscopic binaries (HD46149 in NGC2244 and HD46573 in MonOB2). The first object is a long-period double-lined spectroscopic binary, though the exact value of its period remains uncertain and the second object is classified as an SB1 system with a period of about 10.67 days but...

  10. After the Fall: Late-Time Spectroscopy of Type IIP Supernovae

    CERN Document Server

    Silverman, Jeffrey M; Wheeler, J Craig; Filippenko, Alexei V; Vinko, Jozsef; Marion, G H; Cenko, S Bradley; Chornock, Ryan; Clubb, Kelsey I; Foley, Ryan J; Graham, Melissa L; Kelly, Patrick L; Matheson, Thomas; Shields, Joseph C

    2016-01-01

    Herein we analyse late-time (post-plateau; 103 < t < 1229 d) optical spectra of low-redshift (z < 0.016), hydrogen-rich Type IIP supernovae (SNe IIP). Our newly constructed sample contains 91 nebular spectra of 38 SNe IIP, which is the largest dataset of its kind ever analysed in one study, and many of the objects have complementary photometric data. We determined the peak and total luminosity, velocity of the peak, HWHM intensity, and profile shape for many emission lines. Temporal evolution of these values and various flux ratios are studied. We also investigate the correlations between these measurements and photometric observables, such as the peak and plateau absolute magnitudes and the late-time light curve decline rates in various optical bands. The strongest and most robust result we find is that the luminosities of all spectral features (except those of helium) tend to be higher in objects with steeper late-time V-band decline rates. A steep late-time V-band slope likely arises from less eff...

  11. Gamma-ray emission from early-type stars interacting with AGN jets

    Directory of Open Access Journals (Sweden)

    Araudo Anabella T.

    2013-12-01

    Full Text Available We study the interaction of early-type stars with the jets of active galactic nuclei. A bow-shock will form as a consequence of the interaction of the jet with the winds of stars and particles can be accelerated up to relativistic energies in these shocks. We compute the non-thermal radiation produced by relativistic electrons from radio to gamma-rays. This radiation may be significant, and its detection might yield information on the properties of the stellar population in the galaxy nucleus, as well as on the relativistic jet. This emission is expected to be relevant for nearby non-blazar sources.

  12. Nine New Variable Stars in Cygnus and Variability Type Determination of [Wm2007] 1176

    CERN Document Server

    Furgoni, Riccardo

    2014-01-01

    I report the discovery of nine new variable stars in Cygnus: five pulsating (VSX J192319.8+280832, VSX J192405.8+280352, VSX J192220.7+275518, VSX J192304.4+280231, VSX J192255.1+274744) and four eclipsing (VSX J192252.4+280217, VSX J192251.4+280456, VSX J192226.0+281019, VSX J192524.9+275342). The variability type of the variable star [WM2007] 1176, that was considered in literature a possible RRC, was found to be a W UMa variable with an obvious O'Connell effect.

  13. First-Ever Census of Variable Mira-Type Stars in Galaxy Outside the Local Group

    Science.gov (United States)

    2003-05-01

    First-Ever Census of Variable Mira-Type Stars in Galaxy Outsidethe Local Group Summary An international team led by ESO astronomer Marina Rejkuba [1] has discovered more than 1000 luminous red variable stars in the nearby elliptical galaxy Centaurus A (NGC 5128) . Brightness changes and periods of these stars were measured accurately and reveal that they are mostly cool long-period variable stars of the so-called "Mira-type" . The observed variability is caused by stellar pulsation. This is the first time a detailed census of variable stars has been accomplished for a galaxy outside the Local Group of Galaxies (of which the Milky Way galaxy in which we live is a member). It also opens an entirely new window towards the detailed study of stellar content and evolution of giant elliptical galaxies . These massive objects are presumed to play a major role in the gravitational assembly of galaxy clusters in the Universe (especially during the early phases). This unprecedented research project is based on near-infrared observations obtained over more than three years with the ISAAC multi-mode instrument at the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory . PR Photo 14a/03 : Colour image of the peculiar galaxy Centaurus A . PR Photo 14b/03 : Location of the fields in Centaurus A, now studied. PR Photo 14c/03 : "Field 1" in Centaurus A (visual light; FORS1). PR Photo 14d/03 : "Field 2" in Centaurus A (visual light; FORS1). PR Photo 14e/03 : "Field 1" in Centaurus A (near-infrared; ISAAC). PR Photo 14f/03 : "Field 2" in Centaurus A (near-infrared; ISAAC). PR Photo 14g/03 : Light variation of six variable stars in Centaurus A PR Photo 14h/03 : Light variation of stars in Centaurus A (Animated GIF) PR Photo 14i/03 : Light curves of four variable stars in Centaurus A. Mira-type variable stars Among the stars that are visible in the sky to the unaided eye, roughly one out of three hundred (0.3%) displays brightness variations and is referred to by astronomers as a

  14. NuSTAR Reveals Extreme Absorption in z < 0.5 Type 2 Quasars

    CERN Document Server

    Lansbury, G B; Alexander, D M; Assef, R J; Aird, J; Annuar, A; Ballantyne, D R; Balokovic, M; Bauer, F E; Boggs, S E; Brandt, W N; Brightman, M; Christensen, F E; Civano, F; Comastri, A; Craig, W W; Del Moro, A; Grefenstette, B W; Hailey, C J; Harrison, F A; Hickox, R C; Koss, M; LaMassa, S M; Luo, B; Puccetti, S; Stern, D; Treister, E; Vignali, C; Zappacosta, L; Zhang, W W

    2015-01-01

    The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z 1.5e24 cm^-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z~ 90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic AGN properties are feasible, and we measure column densities ~2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ~10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of f_CT = 36^{+14}_{-12} %, although higher fractions (up to 76%) are possible if indire...

  15. Molecular Gas and Star Formation in Local Early-Type Galaxies

    CERN Document Server

    Bureau, M; Alatalo, K; Crocker, A F; Blitz, L; Young, L M; Combes, F; Bois, M; Bournaud, F; Cappellari, M; Davies, R L; de Zeeuw, P T; Duc, P -A; Emsellem, E; Khochfar, S; Krajnovic, D; Kuntschner, H; Lablanche, P -Y; McDermid, R M; Morganti, R; Naab, T; Oosterloo, T; Sarzi, M; Scott, N; Serra, P; Weijmans, A

    2011-01-01

    The molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the Atlas3D survey, we present the first complete, large (260 objects), volume-limited single-dish survey of CO in normal local early-type galaxies. We find a surprisingly high detection rate of 22%, independent of luminosity and at best weakly dependent on environment. Second, the extent of the molecular gas is constrained with CO synthesis imaging, and a variety of morphologies is revealed. The kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in over a third of the systems, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size decoupled disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Last, early-type gala...

  16. On the metallicity dependance of the [Y/Mg] - age relation for solar type stars

    CERN Document Server

    Feltzing, S; McMillan, P J; Stonkute, E

    2016-01-01

    Several recent studies of Solar twins in the Solar neighbourhood have shown a tight correlation between various elemental abundances and age, in particular [Y/Mg]. If this relation is real and valid for other types of stars as well as elsewhere in the Galaxy it would provide a very powerful tool to derive ages of stars without the need to resort to determining their masses (evolutionary stage) very precisely. The method would also likely work if the stellar parameters have relatively large errors. The studies presented in the recent literature span a narrow range of [Fe/H]. By studying a larger sample of Solar neighbourhood dwarfs with a much larger range in [Fe/H], we find that the relation between [Y/Mg] and age depends on the [Fe/H] of the stars. Hence, it appears that the [Y/Mg] - age relation is unique to Solar analogues.

  17. On the metallicity dependence of the [Y/Mg]-age relation for solar-type stars

    Science.gov (United States)

    Feltzing, Sofia; Howes, Louise M.; McMillan, Paul J.; Stonkutė, Edita

    2017-02-01

    Several recent studies of solar twins in the solar neighbourhood have shown a tight correlation between various elemental abundances and age, in particular [Y/Mg]. If this relation is real and valid for other types of stars as well as elsewhere in the Galaxy, it would provide a very powerful tool to derive ages of stars without the need to resort to determining their masses (evolutionary stage) very precisely. The method would also likely work if the stellar parameters have relatively large errors. The studies presented in the recent literature span a narrow range of [Fe/H]. By studying a larger sample of solar neighbourhood dwarfs with a much larger range of [Fe/H], we find that the relation between [Y/Mg] and age depends on the [Fe/H] of the stars. Hence, it appears that the [Y/Mg]-age relation is unique to solar analogues.

  18. OBSERVATIONS OF HIERARCHICAL SOLAR-TYPE MULTIPLE STAR SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Lewis C. Jr. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109 (United States); Tokovinin, Andrei [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Mason, Brian D.; Hartkopf, William I. [U.S. Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 (United States); Riddle, Reed L., E-mail: lewis.c.roberts@jpl.nasa.gov [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-10-15

    Twenty multiple stellar systems with solar-type primaries were observed at high angular resolution using the PALM-3000 adaptive optics system at the 5 m Hale telescope. The goal was to complement the knowledge of hierarchical multiplicity in the solar neighborhood by confirming recent discoveries by the visible Robo-AO system with new near-infrared observations with PALM-3000. The physical status of most, but not all, of the new pairs is confirmed by photometry in the Ks band and new positional measurements. In addition, we resolved for the first time five close sub-systems: the known astrometric binary in HIP 17129AB, companions to the primaries of HIP 33555, and HIP 118213, and the companions to the secondaries in HIP 25300 and HIP 101430. We place the components on a color–magnitude diagram and discuss each multiple system individually.

  19. Observations of Hierarchical Solar-Type Multiple Star Systems

    CERN Document Server

    Roberts,, Lewis C; Mason, Brian D; Hartkopf, William I; Riddle, Reed L

    2015-01-01

    Twenty multiple stellar systems with solar-type primaries were observed at high angular resolution using the PALM-3000 adaptive optics system at the 5 m Hale telescope. The goal was to complement the knowledge of hierarchical multiplicity in the solar neighborhood by confirming recent discoveries by the visible Robo-AO system with new near-infrared observations with PALM-3000. The physical status of most, but not all, of the new pairs is confirmed by photometry in the Ks band and new positional measurements. In addition, we resolved for the first time five close sub-systems: the known astrometric binary in HIP 17129AB, companions to the primaries of HIP 33555, and HIP 118213, and the companions to the secondaries in HIP 25300 and HIP 101430. We place the components on a color-magnitude diagram and discuss each multiple system individually.

  20. PyHammer: An Automatic and Visual Suite for Spectral Typing Stars

    Science.gov (United States)

    Kesseli, Aurora; West, Andrew A.; Harrison, Brandon; Veyette, Mark; Feldman, Daniel

    2017-01-01

    We present a computing product (dubbed "PyHammer"), which can automatically assign estimates of spectral type, metallicity and radial velocity, and/or be used to visually classify stellar spectra. PyHammer uses empirical templates with known spectral types and metallicities as comparisons to automatically determine the spectral type and an estimate of the metallicity of a star by measuring prominent line indices and performing a weighted least squares minimization. The PyHammer GUI allows the user to visually compare their spectra to the templates and determine the spectral type and metallicity. We have created the templates used by PyHammer by co-adding individual spectra from the Sloan Digital Sky Survey's Baryon Oscillation Spectroscopic Survey (BOSS). The templates cover spectral types O5 through L3, are binned by metallicity from -2.0 dex through +1.0 dex, and are separated into main sequence (dwarf) stars and giant stars. This code is based on the “Hammer” spectral typing facility (Covey et al. 2007) and has been updated to include metallicity information, radial velocity calculations, improved automatic estimates, and now is in python (instead of IDL). PyHammer is publicly available to the community on GitHub (github.com/BU-hammerTeam/PyHammer).

  1. Globular Cluster Populations: Results Including S$^4$G Late-Type Galaxies

    CERN Document Server

    Zaritsky, Dennis; Aravena, Manuel; Athanassoula, E; Bosma, Albert; Comerón, Sébastien; Courtois, Helene M; Elmegreen, Bruce G; Elmegreen, Debra M; Erroz-Ferrer, Santiago; Gadotti, Dimitri A; Hinz, Joannah L; Ho, Luis C; Holwerda, Benne; Kim, Taehyun; Knapen, Johan H; Laine, Jarkko; Laurikainen, Eija; Muñoz-Mateos, Juan Carlos; Salo, Heikki; Sheth, Kartik

    2015-01-01

    Using 3.6 and 4.5$\\mu$m images of 73 late-type, edge-on galaxies from the S$^4$G survey, we compare the richness of the globular cluster populations of these galaxies to those of early type galaxies that we measured previously. In general, the galaxies presented here fill in the distribution for galaxies with lower stellar mass, M$_*$, specifically $\\log({\\rm M}_*/{\\rm M}_\\odot) < 10$, overlap the results for early-type galaxies of similar masses, and, by doing so, strengthen the case for a dependence of the number of globular clusters per $10^9\\ {\\rm M}_\\odot$ of galaxy stellar mass, T$_{\\rm N}$, on M$_*$. For $8.5 < \\log ({\\rm M}_*/{\\rm M}_\\odot) < 10.5$ we find the relationship can be satisfactorily described as T$_{\\rm N} = ({\\rm M}_*/10^{6.7})^{-0.56}$ when M$_*$ is expressed in solar masses. The functional form of the relationship is only weakly constrained and extrapolation outside this range is not advised. Our late-type galaxies, in contrast to our early-types, do not show the tendency for l...

  2. Photometry and Polarization of the UXor Type Young Star GM Cep

    Science.gov (United States)

    Huang, Po-Chieh; Chen, Chang-Yao; Hu, Chia-Ling; Chen, Wen-Ping

    2015-08-01

    UX Orionis stars, or UXORs, are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such a UXOR in the young (~4 Myr) open cluster Trumper 37 at ~900 pc, showing prominent infrared access, H-alpha emission, and abrupt brightness variation. Here we present intense multi-color photometric monitoring from 2009 to 2015, together with the century-long photometric behavior reported in the literature, to add to the study by Chen et al. (2012) that GM Cep showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual “blueing” phenomena near the brightness minima when the star appeared bluer when dimmer. The occultation events may be caused by a dust clump, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. We present evidence of possible radial drift of the clump toward the star, stretching longer along the orbit and thinner in the line of sight. GM Cep is moderately polarized, from 4% to 9% in g, r, and i bands, with the level of polarization anticorrelated with the brightness in the bright state, during which the dust clump is back-scattering stellar light.

  3. On Iron Enrichment, Star Formation, and Type Ia Supernovae in Galaxy Clusters

    CERN Document Server

    Loewenstein, M

    2006-01-01

    The nature of star formation and Type Ia supernovae (SNIa) in galaxies in the field and in rich galaxy clusters are contrasted by juxtaposing the build-up of heavy metals in the universe inferred from observed star formation and supernovae rate histories with data on the evolution of Fe abundances in the intracluster medium (ICM). Models for the chemical evolution of Fe in these environments are constructed, subject to observational constraints, for this purpose. While models with a mean delay for SNIa of 3 Gyr and standard initial mass function (IMF) are consistent with observations in the field, cluster Fe enrichment immediately tracks a rapid, top-heavy phase of star formation -- although transport of Fe into the ICM may be more prolonged and star formation likely continues to redshifts 3 times more efficient in rich clusters than in the field, mitigating the overcooling problem in numerical cluster simulations. Both the fraction of baryons cycled through stars, and the fraction of the total present-day st...

  4. Oxygen abundances in G- and F-type stars from HARPS

    CERN Document Server

    de Lis, S Bertran; Adibekyan, V Zh; Santos, N C; Sousa, S G

    2015-01-01

    We present a detailed and uniform study of oxygen abundance from two different oxygen lines at 6158$\\AA$ and 6300$\\AA$ in a large sample of solar-type stars. The results are used to check the behaviour of these spectral lines as oxygen abundance indicators and to study the evolution of oxygen in thick and thin disk populations of the Galaxy. Equivalent width measurements were carried out for the [OI]~6158$\\AA$ and OI~6300$\\AA$ lines. LTE abundances were obtained from these two lines in 610 and 535 stars, respectively. We were able to measure oxygen abundance from both indicators in 447 stars, enabling us, for the first time, to compare them in a uniform way. Careful error analysis has been performed. We found that oxygen abundances derived from the 6158$\\AA$ and 6300$\\AA$ lines agree to within 0.1dex in 58\\% of the stars in our sample, and this result improves for higher signal-to-noise values. We confirm an oxygen enhancement in stars of the thick disk, as has also been seen for other $\\alpha$-elements. The ...

  5. Superflare occurrence and energies on G, K and M type stars

    CERN Document Server

    Candelaresi, Simon; Maehara, Hiroyuki; Brandenburg, Alex; Shibata, Kazunari

    2014-01-01

    Kepler data from G, K and M type stars are used to study conditions that lead to superflares of energies above $10^{34} {\\rm erg}$. From the 117661 included stars, 795 show superflares with a total of 6830 such events. We study if parameters, like the surface temperature or the rotation rate, have any effect on the superflare occurrence rate or energy. For slowly rotating stars we find a quadratic increase of the mean occurrence rate with the rotation rate up to a critical point, after which the rate decreases linearly. Motivated by standard dynamo theory, we study the behavior of the relative starspot coverage, approximated as the relative brightness variation. For faster rotating stars, an increased fraction of stars shows higher spot coverage, which leads to higher superflare rates. A turbulent dynamo is used to study the dependence of the Ohmic dissipation as a proxy of the flare energy on the differential rotation or shear rate. The resulting statistics of the dissipation energy as a function of dynamo n...

  6. Mid- to Far-IR Emission and Star Formation in Early-Type Galaxies

    CERN Document Server

    Young, L M; Lucero, Danielle

    2008-01-01

    Many early-type galaxies have been detected at wavelengths of 24 to 160 micron, but the emission is usually dominated by heating from an AGN or from the evolved stellar population. Here we present Spitzer MIPS observations of a sample of elliptical and lenticular galaxies that are rich in cold molecular gas, and we investigate whether the MIR to FIR emission could be associated with star formation activity. The 24 micron images show a rich variety of structures, including nuclear point sources, rings, disks, and smooth extended emission. Comparisons to matched-resolution CO and radio continuum images suggest that the bulk of the 24 micron emission can be traced to star formation with some notable exceptions. The 24 micron luminosities of the CO-rich galaxies are typically a factor of 15 larger than what would be expected from the dust associated with their evolved stars. In addition, FIR/radio flux density ratios are consistent with star formation. We conclude that the star formation rates in z=0 elliptical a...

  7. The VLT-FLAMES Tarantula Survey: The fastest rotating O-type star and shortest period LMC pulsar - remnants of a supernova disrupted binary?

    CERN Document Server

    Dufton, P L; Evans, C J; Brott, I; Cantiello, M; de Koter, A; de Mink, S E; Fraser, M; Hénault-Brunet, V; Howarth, I D; Langer, N; Lennon, D J; Markova, N; Sana, H; Taylor, W D

    2011-01-01

    We present a spectroscopic analysis of an extremely rapidly rotating late O-type star, VFTS102, observed during a spectroscopic survey of 30 Doradus. VFTS102 has a projected rotational velocity larger than 500\\kms\\ and probably as large as 600\\kms; as such it would appear to be the most rapidly rotating massive star currently identified. Its radial velocity differs by 40\\kms\\ from the mean for 30 Doradus, suggesting that it is a runaway. VFTS102 lies 12 pcs from the X-ray pulsar PSR J0537-6910 in the tail of its X-ray diffuse emission. We suggest that these objects originated from a binary system with the rotational and radial velocities of VFTS102 resulting from mass transfer from the progenitor of PSR J0537-691 and the supernova explosion respectively.

  8. Deriving precise parameters for cool solar-type stars. Optimizing the iron line list

    Science.gov (United States)

    Tsantaki, M.; Sousa, S. G.; Adibekyan, V. Zh.; Santos, N. C.; Mortier, A.; Israelian, G.

    2013-07-01

    Context. Temperature, surface gravity, and metallicitity are basic stellar atmospheric parameters necessary to characterize a star. There are several methods to derive these parameters and a comparison of their results often shows considerable discrepancies, even in the restricted group of solar-type FGK dwarfs. Aims: We want to check the differences in temperature between the standard spectroscopic technique based on iron lines and the infrared flux method (IRFM). We aim to improve the description of the spectroscopic temperatures especially for the cooler stars where the differences between the two methods are higher, as presented in a previous work. Methods: Our spectroscopic analysis was based on the iron excitation and ionization balance, assuming Kurucz model atmospheres in LTE. The abundance analysis was determined using the code MOOG. We optimized the line list using a cool star (HD 21749) with high resolution and high signal-to-noise spectrum, as a reference in order to check for weak, isolated lines. Results: We test the quality of the new line list by re-deriving stellar parameters for 451 stars with high resolution and signal-to-noise HARPS spectra, that were analyzed in a previous work with a larger line list. The comparison in temperatures between this work and the latest IRFM for the stars in common shows that the differences for the cooler stars are significantly smaller and more homogeneously distributed than in previous studies for stars with temperatures below 5000 K. Moreover, a comparison is presented between interferometric temperatures with our results that shows good agreement, even though the sample is small and the errors of the mean differences are large. We use the new line list to re-derive parameters for some of the cooler stars that host planets. Finally, we present the impact of the new temperatures on the [Cr i/Cr ii] and [Ti i/Ti ii] abundance ratios that previously showed systematic trends with temperature. We show that the slopes

  9. Sulphur molecules in the circumstellar envelopes of M-type AGB stars

    CERN Document Server

    Danilovich, Taissa; Black, J H; Olofsson, H; Justtanont, K

    2016-01-01

    The sulphur compounds SO and SO$_2$ have not been widely studied in the circumstellar envelopes of asymptotic giant branch (AGB) stars. By presenting and modelling a large number of SO and SO$_2$ lines in the low mass-loss rate M-type AGB star R Dor, and modelling the available lines of those molecules in a further four M-type AGB stars, we aim to determine their circumstellar abundances and distributions. We use a detailed radiative transfer analysis based on the accelerated lambda iteration method to model circumstellar SO and SO$_2$ line emission and molecular data files for both SO and SO$_2$ that are more extensive than those previously available. Using 17 SO lines and 98 SO2 lines to constrain our models for R Dor, we find an SO abundance of 6.7x10$^{-6}$ and an SO$_2$ abundance of 5x10$^{-6}$ with both species having high abundances close to the star. We also modelled $^{34}$SO and found an abundance of 3.1x10$^{-7}$, giving an $^{32}$SO/$^{34}$SO ratio of 21.6. We derive similar results for the circum...

  10. A barium central star binary in the Type-I diamond ring planetary nebula Abell 70

    CERN Document Server

    Miszalski, B; Frew, D J; Acker, A; Köppen, J; Moffat, A F J; Parker, Q A

    2011-01-01

    Abell 70 (PN G038.1-25.4, hereafter A 70) is a planetary nebula (PN) known for its diamond ring appearance due a superposition with a background galaxy. The previously unstudied central star is found to be a binary consisting of a G8IV-V secondary at optical wavelengths and a hot white dwarf (WD) at UV wavelengths. The secondary shows Ba II and Sr II features enhanced for its spectral type that, combined with the chromospheric Halpha emission and possible 20-30 km/s radial velocity amplitude, firmly classifies the binary as a Barium star. The proposed origin of Barium stars is intimately linked to PNe whereby wind accretion pollutes the companion with dredged-up material rich in carbon and s-process elements when the primary is experiencing thermal pulses on the Asymptotic Giant Branch (AGB). A 70 provides further evidence for this scenario together with the other very few examples of Barium central stars. The nebula is found to have Type-I chemical abundances with helium and nitrogen enrichment, which when c...

  11. 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...

  12. Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler

    Energy Technology Data Exchange (ETDEWEB)

    Mazumdar, A. [Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088 (India); Monteiro, M. J. P. F. G.; Cunha, M. S. [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Ballot, J. [CNRS, Institut de Recherche en Astrophysique et Planétologie, 14 avenue Edouard Belin, F-31400 Toulouse (France); Antia, H. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Basu, S. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 065208101 (United States); Houdek, G.; Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Mathur, S. [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); García, R. A. [Laboratoire AIM, CEA/DSM, CNRS, Université Paris Diderot, IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Salabert, D. [Laboratoire Lagrange, UMR7293, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d' Azur, F-06304 Nice (France); Verner, G. A.; Chaplin, W. J. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Sanderfer, D. T. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Seader, S. E.; Smith, J. C. [SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035 (United States)

    2014-02-10

    For the very best and brightest asteroseismic solar-type targets observed by Kepler, the frequency precision is sufficient to determine the acoustic depths of the surface convective layer and the helium ionization zone. Such sharp features inside the acoustic cavity of the star, which we call acoustic glitches, create small oscillatory deviations from the uniform spacing of frequencies in a sequence of oscillation modes with the same spherical harmonic degree. We use these oscillatory signals to determine the acoustic locations of such features in 19 solar-type stars observed by the Kepler mission. Four independent groups of researchers utilized the oscillation frequencies themselves, the second differences of the frequencies and the ratio of the small and large separation to locate the base of the convection zone and the second helium ionization zone. Despite the significantly different methods of analysis, good agreement was found between the results of these four groups, barring a few cases. These results also agree reasonably well with the locations of these layers in representative models of the stars. These results firmly establish the presence of the oscillatory signals in the asteroseismic data and the viability of several techniques to determine the location of acoustic glitches inside stars.

  13. WASP-26b: a 1-Jupiter-mass planet around an early-G-type star

    Science.gov (United States)

    Smalley, B.; Anderson, D. R.; Collier Cameron, A.; Gillon, M.; Hellier, C.; Lister, T. A.; Maxted, P. F. L.; Queloz, D.; Triaud, A. H. M. J.; West, R. G.; Bentley, S. J.; Enoch, B.; Pepe, F.; Pollacco, D. L.; Segransan, D.; Smith, A. M. S.; Southworth, J.; Udry, S.; Wheatley, P. J.; Wood, P. L.; Bento, J.

    2010-09-01

    We report the discovery of WASP-26b, a moderately over-sized Jupiter-mass exoplanet transiting its 11.3-mag early-G-type host star (1SWASP J001824.70-151602.3; TYC 5839-876-1) every 2.7566 days. A simultaneous fit to transit photometry and radial-velocity measurements yields a planetary mass of 1.02 ± 0.03 MJup and radius of 1.32 ± 0.08 RJup. The host star, WASP-26, has a mass of 1.12 ± 0.03 M⊙ and a radius of 1.34 ± 0.06 R⊙ and is in a visual double with a fainter K-type star. The two stars are at least a common-proper motion pair with a common distance of around 250 ± 15 pc and an age of 6 ± 2 Gy. RV and photometric data are only available in electronic form 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/520/A56

  14. The VLT-FLAMES Tarantula Survey VIII. Multiplicity properties of the O-type star population

    CERN Document Server

    Sana, H; de Mink, S E; Dunstall, P R; Evans, C J; Henault-Brunet, V; Apellaniz, J Maiz; Ramirez-Agudelo, O H; Taylor, W D; Walborn, N R; Clark, J S; Crowther, P A; Herrero, A; Gieles, M; Langer, N; Lennon, D J; Vink, J S

    2012-01-01

    Aims. We analyze the multiplicity properties of the massive O-type star population. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods. We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. Results. We observe a spectroscopic binary fraction of 0.35\\pm0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20km/s. We compute the intrinsic binary fraction to be 0.51\\pm0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f_P ~ (log P)^\\pi\\ (with 0.15 7.8', i.e. approx117 pc) and among the O9.7 I/II objects are however significantly lower than expected from statistical fluctuations. Conclusions. Using simple evolutionary considerations, we estimate that over 50% of the current O star population in 30 Dor will exchange mass with ...

  15. CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. I. S-TYPE BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Kaltenegger, Lisa [MPIA, Koenigstuhl 17, D-69117 Heidelberg (Germany); Haghighipour, Nader, E-mail: kaltenegger@mpia.de [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States)

    2013-11-10

    We have developed a comprehensive methodology for calculating the boundaries of the habitable zone (HZ) of planet-hosting S-type binary star systems. Our approach is general and takes into account the contribution of both stars to the location and extent of the binary HZ with different stellar spectral types. We have studied how the binary eccentricity and stellar energy distribution affect the extent of the HZ. Results indicate that in binaries where the combination of mass-ratio and orbital eccentricity allows planet formation around a star of the system to proceed successfully, the effect of a less luminous secondary on the location of the primary's HZ is generally negligible. However, when the secondary is more luminous, it can influence the extent of the HZ. We present the details of the derivations of our methodology and discuss its application to the binary HZ around the primary and secondary main-sequence stars of an FF, MM, and FM binary, as well as two known planet-hosting binaries α Cen AB and HD 196886.

  16. Searching for Line Profile Variability in HgMn Stars

    CERN Document Server

    Turcotte, S; Knoglinger, P

    2002-01-01

    Spectra of four non-magnetic chemically peculiar late B type stars (HgMn) stars are analysed to detect periodic spectral line variations (LPVs). A procedure developed to study LPVs in Slowly Pulsating B stars has been adopted as pulsational properties of HgMn stars should be expected to be similar. In the preliminary results discussed here no conclusive evidence for periodic LPVs was uncovered. A more sensitive re-analysis of the data is under way.

  17. Know the Star, Know the Planet. III. Discovery of the Late-Type Companions to Two Exoplanet Host Stars

    Science.gov (United States)

    2015-03-04

    main sequence. The masses in Table 3 are determined from the isochrone and the absolute magnitudes in the i band. We estimate the orbital period, P , of... orbit orientation, and eccentricity. The strict lower limit is >a d 2 . Statistical period estimates using the assumption a = d are denoted as P *. The...separations to compute orbital periods of the new stellar companions, HD 2638 has a period of 130 yr and 30 Ari B has a period of 80 yr. Previous

  18. Numerical models of protoneutron stars and type-II supernovae - recent developments

    Energy Technology Data Exchange (ETDEWEB)

    Janka, H.T. [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    1996-11-01

    The results of recent multi-dimensional simulations of type-II supernovae are reviewed. They show that convective instabilities in the collapsed stellar core might play an important role already during the first second after the formation of the supernovae shock. Convectively unstable situations occur below and near the neutrinosphere as well as in the neutrino-heated region between the nascent neutron star and the supernova shock after the latter has stalled at a radiums of typically 100-200 km. While convective overturn in the layer of neutrino energy deposition clearly helps the explosion to develop and potentially provides an explanation of strong mantle and envelope mixing, asphericities, and non-uniform {sup 56}Ni distribution observed in supernova SN 1987A, its presence and importance depends on the strength of the neutrino heating and thus on the size of the neutrino fluxes from the neutrino star. Convection in the hot-bubble region can only be developed if the growth timescale of the instabilities and the heating timescale are both shorter than the accretion timescale of the matter advected through the stagnant shock. For too small neutrino luminosities this requirement is not fulfilled and convective activity cannot develop, leading to very weak explosions or even fizzling models, just as in the one-dimensional situations. Convectively enhanced neutrino luminosities from the protoneutron star can therefore provide an essential condition for the explosion of the star. Very recent two-dimensional, self-consistent, general relativistic simulations of the cooling of a newly-formed neutron star demonstrate and confirm the possibility that Ledoux convection, driven by negative lepton number and entropy gradients, may encompass the whole protoneutron star within less than one second and can lead to an increase of the neutrino fluxes by up to a factor of two. (author) 9 figs., refs.

  19. EXPORT optical photometry and polarimetry of Vega-type and pre-main sequence stars

    CERN Document Server

    Oudmaijer, R D; Eiroa, C

    2001-01-01

    This paper presents optical UBVRI broadband photo-polarimetry of the EXPORT sample obtained at the 2.5m Nordic Optical Telescope. The database consists of multi-epoch photo-polarimetry of 68 pre-main-sequence and main-sequence stars. An investigation of the polarization variability indicates that 22 objects are variable at the 3sigma level in our data. All these objects are pre-main sequence stars, consisting of both T Tauri and Herbig Ae/Be objects while the main sequence, Vega type and post-T Tauri type objects are not variable. The polarization properties of the variable sources are mostly indicative of the UXOR-type behaviour; the objects show highest polarization when the brightness is at minimum. We add seven new objects to the class of UXOR variables (BH Cep, VX Cas, DK Tau, HK Ori, LkHa 234, KK Oph and RY Ori). The main reason for their discovery is the fact that our data-set is the largest in its kind, indicating that many more young UXOR-type pre-main sequence stars remain to be discovered. The set ...

  20. Progressive Red Shifts in the Late-Time Spectra of Type Ia Supernovae

    CERN Document Server

    Black, C S; Parrent, J T

    2016-01-01

    We examine the evolution of late-time, optical nebular features of Type Ia supernovae (SNe Ia) using a sample consisting of 160 spectra of 27 normal SNe Ia taken from the literature as well as unpublished spectra of SN 2008Q and ASASSN-14lp. Particular attention was given to nebular features between 4000$-$6000 \\AA\\ in terms of temporal changes in width and central wavelength. Analysis of the prominent late-time 4700 \\AA\\ feature shows a progressive central wavelength shift from $\\sim$4600 \\AA\\ to longer wavelengths out to at least day +300 for our entire sample. We find no evidence for the feature's red-ward shift slowing or halting at an [Fe III] blend centroid of 4701 \\AA\\ as has been proposed. The width of the feature also steadily increases with a FWHM $\\sim$170 \\AA\\ at day +100 growing to 200 \\AA\\ or more by day +350. Two weaker adjacent features around 4850 and 5000 \\AA\\ exhibit very similar red shifts to that of the 4700 \\AA\\ feature but show no change in width until very late times. We discuss possib...

  1. Repair of Late Retrograde Type A Aortic Dissection After TEVAR: Causes and Management.

    Science.gov (United States)

    Mosquera, Victor X; Marini, Milagros; Fraga-Manteiga, Daniel; Gulias, Daniel; Cuenca, Jose J

    2016-03-01

    One of the most feared complications of thoracic endovascular aortic repair (TEVAR) and hybrid arch repair is retrograde type A aortic dissection (RTAD). More than two-thirds of RTAD occurs in the immediate postoperative period and first postoperative month. In presentations beyond that point, progression of the native aortopathy must be considered. We report a late presentation of an RTAD seven months after hybrid repair of an aortic intramural hematoma with an ulcer-like projection, and review the causes and management of this TEVAR complication.

  2. Light curve analysis of the late type binary V523 Cassiopeiae

    Directory of Open Access Journals (Sweden)

    Latković O.

    2009-01-01

    Full Text Available We present the analysis of V and R light curves of the late type contact binary V523 Cas for the season of 2006. These observations make part of the monitoring program aimed at studying the long-term light curve variability in this system. Our results confirm that the system is in an over contact configuration, and include a bright spot in the neck region of the cooler and larger primary. We compare these results with the previous solution, obtained for the season 2005 dataset and discuss the differences.

  3. Far-infrared colours of nearby late-type galaxies in the Herschel Reference Survey

    OpenAIRE

    Boselli, A.; Ciesla, L.; Cortese, L.; Buat, V.; Boquien, M.; Bendo, GJ; Boissier, S.; Eales, S; Gavazzi, G.; Hughes, TM; Pohlen, M.; Smith, MWL; Baes, Maarten; S. Bianchi; Clements, DL

    2012-01-01

    We study the far infrared (60-500 mu m) colours of late-type galaxies in the Herschel Reference Survey, a K-band selected, volume limited sample of nearby galaxies. The far infrared colours are correlated with each other, with tighter correlations for the indices that are closer in wavelength. We also compare the different colour indices to various tracers of the physical properties of the target galaxies, such as the surface brightness of the ionising and non-ionising stellar radiation, the ...

  4. FIR colours of nearby late-type galaxies in the Herschel Reference Survey

    OpenAIRE

    Boselli, A.; Ciesla, L.; Cortese, L.; Buat, V.; Boquien, M.; G.J. Bendo; Boissier, S.; Eales, S; Gavazzi, G.; Hughes, T. M.; Pohlen, M.; Smith, M. W. L.; Baes, M.; S. Bianchi; Clements, D. L.

    2012-01-01

    We study the far infrared (60-500 $\\mu$m) colours of late-type galaxies in the $Herschel$ Reference Survey, a K-band selected, volume limited sample of nearby galaxies. The far infrared colours are correlated with each other, with tighter correlations for the indices that are closer in wavelength. We also compare the different colour indices to various tracers of the physical properties of the target galaxies, such as the surface brightness of the ionising and non-ionising stellar radiation, ...

  5. Chromospheric activity on late-type star DM UMa using high-resolution spectroscopic observations

    CERN Document Server

    Zhang, LiYun; Han, Xianming L; Chang, Liang; Wang, Daimei

    2016-01-01

    We present new 14 high-resolution echelle spectra to discuss the level of chromospheric activity of DM UMa in {He I} D3, {Na I} D1, D2, Halpha, and {Ca II} infrared triplet lines (IRT). It is the first time to discover the emissions above the continuum in the {He I} D3 lines on 2015 February 9 and 10. The emission on February 9 is the strongest one ever detected for DM UMa. We analysed these chromospheric active indicators by employing the spectral subtraction technique. The subtracted spectra reveal weak emissions in the {Na I} D1, D2 lines, strong emission in the Halpha line, and clear excess emissions in the {Ca II} IRT lines. Our values for the EW8542/EW8498 ratio are on the low side, in the range of 1.0-1.7. There are also clear phase variations of the level of chromospheric activity in equivalent width (EW) light curves in these chromospheric active lines (especially the Halpha line). These phenomena might be explained by flare events or rotational modulations of the level of chromospheric activity.

  6. X-ray spectroscopy of late-type stars. [HEAO 2 observations

    Science.gov (United States)

    Swank, J. H.; White, N. E.

    1980-01-01

    The solid state spectrometer on the Einstein Observatory determined .4 - 4.5 keV spectra for Capella, Algol and 6 RS CVn binaries. All show evidence for a bimodal distribution of emission measure with temperature with one component approximately 7 million degrees and one approximately 40 million degrees. The spread in values of both luminosity and emission measure is 10 for the low temperature component and approximately 500 for the high temperature component. Line emission due to Fe can be identified in most of them and abundances of Si, S and Fe are consistent with approximately solar values in all cases. Estimates indicate dimensions of the emitting regions are on the order of the stellar size and the binary separation for the low and high temperature components, respectively, unless the pressures are high. Variations in the flux were observed, mostly in the hard component for the RS CVn binaries, in the soft component for Capella. A flare was observed during primary eclipse of Algol. The possibility is discussed that the other variations could all be due to intrinsic variability with a time scale of hours-days rather than eclipse or modulation with photometric phase.

  7. VizieR Online Data Catalog: Abundances of late-type stars (Roederer+, 2014)

    Science.gov (United States)

    Roederer, I. U.; Jacobson, H. R.; Thanathibodee, T.; Frebel, A.; Toller, E.

    2017-01-01

    We obtained observations covering the NUV spectral range from the Barbara A. Mikulski Archive for Space Telescopes (MAST). These observations were taken using the medium- or high-resolution echelle gratings in the Space Telescope Imaging Spectrograph (STIS; Kimble et al. 1998ApJ...492L..83K; Woodgate et al. 1998PASP..110.1183W) on board the Hubble Space Telescope (HST). Spectra downloaded from the MAST have been reduced by the calstis pipeline and combined by Ayres (2010, Cat. J/ApJS/187/149). Spectra obtained previously by our own observing programs were reduced by the calstis pipeline and processed as described in Roederer et al. (2012ApJS..203...27R, 2014ApJ...791...32R) and Placco et al. (2014ApJ...790...34P). (4 data files).

  8. Circular Polarization of Water Masers in the Circumstellar Envelopes of Late Type Stars

    CERN Document Server

    Vlemmings, W H T; Van Langevelde, H J

    2002-01-01

    We present circular polarization measurements of circumstellar H_2O masers. The circular polarization detected in the (6_{16}-5_{23}) rotational transition of the H_{2}O maser can be attributed to Zeeman splitting in the intermediate temperature and density regime. The magnetic fields are derived using a general, LTE Zeeman analysis as well as a full radiative transfer method (non-LTE), which includes a treatment of all hyperfine components simultaneously as well as the effects of saturation and unequal populations of the magnetic substates. The differences and relevances of these interpretations are discussed extensively. The field strengths are compared with previous detections of the magnetic field on the SiO and OH masers. We show that the magnetic pressure dominates the thermal pressure by a factor of 20 or more.

  9. Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler

    CERN Document Server

    Mazumdar, A; Ballot, J; Antia, H M; Basu, S; Houdek, G; Mathur, S; Cunha, M S; Aguirre, V Silva; Garcia, R A; Salabert, D; Verner, G A; Christensen-Dalsgaard, J; Metcalfe, T S; Sanderfer, D T; Seader, S E; Smith, J C; Chaplin, W J

    2013-01-01

    For the very best and brightest asteroseismic solar-type targets observed by Kepler, the frequency precision is sufficient to determine the acoustic depths of the surface convective layer and the helium ionization zone. Such sharp features inside the acoustic cavity of the star, which we call acoustic glitches, create small oscillatory deviations from the uniform spacing of frequencies in a sequence of oscillation modes with the same spherical harmonic degree. We use these oscillatory signals to determine the acoustic locations of such features in 19 solar-type stars observed by the Kepler mission. Four independent groups of researchers utilized the oscillation frequencies themselves, the second differences of the frequencies and the ratio of the small and large separation to locate the base of the convection zone and the second helium ionization zone. Despite the significantly different methods of analysis, good agreement was found between the results of these four groups, barring a few cases. These results ...

  10. Predicting the Detectability of Oscillations in Solar-type Stars Observed by Kepler

    DEFF Research Database (Denmark)

    Chaplin, William J.; Kjeldsen, Hans; Bedding, Timothy R.

    2011-01-01

    Asteroseismology of solar-type stars has an important part to play in the exoplanet program of the NASA Kepler Mission. Precise and accurate inferences on the stellar properties that are made possible by the seismic data allow very tight constraints to be placed on the exoplanetary systems. Here,......, we outline how to make an estimate of the detectability of solar-like oscillations in any given Kepler target, using rough estimates of the temperature and radius, and the Kepler apparent magnitude....

  11. The Effects of Intensive Nutrition Education on Late Middle-Aged Adults with Type 2 Diabetes

    Directory of Open Access Journals (Sweden)

    Ye Li

    2016-09-01

    Full Text Available Objective: Many patients with type 2 diabetes find it difficult to maintain good glycemic control. Undesirable glycemic control occurs greatly due to deficiencies of nutritional knowledge and difficulty in obtaining dietary prescriptions. The late middle-aged and elder individuals are the main populations that are affected by type 2 diabetes. The main purpose of this study was to investigate whether intensive nutrition education would make benefits for late middle-aged patients with type 2 diabetes. Method: 196 patients between 50 to 65 years old meeting type 2 diabetes criteria and eligible for the program were included in a single-blinded, 30-day centralized management of an education program in China. Participants in the program were randomly divided into a usual nutrition education group or an intensive nutrition education group. The usual nutrition education group was used as a control group and received only basic health advice and principles of diabetic diets at the beginning and the end of the study. Participants in the intensive nutrition education group were arranged to receive intensive nutritional lectures about diabetes for 30 days. The primary outcomes were the changes in weight, body mass index (BMI, fasting plasma glucose (FPG, 2-h postprandial plasma glucose (PG, glycosylated hemoglobin (HbA1c, total glycerin (TG, total cholesterol (TC, high-density lipoprotein cholesterol (HDL-c, and low-density lipoprotein cholesterol (LDL-c. Results: After 30 days of intervention, FPG, PG, and HbA1c in the treatment group decreased significantly than the control group (p < 0.05. HbA1c reduced significantly by 0.6% in the intervention group. No significant differences in the change of blood lipids were observed between groups. However, TG, TC, and HDL-c made improvements compared with the baseline in the experimental group. Both groups had a reduction in weight and BMI within groups, especially in intensive nutrition education group. However

  12. The Effects of Intensive Nutrition Education on Late Middle-Aged Adults with Type 2 Diabetes

    Science.gov (United States)

    Li, Ye; Xu, Meihong; Fan, Rui; Ma, Xiaotao; Gu, Jiaojiao; Cai, Xiaxia; Liu, Rui; Chen, Qihe; Ren, Jinwei; Mao, Ruixue; Bao, Lei; Zhang, Zhaofeng; Wang, Junbo; Li, Yong

    2016-01-01

    Objective: Many patients with type 2 diabetes find it difficult to maintain good glycemic control. Undesirable glycemic control occurs greatly due to deficiencies of nutritional knowledge and difficulty in obtaining dietary prescriptions. The late middle-aged and elder individuals are the main populations that are affected by type 2 diabetes. The main purpose of this study was to investigate whether intensive nutrition education would make benefits for late middle-aged patients with type 2 diabetes. Method: 196 patients between 50 to 65 years old meeting type 2 diabetes criteria and eligible for the program were included in a single-blinded, 30-day centralized management of an education program in China. Participants in the program were randomly divided into a usual nutrition education group or an intensive nutrition education group. The usual nutrition education group was used as a control group and received only basic health advice and principles of diabetic diets at the beginning and the end of the study. Participants in the intensive nutrition education group were arranged to receive intensive nutritional lectures about diabetes for 30 days. The primary outcomes were the changes in weight, body mass index (BMI), fasting plasma glucose (FPG), 2-h postprandial plasma glucose (PG), glycosylated hemoglobin (HbA1c), total glycerin (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c). Results: After 30 days of intervention, FPG, PG, and HbA1c in the treatment group decreased significantly than the control group (p < 0.05). HbA1c reduced significantly by 0.6% in the intervention group. No significant differences in the change of blood lipids were observed between groups. However, TG, TC, and HDL-c made improvements compared with the baseline in the experimental group. Both groups had a reduction in weight and BMI within groups, especially in intensive nutrition education group. However, there was

  13. Oxygen abundance determination of B-type stars with the OI 7771-5A lines

    CERN Document Server

    Takeda, Yoichi

    2016-01-01

    Oxygen abundances of 34 B-type stars in the effective temperature range of Teff~10000-28000K with diversified rotational velocities (vesini~ 0-250km/s) were determined from the OI triplet lines at 7771-5A, with an aim to examine whether this OI feature can be a reliable abundance indicator for such high-temperature stars including rapid rotators. It revealed that the required non-LTE abundance correction is distinctly large (ranging from ~-0.6dex to ~-1.7dex) and its consideration is indispensable. On the condition that the non-LTE effect is taken into account, this triplet is a useful O abundance indicator (with a precision of ~200mA). In contrast, it is not adequate for abundance derivation for stars at Teff >~25000K, where its strength rapidly drops down toward a hardly detectable level (except for sharp-lined stars) and its sensitivity to Teff or log g becomes considerably large. The resulting non-LTE oxygen abundances turned out to be almost normal (i.e., near-solar around ~8.7-8.8 within +/-~0.2dex) for...

  14. Time-resolved multicolour photometry of bright B-type variable stars in Scorpius

    CERN Document Server

    Handler, G

    2013-01-01

    The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. We acquired 117 h of Stromgren uvy data during 19 nights. Our targets comprised the Beta Cephei stars Kappa and Lambda Sco, the eclipsing binary Mu 1 Sco, and the variable super/hypergiant Zeta 1 Sco. For Kappa Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l, m) = (1, -1) Beta Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For Lambda Sco, we recover the known dominant Beta Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spe...

  15. HE 0437-5439 -- an unbound hyper-velocity main-sequence B-type star

    CERN Document Server

    Edelmann, H; Heber, U; Christlieb, N; Reimers, D; Edelmann, Heinz; Napiwotzki, Ralf; Heber, Uli; Christlieb, Norbert; Reimers, Dieter

    2005-01-01

    We report the discovery of a 16th magnitude star, HE0437-5439, with a heliocentric radial velocity of +723+-3km/s. A quantitative spectral analysis of high-resolution optical spectra obtained with the VLT and the UVES spectrograph shows that HE0437-5439 is a main sequence B-type star with Teff=20350K, log g=3.77, solar within a factor of a few helium abundance and metal content, rotating at v sin i=54km/s. Using appropriate evolutionary tracks we derive a mass of 8 Msun and a corresponding distance of 61 kpc. Its galactic rest frame velocity is at least 563km/s, almost twice the local Galactic escape velocity, indicating that the star is unbound to the Galaxy. Numerical kinematical experiments are carried out to constrain its place of birth. It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole at the Galactic center (GC). HE0437-5439 needs about 100Myrs to travel from the GC to its presentposition, much lon...

  16. The VLT-FLAMES Tarantula Survey XXII. Multiplicity properties of the B-type stars

    CERN Document Server

    Dunstall, P R; Sana, H; Evans, C J; Howarth, I D; Simón-Díaz, S; de Mink, S E; Langer, N; Apellániz, J Maíz; Taylor, W D

    2015-01-01

    We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects with significant radial-velocity variations (and with an amplitude larger than 16 km/s) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of 0.1) for the B-type stars, f_B(obs) = 0.25 +/- 0.02, which appears constant across the field of view, except for the two older clusters (Hodge 301 and SL 639). These two clusters have significantly lower fractions of 0.08 +/- 0.08 and 0.10 +/- 0.09, respectively. Using synthetic populations and a model of our observed epochs and their potential biases, we constrain the intrinsic multiplicity properties of the dwarf and giant (i.e. relatively unevolved) B-type stars ...

  17. The SAURON project - XV. Modes of star formation in early-type galaxies and the evolution of the red sequence

    NARCIS (Netherlands)

    Shapiro, Kristen L.; Falcón-Barroso, Jesús; van de Ven, Glenn; de Zeeuw, P. Tim; Sarzi, Marc; Bacon, Roland; Bolatto, Alberto; Cappellari, Michele; Croton, Darren; Davies, Roger L.; Emsellem, Eric; Fakhouri, Onsi; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Peletier, Reynier F.; van den Bosch, Remco C. E.; van der Wolk, Guido

    2010-01-01

    We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/Infrared Array Camera imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star for

  18. The SAURON project : XV. Modes of star formation in early-type galaxies and the evolution of the red sequence

    NARCIS (Netherlands)

    Shapiro, Kristen L.; Falcon-Barroso, Jesus; van de Ven, Glenn; de Zeeuw, P. Tim; Sarzi, Marc; Bacon, Roland; Bolatto, Alberto; Cappellari, Michele; Croton, Darren; Davies, Roger L.; Emsellem, Eric; Fakhouri, Onsi; Krajnovic, Davor; Kuntschner, Harald; McDermid, Richard M.; Peletier, Reynier F.; van den Bosch, Remco C. E.; van der Wolk, Guido

    2010-01-01

    We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/Infrared Array Camera imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star for

  19. The central dark matter content of early-type galaxies: scaling relations and connections with star formation histories

    CERN Document Server

    Napolitano, Nicola R; Tortora, Crescenzo

    2010-01-01

    We examine correlations between the masses, sizes, and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar populations models. We confirm an anti-correlation between size and stellar age, and survey for trends with the central content of dark matter (DM). An average relation between central DM density and galaxy size of ~ Reff^-2 provides the first clear indication of cuspy DM haloes in these galaxies -- akin to standard LCDM haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as expected, deviating from suggestions of a universal halo profile for dwarf and late-type galaxies. We introduce a new fundamental constraint on galaxy formation by finding that the central DM fraction decreases with stellar age. This result is only partially explained by the size-age dependencies, and the residual trend is in the opposite direction to basic DM halo expectations. Therefore we suggest that there may be a con...

  20. Models of Late-Type Disk Galaxies: 1-D Versus 2-D

    CERN Document Server

    Mineikis, Tadas

    2015-01-01

    We investigate the effects of stochasticity on the observed galaxy parameters by comparing our stochastic star formation two-dimensional (2-D) galaxy evolution models with the commonly used one-dimensional (1-D) models with smooth star formation. The 2-D stochastic models predict high variability of the star formation rate and the surface photometric parameters across the galactic disks and in time.

  1. The VLT-FLAMES Tarantula Survey. VIII. Multiplicity properties of the O-type star population

    Science.gov (United States)

    Sana, H.; de Koter, A.; de Mink, S. E.; Dunstall, P. R.; Evans, C. J.; Hénault-Brunet, V.; Maíz Apellániz, J.; Ramírez-Agudelo, O. H.; Taylor, W. D.; Walborn, N. R.; Clark, J. S.; Crowther, P. A.; Herrero, A.; Gieles, M.; Langer, N.; Lennon, D. J.; Vink, J. S.

    2013-02-01

    Context. The Tarantula Nebula in the Large Magellanic Cloud is our closest view of a starburst region and is the ideal environment to investigate important questions regarding the formation, evolution and final fate of the most massive stars. Aims: We analyze the multiplicity properties of the massive O-type star population observed through multi-epoch spectroscopy in the framework of the VLT-FLAMES Tarantula Survey. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods: We use multi-epoch spectroscopy and variability analysis to identify spectroscopic binaries. We also use a Monte-Carlo method to correct for observational biases. By modeling simultaneously the observed binary fraction, the distributions of the amplitudes of the radial velocity variations and the distribution of the time scales of these variations, we constrain the intrinsic current binary fraction and period and mass-ratio distributions. Results: We observe a spectroscopic binary fraction of 0.35 ± 0.03, which corresponds to the fraction of objects displaying statistically significant radial velocity variations with an amplitude of at least 20 km s-1. We compute the intrinsic binary fraction to be 0.51 ± 0.04. We adopt power-laws to describe the intrinsic period and mass-ratio distributions: f(log 10P/d) ~ (log 10P/d)π (with log 10P/d in the range 0.15-3.5) and f(q) ~ qκ with 0.1 ≤ q = M2/M1 ≤ 1.0. The power-law indexes that best reproduce the observed quantities are π = -0.45 ± 0.30 and κ = -1.0 ± 0.4. The period distribution that we obtain thus favours shorter period systems compared to an Öpik law (π = 0). The mass ratio distribution is slightly skewed towards low mass ratio systems but remains incompatible with a random sampling of a classical mass function (κ = -2.35). The binary fraction seems mostly uniform across the field of view and independent of the spectral types and luminosity classes. The binary fraction in the outer

  2. AGN III - primordial activity in nuclei of late-type galaxies with pseudobulges

    CERN Document Server

    Komberg, B V

    2013-01-01

    1. Based on observational data on evolution of quasars and galaxies of different types along with the results of numerical simulations we make a conclusion that on low redshifts ($z<0.5$) QSOI/II objects in massive elliptical and spiral galaxies with classical bulges cannot be in late single activity event (be "primordial"). Instead of it they have had events of activity earlier in their evolution. It means that their presence on low redshifts is connected with the recurrence phenomenon, sequential wet minor mergings, because timescale of the activity does not exceed several units of $10^7$ years. 2. We define a new class - "AGN III" as active galactic nuclei in isolated late-type spirals with low-mass rapidly rotating pseudobulges. We also state that only such objects can be in the primordial phase of activity at low redshifts. Black holes in such galaxies have masses $M_{BH}<10^7M_\\odot$ and also, probably very high spin. Such properties can explain their peculiar emission spectra. A good representati...

  3. Pitch Angle Restrictions in Late Type Spiral Galaxies Based on Chaotic and Ordered Orbital Behavior

    CERN Document Server

    Perez-Villegas, Angeles; Moreno, Edmundo; Peimbert, Antonio; Velazquez, Hector M

    2011-01-01

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a 3-D self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, going from 10$\\deg$ to 60$\\deg$. Testing undirectly orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately $\\sim 20\\deg$, the response supports closely the potential permitting readily the presence of long lasting spiral structures. The density response tends to "avoid" larger pitch angles in the potential, by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than $\\sim 20\\deg$, would not be long-lasting structures but rather transient. On the other hand, from an extensive orbital study in phase space, we also find that for late type galaxies with pitch angles larger than $\\sim 50\\deg$, chaos becomes pervasive destroying the ordered phase space surrounding the main sta...

  4. 3D climate modeling of Earth-like extrasolar planets orbiting different types of host stars

    Science.gov (United States)

    Godolt, M.; Grenfell, J. L.; Hamann-Reinus, A.; Kitzmann, D.; Kunze, M.; Langematz, U.; von Paris, P.; Patzer, A. B. C.; Rauer, H.; Stracke, B.

    2015-06-01

    The potential habitability of a terrestrial planet is usually defined by the possible existence of liquid water on its surface, since life as we know it needs liquid water at least during a part of its life cycle. The potential presence of liquid water on a planetary surface depends on many factors such as, most importantly, surface temperatures. The properties of the planetary atmosphere and its interaction with the radiative energy provided by the planet's host star are thereby of decisive importance. In this study we investigate the influence of different main-sequence stars (F, G, and K-type stars) upon the climate of Earth-like extrasolar planets and their potential habitability by applying a state-of-the-art three-dimensional (3D) Earth climate model accounting for local and dynamical processes. The calculations have been performed for planets with Earth-like atmospheres at orbital distances (and corresponding orbital periods) where the total amount of energy received from the various host stars equals the solar constant. In contrast to previous 3D modeling studies, we include the effect of ozone radiative heating upon the vertical temperature structure of the atmospheres. The global orbital mean results obtained have been compared to those of a one-dimensional (1D) radiative convective climate model to investigate the approximation of global mean 3D results by those of 1D models. The different stellar spectral energy distributions lead to different surface temperatures and due to ozone heating to very different vertical temperature structures. As previous 1D studies we find higher surface temperatures for the Earth-like planet around the K-type star, and lower temperatures for the planet around the F-type star compared to an Earth-like planet around the Sun. However, this effect is more pronounced in the 3D model results than in the 1D model because the 3D model accounts for feedback processes such as the ice-albedo and the water vapor feedback. Whether the

  5. PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-08-01

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

  6. Evidence of Significant Energy Input in the Late Phase of A Solar Flare from NuSTAR X-Ray Observations

    Science.gov (United States)

    Kuhar, Matej; Krucker, Sam; Hannah, Iain G.; Glesener, Lindsay; Saint-Hilaire, Pascal; Grefenstette, Brian W.; Hudson, Hugh S.; White, Stephen M.; Smith, David M.; Marsh, Andrew J.; hide

    2017-01-01

    We present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory (SDO)/ AIA and FOXSI-2 sounding rocket observations. The active region produced a medium-size solar flare 1 day before the observations, at approximately 18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8-4.6 MK, emission measure (0.3-1.8) × 1046 cm-3, and density estimated at (2.5-6.0) × 108 cm-3. The observed AIA fluxes are consistent with the derived NuSTAR temperature range, favoring temperature values in the range of 4.0-4.3 MK. By examining the post-flare loops' cooling times and energy content, we estimate that at least 12 sets of post-flare loops were formed and subsequently cooled between the onset of the flare and NuSTAR observations, with their total thermal energy content an order of magnitude larger than the energy content at flare peak time. This indicates that the standard approach of using only the flare peak time to derive the total thermal energy content of a flare can lead to a large underestimation of its value.

  7. Evidence of Significant Energy Input in the Late Phase of a Solar Flare from NuSTAR X-Ray Observations

    Science.gov (United States)

    Kuhar, Matej; Krucker, Säm; Hannah, Iain G.; Glesener, Lindsay; Saint-Hilaire, Pascal; Grefenstette, Brian W.; Hudson, Hugh S.; White, Stephen M.; Smith, David M.; Marsh, Andrew J.; Wright, Paul J.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles J.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

    2017-01-01

    We present observations of the occulted active region AR 12222 during the third Nuclear Spectroscopic Telescope ARray (NuSTAR) solar campaign on 2014 December 11, with concurrent Solar Dynamics Observatory (SDO)/AIA and FOXSI-2 sounding rocket observations. The active region produced a medium-size solar flare 1 day before the observations, at ∼18 UT on 2014 December 10, with the post-flare loops still visible at the time of NuSTAR observations. The time evolution of the source emission in the SDO/AIA 335 Å channel reveals the characteristics of an extreme-ultraviolet late-phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. The spectral fitting of NuSTAR observations yields an isothermal source, with temperature 3.8–4.6 MK, emission measure (0.3–1.8) × 1046 cm‑3, and density estimated at (2.5–6.0) × 108 cm‑3. The observed AIA fluxes are consistent with the derived NuSTAR temperature range, favoring temperature values in the range of 4.0–4.3 MK. By examining the post-flare loops’ cooling times and energy content, we estimate that at least 12 sets of post-flare loops were formed and subsequently cooled between the onset of the flare and NuSTAR observations, with their total thermal energy content an order of magnitude larger than the energy content at flare peak time. This indicates that the standard approach of using only the flare peak time to derive the total thermal energy content of a flare can lead to a large underestimation of its value.

  8. Star formation associated with neutral hydrogen in the outskirts of early-type galaxies

    Science.gov (United States)

    Yldz, Mustafa K.; Serra, Paolo; Peletier, Reynier F.; Oosterloo, Tom A.; Duc, Pierre-Alain

    2016-09-01

    About 20 percent of all nearby early-type galaxies (M⋆ ≳ ~6~ × 109~M⊙) outside the Virgo cluster are surrounded by a disc or ring of low-column-density neutral hydrogen (H I) gas with typical radii of tens of kpc, much larger than the stellar body. In order to understand the impact of these gas reservoirs on the host galaxies, we analyse the distribution of star formation out to large radii as a function of H I properties using GALEX UV and SDSS optical images. Our sample consists of 18 H I-rich galaxies as well as 55 control galaxies where no H I has been detected. In half of the H I-rich galaxies the radial UV profile changes slope at the position of the H I radial profile peak. To study the stellar populations, we calculate the FUV-NUV and UV-optical colours in two apertures, 1-3 and 3-10 Reff. We find that H I-rich galaxies are on average 0.5 and 0.8 mag bluer than the H I-poor ones, respectively. This indicates that a significant fraction of the UV emission traces recent star formation and is associated with the H I gas. Using FUV emission as a proxy for star formation, we estimate the integrated star formation rate in the outer regions (R > 1Reff) to be on average ˜ 6× 10-3 M⊙~yr-1 for the H I-rich galaxies. This rate is too low to build a substantial stellar disc and, therefore, change the morphology of the host. We find that the star formation efficiency and the gas depletion time are similar to those at the outskirts of spirals.

  9. Star formation associated with neutral hydrogen in the outskirts of early-type galaxies

    Science.gov (United States)

    Yıldız, Mustafa K.; Serra, Paolo; Peletier, Reynier F.; Oosterloo, Tom A.; Duc, Pierre-Alain

    2017-01-01

    About 20 per cent of all nearby early-type galaxies (M⋆ ≳ 6 × 109 M⊙) outside the Virgo cluster are surrounded by a disc or ring of low-column-density neutral hydrogen (H I) gas with typical radii of tens of kpc, much larger than the stellar body. In order to understand the impact of these gas reservoirs on the host galaxies, we analyse the distribution of star formation out to large radii as a function of H I properties using GALEX UV and SDSS optical images. Our sample consists of 18 H I-rich galaxies as well as 55 control galaxies where no H I has been detected. In half of the H I-rich galaxies, the radial UV profile changes slope at the position of the H I radial profile peak. To study the stellar populations, we calculate the FUV-NUV and UV-optical colours in two apertures, 1-3 and 3-10 Reff. We find that H I-rich galaxies are on average 0.5 and 0.8 mag bluer than the H I-poor ones, respectively. This indicates that a significant fraction of the UV emission traces recent star formation and is associated with the H I gas. Using FUV emission as a proxy for star formation, we estimate the integrated star formation rate in the outer regions (R > 1Reff) to be on average ˜6 × 10-3 M⊙ yr-1 for the H I-rich galaxies. This rate is too low to build a substantial stellar disc and, therefore, change the morphology of the host. We find that the star formation efficiency and the gas depletion time are similar to those at the outskirts of spirals.

  10. A STATISTICAL RECONSTRUCTION OF THE PLANET POPULATION AROUND KEPLER SOLAR-TYPE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Silburt, Ari; Wu, Yanqin [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Gaidos, Eric [Department of Geology and Geophysics, University of Hawai' i at Mānoa, Honolulu, HI 96822 (United States)

    2015-02-01

    Using the cumulative catalog of planets detected by the NASA Kepler mission, we reconstruct the intrinsic occurrence of Earth- to Neptune-size (1-4 R {sub ⊕}) planets and their distributions with radius and orbital period. We analyze 76,711 solar-type (0.8 < R {sub *}/R {sub ☉} < 1.2) stars with 430 planets on 20-200 day orbits, excluding close-in planets that may have been affected by the proximity to the host star. Our analysis considers errors in planet radii and includes an ''iterative simulation'' technique that does not bin the data. We find a radius distribution that peaks at 2-2.8 Earth radii, with lower numbers of smaller and larger planets. These planets are uniformly distributed with logarithmic period, and the mean number of such planets per star is 0.46 ± 0.03. The occurrence is ∼0.66 if planets interior to 20 days are included. We estimate the occurrence of Earth-size planets in the ''habitable zone'' (defined as 1-2 R {sub ⊕}, 0.99-1.7 AU for solar-twin stars) as 6.4{sub −1.1}{sup +3.4}%. Our results largely agree with those of Petigura et al., although we find a higher occurrence of 2.8-4 Earth-radii planets. The reasons for this excess are the inclusion of errors in planet radius, updated Huber et al. stellar parameters, and also the exclusion of planets that may have been affected by proximity to the host star.

  11. The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars

    CERN Document Server

    Grunhut, J H; Neiner, C; Oksala, M E; Petit, V; Alecian, E; Bohlender, D A; Bouret, J -C; Henrichs, H F; Hussain, G A J; Kochukhov, O

    2016-01-01

    We present the analysis performed on spectropolarimetric data of 97 O-type targets included in the framework of the MiMeS (Magnetism in Massive Stars) Survey. Mean Least-Squares Deconvolved Stokes I and V line profiles were extracted for each observation, from which we measured the radial velocity, rotational and non-rotational broadening velocities, and longitudinal magnetic field. The investigation of the Stokes I profiles led to the discovery of 2 new multi-line spectroscopic systems (HD46106, HD204827) and confirmed the presence of a suspected companion in HD37041. We present a modified strategy of the Least-Squares Deconvolution technique aimed at optimising the detection of magnetic signatures while minimising the detection of spurious signatures in Stokes V. Using this analysis, we confirm the detection of a magnetic field in 6 targets previously reported as magnetic by the MiMeS collaboration (HD108, HD47129A2, HD57682, HD148937, CPD-28 2561, and NGC 1624-2), as well as report the presence of signal i...

  12. Star formation in early-type galaxies: the role of stellar winds and kinematics

    CERN Document Server

    Pellegrini, S; Ciotti, L

    2015-01-01

    Early-type galaxies (ETGs) host a hot ISM produced mainly by stellar winds, and heated by Type Ia supernovae and the thermalization of stellar motions. High resolution 2D hydrodynamical simulations showed that ordered rotation in the stellar component results in the formation of a centrifugally supported cold equatorial disc. In a recent numerical investigation we found that subsequent generations of stars are formed in this cold disc; this process consumes most of the cold gas, leaving at the present epoch cold masses comparable to those observed. Most of the new stellar mass formed a few Gyrs ago, and resides in a disc.

  13. The Effective Temperatures of O-type Stars from UV spectroscopy

    CERN Document Server

    Bianchi, Luciana

    2013-01-01

    We present an analysis of high resolution spectra in the far-UV -- UV range (~905-2000\\AA) with non-LTE, spherical, hydrodynamical, line-blanketed models, of three O-type Galactic stars, and derive their photospheric and wind parameters. These data extend previously analyzed samples and fill a gap in spectral type coverage. The combined sample confirms a revised (downward) effective temperature scale with respect to canonical calibrations, as found in our previous works from UV and optical spectra, and in recent works by other authors.

  14. ALFALFA HI Content and Star Formation in Virgo Cluster Early-Type Dwarfs

    CERN Document Server

    Koopmann, R A; Haynes, M P; Brosch, N

    2009-01-01

    The ALFALFA (Arecibo Legacy Fast ALFA) blind survey is providing a census of HI in galaxies of all types in a range of environments. Here we report on ALFALFA results for Virgo Cluster early-type dwarfs between declinations of 4 and 16 degrees. Less than 2% of the Virgo early-type dwarf population is detected, compared to 70-80% of the Im/BCD dwarf population. Most of the dwarfs detected in HI show evidence for ongoing or recent star formation. Early-type galaxies with HI tend to be located in the outer regions of the cluster and to be brighter. Early-type dwarfs with HI may be undergoing morphological transition due to cluster environmental effects.

  15. Link between Mass-loss and Variability Type for AGB Stars?

    CERN Document Server

    Ivezic, Z; Ivezic, Zeljko; Knapp, Gillian R.

    1998-01-01

    We find that AGB stars separate in the 25-12 vs. 12-K color-color diagram according to their chemistry (O, S vs. C) and variability type (Miras vs. SRb/Lb). While discrimination according to the chemical composition is not surprising, the separation of Miras from SRb/Lb variables is unexpected. We show that ``standard'' steady-state radiatively driven models provide excellent fits to the color distribution of Miras of all chemical types. However, these models are incapable of explaining the dust emission from O-rich SRb/Lb stars. The models can be altered to fit the data by postulating different optical properties for silicate grains, or by assuming that the dust temperature at the inner envelope radius is significantly lower (300-400 K) than typical condensation temperatures (800-1000 K), a possibility which is also supported by the detailed characteristics of LRS data. The absence of hot dust for SRb/Lb stars can be interpreted as a recent (order of 100 yr) decrease in the mass-loss rate. The distribution o...

  16. New bright optical spectrophotometric standards: A-type stars from the STIS Next Generation Spectral Library

    CERN Document Server

    Prieto, Carlos Allende

    2015-01-01

    Exoplanets have sparked interest in extremely high signal-to-noise ratio spectroscopic observations of very bright stars, in a regime where flux calibrators, in particular DA white dwarfs, are not available. We argue that A-type stars offer a useful alternative and reliable space-based spectrophotometry is now available for a number of bright ones in the range 3type flux standards for the optical range (400-800 nm), and provide scaled model fluxes for them. Our tests suggest that the absolute fluxes for these stars in the optical are reliable to within 3%. We limit the spectral range to 400-800 nm, since our models have difficulties to reproduce the observed fluxes in the near-infrared and, especially, in the near-UV, where the discrepancies rise up to ~ 10%. Based on our model fits, we derive angular diameters with an estimated accuracy of about 1%.

  17. Membership, metallicity and lithium abundances for solar-type stars in NGC 6633

    CERN Document Server

    Jeffries, R D; Harmer, S; Deliyannis, C P

    2002-01-01

    We present spectroscopic observations of candidate F, G and K type stars in NGC 6633, an open cluster with a similar age to the Hyades. We identify 10 new cluster members including one short period binary system. Combining this survey with that of Jeffries (1997), we identify a total of 30 solar-type members. We have used the F and early G stars to spectroscopically estimate [Fe/H]=-0.096+/-0.081 for NGC 6633 and with more precision that NGC 6633 has (0.074+/-0.041) dex less iron than the Pleiades and (0.206+/-0.040) dex less iron than the Hyades. Lithium abundances have been estimated for the NGC 6633 members and compared with consistently determined Li abundances in other clusters. Several mid F stars in NGC 6633 show strong Li depletion at approximately the same effective temperature that this phenomenon is seen in the Hyades. At cooler temperatures the Li abundance patterns in several open clusters with similar ages (NGC 6633, Hyades, Praesepe and Coma Berenices) are remarkably similar, despite their diff...

  18. Oscillation frequencies for 35 \\Kepler solar-type planet-hosting stars using Bayesian techniques and machine learning

    CERN Document Server

    Davies, G R; Bedding, T R; Handberg, R; Lund, M N; Chaplin, W J; Huber, D; White, T R; Benomar, O; Hekker, S; Basu, S; Campante, T L; Christensen-Dalsgaard, J; Elsworth, Y; Karoff, C; Kjeldsen, H; Lundkvist, M S; Metcalfe, T S; Stello, D

    2015-01-01

    \\Kepler has revolutionised our understanding of both exoplanets and their host stars. Asteroseismology is a valuable tool in the characterisation of stars and \\Kepler is an excellent observing facility to perform asteroseismology. Here we select a sample of 35 \\Kepler solar-type stars which host transiting exoplanets (or planet candidates) with detected solar-like oscillations. Using available \\Kepler short cadence data up to Quarter 16 we create power spectra optimised for asteroseismology of solar-type stars. We identify modes of oscillation and estimate mode frequencies by ``peak bagging'' using a Bayesian MCMC framework. In addition, we expand the methodology of quality assurance using a Bayesian unsupervised machine learning approach. We report the measured frequencies of the modes of oscillation for all 35 stars and frequency ratios commonly used in detailed asteroseismic modelling. Due to the high correlations associated with frequency ratios we report the covariance matrix of all frequencies measured ...

  19. SUPERFLARES ON SOLAR-TYPE STARS OBSERVED WITH KEPLER II. PHOTOMETRIC VARIABILITY OF SUPERFLARE-GENERATING STARS: A SIGNATURE OF STELLAR ROTATION AND STARSPOTS

    Energy Technology Data Exchange (ETDEWEB)

    Notsu, Yuta; Shibayama, Takuya; Notsu, Shota; Nagao, Takashi [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Maehara, Hiroyuki; Honda, Satoshi; Ishii, Takako T.; Nogami, Daisaku; Shibata, Kazunari, E-mail: ynotsu@kwasan.kyoto-u.ac.jp [Kwasan and Hida Observatories, Kyoto University, Kitakazan-ohmine-cho, Yamashina-ku, Kyoto 607-8471 (Japan)

    2013-07-10

    We performed simple spot-model calculations for quasi-periodic brightness variations of solar-type stars showing superflares using Kepler photometric data. Most of the superflare stars show quasi-periodic brightness modulations with a typical period of one to a few tens of days. Our results indicate that these brightness variations can be explained by the rotation of a star with fairly large starspots. Using the results of the period analysis, we investigated the relation between the energy and frequency of superflares and the rotation period. Stars with relatively slower rotation rates can still produce flares that are as energetic as those of more rapidly rotating stars although the average flare frequency is lower for more slowly rotating stars. We found that the energy of superflares is related to the total coverage of the starspot. The correlation between the spot coverage and the flare energy in superflares is similar to that in solar flares. These results suggest that the energy of superflares can be explained by the magnetic energy stored around the starspots.

  20. Asteroseismic fundamental properties of solar-type stars observed by the NASA Kepler Mission

    CERN Document Server

    Chaplin, W J; Huber, D; Serenelli, A; Casagrande, L; Aguirre, V Silva; Ball, W H; Creevey, O L; Gizon, L; Handberg, R; Karoff, C; Lutz, R; Marques, J P; Miglio, A; Stello, D; Suran, M D; Pricopi, D; Metcalfe, T S; Monteiro, M J P F G; Molenda-Zakowicz, J; Appourchaux, T; Christensen-Dalsgaard, J; Elsworth, Y; Garcia, R A; Houdek, G; Kjeldsen, H; Bonanno, A; Campante, T L; Corsaro, E; Gaulme, P; Hekker, S; Mathur, S; Mosser, B; Regulo, C; Salabert, D

    2013-01-01

    We use asteroseismic data obtained by the NASA Kepler Mission to estimate the fundamental properties of more than 500 main-sequence and sub-giant stars. Data obtained during the first 10 months of Kepler science operations were used for this work, when these solar-type targets were observed for one month each in a survey mode. Stellar properties have been estimated using two global asteroseismic parameters and complementary photometric and spectroscopic data. Homogeneous sets of effective temperatures were available for the entire ensemble from complementary photometry; spectroscopic estimates of T_eff and [Fe/H] were available from a homogeneous analysis of ground-based data on a subset of 87 stars. [Abbreviated version... see paper for full abstract.

  1. New radio detections of early-type pre-main-sequence stars

    Science.gov (United States)

    Skinner, Stephen L.; Brown, Alexander; Linsky, Jeffrey L.

    1990-01-01

    Results of VLA radio continuum observations of 13 early-type pre-main-sequence stars selected from the 1984 catalog of Finkenzeller and Mundt are presented. The stars HD 259431 and MWC 1080 were detected at 3.6 cm, while HD 200775 and TY CrA were detected at both 3.6 and 6 cm. The flux density of HD 200775 has a frequency dependence consistent with the behavior expected for free-free emission originating in a fully ionized wind. However, an observation in A configuration suggests that the source geometry may not be spherically symmetric. In contrast, the spectral index of TY CrA is negative with a flux behavior implying nonthermal emission. The physical mechanism responsible for the nonthermal emission has not yet been identified, although gyrosynchrotron and synchrotron processes cannot be ruled out.

  2. 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.

  3. Simulations of core convection in rotating A-type stars: Magnetic dynamo action

    CERN Document Server

    Brun, A S; Toomre, J; Brun, Allan Sacha; Browning, Matthew K.; Toomre, Juri

    2005-01-01

    Core convection and dynamo activity deep within rotating A-type stars of 2 solar masses are studied with 3--D nonlinear simulations. Our modeling considers the inner 30% by radius of such stars, thus capturing within a spherical domain the convective core and a modest portion of the surrounding radiative envelope. The MHD equations are solved using the ASH code to examine turbulent flows and magnetic fields, both of which exhibit intricate time dependence. By introducing small seed magnetic fields into our progenitor hydrodynamic models rotating at one and four times the solar rate, we assess here how the vigorous convection can amplify those fields and sustain them against ohmic decay. Dynamo action is indeed realized, ultimately yielding magnetic fields that are in energy equipartion with the flow. Such magnetism reduces the differential rotation obtained in the progenitors, partly by Maxwell stresses that transport angular momentum poleward and oppose the Reynolds stresses in the latitudinal balance. In co...

  4. Suppression of star formation in early-type galaxies by feedback from supermassive black holes.

    Science.gov (United States)

    Schawinski, Kevin; Khochfar, Sadegh; Kaviraj, Sugata; Yi, Sukyoung K; Boselli, Alessandro; Barlow, Tom; Conrow, Tim; Forster, Karl; Friedman, Peter G; Martin, D Chris; Morrissey, Patrick; Neff, Susan; Schiminovich, David; Seibert, Mark; Small, Todd; Wyder, Ted K; Bianchi, Luciana; Donas, Jose; Heckman, Tim; Lee, Young-Wook; Madore, Barry; Milliard, Bruno; Rich, R Michael; Szalay, Alex

    2006-08-24

    Detailed high-resolution observations of the innermost regions of nearby galaxies have revealed the presence of supermassive black holes. These black holes may interact with their host galaxies by means of 'feedback' in the form of energy and material jets; this feedback affects the evolution of the host and gives rise to observed relations between the black hole and the host. Here we report observations of the ultraviolet emissions of massive early-type galaxies. We derive an empirical relation for a critical black-hole mass (as a function of velocity dispersion) above which the outflows from these black holes suppress star formation in their hosts by heating and expelling all available cold gas. Supermassive black holes are negligible in mass compared to their hosts but nevertheless seem to play a critical role in the star formation history of galaxies.

  5. PREDICTION OF THE RHEOLOGICAL PROPERTIES OF STAR-TYPE BRANCHED POLYMER SOLUTIONS BY MEANS OF THE FIXED SPECTRUM MODEL

    Institute of Scientific and Technical Information of China (English)

    WU Qiye

    1995-01-01

    The Rouse-Zimm model with slippage was improved and the basic parameters of modelwere modified to explain the rheological properties of star-type branched polymersolutions. The theoretical results show good agreement with experimental data.

  6. Discovery of a magnetic field in the early B-type star σ Lupi

    Science.gov (United States)

    Henrichs, H. F.; Kolenberg, K.; Plaggenborg, B.; Marsden, S. C.; Waite, I. A.; Landstreet, J. D.; Wade, G. A.; Grunhut, J. H.; Oksala, M. E.

    2012-09-01

    Context. Magnetic early B-type stars are rare. Indirect indicators are needed to identify them before investing in time-intensive spectropolarimetric observations. Aims: We use the strongest indirect indicator of a magnetic field in B stars, which is periodic variability of ultraviolet (UV) stellar wind lines occurring symmetric about the approximate rest wavelength. Our aim is to identify probable magnetic candidates which would become targets for follow-up spectropolarimetry to search for a magnetic field. Methods: From the UV wind line variability the B1/B2V star σ Lupi emerged as a new magnetic candidate star. AAT spectropolarimetric measurements with SEMPOL were obtained. The longitudinal component of the magnetic field integrated over the visible surface of the star was determined with the least-squares deconvolution method. Results: The UV line variations of σ Lupi are similar to what is known in magnetic B stars, but no periodicity could be determined. We detected a varying longitudinal magnetic field with amplitude of about 100 G with error bars of typically 20 G, which supports an oblique magnetic-rotator configuration. The equivalent width variations of the UV lines, the magnetic and the optical-line variations are consistent with the photometric period of 3.02 d, which we identify with the rotation period of the star. Additional observations with ESPaDOnS attached to the CFHT confirmed this discovery, and allowed the determination of a precise magnetic period. Analysis revealed that σ Lupi is a helium-strong star, with an enhanced nitrogen abundance and an underabundance of carbon, and has a chemically spotted surface. Conclusions.σ Lupi is a magnetic oblique rotator, and is a He-strong star. Like in other magnetic B stars the UV wind emission appears to originate close to the magnetic equatorial plane, with maximum emission occurring when a magnetic pole points towards the Earth. The 3.01972 ± 0.00043 d magnetic rotation period is consistent with

  7. A UNIFORM ASTEROSEISMIC ANALYSIS OF 22 SOLAR-TYPE STARS OBSERVED BY KEPLER

    Energy Technology Data Exchange (ETDEWEB)

    Mathur, S.; Metcalfe, T. S.; Christensen-Dalsgaard, J.; Dogan, G. [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); Woitaszek, M. [Computational and Information Systems Laboratory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States); Bruntt, H.; Karoff, C.; Campante, T. L. [Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark); Verner, G. A.; Chaplin, W. J.; Elsworth, Y. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Creevey, O. L. [Laboratoire Lagrange, UMR7293, Universite de Nice Sophia-Antipolis, CNRS, Observatoire de la Cote d' Azur, BP 4229, 06304 Nice Cedex 4 (France); Basu, S.; Deheuvels, S. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Stello, D.; Bedding, T. R.; Benomar, O. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Appourchaux, T. [Institut d' Astrophysique Spatiale, UMR8617, Universite Paris XI, Batiment 121, 91405 Orsay Cedex (France); Garcia, R. A. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, 91191 Gif-sur-Yvette Cedex (France); Bonanno, A. [INAF Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy); and others

    2012-04-20

    Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure and evolution for the large sample of solar-type stars in the field. We perform a uniform analysis of 22 of the brightest asteroseismic targets with the highest signal-to-noise ratio observed for 1 month each during the first year of the mission, and we quantify the precision and relative accuracy of asteroseismic determinations of the stellar radius, mass, and age that are possible using various methods. We present the properties of each star in the sample derived from an automated analysis of the individual oscillation frequencies and other observational constraints using the Asteroseismic Modeling Portal (AMP), and we compare them to the results of model-grid-based methods that fit the global oscillation properties. We find that fitting the individual frequencies typically yields asteroseismic radii and masses to {approx}1% precision, and ages to {approx}2.5% precision (respectively, 2, 5, and 8 times better than fitting the global oscillation properties). The absolute level of agreement between the results from different approaches is also encouraging, with model-grid-based methods yielding slightly smaller estimates of the radius and mass and slightly older values for the stellar age relative to AMP, which computes a large number of dedicated models for each star. The sample of targets for which this type of analysis is possible will grow as longer data sets are obtained during the remainder of the mission.

  8. Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample

    Science.gov (United States)

    Borgniet, S.; Lagrange, A.-M.; Meunier, N.; Galland, F.

    2017-03-01

    Context. Massive, main-sequence (MS) AF-type stars have so far remained unexplored in past radial velocities (RV) surveys due to their small number of spectral lines and high rotational velocities that prevent the classic RV computation method. Aims: Our aim is to search for giant planets (GPs) around AF MS stars, to get primary statistical information on their occurrence rate and to compare the results with evolved stars and lower-mass MS stars. Methods: We used the HARPS spectrograph located on the 3.6 m telescope at ESO La Silla Observatory to observe 108 AF MS stars with B-V in the range -0.04 to 0.58 and masses in the range 1.1 to 3.6 M⊙. We used our SAFIR software developed to compute the RV and other spectroscopic observables of these early-type stars. We characterized the detected companions as well as the intrinsic stellar variability. We computed the detection limits and used them as well as the detected companions to derive the first estimates of the close-in brown dwarf (BD) and GP frequencies around AF stars. Results: We report the detection of a mpsini = 4.51MJup planetary companion with an 826-day period to the F6V dwarf HD 111998. We also present new data on the two-planet system around the F6IV-V dwarf HD 60532. We also report the detections of 14 binaries with long-term RV trends and/or high-amplitude RV variations combined to a flat RV-bisector span diagram. We constrain the minimal masses and semi-major axes of these companions and check that these constraints are compatible with the stellar companions previously detected by direct imaging or astrometry for six of these targets. We get detection limits deep into the planetary domain with 70% of our targets showing detection limits between 0.1 and 10 MJup at all orbital periods in the 1- to 103-day range. We derive BD (13 ≤mpsini ≤ 80 MJup) occurrence rates in the 1- to 103-day period range of 2-2+5% and 2.6-2.6+6.7% for stars with M⋆ in the ranges 1.1 to 1.5 and 1.5 to 3 M

  9. Magnetic field structure in single late-type giants: The weak G-band giant 37 Comae from 2008 to 2011

    Science.gov (United States)

    Tsvetkova, S.; Petit, P.; Konstantinova-Antova, R.; Aurière, M.; Wade, G. A.; Palacios, A.; Charbonnel, C.; Drake, N. A.

    2017-03-01

    Aims: This work studies the magnetic activity of the late-type giant 37 Com. This star belongs to the group of weak G-band stars that present very strong carbon deficiency in their photospheres. The paper is a part of a global investigation into the properties and origin of magnetic fields in cool giants. Methods: We use spectropolarimetric data, which allows the simultaneous measurement of the longitudinal magnetic field Bl, line activity indicators (Hα, Ca ii IRT, S-index) and radial velocity of the star, and consequently perform a direct comparison of their time variability. Mean Stokes V profiles are extracted using the least squares deconvolution (LSD) method. One map of the surface magnetic field of the star is reconstructed via the Zeeman Doppler imaging (ZDI) inversion technique. Results: A periodogram analysis is performed on our dataset and it reveals a rotation period of 111 days. We interpret this period to be the rotation period of 37 Com. The reconstructed magnetic map reveals that the structure of the surface magnetic field is complex and features a significant toroidal component. The time variability of the line activity indicators, radial velocity and magnetic field Bl indicates a possible evolution of the surface magnetic structures in the period from 2008 to 2011. For completeness of our study, we use customized stellar evolutionary models suited to a weak G-band star. Synthetic spectra are also calculated to confirm the peculiar abundance of 37 Com. Conclusions: We deduce that 37 Com is a 6.5 M⊙ weak G-band star located in the Hertzsprung gap, whose magnetic activity is probably due to dynamo action. Based on observations obtained at the Télescope Bernard Lyot (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France and Université de Toulouse, and at the Canada-France-Hawaii Telescope (CFHT) which is

  10. Late-time behaviour of the tilted Bianchi type VIh models

    Science.gov (United States)

    Hervik, S.; van den Hoogen, R. J.; Lim, W. C.; Coley, A. A.

    2007-08-01

    We study tilted perfect fluid cosmological models with a constant equation of state parameter in spatially homogeneous models of Bianchi type VIh using dynamical systems methods and numerical experimentation, with an emphasis on their future asymptotic evolution. We determine all of the equilibrium points of the type VIh state space (which correspond to exact self-similar solutions of the Einstein equations, some of which are new), and their stability is investigated. We find that there are vacuum plane-wave solutions that act as future attractors. In the parameter space, a 'loophole' is shown to exist in which there are no stable equilibrium points. We then show that a Hopf-bifurcation can occur resulting in a stable closed orbit (which we refer to as the Mussel attractor) corresponding to points both inside the loophole and points just outside the loophole; in the former case the closed curves act as late-time attractors while in the latter case these attracting curves will co-exist with attracting equilibrium points. In the special Bianchi type III case, centre manifold theory is required to determine the future attractors. Comprehensive numerical experiments are carried out to complement and confirm the analytical results presented. We note that the Bianchi type VIh case is of particular interest in that it contains many different subcases which exhibit many of the different possible future asymptotic behaviours of Bianchi cosmological models.

  11. Proton and Fe Ion-Induced Early and Late Chromosome Aberrations in Different Cell Types

    Science.gov (United States)

    Wu, Honglu; Lu, Tao; Yeshitla, Samrawit; Zhang, Ye; Kadhim, Munira

    2016-01-01

    An early stage of cancer development is believed to be genomic instability (GI) which accelerates the mutation rate in the descendants of the cells surviving radiation exposure. To investigate GI induced by charged particles, we exposed human lymphocytes, human fibroblast cells, and human mammary epithelial cells to high energy protons and Fe ions. In addition, we also investigated GI in bone marrow cells isolated from CBA/CaH (CBA) and C57BL/6 (C57) mice, by analyzing cell survival and chromosome aberrations in the cells after multiple cell divisions. Results analyzed so far from the experiments indicated different sensitivities to charged particles between CBA/CaH (CBA) and C57BL/6 (C57) mouse strains, suggesting that there are two main types of response to irradiation: 1) responses associated with survival of damaged cells and 2) responses associated with the induction of non-clonal chromosomal instability in the surviving progeny of stem cells. Previously, we reported that the RBE for initial chromosome damages was high in human lymphocytes exposed to Fe ions. Our results with different cell types demonstrated different RBE values between different cell types and between early and late chromosomal damages. This study also attempts to offer an explanation for the varying RBE values for different cancer types.

  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. Physical parameters of late M-type members of Chamaeleon I and TW Hydrae Association: dust settling, age dispersion and activity

    Science.gov (United States)

    Bayo, A.; Barrado, D.; Allard, F.; Henning, T.; Comerón, F.; Morales-Calderón, M.; Rajpurohit, A. S.; Peña Ramírez, K.; Beamín, J. C.

    2017-02-01

    Although mid-to-late type M dwarfs are the most common stars in our stellar neighbourhood, our knowledge of these objects is still limited. Open questions include the evolution of their angular momentum, internal structures, dust settling in their atmospheres and age dispersion within populations. In addition, at young ages, late-type Ms have masses below the hydrogen burning limit and therefore are key objects in the debate on the brown dwarf mechanism of formation. In this work, we determine and study in detail the physical parameters of two samples of young, late M-type sources belonging to either the Chamaeleon I dark cloud or the TW Hydrae Association and compare them with the results obtained in the literature for other young clusters and also for older, field, dwarfs. We used multiwavelength photometry to construct and analyse SEDs to determine general properties of the photosphere and disc presence. We also used low-resolution optical and near-infrared spectroscopy to study activity, accretion, gravity and effective temperature sensitive indicators. We propose a Virtual Observatory-based spectral index that is both temperature and age sensitive. We derived physical parameters using independent techniques confirming the already common feature/problem of the age/luminosity spread. In particular, we highlight two brown dwarfs showing very similar temperatures but clearly different surface gravity (explained invoking extreme early accretion). We also show how, despite large improvement in the dust treatment in theoretical models, there is still room for further progress in the simultaneous reproduction of the optical and near-infrared features of these cold young objects.

  14. Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T

    CERN Document Server

    Marsh, Kenneth A; Kirkpatrick, J Davy; Gelino, Christopher R; Cushing, Michael C; Griffith, Roger L; Skrutskie, Michael F; Eisenhardt, Peter R

    2012-01-01

    We present astrometric measurements of eleven nearby ultracool brown dwarfs of spectral types Y and late-T, based on imaging observations from a variety of space-based and ground-based telescopes. These measurements have been used to estimate relative parallaxes and proper motions via maximum likelihood fitting of geometric model curves. To compensate for the modest statistical significance (~ 3 pc. In addition, we have obtained significant estimates of Vtan for two of the Y dwarfs; both are <100 km/s, consistent with membership in the thin disk population. Comparison of absolute magnitudes with model predictions as a function of color shows that the Y dwarfs are significantly redder in J-H than predicted by a cloud-free model

  15. Understanding Mass-Loss and the late Evolution of Intermediate Mass Stars: Jets, Disks, Binarity, Dust and Magnetic Fields

    CERN Document Server

    Sahai, Raghvendra; Blackman, Eric; Kastner, Joel; Claussen, Mark; Morris, Mark; De Marco, Orsola; Speck, Angela; Frank, Adam; Turner, Neal

    2009-01-01

    Almost all stars in the 1-8 Msun range evolve through the Asymptotic Giant Branch (AGB), preplanetary nebula (PPN) and planetary nebula (PN) evolutionary phases. Most stars that leave the main sequence in a Hubble time will end their lives in this way. The heavy mass loss which occurs during the AGB phase is important across astrophysics, and the particulate matter crucial for the birth of new solar systems is made and ejected by AGB stars. Yet stellar evolution from the beginning of the AGB phase to the PN phase remains poorly understood. We do not understand how the mass-loss (rate, geometry, temporal history) depends on fundamental stellar parameters or the presence of a binary companion. While the study of evolved non-massive stars has maintained a relatively modest profile in recent decades, we are nonetheless in the midst of a quiet but exciting revolution in this area, driven by new observational results, such as the discovery of jets and disks in stellar environments where these were never expected, a...

  16. The ALHAMBRA survey: reliable morphological catalogue of 22,051 early- and late-type galaxies

    CERN Document Server

    Pović, M; Aguerri, J A L; Márquez, I; Masegosa, J; Husillos, C; Molino, A; Cristóbal-Hornillos, D; Perea, J; Benítez, N; del Olmo, A; Jiménez-Teja, Y; Moles, M; Alfaro, E; Aparicio-Villegas, T; Ascaso, B; Broadhurst, T; Cabrera-Caño, J; Castander, F J; Cepa, J; Cerviño, M; Lorenzo, M Fernández; Fernández-Soto, A; Delgado, R M González; Infante, L; López-Sanjuan, C; Martínez, V J; Matute, I; Oteo, I; Pérez-García, A M; Prada, F; Quintana, J M

    2013-01-01

    ALHAMBRA is a photometric survey designed to trace the cosmic evolution and cosmic variance. It covers a large area of ~ 4 sq. deg in 8 fields, where 7 fields overlap with other surveys, allowing to have complementary data in other wavelengths. All observations were carried out in 20 continuous, medium band (30 nm width) optical and 3 near-infrared (JHK) bands, providing the precise measurements of photometric redshifts. In addition, morphological classification of galaxies is crucial for any kind of galaxy formation and cosmic evolution studies, providing the information about star formation histories, their environment and interactions, internal perturbations, etc. We present a morphological classification of > 40,000 galaxies in the ALHAMBRA survey. We associate to every galaxy a probability to be early-type using the automated Bayesian code galSVM. Despite of the spatial resolution of the ALHAMBRA images (~ 1 arcsec), for 22,051 galaxies we obtained the contamination by other type of less than 10%. Of tho...

  17. A Survey of Stellar Families: Multiplicity of Solar-Type Stars

    CERN Document Server

    Raghavan, Deepak; Henry, Todd J; Latham, David W; Marcy, Geoffrey W; Mason, Brian D; Gies, Douglas R; White, Russel J; Brummelaar, Theo A ten

    2010-01-01

    We present the results of a comprehensive assessment of companions to solar-type stars. A sample of 454 stars, including the Sun, was selected from the Hipparcos catalog with {\\pi} > 40 mas, {\\sigma}_{\\pi}/{\\pi} < 0.05, 0.5 < B - V < 1.0 (~ F6-K3), and constrained by absolute magnitude and color to exclude evolved stars. New observational aspects of this work include surveys for (1) very close companions with long-baseline interferometry at the CHARA Array, (2) close companions with speckle interferometry, and (3) wide proper motion companions identified by blinking multi-epoch archival images. In addition, we include the results from extensive radial-velocity monitoring programs and evaluate companion information from various catalogs. The overall observed fractions of single, double, triple, and higher order systems are 56% \\pm 2%, 33% \\pm 2%, 8% \\pm 1%, and 3% \\pm 1%, respectively, counting all confirmed stellar and brown dwarf companions. Our completeness analysis indicates that only a few undisc...

  18. Star formation associated with neutral hydrogen in the outskirts of early-type galaxies

    CERN Document Server

    Yıldız, Mustafa K; Peletier, Reynier F; Oosterloo, Tom A; Duc, Pierre-Alain

    2016-01-01

    About 20 percent of all nearby early-type galaxies ($M_{\\star} \\gtrsim 6 \\times 10^{9}$ M$_{\\odot}$) outside the Virgo cluster are surrounded by a disc or ring of low-column-density neutral hydrogen (HI) gas with typical radii of tens of kpc, much larger than the stellar body. In order to understand the impact of these gas reservoirs on the host galaxies, we analyse the distribution of star formation out to large radii as a function of HI properties using GALEX UV and SDSS optical images. Our sample consists of 18 HI-rich galaxies as well as 55 control galaxies where no HI has been detected. In half of the HI-rich galaxies the radial UV profile changes slope at the position of the HI radial profile peak. To study the stellar populations, we calculate the FUV-NUV and UV-optical colours in two apertures, 1-3 and 3-10 R$_{eff}$ . We find that HI -rich galaxies are on average 0.5 and 0.8 mag bluer than the HI-poor ones, respectively. This indicates that a significant fraction of the UV emission traces recent star...

  19. Pulsational mode-typing in line profile variables. I - Four Beta Cephei stars

    Science.gov (United States)

    Campos, A. J.; Smith, M. A.

    1980-01-01

    The detailed variations of line profiles in the Beta Cephei-type variable stars Gamma Pegasi, Beta Cephei, Delta Ceti and Sigma Scorpii are modeled throughout their pulsation cycles in order to classify the dominant pulsation mode as radial or nonradial. High-dispersion Reticon observations of the variables were obtained for the Si III line at 4567 A, and line profiles broadened by radial or nonradial pulsations, rotation and radial-tangential macroturbulence were calculated based on a model atmosphere. It is found that only a radial pulsation mode can reproduce the radial velocity amplitude, changes in line asymmetry and uniform line width observed in all four stars. Results are in agreement with the color-to-light arguments of Stamford and Watson (1978), and suggest that radial pulsation plays the dominant role in the observed variations in most Beta Cephei stars. Evidence for shocks or moving shells is also found in visual line data for Sigma Scorpii and an ultraviolet line of Beta Cephei, together with evidence of smooth, secular period changes in Beta Cephei and Delta Ceti.

  20. THE NEAR-ULTRAVIOLET LUMINOSITY FUNCTION OF YOUNG, EARLY M-TYPE DWARF STARS

    Energy Technology Data Exchange (ETDEWEB)

    Ansdell, Megan; Baranec, Christoph [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Gaidos, Eric [Department of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822 (United States); Mann, Andrew W. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Lépine, Sebastien [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States); James, David [Cerro Tololo Inter-American Observatory, Casilla 603 La Serena (Chile); Buccino, Andrea; Mauas, Pablo; Petrucci, Romina [Instituto de Astronomía y Física del Espacio, C1428EHA Buenos Aires (Argentina); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Riddle, Reed [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-01-01

    Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magnetohydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lépine and Gaidos catalog of bright M dwarfs with the Galaxy Evolution Explorer (GALEX) catalog of NUV (1771-2831 Å) sources. Of the 4805 sources with GALEX counterparts, 797 have NUV emission significantly (>2.5σ) in excess of an empirical basal level. We inspected these candidate active stars using visible-wavelength spectra, high-resolution adaptive optics imaging, time-series photometry, and literature searches to identify cases where the elevated NUV emission is due to unresolved background sources or stellar companions; we estimated the overall occurrence of these ''false positives'' (FPs) as ∼16%. We constructed an NUV luminosity function that accounted for FPs, detection biases of the source catalogs, and GALEX upper limits. We found the NUV luminosity function to be inconsistent with predictions from a constant star-formation rate and simplified age-activity relation defined by a two-parameter power law.

  1. Rotational properties of the O-type star population in the Tarantula region

    CERN Document Server

    Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2013-01-01

    The 30 Doradus (30\\,Dor) region in the Large Magellanic Cloud (also known as the Tarantula Nebula) is the nearest massive starburst region, containing the richest sample of massive stars in the Local Group. It is the best possible laboratory to investigate aspects of the formation and evolution of massive stars. Here, we focus on rotation which is a key parameter in the evolution of these objects. We establish the projected rotational velocity, $v_{e}\\sin i$, distribution of an unprecedented sample of 216 radial velocity constant ($\\rm{\\Delta RV\\, \\leq\\, 20 \\,km s^{-1}}$) O-type stars in 30\\,Dor observed in the framework of the VLT-FLAMES Tarantula Survey (VFTS). The distribution of $v_{e}\\sin i$ shows a two-component structure: a peak around 80 $\\rm{km s^{-1}}$ and a high-velocity tail extending up to $\\sim$600 $\\rm{km s^{-1}}$. Around 75% of the sample has 0 $\\leq\\, v_{e}\\sin i \\leq$ 200 $\\rm{km s^{-1}}$ with the other 25% distributed in the high-velocity tail. The presence of the low-velocity peak is consi...

  2. Properties of the ionized gas of circumnuclear star-forming regions in early type spirals

    CERN Document Server

    Diaz, Angeles I; Terlevich, Elena; Terlevich, Roberto

    2008-01-01

    (Abbr.) A study of cicumnuclear star-forming regions (CNSFRs) in several early type spirals has been made in order to investigate their main properties: stellar and gas kinematics, dynamical masses, ionising stellar masses, chemical abundances and other properties of the ionised gas. Both high resolution (R$ \\sim $20000) and moderate resolution (R ~ 5000) have been used. In some cases these regions, about 100 to 150 pc in size, are seen to be composed of several individual star clusters with sizes between 1.5 and 4.9 pc estimated from Hubble Space Telescope (HST) images. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km/s with the H$\\beta$ emission lines being narrower than both the stellar lines and the [OIII] $\\lambda$ 5007 \\AA lines. The twice ionized oxygen, on the other hand, shows velocity dispersions comparable to those shown by stars. We have applied the virial theorem to estimate dynamical masses of the clusters, assuming that systems are gravitationally bounded and spheri...

  3. Geochemistry of Late Triassic weak Peraluminous A-Type Karimun Granite, Karimun Regency, Riau Islands Province

    Directory of Open Access Journals (Sweden)

    Ronaldo Irzon

    2016-12-01

    Full Text Available DOI: 10.17014/ijog.4.1.21-37Karimun is an island with various geological deposits: tin, granite, sand, and others. The tin deposit in Karimun is related to the granitoid tin belt which extends from Myanmar to western Indonesia. Late Triassic Karimun Granite is composed of quartz, K-feldspar, plagioclase, biotite, and/or muscovite with small amounts of accessory minerals. The granitoid unit is different with other felsic intrusive rocks in Malay Peninsular because of its A-type affinity although it is classified as part of the Tin Islands. All eight samples can be classified as altered rocks since the occurrence of secondary chlorite was identifed both macroscopically and microscopically. Petrography was used to describe the minerals that form the samples, whereas XRF and ICP-MS were used to study Karimun Granite from the geochemical point of view. Harker diagrams confirm that the granites show similarity to other granite units in Malaysia except for CaO. Whalen diagrams indicate the granite as A-type as well as the SiO2, REE, and LILE amounts. REE content in the weak peraluminous granitoid ranges from 183 to 3,296 ppm with Eu and Ce show negative anomalies in the REE spider diagram. Negative anomalies of Eu, Ba, Sr, P, and Ti in normalized spider plot also conclude that the studied granitoid indicates A-type.

  4. Discovery of Peculiar Periodic Spectral Modulations in a Small Fraction of Solar-type Stars

    Science.gov (United States)

    Borra, Ermanno F.; Trottier, Eric

    2016-11-01

    A Fourier transform analysis of 2.5 million spectra in the Sloan Digital Sky Survey was carried out to detect periodic spectral modulations. Signals having the same period were found in only 234 stars overwhelmingly in the F2 to K1 spectral range. The signals cannot be caused by instrumental or data analysis effects because they are present in only a very small fraction of stars within a narrow spectral range and because signal-to-noise ratio considerations predict that the signal should mostly be detected in the brightest objects, while this is not the case. We consider several possibilities, such as rotational transitions in molecules, rapid pulsations, Fourier transform of spectral lines, and signals generated by extraterrestrial intelligence (ETI). They cannot be generated by molecules or rapid pulsations. It is highly unlikely that they come from the Fourier transform of spectral lines because too many strong lines located at nearly periodic frequencies are needed. Finally, we consider the possibility, predicted in a previous published paper, that the signals are caused by light pulses generated by ETI to makes us aware of their existence. We find that the detected signals have exactly the shape of an ETI signal predicted in the previous publication and are therefore in agreement with this hypothesis. The fact that they are only found in a very small fraction of stars within a narrow spectral range centered near the spectral type of the Sun is also in agreement with the ETI hypothesis. However, at this stage, this hypothesis needs to be confirmed with further work. Although unlikely, there is also a possibility that the signals are due to highly peculiar chemical compositions in a small fraction of galactic halo stars.

  5. Star formation and nuclear activity in the blue early-type galaxy NGC 5373

    Science.gov (United States)

    Zaidi, Tayeb; Miller, Brendan P.; Gallo, Elena; Alfvin, Erik; Martinkus, Charlotte; Molter, Edward

    2015-01-01

    We present new optical and X-ray observations of NGC 5373, an isolated star-forming elliptical that has a stellar mass of 7e10 solar and lies at a distance of 175 Mpc. Our B and R band Magellan IMACS imaging substantially improves on SDSS resolution and sensitivity, enabling accurate modeling of the galaxy surface brightness profile. As expected from its mass, NGC 5373 is a core galaxy with a best-fit Sersic profile of n~3.8; no prominent tidal tails or shells are found, although there are slight residual asymmetries. The H-alpha emission in the SDSS spectrum is narrow, and the line ratios confirm a star-forming classification in the BPT diagram, near the transition/composite line. The star formation rate is about 6 solar masses per year, making NGC 5373 an extreme outlier relative to typical local early-type galaxies of similar mass. Our 50 ks Chandra ACIS-S exposure provides a clear detection of a central X-ray source, with a hardness ratio consistent with a power-law photon index of 2.0+/-0.5. The unabsorbed luminosity is Lx = 2e40 erg/s over 0.3-8 keV. Comparison with a MARX simulated point spread function suggests the central source may be extended, for example due to contributions from one or more unresolved high-mass X-ray binaries, as might be present given the high star formation rate. For a black hole of 1.6e8 solar masses as predicted from scaling relations, Lx/Ledd is then around 1e-6 (or potentially lower).

  6. Late-type galaxies observed with SAURON : two-dimensional stellar and emission-line kinematics of 18 spirals

    NARCIS (Netherlands)

    Ganda, K; Falcon-Barroso, J; Peletier, RF; Cappellari, M; Emsellem, E; McDermid, RM; de Zeeuw, PT; Carollo, CM; Andersen, DR; Swaters, RA

    2006-01-01

    We present the stellar and gas kinematics of a sample of 18 nearby late-type spiral galaxies (Hubble types ranging from Sb to Sd), observed with the integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope. SAURON covers the spectral range 4800-5380 angstrom, allowing us to measure

  7. Spectroscopic Evidence of Sporadic Gas Accretion onto the Herbig AE Stars with Non-Periodic Algol-Type Minima

    Science.gov (United States)

    Kozlova, O. V.; Grinin, V. P.; Rostopchina, A. N.

    We present the results of simultaneous spectroscopic and photometric observations for six isolated Herbig Ae stars with non-periodic Algol-like minima: UX Ori, BF Ori, CQ Tau, SV Cep, VX Gas, and WW Vul. In all cases the Ha line has the profile typical for axially symmetric accretion. In the spectra of five stars (CQ Tau is the exception) the strong He I 5876 Å line has been observed in absorption which is not typical of normal A stars. In three cases: UX Ori, VX Cas, and WW Vul, variability of this line is found. We did not observe any correlation between the strength of this line and the brightness of the stars. These observational facts are considered as evidence for gas accretion, which is probably an important property of young stars with non-periodic Algol-type minima.

  8. Very Short-Duration UV-B Optical Flares in RS CVn-type Star Systems

    Science.gov (United States)

    Vander Haagen, G. A.

    2013-06-01

    Very short duration UV-B optical flares were observed during a high-cadence search for conventional flares on three RS CVn type stars: AR Lac, II Peg, and UX Ari. A statistical criterion was developed for isolating these short-duration optical flares from random photon events. Five flares, ranging in duration from 30 to 85 ms with peaks 0.29-0.51 mag. above the mean, were detected within the 132 hours of monitoring time. The time resolution of the observations was 5 ms for AR Lac and 10 ms for II Peg and UX Ari.

  9. VizieR Online Data Catalog: Spectrocopic Binarity of O and B type stars (Chini+, 2012)

    Science.gov (United States)

    Chini, R.; Hoffmeister, V. H.; Nasseri, A.; Stahl, O.; Zinnecker, H.

    2013-05-01

    We have performed a comprehensive spectroscopic survey on a large representative sample of 249 O- and 581 B-type stars. Using the high-resolution spectrograph BESO at the Hexapod Telescope at the Universitatssternwarte Bochum near Cerro Armazones in Chile, we obtained 3632 multi-epoch optical spectra. The observing period started in 2009 January and is still going on. The spectra comprise a wavelength range from 3620 to 8530Å and provide a mean spectral resolution of R=50000. (1 data file).

  10. Dwarf nova-type cataclysmic variable stars are significant radio emitters

    CERN Document Server

    Coppejans, Deanne L; Miller-Jones, James C A; Rupen, Michael P; Sivakoff, Gregory R; Knigge, Christian; Groot, Paul J; Woudt, Patrick A; Waagen, Elizabeth O; Templeton, Matthew

    2016-01-01

    We present 8--12\\,GHz radio light curves of five dwarf nova (DN) type Cataclysmic Variable stars (CVs) in outburst (RX And, U Gem and Z Cam), or superoutburst (SU UMa and YZ Cnc), increasing the number of radio-detected DN by a factor of two. The observed radio emission was variable on time-scales of minutes to days, and we argue that it is likely to be synchrotron emission. This sample shows no correlation between the radio luminosity and optical luminosity, orbital period, CV class, or outburst type; however higher-cadence observations are necessary to test this, as the measured luminosity is dependent on the timing of the observations in these variable objects. The observations show that the previously detected radio emission from SS Cyg is not unique in type, luminosity (in the plateau phase of the outburst), or variability time-scales. Our results prove that DN, as a class, are radio emitters in outburst.

  11. ASASSN-15jd: WZ Sge-type star with intermediate superoutburst between single and double ones

    Science.gov (United States)

    Kimura, Mariko; Isogai, Keisuke; Kato, Taichi; Imada, Akira; Kojiguchi, Naoto; Sugiura, Yuki; Fukushima, Daiki; Takeda, Nao; Matsumoto, Katsura; Dvorak, Shawn; Vanmunster, Tonny; Dubovsky, Pavol A.; Kudzej, Igor; Miller, Ian; Pavlenko, Elena P.; Babina, Julia V.; Antonyuk, Oksana I.; Baklanov, Aleksei V.; Stein, William L.; Andreev, Maksim V.; Tordai, Tamás; Itoh, Hiroshi; Pickard, Roger D.; Nogami, Daisaku

    2016-08-01

    We present optical photometry of a WZ Sge-type dwarf nova (DN), ASASSN-15jd. Its light curve showed a small dip in the middle of the superoutburst in 2015 for the first time among WZ Sge-type DNe. The unusual light curve implies a delay in the growth of the 3 : 1 resonance tidal instability. Also, the light curve is similar to those of two other WZ Sge-type stars, SSS J122221.7-311523 and OT J184228.1+483742, which are believed to be the best candidates for period bouncers on the basis of their small values of the mass ratio (q ≡ M2/M1). Additionally, the small mean superhump amplitude (accounting for the missing population of post-period minimum cataclysmic variables-based on the above characteristics.

  12. B fields in OB stars (BOB): on the detection of weak magnetic fields in the two early B-type stars beta CMa and epsilon CMa

    CERN Document Server

    Fossati, L; Morel, T; Langer, N; Briquet, M; Carroll, T A; Hubrig, S; Nieva, M F; Oskinova, L M; Przybilla, N; Schneider, F R N; Scholler, M; Simon-Diaz, S; Ilyin, I; de Koter, A; Reisenegger, A; Sana, H

    2014-01-01

    Within the context of the "B fields in OB stars (BOB)" collaboration, we used the HARPSpol spectropolarimeter to observe the early B-type stars beta CMa (HD44743; B1 II/III) and epsilon CMa (HD52089; B1.5 II). For both stars, we consistently detected the signature of a weak (<30 G in absolute value) longitudinal magnetic field. We determined the physical parameters of both stars and characterise their X-ray spectrum. For beta CMa, our mode identification analysis led to determining a rotation period of 13.6+/-1.2 days and of an inclination angle of the rotation axis of 57.6+/-1.7 degrees, with respect to the line of sight. On the basis of these measurements and assuming a dipolar field geometry, we derived a best fitting obliquity of ~22 degrees and a dipolar magnetic field strength (Bd) of ~100 G (60stars. For epsilon CMa we could only determine a lower limit on the dipolar magnetic field strength of 13 G. For this s...

  13. Rotating Massive Main-Sequence Stars II: Simulating a Population of LMC early B-type Stars as a Test of Rotational Mixing

    CERN Document Server

    Brott, Ines; Hunter, Ian; de Koter, Alex; Langer, Norbert; Dufton, Philip L; Cantiello, Matteo; Trundle, Carrie; Lennon, Danny J; de Mink, Selma E; Yoon, Sung-Chul; Anders, Peter

    2011-01-01

    Rotational mixing in massive stars is a widely applied concept, with far reaching consequences for stellar evolution. Nitrogen surface abundances for a large and homogeneous sample of massive B-type stars in the LMC were obtained by the VLT-FLAMES Survey of Massive Stars. This sample is the first covering a broad range of projected stellar rotational velocities, with a large enough sample of high quality data to allow for a statistically significant analysis. We use the sample to provide the first rigorous test of the theory of rotational mixing in massive stars. We calculated a grid of stellar evolution models, using the FLAMES sample to calibrate some of the uncertain mixing processes. We developed a new population-synthesis code, which uses this grid to simulate a large population of stars with masses, ages and rotational velocity distributions consistent with those from the FLAMES sample. The synthesized population is then filtered by the selection effects in the observed sample, to enable a direct compar...

  14. The ATLAS3D project - XXII. Low-efficiency star formation in early-type galaxies: hydrodynamic models and observations

    CERN Document Server

    Martig, Marie; Bournaud, Frederic; Emsellem, Eric; Gabor, Jared M; Alatalo, Katherine; Blitz, Leo; Bois, Maxime; Bureau, Martin; Cappellari, Michele; Davies, Roger L; Davis, Timothy A; Dekel, Avishai; de Zeeuw, P T; Duc, Pierre-Alain; Falcon-Barroso, Jesus; Khochfar, Sadegh; Krajnovic, Davor; Kuntschner, Harald; Morganti, Raffaella; McDermid, Richard M; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Griffin, Kristen Shapiro; Teyssier, Romain; Weijmans, Anne-Marie; Young, Lisa M

    2012-01-01

    We study the global efficiency of star formation in high resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars 2 to 5 times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (above 10^4 cm-3) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and HI surface densities and their star...

  15. Characterization of a major late herpes simplex virus type 1 mRNA.

    Science.gov (United States)

    Costa, R H; Devi, B G; Anderson, K P; Gaylord, B H; Wagner, E K

    1981-05-01

    A major, late 6-kilobase (6-kb) mRNa mapping in the large unique region of herpes simplex virus type 1 (HSV-1) was characterized by using two recombinant DNA clones, one containing EcoRI fragment G (0.190 to 0.30 map units) in lambda. WES.B (L. Enquist, M. Madden, P. Schiop-Stansly, and G. Vandl Woude, Science 203:541-544, 1979) and one containing HindIII fragment J (0.181 to 0.259 map units) in pBR322. This 6-kb mRNA had its 3' end to the left of 0.231 on the prototypical arrangement of the HSV-1 genome and was transcribed from right to left. It was bounded on both sides by regions containing a large number of distinct mRNA species, and its 3' end was partially colinear with a 1.5-kb mRNA which encoded a 35,000-dalton polypeptide. The 6-kb mRNA encoded a 155,000-dalton polypeptide which was shown to be the only one of this size detectable by hybrid-arrested translation encoded by late polyadenylated polyribosomal RNA. The S1 nuclease mapping experiments indicated that there were no introns in the coding sequence for this mRNA and that its 3' end mapped approximately 800 nucleotides to the left of the BglII site at 0.231, whereas its 5' end extended very close to the BamHI site at 0.266.

  16. Late-time behaviour of the tilted Bianchi type VIh models

    CERN Document Server

    Hervik, S; Lim, W C; Coley, A A

    2007-01-01

    We study tilted perfect fluid cosmological models with a constant equation of state parameter in spatially homogeneous models of Bianchi type VI$_h$ using dynamical systems methods and numerical experimentation, with an emphasis on their future asymptotic evolution. We determine all of the equilibrium points of the type VI$_h$ state space (which correspond to exact self-similar solutions of the Einstein equations, some of which are new), and their stability is investigated. We find that there are vacuum plane-wave solutions that act as future attractors. In the parameter space, a `loophole' is shown to exist in which there are no stable equilibrium points. We then show that a Hopf-bifurcation can occur resulting in a stable closed orbit (which we refer to as the Mussel attractor) corresponding to points both inside the loophole and points just outside the loophole; in the former case the closed curves act as late-time attractors while in the latter case these attracting curves will co-exist with attracting eq...

  17. Immunohistochemistry Detected and Localized Cannabinoid Receptor Type 2 in Bovine Fetal Pancreas at Late Gestation

    Science.gov (United States)

    Dall’Aglio, Cecilia; Polisca, Angela; Cappai, Maria Grazia; Mercati, Francesca; Troisi, Alessandro; Pirino, Carolina; Scocco, Paola; Maranesi, Margherita

    2017-01-01

    At present, data on the endocannabinoid system expression and distribution in the pancreatic gland appear scarce and controversial as descriptions are limited to humans and laboratory animals. Since the bovine pancreas is very similar to the human in endocrine portion development and control, studies on the fetal gland could prove to be very interesting, as an abnormal maternal condition during late pregnancy may be a predisposing trigger for adult metabolic disorders. The present investigation studied cannabinoid receptor type 2 presence and distribution in the bovine fetal pancreas towards the end of gestation. Histological analyses revealed numerous endocrinal cell clusters or islets which were distributed among exocrine adenomeri in connectival tissue. Immunohistochemistry showed that endocrine-islets contained some CB2-positive cells with a very peculiar localization that is a few primarily localized at the edges of islets and some of them also scattered in the center of the cluster. Characteristically, also the epithelium of the excretory ducts and the smooth muscle layers of the smaller arteries, in the interlobular glandular septa, tested positive for the CB2 endocannabinoid receptor. Consequently, the endocannabinoid system, via the cannabinoid receptor type 2, was hypothesized to play a major role in controlling pancreas function from normal fetal development to correct metabolic functioning in adulthood. PMID:28348424

  18. A KEPLERIAN-LIKE DISK AROUND THE FORMING O-TYPE STAR AFGL 4176

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Katharine G.; Hoare, Melvin G. [School of Physics and Astronomy, E.C. Stoner Building, The University of Leeds, Leeds LS2 9JT (United Kingdom); Robitaille, Thomas P.; Beuther, Henrik; Linz, Hendrik; Kuiper, Rolf; Boekel, Roy van [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Boley, Paul [Ural Federal University, Astronomical Observatory, 51 pr. Lenina, Ekaterinburg (Russian Federation); Keto, Eric, E-mail: k.g.johnston@leeds.ac.uk [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2015-11-01

    We present Atacama Large Millimeter/submillimeter Array line and continuum observations at 1.2 mm with ∼0.″3 resolution that uncover a Keplerian-like disk around the forming O-type star AFGL 4176. The continuum emission from the disk at 1.21 mm (source mm1) has a deconvolved size of 870 ± 110 AU × 330 ± 300 AU and arises from a structure ∼8 M{sub ⊙} in mass, calculated assuming a dust temperature of 190 K. The first-moment maps, pixel-to-pixel line modeling, assuming local thermodynamic equilibrium (LTE), and position–velocity diagrams of the CH{sub 3}CN J = 13–12 K-line emission all show a velocity gradient along the major axis of the source, coupled with an increase in velocity at small radii, consistent with Keplerian-like rotation. The LTE line modeling shows that where CH{sub 3}CN J = 13–12 is excited, the temperatures in the disk range from ∼70 to at least 300 K and that the H{sub 2} column density peaks at 2.8 × 10{sup 24} cm{sup −2}. In addition, we present Atacama Pathfinder Experiment {sup 12}CO observations that show a large-scale outflow from AFGL 4176 perpendicular to the major axis of mm1, supporting the disk interpretation. Finally, we present a radiative transfer model of a Keplerian disk surrounding an O7 star, with a disk mass and radius of 12 M{sub ⊙} and 2000 AU that reproduces the line and continuum data, further supporting our conclusion that our observations have uncovered a Keplerian-like disk around an O-type star.

  19. The evolution of surface magnetic fields in young solar-type stars - I. The first 250 Myr

    Science.gov (United States)

    Folsom, C. P.; Petit, P.; Bouvier, J.; Lèbre, A.; Amard, L.; Palacios, A.; Morin, J.; Donati, J.-F.; Jeffers, S. V.; Marsden, S. C.; Vidotto, A. A.

    2016-03-01

    The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution, which should be observable in their surface magnetic fields. Here we present a study aimed at observing the evolution of these magnetic fields through this critical time period. We observed stars in open clusters and stellar associations of known ages, and used Zeeman Doppler imaging to characterize their complex magnetic large-scale fields. Presented here are results for 15 stars, from five associations, with ages from 20 to 250 Myr, masses from 0.7 to 1.2 M⊙, and rotation periods from 0.4 to 6 d. We find complex large-scale magnetic field geometries, with global average strengths from 14 to 140 G. There is a clear trend towards decreasing average large-scale magnetic field strength with age, and a tight correlation between magnetic field strength and Rossby number. Comparing the magnetic properties of our zero-age main-sequence sample to those of both younger and older stars, it appears that the magnetic evolution of solar-type stars during the pre-main sequence is primarily driven by structural changes, while it closely follows the stars' rotational evolution on the main sequence.

  20. The SAURON project - XV. Modes of star formation in early-type galaxies and the evolution of the red sequence

    CERN Document Server

    Shapiro, K L; van de Ven, G; de Zeeuw, P T; Sarzi, M; Bacon, R; Bolatto, A; Cappellari, M; Croton, D; Davies, R L; Emsellem, E; Fakhouri, O; Krajnovic, D; Kuntschner, H; McDermid, R M; Peletier, R F; Bosch, R C E van den; van der Wolk, G

    2009-01-01

    We combine SAURON integral field data of a representative sample of local early-type, red sequence galaxies with Spitzer/IRAC imaging in order to investigate the presence of trace star formation in these systems. With the Spitzer data, we identify galaxies hosting low-level star formation, as traced by PAH emission, with measured star formation rates that compare well to those estimated from other tracers. This star formation proceeds according to established scaling relations with molecular gas content, in surface density regimes characteristic of disk galaxies and circumnuclear starbursts. We find that star formation in early-type galaxies happens exclusively in fast-rotating systems and occurs in two distinct modes. In the first, star formation is a diffuse process, corresponding to widespread young stellar populations and high molecular gas content. The equal presence of co- and counter-rotating components in these systems strongly implies an external origin for the star-forming gas, and we argue that the...

  1. How similar is the stellar structure of low-mass late-type galaxies to that of early-type dwarfs?

    CERN Document Server

    Janz, Joachim; Laine, Jarkko; Salo, Heikki; Lisker, Thorsten

    2016-01-01

    We analyse structural decompositions of 500 late-type galaxies (Hubble $T$-type $\\ge 6$) from the Spitzer Survey of Stellar Structure in Galaxies (S$^4$G), spanning a stellar mass range of about $10^7$ to a few times $10^{10}$ M$_\\odot$. Their decomposition parameters are compared with those of the early-type dwarfs in the Virgo cluster from Janz et al. They have morphological similarities, including the fact that the fraction of simple one-component galaxies in both samples increases towards lower galaxy masses. We find that in the late-type two-component galaxies both the inner and outer structures are by a factor of two larger than those in the early-type dwarfs, for the same stellar mass of the component. While dividing the late-type galaxies to low and high density environmental bins, it is noticeable that both the inner and outer components of late types in the high local galaxy density bin are smaller, and lie closer in size to those of the early-type dwarfs. This suggests that, although structural dif...

  2. Radio emission and mass loss rate limits of four young solar-type stars

    Science.gov (United States)

    Fichtinger, Bibiana; Güdel, Manuel; Mutel, Robert L.; Hallinan, Gregg; Gaidos, Eric; Skinner, Stephen L.; Lynch, Christene; Gayley, Kenneth G.

    2017-03-01

    Aims: Observations of free-free continuum radio emission of four young main-sequence solar-type stars (EK Dra, π1 UMa, χ1 Ori, and κ1 Cet) are studied to detect stellar winds or at least to place upper limits on their thermal radio emission, which is dominated by the ionized wind. The stars in our sample are members of The Sun in Time programme and cover ages of 0.1-0.65 Gyr on the main-sequence. They are similar in magnetic activity to the Sun and thus are excellent proxies for representing the young Sun. Upper limits on mass loss rates for this sample of stars are calculated using their observational radio emission. Our aim is to re-examine the faint young Sun paradox by assuming that the young Sun was more massive in its past, and hence to find a possible solution for this famous problem. Methods: The observations of our sample are performed with the Karl G. Jansky Very Large Array (VLA) with excellent sensitivity, using the C-band receiver from 4-8 GHz and the Ku-band from 12-18 GHz. Atacama Large Millimeter/Submillitmeter Array (ALMA) observations are performed at 100 GHz. The Common Astronomy Software Application (CASA) package is used for the data preparation, reduction, calibration, and imaging. For the estimation of the mass loss limits, spherically symmetric winds and stationary, anisotropic, ionized winds are assumed. We compare our results to 1) mass loss rate estimates of theoretical rotational evolution models; and 2) to results of the indirect technique of determining mass loss rates: Lyman-α absorption. Results: We are able to derive the most stringent direct upper limits on mass loss so far from radio observations. Two objects, EK Dra and χ1 Ori, are detected at 6 and 14 GHz down to an excellent noise level. These stars are very active and additional radio emission identified as non-thermal emission was detected, but limits for the mass loss rates of these objects are still derived. The emission of χ1 Ori does not come from the main target

  3. An infrared survey of RW Aurigae stars

    Science.gov (United States)

    Glass, I. S.; Penston, M. V.

    1974-01-01

    An infrared photometric survey of 89 RW Aur type variables in both hemispheres has been made. JHKL magnitudes and colors are listed. The RW Aur variables include a small number of highly reddened late-type stars. All T Tauri and hot Orion population stars show infrared excesses and the infrared properties mark certain field stars as being young. The greatest infrared excesses are found for A and F stars while young variable B stars usually show no excesses. The location of the RW Aur stars in the two-color H-K, K-L diagram favor dust re-radiation over free-free emission as the mechanism responsible for the infrared excess. A weak correlation of H-K with emission class links the occurrence of circumstellar dust and gas shells.

  4. The Rise and Fall of the Type Ib Supernova iPTF13bvn Not a Massive Wolf-Rayet Star

    Science.gov (United States)

    Fremling, C.; Sollerman, J.; Taddia, F.; Ergon, M.; Valenti, S.; Arcavi, I.; Ben-Ami, S.; Cao, Y.; Cenko, S. B.; Filippenko, A. V.; Gal-Yam, A.; Howell, D. A.

    2014-01-01

    Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progenitor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly classify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario. Methods. We present a large set of observational data, consisting of multi-band light curves (UBVRI, g'r'i'z') and optical spectra. We perform standard spectral line analysis to track the evolution of the SN ejecta. We also construct a bolometric light curve and perform hydrodynamical calculations to model this light curve to constrain the synthesized radioactive nickel mass and the total ejecta mass of the SN. Late-time photometry is analyzed to constrain the amount of oxygen. Furthermore, image registration of pre- and post-explosion HST images is performed. Results. Our HST astrometry confirms the location of the progenitor candidate of iPTF13bvn, and follow-up spectra securely classify this as a SN Ib. We use our hydrodynamical model to fit the observed bolometric light curve, estimating the total ejecta mass to be 1.9 solar mass and the radioactive nickel mass to be 0.05 solar mass. The model fit requires the nickel synthesized in the explosion to be highly mixed out in the ejecta. We also find that the late-time nebular r

  5. SDSS IV MaNGA: Deep observations of extra-planar, diffuse ionized gas around late-type galaxies from stacked IFU spectra

    Science.gov (United States)

    Jones, A.; Kauffmann, G.; D'Souza, R.; Bizyaev, D.; Law, D.; Haffner, L.; Bahé, Y.; Andrews, B.; Bershady, M.; Brownstein, J.; Bundy, K.; Cherinka, B.; Diamond-Stanic, A.; Drory, N.; Riffel, R. A.; Sánchez, S. F.; Thomas, D.; Wake, D.; Yan, R.; Zhang, K.

    2017-03-01

    We have conducted a study of extra-planar diffuse ionized gas using the first year data from the MaNGA IFU survey. We have stacked spectra from 49 edge-on, late-type galaxies as a function of distance from the midplane of the galaxy. With this technique we can detect the bright emission lines Hα, Hβ, [O ii]λλ3726, 3729, [O iii]λ5007, [N ii]λλ6549, 6584, and [S ii]λλ6717, 6731 out to about 4 kpc above the midplane. With 16 galaxies we can extend this analysis out to about 9 kpc, i.e. a distance of 2Re, vertically from the midplane. In the halo, the surface brightnesses of the [O ii] and Hα emission lines are comparable, unlike in the disk where Hα dominates. When we split the sample by specific star-formation rate, concentration index, and stellar mass, each subsample's emission line surface brightness profiles and ratios differ, indicating that extra-planar gas properties can vary. The emission line surface brightnesses of the gas around high specific star-formation rate galaxies are higher at all distances, and the line ratios are closer to ratios characteristic of H ii regions compared with low specific star-formation rate galaxies. The less concentrated and lower stellar mass samples exhibit line ratios that are more like H ii regions at larger distances than their more concentrated and higher stellar mass counterparts. The largest difference between different subsamples occurs when the galaxies are split by stellar mass. We additionally infer that gas far from the midplane in more massive galaxies has the highest temperatures and steepest radial temperature gradients based on their [N ii]/Hα and [O ii]/Hα ratios between the disk and the halo. SDSS IV.

  6. V2324Cyg - an F-type star with fast wind

    CERN Document Server

    Klochkova, V G; Panchuk, V E

    2008-01-01

    For the first time high-resolution optical spectroscopy of the variable star V2324Cyg associated with the IR-source IRAS20572+4919 is made. More than 200 absorption features (mostly FeII, TiII, CrII, YII, BaII, and YII) are identified within the wavelength interval 4549-7880AA. The spectral type and rotation velocity of the star are found to be F0III and Vsini=69km/s, respectively. HI and NaID lines have complex PCyg-type profiles with an emission component. Neither systematic trend of radial velocity Vr with line depth Ro nor temporal variability of Vr have been found. We determined the average heliocentric radial velocity Vr=-16.8\\pm 0.6km/s. The radial velocities inferred from the cores of the absorption components of the H$\\beta$ and NaI wind lines vary from -140 to -225km/s (and the expansion velocities of the corresponding layers, from about 120 to 210km/s). The maximum expansion velocity is found for the blue component of the split H$\\alpha$ absorption: 450km/s for December 12, 1995. The model atmosphe...

  7. Internal Anal Sphincter and Late Clinical Outcome in Patients with High Type Anorectal Malformation

    Directory of Open Access Journals (Sweden)

    Mirshemirani Ali Reza

    2009-05-01

    Full Text Available The purpose of this study is to investigate the age -related improvement of defecation function in high type anorectal malformation in relation to the assessment of the internal anal sphincter. The function of defecation was studied every 5 years up to 15 years postoperatively according to the Japanese scoring system in our hospital in 50 patients operated for high type (recto-urethral fistula imperforate anus with posterior sagital anorectoplasty (PSARP procedure in 25 patients, and 25patients with endorectal pull-through (ERPT. The internal anal sphincter was assessed by anorectal manometry and histology, and the results were analyzed with the clinical outcomes. The defecation scores of the PSARP cases exceeded those of ERPT cases at all age groups, the averaged total score were 7.0 in the PSARP cases vs. 4.6 for ERPT cases at 5 years old, 7.5 vs. 5.2 at 10 years old, and 8.0 vs. 6.7 at 15 years old. The anorectal reflex was seen in 17 of 25 (68% PSARP cases examined, whereas seen in 5 (20% of ERPT cases examined. Histologically, the well-developed and thickened internal circular muscle at the rectal end was found only in 40% of the cases, whereas discontinuation and hypoplasty of the muscle were seen in most of the cases examined. The present results indicate that the internal sphincter muscle at the rectal end may be histologically maldeveloped in high type anorectal malformations; however, they can potentially develop after transplanted and contribute to the improvement of passive continence in the late post-operative period.

  8. Continued Kinematic and Photometric Investigations of Hierarchical Solar-type Multiple Star Systems

    Science.gov (United States)

    Roberts, Lewis C., Jr.; Tokovinin, Andrei; Mason, Brian D.; Marinan, Anne D.

    2017-03-01

    We observed 15 of the solar-type binaries within 67 pc of the Sun previously observed by the Robo-AO system in the visible, with the PHARO near-infrared camera and the PALM-3000 adaptive optics system on the 5 m Hale telescope. The physical status of the binaries is confirmed through common proper motion and detection of orbital motion. In the process, we detected a new candidate companion to HIP 95309. We also resolved the primary of HIP 110626 into a close binary, making that system a triple. These detections increase the completeness of the multiplicity survey of the solar-type stars within 67 pc of the Sun. Combining our observations of HIP 103455 with archival astrometric measurements and RV measurements, we are able to compute the first orbit of HIP 103455, showing that the binary has a 68 year period. We place the components on a color–magnitude diagram and discuss each multiple system individually.

  9. The IACOB project: III. New observational clues to understand macroturbulent broadening in massive O- and B-type stars

    CERN Document Server

    Simón-Díaz, S; Castro, N; Herrero, A; Aerts, C; Puls, J; Telting, J; Grassitelli, L

    2016-01-01

    We aim to provide new empirical clues about macroturbulent spectral line broadening in O- and B-type stars to evaluate its physical origin. We use high-resolution spectra of ~430 stars with spectral types in the range O4-B9 (all luminosity classes). We characterize the line-broadening of adequate diagnostic metal lines using a combined FT and GOF technique. We perform a quantitative spectroscopic analysis of the whole sample using automatic tools coupled with a huge grid of FASTWIND models. We also incorporate quantitative information about line asymmetries to our observational description of the characteristics of the line-profiles, and present a comparison of the shape and type of line-profile variability found in a small sample of O stars and B supergiants with still undefined pulsational properties and B main sequence stars with variable line-profiles. We present a homogeneous and statistically significant overview of the (single snapshot) line-broadening properties of stars in the whole O and B star doma...

  10. 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.

  11. 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...

  12. J-type Carbon Stars: A Dominant Source of 14N-rich Presolar SiC Grains of Type AB

    Science.gov (United States)

    Liu, Nan; Stephan, Thomas; Boehnke, Patrick; Nittler, Larry R.; O'D. Alexander, Conel M.; Wang, Jianhua; Davis, Andrew M.; Trappitsch, Reto; Pellin, Michael J.

    2017-07-01

    We report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB (14N/15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%-15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.

  13. Hubble Space Telescope spectroscopy of OB stars in M31

    Science.gov (United States)

    Hutchings, J. B.; Bianchi, L.; Lamers, H. J. G. L. M.; Massey, P.; Morris, S. C.

    1992-01-01

    We have obtained UV spectra of two luminous hot stars in M31 with the Hubble Space Telescope. The stars are of late O and WN spectral type and lie on opposite sides of M31. We derive UV extinction curves for M31 which differ from both the Galaxy and the LMC. We find differences between the IS absorbers in both lines of sight in M31 and in the Galactic halo. The stellar wind-driven mass loss of the stars is found to be 10 times lower than in similar Galactic stars. One star appears to be an eclipsing W-R binary.

  14. Quark-Novae in Neutron Star-White-Dwarf Binaries: A model for dim, sub-Chandrasekhar, Type Ia Supernovae ?

    CERN Document Server

    Ouyed, Rachid

    2011-01-01

    We show that appealing to a Quark-Nova in a tight NS-WD binary system, a Type Ia explosion can occur for a narrow range in white dwarf mass (0.5 2 universe, we expect QNe-Ia to manifest themselves as rare sub-Chandrasekhar Type Ias; most likely in star-forming galaxies.

  15. Oxygen abundance distributions in six late-type galaxies based on SALT spectra of HII regions

    CERN Document Server

    Zinchenko, I A; Grebel, E K; Pilyugin, L S

    2015-01-01

    Spectra of 34 H II regions in the late-type galaxies NGC1087, NGC2967, NGC3023, NGC4030, NGC4123, and NGC4517A were observed with the South African Large Telescope (SALT). In all 34 H II regions, oxygen abundances were determined through the "counterpart" method (C method). Additionally, in two H II regions in which the auroral lines were detected oxygen abundances were measured through the classic Te method. We also estimated the abundances in our H II regions using the O3N2 and N2 calibrations and compared those with the C-based abundances. With these data we examined the radial abundance distributions in the disks of our target galaxies. We derived surface-brightness profiles and other characteristics of the disks (the surface brightness at the disk center and the disk scale length) in three photometric bands for each galaxy using publicly available photometric imaging data. The radial distributions of the oxygen abundances predicted by the relation between abundance and disk surface brightness in the W1 b...

  16. Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components

    CERN Document Server

    Pierini, D; Witt, A N; Madsen, G J

    2004-01-01

    We present results of new Monte Carlo calculations made with the DIRTY code of radiative transfer of stellar and scattered radiation for a dusty giant late-type galaxy like the Milky Way, which illustrate the effect of the attenuation of stellar light by internal dust on the integrated photometry of the individual bulge and disk components. Here we focus on the behavior of the attenuation function, the color excess, and the fraction of light scattered or directly transmitted towards the outside observer as a function of the total amount of dust and the inclination of the galaxy, and the structure of the dusty interstellar medium (ISM) of the disk. We confirm that dust attenuation produces qualitatively and quantitatively different effects on the integrated photometry of bulge and disk, whatever the wavelength. In addition, we find that the structure of the dusty ISM affects more sensitively the observed magnitudes than the observed colors of both bulge and disk. Finally, we show that the contribution of the s...

  17. The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

    Science.gov (United States)

    Kalinova, Veselina; van de Ven, Glenn; Lyubenova, Mariya; Falcón-Barroso, Jesús; Colombo, Dario; Rosolowsky, Erik

    2017-01-01

    We infer the central mass distributions within 0.4-1.2 disc scalelengths of 18 late-type spiral galaxies using two different dynamical modelling approaches - the asymmetric drift correction (ADC) and axisymmetric Jeans anisotropic multi-Gaussian expansion (JAM) model. ADC adopts a thin-disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph {SAURON} to derive the corresponding circular velocity curves from the two models. To find their best-fitting values, we apply the Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5 per cent uncertainty when the ordered motions are significant comparable to the random motions, i.e. overline{v_{φ }}/σ _R is locally greater than 1.5. Below this value, the ratio vc, JAM/vc, ADC gradually increases with decreasing overline{v_{φ }}/σ _R, reaching vc,JAM ≈ 2 × vc, ADC. Such conditions indicate that the stellar masses of the galaxies in our sample are not confined to their disc planes and likely have a non-negligible contribution from their bulges and thick discs.

  18. The inner mass distribution of late-type spiral galaxies from SAURON stellar kinematic maps

    CERN Document Server

    Kalinova, Veselina; Lyubenova, Mariya; Falcón-Barroso, Jesús; Colombo, Dario; Rosolowsky, Erik

    2016-01-01

    We infer the central mass distributions within 0.4-1.2 disc scale lengths of 18 late-type spiral galaxies using two different dynamical modelling approaches - the Asymmetric Drift Correction (ADC) and axisymmetric Jeans Anisotropic Multi-gaussian expansion (JAM) model. ADC adopts a thin disc assumption, whereas JAM does a full line-of-sight velocity integration. We use stellar kinematics maps obtained with the integral-field spectrograph SAURON to derive the corresponding circular velocity curves from the two models. To find their best-fit values, we apply Markov Chain Monte Carlo (MCMC) method. ADC and JAM modelling approaches are consistent within 5% uncertainty when the ordered motions are significant comparable to the random motions, i.e, $\\overline{v_{\\phi}}/\\sigma_R$ is locally greater than 1.5. Below this value, the ratio $v_\\mathrm{c,JAM}/v_\\mathrm{c,ADC}$ gradually increases with decreasing $\\overline{v_{\\phi}}/\\sigma_R$, reaching $v_\\mathrm{c,JAM}\\approx 2 \\times v_\\mathrm{c,ADC}$. Such conditions i...

  19. LONG-ORBITAL-PERIOD PREPOLARS CONTAINING EARLY K-TYPE DONOR STARS. BOTTLENECK ACCRETION MECHANISM IN ACTION

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-01

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

  20. 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...

  1. Diffusion and Settling in Ap/Bp Stars

    CERN Document Server

    Turcotte, S

    2003-01-01

    Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The physics of diffusion in these stars are reviewed briefly and some model predictions are discussed. While models reproduce some observations reasonably well, more work is needed before the behavior of diffusing elements in a complex magnetic field is fully understood.

  2. Diffusion and Settling in Ap/Bp Stars

    Energy Technology Data Exchange (ETDEWEB)

    Turcotte, S

    2003-04-09

    Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The physics of diffusion in these stars are reviewed briefly and some model predictions are discussed. While models reproduce some observations reasonably well, more work is needed before the behavior of diffusing elements in a complex magnetic field is fully understood.

  3. The Origin of Superflares on G-Type Dwarf Stars of Various Ages

    CERN Document Server

    Katsova, M M

    2015-01-01

    We analyze new observations of superflares on G-stars discovered in the optical and near IR ranges with the Kepler mission. An evolution of solar-type activity is discussed. We give an estimate of the maximal total energy, $E_{tot} = 10^{34}\\;\\mbox{erg}$ of a flare that can occur on the young Sun at its age of 1 Gyr when the cycle was formed. We believe that the main source of the flare optical continuum is a low-temperature condensation forming in the course of the response of the chromosphere to an impulsive heating. For a superflare on the young Sun, we adopt the accelerated electron flux, $F_e (E>\\mbox{20 keV}) = 3 \\times 10^{11} \\: \\mbox{erg} \\; \\mbox{cm}^{-2} \\; \\mbox{s}^{-1}$, that is limited by the return current, and obtain the area of the optical continuum source on a G star, $S \\approx 10^{19} \\:\\mbox{cm}^2$. This value is close to the area of the $H_\\alpha$-ribbons in the largest solar flares, while the area of bright patches of a white-light flare on the contemporary Sun is smaller by about two o...

  4. Long-term chromospheric activity of non-eclipsing RS CVn-type stars

    Science.gov (United States)

    Buccino, A. P.; Mauas, P. J. D.

    2009-02-01

    Context: The IUE database provides several UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims: Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22 468 (V711 Tau, HR 1099, K1IV+G5V), HD 21 242 (UX Ari, K0IV+G5V), and HD 224 085 (II Peg, K2IV). Methods: We first obtained the Mount Wilson index S from the IUE high and low-resolution spectra. Secondly, we used the Lomb-Scargle periodogram to analyse the mean annual index and the amplitude of the rotational modulation of the index S. Results: For HD 22 468 (V711 Tau, HR 1099), we find a possible chromospheric cycle with a period of ~18 years and a shorter cycle with a period of ~3 years, which could be associated to a chromospheric “flip-flop” cycle. The data of HD 224 085 (II Peg) also suggest a chromospheric cycle of ~21 years and a flip-flop cycle of ~9 years. Finally, we obtained a possible chromospheric cycle of ~7 years for HD 21 242 (UX Ari).

  5. Gas and dust spectra of the D' type symbiotic star HD330036

    CERN Document Server

    Angeloni, R; Ciroi, S; Rafanelli, P

    2007-01-01

    We present a comprehensive and self-consistent modelling of the D' type symbiotic star (SS) HD330036 from radio to UV. Within a colliding-wind scenario, we analyse the continuum, line and dust spectra by means of SUMA, a code that simulates the physical conditions of an emitting gaseous cloud under the coupled effect of ionization from an external radiation source and shocks. We find that the UV lines are emitted from high density gas between the stars downstream of the reverse shock, while the optical lines are emitted downstream of the shock propagating outwards the system. As regards with the continuum SED, three shells are identified in the IR, at 850K, 320 K and 200 K with radii r = 2.8 10^13 cm, 4 10^14$ cm, and 10^15 cm, respectively, adopting a distance to Earth d=2.3 kpc: interestingly, all these shells appear to be circumbinary. The analysis of the unexploited ISO-SWS spectrum reveals that both PAHs and crystalline silicates coexist in HD330036, with PAHs associated to the internal shell at 850 K, a...

  6. HATS-2b: A transiting extrasolar planet orbiting a K-type star showing starspot activity

    CERN Document Server

    Mohler-Fischer, M; Hartman, J D; Bakos, G B; Penev, K; Bayliss, D; Jordan, A; Csubry, Z; Zhou, G; Rabus, M; Nikolov, N; Brahm, R; Espinoza, N; Buchhave, L A; Beky, B; Suc, V; Csak, B; Henning, T; Wright, D J; Tinney, C G; Addison, B C; Schmidt, B; Noyes, R W; Papp, I; Lazar, J; Sari, P; Conroy, P

    2013-01-01

    We report the discovery of HATS-2b, the second transiting extrasolar planet detected by the HATSouth survey. HATS-2b is moving on a circular orbit around a V=13.6 mag, K-type dwarf star (GSC 6665-00236), at a separation of 0.0230 \\pm 0.0003 AU and with a period of 1.3541 days. The planetary parameters have been robustly determined using a simultaneous fit of the HATSouth, MPG/ESO~2.2\\,m/GROND, Faulkes Telescope South/Spectral transit photometry and MPG/ESO~2.2\\,m/FEROS, Euler~1.2\\,m/CORALIE, AAT~3.9\\,m/CYCLOPS radial-velocity measurements. HATS-2b has a mass of 1.37 \\pm 0.16 M_J, a radius of 1.14 \\pm 0.03 R_J and an equilibrium temperature of 1567 \\pm 30 K. The host star has a mass of 0.88 \\pm 0.04 M_Sun, radius of 0.89 \\pm 0.02 R_Sun and shows starspot activity. We characterized the stellar activity by analysing two photometric follow-up transit light curves taken with the GROND instrument, both obtained simultaneously in four optical bands (covering the wavelength range of 3860-9520 \\AA). The two light curv...

  7. Long Type I X-ray Bursts and Neutron Star Interior Physics

    CERN Document Server

    Cumming, A; in 't Zand, J J M; Page, D; Cumming, Andrew; Macbeth, Jared; Page, Dany

    2005-01-01

    Superbursts are very energetic Type I X-ray bursts discovered in recent years by long term monitoring of X-ray bursters, believed to be due to unstable ignition of carbon in the deep ocean of the neutron star. A number of "intermediate duration" bursts have also been observed, probably associated with ignition of a thick helium layer. We investigate the sensitivity of these long X-ray bursts to the thermal profile of the neutron star crust and core. We first compare cooling models of superburst lightcurves with observations, and derive constraints on the ignition mass and energy release, and then calculate ignition models for superbursts and pure helium bursts, and compare to observations. The superburst lightcurves and ignition models imply that the carbon mass fraction is approximately 20% or greater in the fuel layer, constraining models of carbon production. However, the most important result is that when Cooper pairing neutrino emission is included in the crust, the temperature is too low to support unst...

  8. Time-dependent nonextensivity arising from the rotational evolution of solar-type stars

    CERN Document Server

    Silva, Jose R P; Soares, Braulio B; de Freitas, Daniel B

    2013-01-01

    The nonextensive formalism is a generalization of the Boltzmann-Gibbs Statistics. In this formalism the entropic index q is a quantity characterizing the degree of nonextensivity, and is interpreted as a parameter of long-memory or long-range interactions between the components of the system. Since its proposition in 1988, this formalism has been applied to investigate a wide spectrum of natural phenomena. In stellar astrophysics, theoretical distribution function based on nonextensive formalism (q-distributions) has been successfully applied to reproduce the distribution of stellar radial and rotational velocity data. In this paper, we investigate the time variation of the entropic index q obtained from the distribution of rotation, Vsini, for a sample of 254 rotational data for solar-type star from 11 open clusters aged between 35.5Myr and 2.6Gyr. As a result we have found an anti-correlation between the entropic index q and the age of clusters, and that the distribution of rotation Vsini for these stars be...

  9. Improving stellar parameter and abundance determinations of early B-type stars

    CERN Document Server

    Nieva, Maria-Fernanda

    2009-01-01

    In the past years we have made great efforts to reduce the statistical and systematic uncertainties in stellar parameter and chemical abundance determinations of early B-type stars. Both the construction of robust model atoms for non-LTE line-formation calculations and a novel self-consistent spectral analysis methodology were decisive to achieve results of unprecedented precision. They were extensively tested and applied to high-quality spectra of stars from OB associations and the field in the solar neighbourhood, covering a broad parameter range. Initially, most lines of hydrogen, helium and carbon in the optical/near-IR spectral range were reproduced simultaneously in a consistent way for the first time, improving drastically on the accuracy of results in published work.By taking additional ionization equilibria of oxygen, neon, silicon and iron into account, uncertainties as low as ~1% in effective temperature, ~10% in surface gravity and ~20% in elemental abundances are achieved - compared to ~5-10%, ~2...

  10. AGN-driven quenching of star formation: morphological and dynamical implications for early-type galaxies

    CERN Document Server

    Dubois, Yohan; Peirani, Sébastien; Silk, Joseph

    2013-01-01

    In order to understand the physical mechanisms at work during the formation of massive early-type galaxies, we performed six zoomed hydrodynamical cosmological simulations of halos in the mass range 4.3 10^12 < M_vir < 8.0 10^13 M_sun at z=0, using the Adaptive Mesh Refinement code RAMSES. These simulations explore the role of Active Galactic Nuclei (AGN), through jets powered by the accretion onto supermassive black holes on the formation of massive elliptical galaxies. In the absence of AGN feedback, large amounts of stars accumulate in the central galaxies to form overly massive, blue, compact and rotation-dominated galaxies. Powerful AGN jets transform the central galaxies into red extended and dispersion-dominated galaxies. This morphological transformation of disc galaxies into elliptical galaxies is driven by the efficient quenching of the in situ star formation due to AGN feedback, which transform these galaxies into systems built up by accretion. For galaxies mainly formed by accretion, the pro...

  11. The VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single O-type stars

    CERN Document Server

    Ramírez-Agudelo, O H; Sana, H; de Koter, A; Sabín-Sanjulían, C; de Mink, S E; Dufton, P L; Gräfener, G; Evans, C J; Herrero, A; Langer, N; Lennon, D J; Apellániz, J Maíz; Markova, N; Najarro, F; Puls, J; Taylor, W D; Vink, J S

    2013-01-01

    Aims. Using ground based multi-object optical spectroscopy obtained in the framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to establish the (projected) rotational velocity distribution for a sample of 216 presumably single O-type stars in 30 Doradus (30 Dor). Methods. We measured projected rotational velocities, \\vrot, by means of a Fourier transform method and a profile fitting method applied on a set of isolated spectral lines. We also used an iterative deconvolution procedure to infer the probability density, $\\rm{P(\\veq)}$, of the equatorial rotational velocity, \\veq. Results. The distribution of \\vrot\\ shows a two-component structure: a peak around 80 \\kms\\ and a high-velocity tail extending up to $\\sim$600 \\kms. This structure is also present in the inferred distribution $\\rm{P(\\veq)}$ with around 80% of the sample having 0 $<$ \\veq\\, $\\leq\\, 300$ \\kms\\ and the other 20% distributed in the high-velocity region. Conclusions. Most of the stars in our sample rotate with a rate less than 20%\\...

  12. Optical Interferometry of early-type stars with PAVO@CHARA. I. Fundamental stellar properties

    CERN Document Server

    Maestro, V; Huber, D; Ireland, M J; Monnier, J D; White, T R; Kok, Y; Robertson, J G; Schaefer, G H; Brummelaar, T A Ten; Tuthill, P G

    2013-01-01

    We present interferometric observations of 7 main-sequence and 3 giant stars with spectral types from B2 to F6 using the PAVO beam combiner at the CHARA array. We have directly determined the angular diameters for these objects with an average precision of 2.3%. We have also computed bolometric fluxes using available photometry in the visible and infrared wavelengths, as well as space-based ultraviolet spectroscopy. Combined with precise \\textit{Hipparcos} parallaxes, we have derived a set of fundamental stellar properties including linear radius, luminosity and effective temperature. Fitting the latter to computed isochrone models, we have inferred masses and ages of the stars. The effective temperatures obtained are in good agreement (at a 3% level) with nearly-independent temperature estimations from spectroscopy. They validate recent sixth-order polynomial (B-V)-$T_\\mathrm{eff}$ empirical relations \\citep{Boyajian2012a}, but suggest that a more conservative third-order solution \\citep{vanBelle2009} could ...

  13. Long-term chromospheric activity of non-eclipsing RS CVn-type stars

    CERN Document Server

    Buccino, Andrea P

    2008-01-01

    Context. The IUE database provides a large number of UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims. Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22468 (V711 Tau, HR 1099, K1IV+G5V), HD 21242 (UX Ari, K0IV+G5V) and HD 224085 (II Peg, K2IV). Methods. We first obtain the Mount Wilson index S from the IUE high and low-resolution spectra. Secondly, we analyse with the Lomb-Scargle periodogram the mean annual index S and the amplitude of its rotational modulation. Results. For HD 22468 (V711 Tau, HR 1099), we found a possible chromospheric cycle with a period of 18 years and a shorter cycle with a period of 3 years, which could be associated to a chromospheric "flip-flop" cycle. The data of HD 224085 (II Peg) also suggest a chromospheric cycle of 21 years and a flip-flop cycle of 9 years. Finally, we obtained a p...

  14. The Near-Ultraviolet Luminosity Function of Young, Early M-Type Dwarf Stars

    CERN Document Server

    Ansdell, Megan; Mann, Andrew W; Lepine, Sebastien; James, David; Buccino, Andrea; Baranec, Christoph; Law, Nicholas M; Riddle, Reed; Mauas, Pablo; Petrucci, Romina

    2014-01-01

    Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magneto-hydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lepine & Gaidos (2011) catalog of bright M dwarfs with the GALEX catalog of NUV (1771-2831A) sources. Of the 4805 sources with GALEX counterparts, 797 have NUV emission significantly (> 2.5 sigma) in excess of an empirical basal level. We inspected these candidate active stars using visible-wavelength spectra, high-resolution adaptive optics imaging, time-series photometry, and literature searches to identify cases where the elevated NUV emission is due to unresolved background sources or stellar companions; we estimated ...

  15. BD-22deg3467, a DAO-type Star Exciting the Nebula Abell 35

    Science.gov (United States)

    Ziegler, M.; Rauch, T.; Werner, K.; Koppen, J.; Kruk, J. W.

    2013-01-01

    Spectral analyses of hot, compact stars with non-local thermodynamical equilibrium (NLTE) model-atmosphere techniques allow the precise determination of photospheric parameters such as the effective temperature (T(sub eff)), the surface gravity (log g), and the chemical composition. The derived photospheric metal abundances are crucial constraints for stellar evolutionary theory. Aims. Previous spectral analyses of the exciting star of the nebula A35, BD-22deg3467, were based on He+C+N+O+Si+Fe models only. For our analysis, we use state-of-the-art fully metal-line blanketed NLTE model atmospheres that consider opacities of 23 elements from hydrogen to nickel. We aim to identify all observed lines in the ultraviolet (UV) spectrum of BD-22deg3467 and to determine the abundances of the respective species precisely. Methods. For the analysis of high-resolution and high signal-to-noise ratio (S/N) far-ultraviolet (FUSE) and UV (HST/STIS) observations, we combined stellar-atmosphere models and interstellar line-absorption models to fully reproduce the entire observed UV spectrum. Results. The best agreement with the UV observation of BD-22deg3467 is achieved at T(sub eff) = 80 +/- 10 kK and log g = 7.2 +/- 0.3. While T(sub eff) of previous analyses is verified, log g is significantly lower. We re-analyzed lines of silicon and iron (1/100 and about solar abundances, respectively) and for the first time in this star identified argon, chromium, manganese, cobalt, and nickel and determined abundances of 12, 70, 35, 150, and 5 times solar, respectively. Our results partially agree with predictions of diffusion models for DA-type white dwarfs. A combination of photospheric and interstellar line-absorption models reproduces more than 90% of the observed absorption features. The stellar mass is M approx. 0.48 Solar Mass. Conclusions. BD.22.3467 may not have been massive enough to ascend the asymptotic giant branch and may have evolved directly from the extended horizontal branch

  16. The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type stars

    CERN Document Server

    Evans, C J; Dufton, P L; Howarth, I D; Walborn, N R; Markova, N; Clark, J S; de Mink, S E; de Koter, A; Dunstall, P R; Hénault-Brunet, V; Apellániz, J Maíz; McEvoy, C M; Sana, H; Simón-Díaz, S; Taylor, W D; Vink, J S

    2015-01-01

    We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We investigate the spatial distribution of the radial velocities across the 30 Dor region, and use the results to identify candidate runaway stars. Excluding potential runaways and members of two older clusters in the survey region (SL 639 and Hodge 301), we determine a systemic velocity for 30 Dor of 271.6 +/- 12.2 km/s from 273 presumed single stars. Employing a 3-sigma criterion we identify nine candidate runaway stars (2.9% of the single stars with radial-velocity estimates). The projected rotational velocities of the candidate runaways appear to be significantly different to those of the full B-type sample, with a strong preference for either large (>345 km/s) or...

  17. The young stellar population of IC 1613. III. New O-type stars unveiled by GTC-OSIRIS

    CERN Document Server

    Garcia, Miriam

    2012-01-01

    Recent findings hint that the winds of massive stars with poorer metallicity than the SMC may be stronger than predicted by theory. Besides calling the paradigm of radiation driven winds into question, this result would impact the predicted evolutionary paths of massive stars, their calculated ionizing radiation and mechanical feedback and the role these objects play at different stages of the Universe. The field needs a systematic study of the winds of a large set of very metal poor massive stars, but the sampling of spectral types is particularly poor in the very early types. This paper's goal is to increase the list of known O-type stars in the dwarf irregular galaxy IC1613, whose metallicity is smaller than the SMC's by roughly a factor 2. Using the reddening-free Q-parameter, evolutionary masses and GALEX photometry, we built a list of very likely O-type stars. We obtained low-resolution R~1000 GTC-OSIRIS spectra for a fraction of them and performed spectral classification, the only way to unequivocally ...

  18. Chemical compositions and plasma parameters of planetary nebulae with Wolf-Rayet and wels type central stars

    CERN Document Server

    Girard, P; Acker, A

    2006-01-01

    Aims: Chemical compositions and other properties of planetary nebulae around central stars of spectral types [WC], [WO], and wels are compared with those of `normal' central stars, in order to clarify the evolutionary status of each type and their interrelation. Methods: We use plasma diagnostics to derive from optical spectra the plasma parameters and chemical compositions of 48 planetary nebulae. We also reanalyze the published spectra of a sample of 167 non-WR PN. The results as well as the observational data are compared in detail with those from other studies of the objects in common. Results: The central star's spectral type is clearly correlated with electron density, temperature and excitation class of the nebula, [WC] nebulae tend to be smaller than the other types. All this corroborates the view of an evolutionary sequence from cool [WC 11] central stars inside dense, low excitation nebulae towards hot [WO 1] stars with low density, high excitation nebulae. The wels PN, however, appear to be a separ...

  19. An atlas of 2.4 to 4.1 microns ISO/SWS spectra of early-type stars

    CERN Document Server

    Lenorzer, A; Morris, P; De Koter, A; Geballe, T R; Waters, L B F M; Hony, S; Kaper, L

    2002-01-01

    We present an atlas of spectra of O- and B-type stars, obtained with the Short Wavelength Spectrometer (SWS) during the Post-Helium program of the Infrared Space Observatory (ISO). This program is aimed at extending the Morgan & Keenan classification scheme into the near-infrared. Later type stars will be discussed in a seperate publication. The observations consist of 57 SWS Post-Helium spectra from 2.4 to 4.1 microns, supplemented with 10 spectra acquired during the nominal mission with a similar observational setting. For B-type stars, this sample provides ample spectral converage in terms of subtype and luminosity class. For O-type stars,the ISO sample is coarse and therefore is complemented with 8 UKIRT L'-band observations. In terms of the presence of diagnostic lines, the L'-band is likely the most promising of the near-infrared atmospheric windows for the study of the physical properties of B stars. Specifically, this wavelength interval contains the Brackett alpha, Pfund gamma, and other Pfund li...

  20. The mean light curves of the Mira-type stars in the H- and K-bands

    CERN Document Server

    Kudashkina, L S

    2016-01-01

    For nine Mira-type stars (o Cet, R Leo, S Car, U Her, X Oph, R Aql, RR Aql, S Ori, S Scl,) and one semi-regular star (L2 Pup), the mean light curves have been obtained. The initial values of the brightness (observations) were fitted by a trigonometric polynomial of the statistically optimal order. The Fourier coefficients and the additional parameters (degree of the trigonometric polynomial, amplitude of the brightness, the maximal slope of ascending and descending branch, semi-amplitudes and initial epochs for the brightness maximum (minimum magnitude) of each harmonic contribution, etc., were given in the tables reported earlier (Kudashkina, 2015). In this study, we have received several interesting correlations between these parameters in the bands H and K. It was particularly noted the anomalous position on the figures of the star X Oph. The mean light curves of the investigated stars are commonly symmetric in the near infrared region (H and K).

  1. Spectroscopic characterization of a sample of metal-poor solar-type stars from the HARPS planet search program

    CERN Document Server

    Sousa, Sérgio G; Israelian, Garik; Lovis, C; Mayor, Michel; Silva, Pedro B; Udry, Stephane

    2010-01-01

    Stellar metallicity strongly correlates with the presence of planets and their properties. To check for new correlations between stars and the existence of an orbiting planet, we determine precise stellar parameters for a sample of metal-poor solar-type stars. This sample was observed with the HARPS spectrograph and is part of a program to search for new extrasolar planets. The stellar parameters were determined using an LTE analysis based on equivalent widths (EW) of iron lines and by imposing excitation and ionization equilibrium. The ARES code was used to allow automatic and systematic derivation of the stellar parameters. Precise stellar parameters and metallicities were obtained for 97 low metal-content stars. We also present the derived masses, luminosities, and new parallaxes estimations based on the derived parameters, and compare our spectroscopic parameters with an infra-red flux method calibration to check the consistency of our method in metal poor stars. Both methods seems to give the same effect...

  2. Neisseria gonorrhoeae Sequence Typing for Antimicrobial Resistance (NG-STAR): a novel antimicrobial resistance multilocus typing scheme for tracking the global dissemination of N. gonorrhoeae strains.

    Science.gov (United States)

    Demczuk, W; Sidhu, S; Unemo, M; Whiley, D M; Allen, V G; Dillon, J R; Cole, M; Seah, C; Trembizki, E; Trees, D L; Kersh, E N; Abrams, A J; de Vries, H J C; van Dam, A P; Medina, I; Bharat, A; Mulvey, M R; Van Domselaar, G; Martin, I

    2017-02-22

    A curated web-based user-friendly sequence typing tool based on antimicrobial resistance determinants in Neisseria gonorrhoeae was developed and is publicly accessible at https://ngstar.canada.ca The N. gonorrhoeae Sequence Typing for Antimicrobial Resistance (NG-STAR) molecular typing scheme uses the DNA sequences of 7 genes (penA, mtrR, porB, ponA, gyrA, parC, 23S rRNA) associated with resistance to β-lactam antimicrobials, macrolides, or fluoroquinolones. NG-STAR uses the entire penA sequence combining the historical nomenclature for penA types I-XXXVIII with novel nucleotide sequence designations; the full mtrR sequence and a portion of its promoter region; portions of ponA, porB, gyrA and parC; and 23S rRNA sequences. NG-STAR grouped 768 isolates into 139 sequence types (STs) (n=660) consisting of 29 CCs having a maximum of a single locus variation; and 76 NG-STAR STs (n=109) were identified as unrelated singletons. NG-STAR had a high Simpson's diversity index of 96.5% (CI 95%=0.959-0.969). The most common STs were NG-STAR: ST-90 (n=100, 13.0%), ST-42 and ST-91 (n=45, 5.9%), ST-64 (n=44, 5.72%), and ST-139 (n=42, 5.5%). Decreased susceptibility to azithromycin was associated with NG-STAR ST-58, ST-61, ST-64, ST-79, ST-91 and ST-139(n=156, 92.3%); decreased susceptibility to cephalosporins with NG-STAR ST-90, ST-91 and ST-97 (n=162, 94.2%); and ciprofloxacin resistance with NG-STAR ST-26, ST-90, ST-91, ST-97, ST-150 and ST-158 (n=196, 98.0%). All isolates of NG-STAR ST-42, ST-43, ST-63, ST-81, and ST-160 (n=106) were susceptible to all four antimicrobials. The standardization of nomenclature associated with antimicrobial resistance determinants through an internationally available database will facilitate the monitoring of the global dissemination of antimicrobial resistant N. gonorrhoeae strains.

  3. Gamma ray heating rates due to chromium isotopes in stellar core during late stages of high mass stars (>10M⊙

    Directory of Open Access Journals (Sweden)

    Nabi Jameel-Un

    2017-01-01

    Full Text Available Gamma ray heating rates are thought to play a crucial role during the pre-supernova stage of high mass stars. Gamma ray heating rates, due to β±-decay and electron (positron capture on chromium isotopes, are calculated using proton-neutron quasiparticle random phase approximation theory. The electron capture significantly affects the lepton fraction (Ye and accelerates the core contraction. The gamma rays emitted as a result of weak processes heat the core and tend to hinder the cooling and contraction due to electron capture and neutrino emission. The emitted gamma rays tend to produce enormous entropy and set the convection to play its role at this stage. The gamma heating rates, on 50-60Cr, are calculated for the density range 10 < ρ (g.cm-3 < 1011 and temperature range 107 < T (K < 3.0×1010.

  4. Towards a better understanding of the evolution of Wolf-Rayet stars and Type Ib/Ic supernova progenitors

    Science.gov (United States)

    Yoon, Sung-Chul

    2017-10-01

    Hydrogen-deficient Wolf-Rayet (WR) stars are potential candidates of Type Ib/Ic supernova (SN Ib/Ic) progenitors and their evolution is governed by mass-loss. Stellar evolution models with the most popular prescription for WR mass-loss rates given by Nugis & Lamers have difficulties in explaining the luminosity distribution of WR stars of WC and WO types and the SN Ic progenitor properties. Here, we suggest some improvements in the WR mass-loss rate prescription and discuss its implications for the evolution of WR stars and SN Ib/Ic progenitors. Recent studies on Galactic WR stars clearly indicate that the mass-loss rates of WC stars are systematically higher than those of WNE stars for a given luminosity. The luminosity and initial metallicity dependences of WNE mass-loss rates are also significantly different from those of WC stars. These factors have not been adequately considered together in previous stellar evolution models. We also find that an overall increase of WR mass-loss rates by about 60 per cent compared to the empirical values obtained with a clumping factor of 10 is needed to explain the most faint WC/WO stars. This moderate increase with our new WR mass-loss rate prescription results in SN Ib/Ic progenitor models more consistent with observations than those given by the Nugis & Lamers prescription. In particular, our new models predict that the properties of SN Ib and SN Ic progenitors are distinctively different, rather than they form a continuous sequence.

  5. The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

    Science.gov (United States)

    McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    2015-04-01

    We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, σe, R^maj_e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M⊙), which themselves formed 90 per cent of their stars by z ˜ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.

  6. Chemical abundances for A-and F-type supergiant stars

    CERN Document Server

    Molina, R E

    2016-01-01

    We present the stellar parameters and elemental abundances of a set of A--F-type supergiant stars HD\\,45674, HD\\,180028, HD\\,194951 and HD\\,224893 using high resolution ($R$\\,$\\sim$\\,42,000) spectra taken from ELODIE library. We present the first results of the abundance analysis for HD\\,45674 and HD\\,224893. We reaffirm the abundances for HD\\,180028 and HD\\,194951 studied previously by Luck (2014) respectively. Alpha-elements indicates that objects belong to the thin disc population. From their abundances and its location on the Hertzsprung-Russell diagram seems point out that HD\\,45675, HD\\,194951 and HD\\,224893 are in the post-first dredge-up (post-1DUP) phase and they are moving in the red-blue loop region. HD~180028, on the contary, shows typical abundances of the population I but its evolutionary status could not be satisfactorily defined.

  7. Chemical abundances for A-and F-type supergiant stars

    Science.gov (United States)

    Molina, R. E.; Rivera, H.

    2016-04-01

    We present the stellar parameters and elemental abundances of a set of A-F-type supergiant stars HD 45674, HD 180028, HD 194951 and HD 224893 using high resolution (R≈ 42,000) spectra taken from ELODIE library. We present the first results of the abundance analysis for HD 45674 and HD 224893. We reaffirm the abundances for HD 180028 and HD 194951 studied previously by Luck. Alpha-elements indicate that the objects belong to the thin disc population. Their abundances and their location on the Hertzsprung-Russell diagram seem to indicate that HD 45675, HD 194951 and HD 224893 are in the post-first dredge-up (post-1DUP) phase, and that they are moving in the red-blue loop region. HD 180028, on the contary, shows typical abundances of Population I, but its evolutionary status cannot be satisfactorily defined.

  8. Modelling multi-wavelength observational characteristics of bow shocks from runaway early type stars

    CERN Document Server

    Acreman, David M; Harries, Tim J

    2015-01-01

    We assess the multi-wavelength observable properties of the bow shock around a runaway early type star using a combination of hydrodynamical modelling, radiative transfer calculations and synthetic imaging. Instabilities associated with the forward shock produce dense knots of material which are warm, ionised and contain dust. These knots of material are responsible for the majority of emission at far infra-red, H alpha and radio wavelengths. The large scale bow shock morphology is very similar and differences are primarily due to variations in the assumed spatial resolution. However infra-red intensity slices (at 22 microns and 12 microns) show that the effects of a temperature gradient can be resolved at a realistic spatial resolution for an object at a distance of 1 kpc.

  9. First Detection of Linear Polarization in the Line Profiles of Active Cool Stars

    NARCIS (Netherlands)

    Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Snik, F.; Jeffers, S.V.; Johns-Krull, C. M.; Keller, C.U.; Rodenhuis, M.; Valenti, J. A.

    2011-01-01

    The application of high-resolution spectropolarimetry has led to major progress in understanding the magnetism and activity of late-type stars. During the last decade, magnetic fields have been discovered and mapped for many types of active cool stars using spectropolarimetric data. However, these o

  10. The chemical composition of the Orion star-forming region. III. C, N, Ne, Mg and Fe abundances in B-type stars revisited

    CERN Document Server

    Nieva, Maria-Fernanda

    2011-01-01

    Early B-type stars are invaluable indicators for elemental abundances of their birth environments. In contrast to the surrounding neutral interstellar matter (ISM) and HII regions their chemical composition is unaffected by depletion onto dust grains and by the derivation of different abundances from recombination and collisional lines. In combination with ISM or nebular gas-phase abundances they facilitate the dust-phase composition to be constrained. Precise abundances of C, N, Mg, Ne, Fe in early B-type stars in the Orion star-forming region are determined in order to: a) review previous determinations using a self-consistent quantitative spectral analysis based on modern stellar atmospheres and recently updated model atoms, b) complement results found in Paper I for oxygen and silicon, c) establish an accurate and reliable set of stellar metal abundances to constrain the dust-phase composition of the Orion HII region in Paper II of the series. A detailed, self-consistent spectroscopic study of a sample of...

  11. ASASSN-15jd: WZ Sge-type star with intermediate superoutburst between single and double ones

    CERN Document Server

    Kimura, Mariko; Kato, Taichi; Imada, Akira; Kojiguchi, Naoto; Sugiura, Yuki; Fukushima, Daiki; Takeda, Nao; Matsumoto, Katsura; Dvorak, Shawn; Vanmunster, Tonny; Dubovsky, Pavol A; Kudzej, Igor; Miller, Ian; Pavlenko, Elena P; Babina, Julia V; Antonyuk, Oksana I; Baklanov, Aleksei V; Stein, William L; Andreev, Maksim V; Tordai, Tamás; Itoh, Hiroshi; Pickard, Roger D; Nogami, Daisaku

    2016-01-01

    We present optical photometry of a WZ Sge-type dwarf nova (DN), ASASSN-15jd. Its light curve showed a small dip in the middle of the superoutburst in 2015 for the first time among WZ Sge-type DNe. The unusual light curve implies a delay in the growth of the 3:1 resonance tidal instability. Also, the light curve is similar to those of other two WZ Sge-type stars, SSS J122221.7$-$311523 and OT J184228.1$+$483742, which are believed to be the best candidates for a period bouncer on the basis of their small values of the mass ratio ($q \\equiv M_{2}/M_{1}$). Additionally, the small mean superhump amplitude ($<$ 0.1 mag) and the long duration of no ordinary superhumps at the early stage of the superoutburst are common to the best candidates for a period bouncer. The average superhump period was $P_{\\rm sh}$ = 0.0649810(78) d and no early superhumps were detected. Although we could not estimate the mass ratio of ASASSN-15jd with high accuracy, this object is expected to be a candidate for a period bouncer, a bina...

  12. Spine deformities in patients with Ehlers-Danlos syndrome, type IV - late results of surgical treatment

    Directory of Open Access Journals (Sweden)

    Tesiorowski Maciej

    2010-11-01

    Full Text Available Abstract Background Spinal deformities in Ehlers-Danlos syndrome are usually progressive and may require operative treatment. There is limited number of studies describing late results of surgery in this disease. Methods This is a retrospective study of the records of 11 patients with Ehlers-Danlos syndrome type IV, treated surgically between 1990 and 2007. All patients underwent surgical treatment for spinal deformity. Duration of operation, type of instrumentation, intraoperative blood loss, complications and number of additional surgeries were noted. Radiographic measurement was performed on standing AP and lateral radiographs acquired before surgery, just after and at final follow up. Results The mean follow up period was 5.5 ± 2.9 years (range 1-10 years. The mean preoperative thoracic and lumbar curve were 109.5 ± 19.9° (range 83° - 142° and 75.6 ± 26.7° (range 40° - 108° respectively. Posterior spine fusion alone was performed on 6 patients and combined anterior and posterior fusion (one- or two stage on 5 cases. Posterior segmental spinal instrumentation was applied with use of hooks, screws and wires. The mean postoperative thoracic and lumbar curve improved to 79.3 ± 16.1° (range 56° - 105° and 58.5 ± 27.7° (range 10° - 95° respectively, with a slight loss of correction during follow up. The average thoracic and lumbar correction was 26.4 ± 14.9% (range 5.3 - 50.4% and 26.3 ± 21.2% (range 7.9 - 75%. Postoperatively, the mean kyphosis was 79.5 ± 40.3° (range 21° -170°, and lordosis was 50.8 ± 18.6° (range 20° -79°. Hyperkyphosis increased during follow up while lordosis remained stable. Mean Th12-L2 angle was -3.5 ±9.9° (range -19° - 15° postoperatively and did not change significantly during follow up. Conclusions Huge spinal deformities in patients with Ehlers-Danlos syndrome require complex and extensive surgery. There is a big risk of sagittal imbalance in this group.

  13. Remote Life Detection Criteria, Habitable Zone Boundaries, and the Frequency of Earthlike Planets around M and Late-K Stars

    CERN Document Server

    Kasting, James F; Ramirez, Ramses R; Harman, Chester

    2013-01-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. Historically, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, 'Dune' planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future spa...

  14. Are peculiar Wolf-Rayet Stars of type WN8 Thorne-Zytkow Objects?

    CERN Document Server

    Foellmi, C

    2006-01-01

    Most population I Wolf-Rayet (WR) stars are the He-rich descendants of the most massive stars (M_i = 25 - 100 M_sun). Evidence has been accumulating over the years that among all pop I WR stars, those of the relatively cool, N-rich subtype "WN8" are among the most peculiar: 1. They tend to be runaways, with large space velocity and/or avoid clusters. 2. Unlike their equally luminous WN6,7 cousins, only a very small number of WN8 stars are known to belong to a close binary with an OB companion. 3. They are the systematically most highly stochastically variable among all (single) WR stars. Taken together, these suggest that many WN8 stars may originally have been in close binaries (like half of all stars), in which the original primary exploded as a supernova, leaving behind a very close binary containing a massive star with a neutron star/black hole companion (like Cyg X-3). When the massive remaining star evolved in turn, it engulfed and eventually swallowed the compact companion, leading to the presently puf...

  15. An absence of ex-companion stars in the type Ia supernova remnant SNR 0509-67.5

    Science.gov (United States)

    Schaefer, Bradley E.; Pagnotta, Ashley

    2012-01-01

    A type Ia supernova is thought to begin with the explosion of a white dwarf star. The explosion could be triggered by the merger of two white dwarfs (a `double-degenerate' origin), or by mass transfer from a companion star (the `single-degenerate' path). The identity of the progenitor is still controversial; for example, a recent argument against the single-degenerate origin has been widely rejected. One way to distinguish between the double- and single-degenerate progenitors is to look at the centre of a known type Ia supernova remnant to see whether any former companion star is present. A likely ex-companion star for the progenitor of the supernova observed by Tycho Brahe has been identified, but that claim is still controversial. Here we report that the central region of the supernova remnant SNR 0509-67.5 (the site of a type Ia supernova 400 +/- 50 years ago, based on its light echo) in the Large Magellanic Cloud contains no ex-companion star to a visual magnitude limit of 26.9 (an absolute magnitude of MV = +8.4) within a region of radius 1.43 arcseconds. (This corresponds to the 3σ maximum distance to which a companion could have been `kicked' by the explosion.) This lack of any ex-companion star to deep limits rules out all published single-degenerate models for this supernova. The only remaining possibility is that the progenitor of this particular type Ia supernova was a double-degenerate system.

  16. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars.

    Science.gov (United States)

    Kasting, James F; Kopparapu, Ravikumar; Ramirez, Ramses M; Harman, Chester E

    2014-09-02

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, S(eff), the recently recalculated HZ boundaries are: recent Venus--1.78; runaway greenhouse--1.04; moist greenhouse--1.01; maximum greenhouse--0.35; and early Mars--0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5.

  17. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars

    Science.gov (United States)

    Kasting, James F.; Kopparapu, Ravikumar; Ramirez, Ramses M.; Harman, Chester E.

    2014-09-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, Seff, the recently recalculated HZ boundaries are: recent Venus-1.78; runaway greenhouse-1.04; moist greenhouse-1.01; maximum greenhouse-0.35; and early Mars-0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5.

  18. The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM, and NGC 3109

    Science.gov (United States)

    Tramper, F.; Sana, H.; de Koter, A.; Kaper, L.; Ramírez-Agudelo, O. H.

    2014-12-01

    Context. Massive stars likely played an important role in the reionization of the Universe, and the formation of the first black holes. They are potential progenitors of long-duration gamma-ray bursts, seen up to redshifts of about ten. Massive stars in low-metallicity environments in the local Universe are reminiscent of their high redshift counterparts, emphasizing the importance of the study of their properties and evolution. In a previous paper, we reported on indications that the stellar winds of low-metallicity O stars may be stronger than predicted, which would challenge the current paradigm of massive star evolution. Aims: In this paper, we aim to extend our initial sample of six O stars in low-metallicity environments by four. The total sample of ten stars consists of the optically brightest sources in IC 1613, WLM, and NGC 3109. We aim to derive their stellar and wind parameters, and compare these to radiation-driven wind theory and stellar evolution models. Methods: We have obtained intermediate-resolution VLT/X-shooter spectra of our sample of stars. We derive the stellar parameters by fitting synthetic fastwindline profiles to the VLT/X-shooter spectra using a genetic fitting algoritm. We compare our parameters to evolutionary tracks and obtain evolutionary masses and ages. We also investigate the effective temperature versus spectral type calibration for SMC and lower metallicities. Finally, we reassess the wind momentum versus luminosity diagram. Results: The derived parameters of our target stars indicate stellar masses that reach values of up to 50 M⊙. The wind strengths of our stars are, on average, stronger than predicted from radiation-driven wind theory and reminiscent of stars with an LMC metallicity. We discuss indications that the iron content of the host galaxies is higher than originally thought and is instead SMC-like. We find that the discrepancy with theory is reduced, but remains significant for this higher metallicity. This may

  19. Spectral classification of stars based on LAMOST spectra

    CERN Document Server

    Liu, Chao; Zhang, Bo; Wan, Jun-Chen; Deng, Li-Cai; Hou, Yonghui; Wang, Yuefei; Yang, Ming; Zhang, Yong

    2015-01-01

    In this work, we select the high signal-to-noise ratio spectra of stars from the LAMOST data andmap theirMK classes to the spectral features. The equivalentwidths of the prominent spectral lines, playing the similar role as the multi-color photometry, form a clean stellar locus well ordered by MK classes. The advantage of the stellar locus in line indices is that it gives a natural and continuous classification of stars consistent with either the broadly used MK classes or the stellar astrophysical parameters. We also employ a SVM-based classification algorithm to assignMK classes to the LAMOST stellar spectra. We find that the completenesses of the classification are up to 90% for A and G type stars, while it is down to about 50% for OB and K type stars. About 40% of the OB and K type stars are mis-classified as A and G type stars, respectively. This is likely owe to the difference of the spectral features between the late B type and early A type stars or between the late G and early K type stars are very we...

  20. Water isotopologues in the circumstellar envelopes of M-type AGB stars

    Science.gov (United States)

    Danilovich, T.; Lombaert, R.; Decin, L.; Karakas, A.; Maercker, M.; Olofsson, H.

    2017-06-01

    Aims: In this study we intend to examine rotational emission lines of two isotopologues of water: H217O and H218O. By determining the abundances of these molecules, we aim to use the derived isotopologue - and hence oxygen isotope - ratios to put constraints on the masses of a sample of M-type AGB stars that have not been classified as OH/IR stars. Methods: We have used detailed radiative transfer analysis based on the accelerated lambda iteration method to model the circumstellar molecular line emission of H217O and H218O for IK Tau, R Dor, W Hya, and R Cas. The emission lines used to constrain our models came from Herschel/HIFI and Herschel/PACS observations and are all optically thick, meaning that full radiative transfer analysis is the only viable method of estimating molecular abundance ratios. Results: We find generally low values of the 17O/18O ratio for our sample, ranging from 0.15 to 0.69. This correlates with relatively low initial masses, in the range 1.0 to 1.5 M⊙ for each source, based on stellar evolutionary models. We also find ortho-to-para ratios close to 3, which are expected from warm formation predictions. Conclusions: The 17O/18O ratios found for this sample are at the lower end of the range predicted by stellar evolutionary models, indicating that the sample chosen had relatively low initial masses. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.