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135 results on '"G. Vauclair"'

51. 2006 Whole Earth Telescope Observations of GD358: A New Look at the Prototype DBV

Author: Gerald Handler, H. C. Lin, P. Sherard, D. Childers, J. R. Eggen, Antonio Kanaan, R. Knight, Michael H. Montgomery, Margit Paparo, S. L. Kim, M. Chevreton, Wen Ping Chen, E. Reiff, E. B. Janiashvili, Chien-Cheng Lin, A. Hoffman, T. K. Watson, Philippe M. Binder, G. Stachowski, C. W. Chen, A.-Y. Zhou, Luciano Fraga, J. E. Solheim, Dorota Kozieł, M. Andreev, Andrzej S. Baran, E. Pakstiene, Souza Oliveira Kepler, Michael D. Reed, Susan E. Thompson, N. Purves, Donald E Winget, M. Yang, D. Lorenz, Michal Siwak, R. Crowe, Paul G. Beck, Atsuko Nitta, Harry L. Shipman, G. Vauclair, Rimvydas Janulis, J. Dalessio, Basmah Riaz, David Mkrtichian, Stéphane Charpinet, Zs. Bognár, S. J. Kleinman, J. Slivkoff, Staszek Zola, B. Steininger, Thorsten Nagel, R. Kowalski, D.-J. Kusterer, J. L. Provencal, Xiao-Jun Jiang, A. V. Sergeev, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: oscillations [Stars], FOS: Physical sciences, evolution [Stars], Astrophysics, 01 natural sciences, law.invention, Photometry (optics), Telescope, symbols.namesake, law, Evolucao estelar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, individual (GD358) [Stars], 010303 astronomy & astrophysics, Multiplet, white dwarfs, Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Dinâmica de fluidos astrofísicos, Astrophysics (astro-ph), White dwarfs, White dwarf, Astronomy and Astrophysics, Estrutura estelar, Light curve, Espectros estelares, Estrelas variaveis, Magnetic field, stars: individual: GD358, Amplitude, Fourier transform, Pulsacoes estelares, Anãs brancas, 13. Climate action, Space and Planetary Science, symbols, Magnetismo estelar, Radiação estelar, stars: oscillations
Abstract: We report on the analysis of 436.1 hrs of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated XCOV25. The Fourier transform (FT) of the light curve contains power between 1000 to 4000 microHz, with the dominant peak at 1234 microHz. We find 27 independent frequencies distributed in 10 modes, as well as numerous combination frequencies. Our discussion focuses on a new asteroseismological analysis of GD358, incorporating the 2006 data set and drawing on 24 years of archival observations. Our results reveal that, while the general frequency locations of the identified modes are consistent throughout the years, the multiplet structure is complex and cannot be interpreted simply as l=1 modes in the limit of slow rotation. The high k multiplets exhibit significant variability in structure, amplitude and frequency. Any identification of the m components for the high k multiplets is highly suspect. The k=9 and 8 modes typically do show triplet structure more consistent with theoretical expectations. The frequencies and amplitudes exhibit some variability, but much less than the high k modes. Analysis of the k=9 and 8 multiplet splittings from 1990 to 2008 reveal a long-term change in multiplet splittings coinciding with the 1996 "sforzando" event, where GD358 dramatically altered its pulsation characteristics on a timescale of hours. We explore potential implications, including the possible connections between convection and/or magnetic fields and pulsations. We suggest future investigations, including theoretical investigations of the relationship between magnetic fields, pulsation, growth rates, and convection., 18 pages, 20 figures, 5 tables, accepted for publication in the Astrophysical Journal
Published: 2009
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52. Preliminary XCOV26 results for EC14012-1446

Author: D. Chandler, Andrzej S. Baran, S. L. Kim, Zs. Bognár, S. Galleti, Souza Oliveira Kepler, David Kilkenny, M. Paparo, Michael D. Reed, J.M.G. Perez, Harry L. Shipman, R. Sefako, Rimvydas Janulis, Susan E. Thompson, A. Maksim, Gerald Handler, J. Dalessio, B. G. Castanheira, J. R. Fremy, Michael H. Montgomery, Waldemar Ogloza, N. Loaring, T. K. Watson, Chia-You Shih, Atsuko Nitta, Antonio Kanaan, Hari Om Vats, W. Strickland, B. Walter, Judith L. Provencal, Roberto Silvotti, Kiran S. Baliyan, Timothy M. Brown, C. Clemens, Stanisław Zoła, Denis J. Sullivan, Luciano Fraga, A. V. Sergeev, Wen Ping Chen, N. Dolez, Péter Pápics, Stephane Vennes, G. Vauclair, A. Kniazev, Thorsten Nagel, M. Winiarski, A. Kim, Xiao-Jun Jiang, Matt A. Wood, S. J. Kleinman, M. Yang, D. A. H. Buckley, R. Rosen, J. M. Almenara, P. Henrique, and D. Childers
Subjects: Physics, History, business.industry, White dwarf, Light curve, Computer Science Applications, Education, Computational physics, Photometry (optics), Nonlinear system, symbols.namesake, Optics, Fourier transform, Convection zone, Excited state, symbols, Astrophysics::Solar and Stellar Astrophysics, business, Multiplet
Abstract: EC14012-1446 is a hydrogen atmosphere (DA) white dwarf pulsator. Its rich pulsation spectrum displays a range of excited modes with complex multiplet structure, in addition to numerous combination frequencies. In April 2008, EC14012-1446 was the primary target of XCOV26. We obtained over 300 hrs of nearly continuous high speed photometry with the goal of using the nonlinear pulse shapes to empirically determine the parameters of the convection zone. The Fourier transform (FT) of the light curve contains power between 1000 to 4000 μHz, with the dominant peak at 1234 μHz. We find 13 independent frequencies distributed in 8 modes, as well as a myriad of combination frequencies. In the following, we present preliminary results and lay the groundwork for future investigation leading to light curve fitting of EC14012-1446.
Published: 2009

53. HD 51106 and HD 50747: an ellipsoidal binary and a triple system observed with CoRoT

Author: J. C. Valtier, K. Uytterhoeven, N. Dolez, R. Samadi, C. Catala, A. Hui Bon Hua, P. Mathias, E. Poretti, G. Vauclair, M. Auvergne, E. Michel, M. Rainer, Pedro J. Amado, D. Le Contel, Sylvie Vauclair, A. Baglin, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), INAF-Osservatorio Astronomico di Brera (INAF-OAB), Instituto de Astrofisica de Andalucia, CSIC (IAA), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Subjects: Physics, Oscillation, Triple system, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Star (graph theory), Light curve, Stars, symbols.namesake, Fourier transform, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, symbols, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Variable star, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: We present an analysis of the observations of HD 51106 and HD 50747 by the satellite CoRoT, obtained during its initial run, and of the spectroscopic preparatory observations. AIMS: We complete an analysis of the light curve, extract the main frequencies observed, and discuss some preliminary interpretations about the stars. Methods: We used standard Fourier transform and pre-whitening methods to extract information about the periodicities of the stars. Results: HD 51106 is an ellipsoidal binary, the light curve of which can be completely explained by the tidal deformation of the star and smaller secondary effects. HD 50747 is a triple system containing a variable star, which exhibits many modes of oscillation with periods in the range of a few hours. On the basis of this period range and the analysis of the physical parameters of the star, we conclude that HD 50747 is a Gamma-Doradus star., Comment: 7 pages, 8 figures, use (Astronomy-Astrophysics format/macro LAtex)
Published: 2009
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54. Seismic predictions for the CoRoT main target HD 52265

Author: M. Soriano, S Vauclair, M. Laymand, G Vauclair, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Physics, History, 010504 meteorology & atmospheric sciences, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astrophysics, Star (graph theory), 01 natural sciences, Asteroseismology, Computer Science Applications, Education, Stars, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; HD 52265 is the only exoplanet-host star selected as a main target for the seismology programme of the CoRoT mission, and so it will be observed continuously during five months. This is of great interest in the framework of asteroseismology of exoplanet-host stars, in order to better understand the planetary formation and migration. We performed and extensive analysis of this star, computed models and analysed their frequencies. CoRoT observations should enable us to discriminate between the various models allowed from spectroscopic observations.
Published: 2008
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55. The exoplanet-host star ? Horologii: an evaporated member of the primordial Hyades cluster

Author: Stéphane Charpinet, François Bouchy, M. Laymand, A. Hui Bon Hoa, G. Vauclair, M. Bazot, Sylvie Vauclair, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Laboratoire d'Astrophysique de Marseille (LAM), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Services communs OMP (UMS 831), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Genève = University of Geneva (UNIGE), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Services communs OMP - UMS 831 (UMS 831), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Hyades Stream, stars: abundances, Metallicity, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Star formation, Astrophysics (astro-ph), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Planetary system, Exoplanet, Accretion (astrophysics), Stars, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, stars: planetary systems, Galaxy: open cluster and associations: individual: Hyades
Abstract: We show that the exoplanet-host star iota Horologii, alias HD17051, which belongs to the so-called Hyades stream, was formed within the primordial Hyades stellar cluster and has evaporated towards its present location, 40 pc away. This result has been obtained unambiguously by studying the acoustic oscillations of this star, using the HARPS spectrometer in La Silla Observatory (ESO, Chili). Besides the fact that $\iota$ Hor belongs to the Hyades stream, we give evidence that it has the same metallicity, helium abundance, and age as the other stars of the Hyades cluster. They were formed together, at the same time, in the same primordial cloud. This result has strong implications for theories of stellar formation. It also indicates that the observed overmetallicity of this exoplanet-host star, about twice that of the Sun, is original and not caused by planet accretion during the formation of the planetary system., Comment: to be published in A&A letters
Published: 2008
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56. The detection of ionized helium and carbon in the pulsating DB degenerate GD358

Author: James Liebert, Edward M. Sion, G. Vauclair, and Gary Wegner
Subjects: Physics, Stars, Stellar mass loss, White dwarf, Helium flash, Astrophysics, Atomic physics, Stellar classification, Equivalent width, Astronomical spectroscopy, Main sequence
Abstract: Echelle observations of GD358, prototype of the class of six known pulsating DB stars and one of the hottest DB stars, are presented. Evidence for the existence of He II and C II is demonstrated. The Ly-alpha + He II region reveals no clear evidence of absorption wings flanking the geocoronal emission. The significance of the He II detection is discussed.
Published: 2008
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57. The time dependence of the phases of the harmonics relative to the 1490 sec fundamental in PG1346+082

Author: R. E. Nather, J. C. Clemens, Gregory W. Henry, Don Winget, Brian Warner, Judith L. Provencal, Souza Oliveira Kepler, Lilia Ferrario, Matt A. Wood, D. O'Donoghue, M. Chevreton, Albert D. Grauer, B. P. Hine, and G. Vauclair
Subjects: Rotation period, Physics, Oscillation, Harmonics, Binary star, Astrophysics::Solar and Stellar Astrophysics, White dwarf, Astrophysics::Earth and Planetary Astrophysics, Astrophysics, Variable star, Orbital period, Stellar evolution, Astrophysics::Galaxy Astrophysics
Abstract: On the basis of our preliminary analysis of the harmonic structure, we suggest that the 1493 s oscillation is either the orbital period of the system or the rotation period of a magnetized, accreting white dwarf. The 1471 s is most probably a nonradial oscillation of the primary white dwarf since its character mimics that of oscillations seen in single DB variables.
Published: 2008
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58. The pulsation modes of the pre-white dwarf PG 1159-035

Author: J. E. S. Costa, W. Ogloza, R. Kalytis, T. J. Ahrens, Anjum S. Mukadam, Souza Oliveira Kepler, S. A. Good, J. Larrison, Albert D. Grauer, E. W. Klumpe, Gerald Handler, Donald E Winget, R. Rosen, H. Lee, P. Martinez, Encarni Romero-Colmenero, O. Giovannini, Matt A. Wood, F. Johannessen, M. C. Akan, R. Janulis, Brian Warner, G. Viraghalmy, X. J. Jiang, Michael H. Montgomery, M. Vuckovic, Leandro Gabriel Althaus, T. Sullivan, M. S. O'Brien, N. Dolez, J.-E. Solheim, Denis J. Sullivan, E. G. Meištas, Fergal Mullally, A. F. M. Costa, A. V. Sergeev, Andrzej S. Baran, M. Paparó, Stanisław Zoła, S. Seetha, Judith L. Provencal, Matthew R. Burleigh, J. C. Clemens, Paul A. Bradley, Antonio Kanaan, Travis S. Metcalfe, Stefan Dreizler, J. L. Deetjen, Jian-Ning Fu, Harry L. Shipman, R. E. Nather, T. Lawrence, Jurek Krzesinski, Steven D. Kawaler, J. M. Gonzalez Perez, A. Ulla, Kazuhiro Sekiguchi, Martin A. Barstow, B. N. Ashoka, S. L. Kim, Alejandro H. Córsico, Reed Riddle, Nicole M. Silvestri, Thorsten Nagel, S. Marinoni, Ö. Hürkal, Sonja Schuh, G. Vauclair, E. Pakštienė, Roberto Silvotti, D. O'Donoghue, M. Chevreton, R. Crowe, Atsuko Nitta, Scot Kleinman, Ömür Çakırlı, Mukremin Kilic, Centro de Fìsica Atòmica (CFA), Universidade de Lisboa (ULISBOA), Brain imaging (LIAMA), Laboratoire Franco-Chinois d'Informatique, d'Automatique et de Mathématiques Appliquées (LIAMA), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Chinese Academy of Sciences [Changchun Branch] (CAS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institute of Automation - Chinese Academy of Sciences-Centre National de la Recherche Scientifique (CNRS)-Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut National de la Recherche Agronomique (INRA)-Chinese Academy of Sciences [Changchun Branch] (CAS)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institute of Automation - Chinese Academy of Sciences-Centre National de la Recherche Scientifique (CNRS), Department of Molecular Microbiology and Biotechnology, Tel Aviv University [Tel Aviv], Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Department of Electronic and Electrical Engineering, Pohang University of Science and Technology (POSTECH), Institute of Applied Physics of RAS, Russian Academy of Sciences [Moscow] (RAS), Department of Physics and Astronomy [Ames, Iowa], Iowa State University (ISU), University of Waterloo [Waterloo], Ege Üniversitesi, Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Universidade de Lisboa = University of Lisbon (ULISBOA), Tel Aviv University (TAU), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Rotation period, Astrofísica, Ciencias Astronómicas, 010504 meteorology & atmospheric sciences, individual: PG 1159-035 [Stars], Ciencias Físicas, stars:evolution, stars:white dwarfs, Astrophysics, stars: interiors, 01 natural sciences, stars: individual: PG 1159-035, purl.org/becyt/ford/1 [https], Gravitation, stars:oscillations, asteroseismology: general, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Multiplet, Physics, Solar mass, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], stars: white dwarfs, Astrophysics (astro-ph), stars : white dwarfs, Radius, Magnetic field, Pulsacoes estelares, stars : interiors, Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, CIENCIAS NATURALES Y EXACTAS, Convection, Oscillations, PG 1159-035 (estrella), oscillations [Stars], FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, stars : oscillations, white dwarfs [Stars], [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, stars : individual : PG 1159-035, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, interiors [Stars], White dwarf, White dwarfs, Astronomy and Astrophysics, purl.org/becyt/ford/1.3 [https], VDP::Mathematics and natural science: 400::Physics: 430::Astrophysics, astronomy: 438, Astronomía, Interior stars, white dwarfs: individual( GD358), 13. Climate action, Space and Planetary Science, Oscilacoes, Anãs brancas, oscillations, stars: individual, PG 1159-035, stars: white dwarfs [stars], Interior estelar
Abstract: Context. PG 1159-035, a pre-white dwarf with Teff ≃ 140000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. Analyzing the periods of pulsation, it is possible to measure the stellar mass, the rotational period and the inclination of the rotation axis, to estimate an upper limit for the magnetic field, and even to obtain information about the inner stratification of the star. Aims. We have three principal aims: to increase the number of detected and identified pulsation modes in PG 1159-035, study trapping of the star's pulsation modes, and to improve or constrain the determination of stellar parameters. Methods. We used all available WET photometric data from 1983, 1985, 1989. 1993 and 2002 to identify the pulsation periods. Results. We identified 76 additional pulsation modes, increasing to 198 the number of known pulsation modes in PG 1159-035, the largest number of modes detected in any star besides the Sun. From the period spacing we estimated a mass M/M⊙= 0.59 ±0.02 for PG 1159-035, with the uncertainty dominated by the models, not the observation. Deviations in the regular period spacing suggest that some of the pulsation modes are trapped, even though the star is a pre-white dwarf and the gravitational settling is ongoing. The position of the transition zone that causes the mode trapping was calculated at rc/R* = 0.83 ± 0.05. From the multiplet splitting, we calculated the rotational period Prot = 1.3920 ± 0.0008 days and an upper limit for the magnetic field, B < 2000 G. The total power of the pulsation modes at the stellar surface changed less than 30% for ℓ = 1 modes and less than 50% for ℓ = 2 modes. We find no evidence of linear combinations between the 198 pulsation mode frequencies. PG 1159-035 models have not significative convection zones, supporting the hypothesis that nonlinearity arises in the convection zones in cooler pulsating white dwarf stars., La lista completa de autores que integran el documento puede consultarse en el archivo., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
Published: 2008
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59. CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun

Author: Yveline Lebreton, Ignasi Ribas, Marie-Jo Goupil, C. Catala, Sylvie Vauclair, Philippe Mathias, Coralie Neiner, Malcolm Fridlund, R. Garrido, J. Ballot, Michel Rieutord, Patrick Boumier, Marc-Antoine Dupret, Werner W. Weiss, Conny Aerts, Gabrielle Berthomieu, G. Vauclair, Annie Baglin, Stéphane Charpinet, Frédéric Baudin, R. Samadi, T. Toutain, Eduardo Janot-Pacheco, Rafael A. García, Ian W. Roxburgh, Konstanze Zwintz, Didier Tiphène, M. Auvergne, Thierry Appourchaux, Anne-Marie Hubert, Sylvaine Turck-Chièze, B. Mosser, François Lignières, Eric Michel, Mário J. P. F. G. Monteiro, Caroline Barban, A. Grotsch-Noels, Hans Kjeldsen, G. Alecian, Janine Provost, José Renan de Medeiros, Teodoro Roca Cortés, Anne Thoul, Ennio Poretti, Faculdade de Ciências, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Convection, Astronomy, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, Asteroseismology, Solar-Like Oscillations, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Stars hotter than the sun, Solar-like oscillations, Helioseismology, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Multidisciplinary, Astrofísica, Ciências Físicas, Astronomia, 010308 nuclear & particles physics, Oscillation, Astrophysics (astro-ph), Astrophysics, Physical sciences, Astronomy, CoRoT (Convection Rotation and Planetary Transits) satellite, Stars, Stellar granulation, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics::Earth and Planetary Astrophysics, Main sequence
Abstract: 4 pages, 3 figures.-- Supporting Online Material: Text, Fig. S1, Table S1 and References, available at: http://www.sciencemag.org/cgi/content/full/322/5901/558/DC1, Oscillations of the Sun have been used to understand its interior structure. The extension of similar studies to more distant stars has raised many difficulties despite the strong efforts of the international community over the past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite, launched in December 2006, has now measured oscillations and the stellar granulation signature in three main sequence stars that are noticeably hotter than the sun. The oscillation amplitudes are about 1.5 times as large as those in the Sun; the stellar granulation is up to three times as high. The stellar amplitudes are about 25% below the theoretic values, providing a measurement of the nonadiabaticity of the process ruling the oscillations in the outer layers of the stars.
Published: 2008
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60. Abell 43: Longest period Planetary Nebula Nucleus variable

Author: G. Vauclair, V. Dobrovolskas, Anjum S. Mukadam, R. Janulis, and J.-E. Solheim
Subjects: Physics, Astrophysics (astro-ph), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Planetary nebula, Photometry (optics), Amplitude, medicine.anatomical_structure, Space and Planetary Science, Ionization, medicine, Astrophysics::Solar and Stellar Astrophysics, Nucleus, Astrophysics::Galaxy Astrophysics
Abstract: Based on 24h high speed photometry of the hybrid PG 1159 star Abell 43, we have detected 6 sighificant pulsations with periods between 2380 s and 6075 s. A short (4h) run on the almost spectroscopic twin NGC 7094 central star resulted in detection of 3 low amplitude pulsations with periods between 2000 s and 5000 s. The results are close to predictions for g-mode pulsations driven by the kappa-mechanism induced by the partial ionization of carbon and oxygen., 5 pages, 5 figures, to be published in Astronomy and Astrophysics
Published: 2007

61. The CoRoT primary target HD 52265: models and seismic tests

Author: M. Soriano, M. Laymand, S. Vauclair, G. Vauclair, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: stars: abundances, Metallicity, FOS: Physical sciences, Astrophysics, 01 natural sciences, Asteroseismology, Luminosity, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, planetary systems, Astrophysics::Galaxy Astrophysics, Physics, Observational error, 010308 nuclear & particles physics, Subgiant, stars: individual: HD 52265, Astrophysics (astro-ph), Astronomy and Astrophysics, Planetary system, Effective temperature, Exoplanet, 13. Climate action, Space and Planetary Science, stars: oscillations, Astrophysics::Earth and Planetary Astrophysics
Abstract: HD 52265 is the only known exoplanet-host star selected as a main target for the seismology programme of the CoRoT satellite. As such, it will be observed continuously during five months, which is of particular interest in the framework of planetary systems studies. This star was misclassified as a giant in the Bright Star Catalog, while it is more probably on the main-sequence or at the beginning of the subgiant branch. We performed an extensive analysis of this star, showing how asteroseismology may lead to a precise determination of its external parameters and internal structure. We first reviewed the observational constraints on the metallicity, the gravity and the effective temperature derived from the spectroscopic observations of HD 52265. We also derived its luminosity using the Hipparcos parallax. We computed the evolutionary tracks for models of various metallicities which cross the relevant observational error boxes in the gravity-effective temperature plane. We selected eight different stellar models which satisfy the observational constraints, computed their p-modes frequencies and analysed specific seismic tests. The possible models for HD 52265, which satisfy the constraints derived from the spectroscopic observations, are different in both their external and internal parameters. They lie either on the main sequence or at the beginning of the subgiant branch. The differences in the models lead to quite different properties of their oscillation frequencies. We give evidences of an interesting specific behaviour of these frequencies in case of helium-rich cores: the ``small separations'' may become negative and give constraints on the size of the core. We expect that the observations of this star by the CoRoT satellite wi ll allow choosing between these possible models., Comment: 11 pages, 7 figures, to be published in Astronomy and Astrophysics
Published: 2007
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62. A NEW ANALYSIS OF THE TWO CLASSICAL ZZ CETI WHITE DWARFS GD 165 AND ROSS 548. I. PHOTOMETRY AND SPECTROSCOPY

Author: Pierre Brassard, G. Vauclair, Pierre Bergeron, N. Giammichele, B. Pfeiffer, Gilles Fontaine, and Stéphane Charpinet
Subjects: Physics, Photometry (optics), Stars, Space and Planetary Science, Astronomy, White dwarf, Astronomy and Astrophysics, Astrophysics, Atmospheric model, Emission spectrum, Visible radiation, Spectroscopy, Multiplet
Abstract: We present the first of a two-part seismic analysis of the two bright hot ZZ Ceti stars GD 165 and Ross 548. In this first part, we report the results of frequency extraction exercises based on time-series data sets of exceptional quality. We uncovered up to 13 independent pulsation modes in GD 165, regrouped into six main frequency multiplets. These include 9 secure (signal-to-noise ratio, S/N > 4) detections and 4 possible ones (4 ≥ S/N ≥ 3). Likewise, we isolated 11 independent modes in Ross 548 (9 secure and 2 possible detections), also regrouped into 6 multiplets. The multiplet structure is likely caused by rotational splitting. We also provide updated estimates of the time-averaged atmospheric properties of these two pulsators in the light of recent developments on the front of atmospheric modeling for DA white dwarfs.
Published: 2015
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63. Asteroseismological constraints on the structure of the ZZ Ceti star HL Tau 76

Author: N. Dolez, D. Pech, G. Vauclair, Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (LATT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Laboratoire Astrophysique de Toulouse-Tarbes (LATT)
Subjects: Physics, 010308 nuclear & particles physics, stars: white dwarfs, White dwarf, Astronomy and Astrophysics, Astrophysics, Radius, Parameter space, 01 natural sciences, stars: individual: ZZ Ceti, Luminosity, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Amplitude, Space and Planetary Science, 0103 physical sciences, stars: fundamental parameters, stars: oscillations, Spectroscopy, Adiabatic process, 010303 astronomy & astrophysics, HL Tau 76, Excitation
Abstract: This paper reports the results derived from an asteroseismological study of the cool ZZ Ceti star HL Tau 76. A grid of models has been computed in a parameter space covering the range of log g and T eff , formerly determined by spectroscopy, and a large range of hydrogen mass fraction. The adiabatic non-radial oscillations for all the models have been computed for the modes of degrees l = 1 and l = 2. An algorithm based on a X 2 test was applied to evaluate the quality of the fit between observed and theoretical periods. This method resulted in selecting a best fitting model for which the average relative matching of the periods is 0.7%. Then, a detailed comparison between the observed and the computed periods for the l = 1 and l = 2 modes of the best fitting model was achieved in order to identify as many observed modes as possible. To perform this identification we used the calculated periods for which we applied the rotational splitting as deduced from the observations. Through this process we identify the 36 independent modes observed in HL Tau 76. The best fitting model for HL Tau 76 is well constrained due to the large number of oscillations detected in this ZZ Ceti star. The main stellar parameters of HL Tau 76 derived from this analysis are: the total mass M * = 0.575 ± 0.005 M ○. , the hydrogen mass fraction q H , estimated as thick as 2.35 ± 0.10 x 10 -4 . The helium mass fraction consistent with q H must be q He = 1 x 10 -2 . The method is not sensitive to T eff variations in the narrow domain of temperature derived from spectroscopy for HL Tau 76. The best adjustment is found however for T eff = 11 375 K. The other derived stellar parameters are the luminosity (L/L ○. = 0.00389) and the radius (R/R ○. = 0.0162). We note some trends in the fit of the observed periods with the computed ones which suggest that the rotational splitting could be non-uniform and that the large amplitude modes might contain information on the convection-driven excitation mechanism.
Published: 2006
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64. Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067

Author: M. Vučković, S. D. Kawaler, S. O’Toole, Z. Csubry, A. Baran, S. Zola, P. Moskalik, E. W. Klumpe, R. Riddle, M. S. O’Brien, F. Mullally, M. A. Wood, V. Wilkat, A.‐Y. Zhou, M. D. Reed, D. M. Terndrup, D. J. Sullivan, S.‐L. Kim, W. P. Chen, C.‐W. Chen, W.‐S. Hsiao, K. Sanchawala, H.‐T. Lee, X. J. Jiang, R. Janulis, M. Siwak, W. Ogloza, M. Paparo, Zs. Bognar, A. Sodor, G. Handler, D. Lorenz, B. Steininger, R. Silvotti, G. Vauclair, R. Oreiro, R. Ostensen, A. Bronowska, B. G. Castanheira, S. O. Kepler, L. Fraga, H. L. Shipman, J. L. Provencal, and D. Childers
Subjects: Subdwarf B star, oscillations [Stars], Subdwarfs, FOS: Physical sciences, Astrophysics, Star (graph theory), law.invention, Telescope, Observacoes astronomicas, law, Telescopios, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Astrophysics (astro-ph), High mode, Astronomy and Astrophysics, Subdwarf, Stars, Space and Planetary Science, Pulsacoes estelares, Anãs brancas, individual (PG 0014+067) [Stars], Astrophysics::Earth and Planetary Astrophysics, Longitude, Earth (classical element)
Abstract: PG 0014+067 is one of the most promising pulsating subdwarf B stars for seismic analysis, as it has a rich pulsation spectrum. The richness of its pulsations, however, poses a fundamental challenge to understanding the pulsations of these stars, as the mode density is too complex to be explained only with radial and nonradial low degree (l < 3) p-modes without rotational splittings. One proposed solution, for the case of PG 0014+067 in particular, assigns some modes with high degree (l=3). On the other hand, theoretical models of sdB stars suggest that they may retain rapidly rotating cores, and so the high mode density may result from the presence of a few rotationally-split triplet (l=1), quintuplet (l=2) modes, along with radial (l=0) p-modes. To examine alternative theoretical models for these stars, we need better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in October 2004. In this paper we report the results of Whole Earth Telescope observations of the pulsating subdwarf B star PG 0014+067. We find that the frequencies seen in PG 0014+067 do not appear to fit any theoretical model currently available; however, we find a simple empirical relation that is able to match all of the well-determined frequencies in this star., 19 pages, preprint of paper accepted for publication in The Astrophysical Journal
Published: 2006

65. Whole Earth Telescope observations of BPM 37093: A seismological test of crystallization theory in white dwarfs

Author: A. Kanaan, A. Nitta, D. E. Winget, S. O. Kepler, M. H. Montgomery, T. S. Metcalfe, H. Oliveira, L. Fraga, A. F. M. da Costa, J. E. S. Costa, B. G. Castanheira, O. Giovannini, R. E. Nather, A. Mukadam, S. D. Kawaler, M. S. O'Brien, M. D. Reed, S. J. Kleinman, J. L. Provencal, T. K. Watson, D. Kilkenny, D. J. Sullivan, T. Sullivan, B. Shobbrook, X. J. Jiang, B. N. Ashoka, S. Seetha, E. Leibowitz, P. Ibbetson, H. Mendelson, E. G. Meištas, R. Kalytis, D. Ališauskas, D. O'Donoghue, D. Buckley, P. Martinez, F. van Wyk, R. Stobie, F. Marang, L. van Zyl, W. Ogloza, J. Krzesinski, S. Zola, P. Moskalik, M. Breger, A. Stankov, R. Silvotti, A. Piccioni, G. Vauclair, N. Dolez, M. Chevreton, J. Deetjen, S. Dreizler, S. Schuh, J. M. Gonzalez Perez, R. Østensen, A. Ulla, M. Manteiga, O. Suarez, M. R. Burleigh, M. A. Barstow, Departamento de Física (CFM), Universidade Federal de Santa Catarina, Apache Point Observatory, Department of Astronomy, University of Texas, Instituto de Física, Universidade Federal do Rio Grande do Sul, Institute of Astronomy, University of Cambridge (IoA), Harvard-Smithsonian Center for Astrophysics, Departamento de Física e Química, Universidade de Caxias do Sul, Department of Physics and Astronomy, Iowa State University, Department of Physics and Astronomy, University of Delaware, Southwestern University, South African Astronomical Observatory (SAAO), Victoria University of Wellington, Chatterton Astronomy Department, University of Sydney, Astronomical Observatory, Academy of Sciences, Indian Space Research Organization, Tel Aviv University (TAU), Institute of Theoretical Physics and Astronomy, Vilnius University, Vilnius University, Mount Suhora Observatory, Cracow Pedagogical University, Centrum Astronomiczne im. M. Kopernika, Warszawa (CAMK), Institut für Astronomie, Universität Wien (IfA), INAF-Osservatorio Astronomico di Capodimonte (INAF-OAC), Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, University of Tromsø, Isaac Newton Group of Telescopes, Universidade de Vigo, and University of Leicester
Subjects: 010504 meteorology & atmospheric sciences, Stellar mass, oscillations [Stars], Hidrogênio, evolution [Stars], FOS: Physical sciences, Astrophysics, Trapping, Massa estelar, 01 natural sciences, law.invention, Telescope, law, Evolucao estelar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Crystallization, individual: BPM 37093 [Stars], 010303 astronomy & astrophysics, evolution, individual, BPM 37093, interiors, stars, oscillations, white dwarfs, 0105 earth and related environmental sciences, Physics, SIMPLE (dark matter experiment), Astrophysics (astro-ph), interiors [Stars], White dwarfs, White dwarf, Astronomy and Astrophysics, Estrelas variaveis, Core (optical fiber), Anãs brancas, Pulsacoes estelares, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Interior estelar, Instability strip, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~ 1.1 M_sun) to theoretically crystallize while still inside the ZZ Ceti instability strip (T_eff ~ 12,000 K). As a consequence, this star represents our first opportunity to test crystallization theory directly. If the core is substantially crystallized, then the inner boundary for each pulsation mode will be located at the top of the solid core rather than at the center of the star, affecting mainly the average period spacing. This is distinct from the "mode trapping" caused by the stratified surface layers, which modifies the pulsation periods more selectively. In this paper we report on Whole Earth Telescope observations of BPM 37093 obtained in 1998 and 1999. Based on a simple analysis of the average period spacing we conclude that a large fraction of the total stellar mass is likely to be crystallized., Comment: 7 pages, 3 figures, 3 tables, accepted for Astronomy & Astrophysics
Published: 2005
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66. Pushing the ground-based limit : 14-$\mu$mag photometric precision with the definitive Whole Earth Telescope asteroseismic data set for the rapidly oscillating Ap star HR 1217

Author: K. Sekiguchi, R. R. Shobbrook, Antonio Kanaan, Jaymie M. Matthews, P. V. Birch, J. E. Solheim, B. N. Ashoka, L. Bigot, Paul A. Bradley, Souza Oliveira Kepler, Michael D. Reed, S. Seetha, R. L. Riddle, Denis J. Sullivan, S. D. Kawaler, T. K. Watson, Chris Cameron, O. Giovannini, M. Mueller, T. Sullivan, D. W. Kurtz, Anjum S. Mukadam, Donald E Winget, Donal O'Donoghue, Travis S. Metcalfe, F. Johannessen, V. Girish, E. Pallier, Matt A. Wood, S. J. Kleinman, Margarida S. Cunha, Santosh Joshi, Ana Ulla, Luciano Fraga, Atsuko Nitta, R. E. Nather, Staszek Zola, Joyce A. Guzik, G. Vauclair, Gerald Handler, Pawel Moskalik, J. M. Gonzalez Perez, Xiao-Jun Jiang, Nicole M. Silvestri, N. Dolez, and A. F. M. da Costa
Subjects: Physics, oscillations [stars], Frequency analysis, variables: other [stars], Astronomy, Perturbation (astronomy), Astronomy and Astrophysics, Observable, Astrophysics, law.invention, Magnetic field, Telescope, Stars, individual: HR 1217 [stars], Space and Planetary Science, law, Astrophysics::Solar and Stellar Astrophysics, Limit (mathematics), magnetic fields [stars], Rapidly oscillating Ap star
Abstract: HR 1217 is one of the best-studied rapidly oscillating Ap (roAp) stars, with a frequency spectrum of alternating even- and odd-� modes that are distorted by the presence of a strong, global magnetic field. Several recent theoretical studies have found that within the observable
Published: 2005

67. ZZ�Ceti Stars

Author: G. Vauclair
Subjects: Physics, Stars, Astrophysics
Published: 2004
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68. Observations of the Pulsating White Dwarf G 185-32

Author: J. Krzesinski, Donald E Winget, J. E. Solheim, Denis J. Sullivan, G. Vauclair, G. Pajdosz, K. Yanagida, J. C. Clemens, Antonio Kanaan, T. K. Watson, E. G. Meištas, N. Dolez, Matt A. Wood, S. J. Kleinman, S. Zola, P. Moskalik, Donal O'Donoghue, M. Chevreton, Barbara G. Castanheira, Tsevi Mazeh, Martin A. Barstow, Steven D. Kawaler, Elia M. Leibowitz, O. Giovannini, R. E. Nather, J. S. Dixson, Souza Oliveira Kepler, Detlev Koester, A. Bruvold, J. L. Provencal, Paul A. Bradley, Carl J. Hansen, D. A. H. Buckley, Michael H. Montgomery, M. Katz, Instituto de Física, Universidade Federal do Rio Grande do Sul, Centrum Astronomiczne im. M. Kopernika, Warszawa (CAMK), Mount Suhora Observatory, Cracow Pedagogical University, South African Astronomical Observatory (SAAO), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Departement d'Astrophysique Extragalactique et de Cosmologie (DAEC), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Department of Physics and Astronomy, University of Leicester, Departamento de Física, Universidade Federal de Santa Catarina, Departamento de Física e Química, Universidade de Caxias do Sul, Department of Physics and Astronomy, University of Delaware, Department of Physics and Astronomy, Iowa State University, Department of Physics, University of North Carolina, Department of Astronomy and McDonald Observatory, University of Texas, Austin, Southwestern University, University of Colorado, Joint Institute for Laboratory Astrophysics (JILA), Los Alamos National Laboratory (LANL), Department of Physics and Space Sciences and SARA Observatory, Florida Institute of Technology, Melbourne, Victoria University of Wellington, Sloan Digital Sky Survey, Apache Point Observatory, PO Box 59, Sunspot, Institute of Theoretical Physics and Astronomy, Vilnius University, Institutt for Fysikk, Universitetet i Tromsø, Tel Aviv University (TAU), Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, and Institute of Astronomy, University of Cambridge (IoA)
Subjects: oscillations [Stars], evolution [Stars], Fotometria estelar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, variables: general [Stars], law.invention, white dwarfs [Stars], Telescope, law, Evolucao estelar, individual: G 185–32 [Stars], Astrophysics::Solar and Stellar Astrophysics, Stellar evolution, Astrophysics::Galaxy Astrophysics, Physics, Faint Object Spectrograph, Astrophysics::Instrumentation and Methods for Astrophysics, White dwarf, Astronomy, Astronomy and Astrophysics, Effective temperature, Light curve, Surface gravity, Wavelength, Pulsacoes estelares, Anãs brancas, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Transformada de Fourier, Atmosferas estelares, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; We observed the pulsating hydrogen atmosphere white dwarf G 185-32 with the Whole Earth Telescope in 1992. We report on a weighted Fourier transform of the data detecting 18 periodicities in its light curve. Using the Hubble Space Telescope Faint Object Spectrograph time resolved spectroscopy, and the wavelength dependence of the relative amplitudes, we identify the spherical harmonic degree (l) for 14 pulsation signals. We also compare the determinations of effective temperature and surface gravity using the excited modes and atmospheric methods, obtaining Teff=11 960 ± 80 K, \log g=8.02 ± 0.04 and M=0.617 ± 0.024 M&sun;.
Published: 2004
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69. Preface

Author: Y. Lebreton, G. Vauclair, G. Alecian, and O. Richard
Subjects: Physics, Space and Planetary Science, Stellar physics, General Engineering, Astronomy, Astronomy and Astrophysics
Published: 2013
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70. Amplitude and frequency variability of the pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 observed with the Whole Earth Telescope

Author: G. Handler, D. O'Donoghue, M. Muller, J.- E. Solheim, J. M. Gonzalez-Perez, F. Johannessen, M. Paparo, B. Szeidl, G. Viraghalmy, R. Silvotti, G. Vauclair, N. Dolez, E. Pallier, M. Chevreton, D. W. Kurtz, G. E. Bromage, M. S. Cunha, R. Ostensen, L. Fraga, A. Kanaan, A. Amorim, O. Giovannini, S. O. Kepler, A. F. M. Da Costa, R. F. Anderson, M. A. Wood, N. Silvestri, E. W. Klumpe, R. F. Carlton, R. H. Miller, J. P. McFarland, A. D. Grauer, S. D. Kawaler, R. L. Riddle, M. D. Reed, R. E. Nather, D. E. Winget, J. A. Hill, T. S. Metcalfe, A. S. Mukadam, M. Kilic, T. K. Watson, S. J. Kleinman, A. Nitta, J. A. Guzik, P. A. Bradley, K. Sekiguchi, D. J. Sullivan, T. Sullivan, R. R. Shobbrook, X. Jiang, P. V. Birch, B. N. Ashoka, S. Seetha, V. Girish, S. Joshi, T. N. Dorokhova, N. I. Dorokhov, M. C. Akan, E. G. Meistas, R. Janulis, R. Kalytis, D. Alisauskas, S. K. Anguma, P. C. Kalebwe, P. Moskalik, W. Ogloza, G. Stachowski, G. Pajdosz, S. Zola, Ege Üniversitesi, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: 010504 meteorology & atmospheric sciences, individual: KUV 05134+2605 [Stars], oscillations [Stars], FOS: Physical sciences, Fotometria estelar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, stars : individual : KUV 05134+2605, 01 natural sciences, stars : oscillations, law.invention, Telescope, Photometry (optics), stars : individual : PG 1654+160, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, individual: PG 1654+160 [Stars], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Astrophysics (astro-ph), White dwarf, Astronomy and Astrophysics, stars : variables : other, Estrelas variaveis, variables: other [Stars], Stars, Amplitude, [SDU]Sciences of the Universe [physics], Pulsacoes estelares, Anãs brancas, Space and Planetary Science, Mode coupling, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: WOS: 000182039700036, We have acquired new time series photometry of the two pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 with the Whole Earth Telescope. Additional single-site photometry is also presented. We use all these data plus all available archival measurements to study the temporal behaviour of the pulsational amplitudes and frequencies of these stars for the first time. We demonstrate that both KUV 05134+2605 and PG 1654+160 pulsate in many modes, the amplitudes of which are variable in time; some frequency variability of PG 1654+160 is also indicated. Beating of multiple pulsation modes cannot explain our observations; the amplitude variability must therefore be intrinsic. We cannot find stable modes to be used for determinations of the evolutionary period changes of the stars. Some of the modes of PG 1654+160 appear at the same periods whenever detected. The mean spacing of these periods (approximate to40 s) suggests that they are probably caused by non-radial gravity-mode pulsations of spherical degree l = 1. If so, PG 1654+160 has a mass around 0.6 M.. The time-scales of the amplitude variability of both stars (down to two weeks) are consistent with theoretical predictions of resonant mode coupling, a conclusion which might however be affected by the temporal distribution of our data.
Published: 2003
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71. The Everchanging Pulsating White Dwarf GD358

Author: Donald E Winget, Antonio Kanaan, Encarni Romero-Colmenero, Nicole M. Silvestri, J. E. Solheim, R. E. Nather, J. Larrison, Waldemar Ogloza, Jam Shaw, R. Kalytis, T. Sullivan, Paul A. Bradley, J. Xiaojun, Thorsten Nagel, Fu J. Ning, K. Sekiguchi, A. F. M. Costa, Souza Oliveira Kepler, M. Chevreton, Staszek Zola, E. W. Klumpe, D. Sullivan, F. Johannessen, Reed Riddle, J. L. Deetjen, Steven D. Kawaler, Martha L. Boyer, Matt A. Wood, G. Vauclair, T. S. Metcalfe, R. Janulis, J. Krzesinski, E. G. Meištas, P. Martinez, A. E. Collins, A. K. Jones, S. J. Kleinman, J. E. S. Costa, Ana Ulla, T. J. Ahrens, Anjum S. Mukadam, Donal O'Donoghue, J. M. Gonzalez Perez, Atsuko Nitta, S. Dreizler, Sonja Schuh, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: oscillations [Stars], FOS: Physical sciences, evolution [Stars], Fotometria estelar, Astrophysics, 01 natural sciences, law.invention, variables: general [Stars], Telescope, white dwarfs [Stars], law, 0103 physical sciences, Stellar structure, Linear combination, 010303 astronomy & astrophysics, Multiplet, Physics, 010308 nuclear & particles physics, Astrophysics (astro-ph), Mode (statistics), White dwarf, Astronomy and Astrophysics, Pulse (physics), Estrelas variaveis, Amplitude, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Pulsacoes estelares, white dwarfs, stars: variables: general, stars: oscillations, stars: individual: GD 358, stars: evolution [stars], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], individual: GD 358 [Stars]
Abstract: We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree l=1 and radial order 8 to 20 and their linear combinations up to 6th order.We also detect, for the first time, a high amplitude l=2 mode, with a period of 796s. In the 2000 WET data, the largest amplitude modes are similar to those detected with the WET observations of 1990 and 1994, but the highest combination order previously detected was 4th order. At one point during the 1996 observations, most of the pulsation energy was transferred into the radial order k=8 mode, which displayed a sinusoidal pulse shape in spite of the large amplitude. The multiplet structure of the individual modes changes from year to year, and during the 2000 observations only the k=9 mode displays clear normal triplet structure. Even though the pulsation amplitudes change on timescales of days and years, the eigenfrequencies remain essentially the same, showing the stellar structure is not changing on any dynamical timescale., 34 pages, 14 figures, WET data, accepted to A&A
Published: 2003
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72. High Precision with the Whole Earth Telescope: Lessons and Some Results from XCov20 for the roAp Star HR 1217

Author: Michael D. Reed, R. E. Nather, R. L. Riddle, Souza Oliveira Kepler, Don Winget, S. Zola, Santosh Joshi, Joyce A. Guzik, P. V. Birch, S. D. Kawaler, E. Pallier, Pawel Moskalik, Chris Cameron, Matt A. Wood, Antonio Kanaan, Margarida S. Cunha, Jaymie M. Matthews, S. Seetha, O. Giovannini, J. E. Solheim, Ana Ulla, V. Girish, M. Mueller, Denis J. Sullivan, B. N. Ashoka, J. M. Gonzalez Perez, T. Sullivan, T. K. Watson, G. Vauclair, D. W. Kurtz, Kazuhiro Sekiguchi, Atsuko Nitta, Travis S. Metcalfe, F. Johannessen, Nicole M. Silvestri, Luciano Fraga, Donal O'Donoghue, Anjum S. Mukadam, Xiao-Jun Jiang, R. R. Shobbrook, Gerald Handler, Scot Kleinman, A. F. M. da Costa, and N. Dolez
Subjects: stars, Physics, lcsh:Astronomy, Astronomy, Astronomy and Astrophysics, Astrophysics, Star (graph theory), law.invention, lcsh:QB1-991, Telescope, Stars, HR1217, Space and Planetary Science, law, roAp stars - stars, Astrophysics::Solar and Stellar Astrophysics, individual
Abstract: HR1217 is a prototypical rapidly oscillating Ap star that has presented a test to the theory of nonradial stellar pulsation. Prior observations showed a clear pattern of five modes with alternating frequency spacings of 33.3 μHz and 34.6 μHz, with a sixth mode at a problematic spacing of 50.0 μHz (which equals 1.5 × 33.3 μHz) to the highfrequency side. Asymptotic pulsation theory allowed for a frequency spacing of 34 μHz, but hipparcos observations rule out such a spacing. Theoretical calculations of magnetoacoustic modes in Ap stars by Cunha (2001) predicted that there should be a previously undetected mode 34 μHz higher than the main group, with a smaller spacing between it and the highest one. The 20th extended coverage campaign of the Whole Earth Telescope (XCov20) has discovered this frequency as predicted by Cunha (2001). Amplitude modulation of several of the pulsation modes between the 1986 and 2000 data sets has also been discovered, while important parameters for modelling the geometry of the pulsation modes have been shown to be unchanged. With stringent selection of the best data from the WET network the amplitude spectrum shows highest peaks at only 50 μmag and formal errors on the determined amplitudes are 14 μmag. Some lessons for future use of WET for the highest precision photometry on bright stars are discussed.
Published: 2003
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73. WET Observations of the DAV G185-32

Author: Tsevi Mazeh, Paul A. Bradley, S. Zola, Don Winget, B. Pfeiffer, J. Krzesinski, A. V. Chernyshev, R. E. Nather, B. Serre, Matt A. Wood, G. Pajdosz, J. E. S. Costa, M. Chevreton, Anne E. Sansom, B. N. Ashoka, N. Dolez, Barbara G. Castanheira, Elia M. Leibowitz, J. E. Solheim, Souza Oliveira Kepler, S. D. Kawaler, J. N. Fu, T. K. Watson, S. J. Kleinman, E. G. Meištas, J. C. Clemens, Antonio Kanaan, T. M. K. Marar, Nicholas Achilleos, J.S. Yang, Judith L. Provencal, G. Vauclair, Pawel Moskalik, Juan Antonio Belmonte, Albert D. Grauer, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: stars, Physics, lcsh:Astronomy, Astrophysics::High Energy Astrophysical Phenomena, pulsations - stars, White dwarf, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, G185-32, lcsh:QB1-991, Stars, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, individual, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics::Galaxy Astrophysics
Abstract: The pulsating DAV white dwarf G185-32 was observed with the Whole Earth Telescope in 1992, during XCov8. We briefly report on the weighted Fourier transform of the data obtained.
Published: 2003
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74. A Whole Earth Telescope campaign on the pulsating subdwarf B binary system PG 1336-018 (NY Vir)

Author: P. Martinez, R. Kalytis, J. E. Solheim, Elia M. Leibowitz, T. K. Watson, M. Chevreton, B. N. Ashoka, T. Sullivan, R. S. Stobie, O. Giovannini, Xiao-Jun Jiang, Anjum S. Mukadam, S. J. Kleinman, Roberto Silvotti, Pawel Moskalik, Sonja Schuh, Ana Ulla, A. Nitta, J. L. Deetjen, Santosh Joshi, J. M. Gonzalez Perez, D. Ališauskas, D. Kilkenny, Olga Suarez, Matthew R. Burleigh, Stefan Dreizler, Waldemar Ogloza, Minia Manteiga, R. R. Shobbrook, Antonio Kanaan, Denis J. Sullivan, H. Mendelson, Steven D. Kawaler, Donal O'Donoghue, Judith L. Provencal, Souza Oliveira Kepler, Freddy Marang, Adalberto Piccioni, G. Vauclair, Michael D. Reed, E. G. Meištas, T. S. Metcalfe, R. H. Østensen, F. van Wyk, N. Dolez, S. Seetha, Staszek Zola, J. Krzesinski, P. Ibbetson, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Astrophysics::High Energy Astrophysical Phenomena, oscillations [Stars], Fotometria estelar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Asteroseismology, law.invention, Telescope, law, Astrophysics::Solar and Stellar Astrophysics, Estrelas, Binary system, Astrophysics::Galaxy Astrophysics, Physics, Astronomy, Astronomy and Astrophysics, Subdwarf, individual: PG 1336−018 [Stars], variables: other [Stars], Fotometria astronômica, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Pulsacoes estelares, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Earth (classical element)
Abstract: We present results from a multisite (‘Whole Earth Telescope’) photometric campaign on PG 1336−018, the close eclipsing binary system containing a pulsating subdwarf B (sdB) star. The main part of the campaign (1999 April) resulted in ~172 h of observations, representing a coverage of about 47 per cent, and additional data were obtained outside the core campaign. Periodogram analysis shows that the light variations are dominated by three frequencies near 5757, 5585 and 5369 μHz (~174, 179 and 186s, respectively), although many frequencies are present, particularly in the range 5000–6000 μHz (~200–170 s). We identify, with some confidence, 28 frequencies down to a semi-amplitude of 0.0005 in fractional intensity (equivalent to about 0.5 mmag). It is clear that the pulsation frequencies of PG 1336−018 have changed substantially since the 1996 discovery observations were made, and that amplitude changes occur, at least in the dominant three frequencies, on relatively short time-scales (of the order of a day). On the assumption that the pulsating star is phase-locked in the binary system, we have searched for rotational splitting of frequencies near the orbital and half of the orbital period, but the results are confused by aliasing at those frequencies (due to the data gaps caused by the eclipses). A preliminary model qualitatively matches the distribution of frequencies in PG 1336−018, with some good individual correspondences, but cannot be considered adequate because geometric cancellation should hide some of the modes which are apparently detected. Analysis of the pulsations during eclipse recovers three of the strongest modes, but the limited eclipse data – which can, at best, be only about 9 per cent of the total – do not allow mode identification at this stage. Simulations indicate that an overall coverage of about 80 per cent would be required for this to be viable. An attempt was made to determine phase shifts in the pulsation frequencies as a way of directly measuring the size of the binary orbit, but the uncertainties in the method are comparable to the light travel time across the orbit (probably less than a second).
Published: 2003
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75. DISCOVERY OF MULTIPLE PULSATIONS IN THE NEWδSCUTI STAR HD 92277: ASTEROSEISMOLOGY FROM DOME A, ANTARCTICA

Author: Xu Zhou, Xiangyan Yuan, Xuefei Gong, Jia Shu Niu, Jian-Ning Fu, Weikai Zong, Lifan Wang, Lingzhi Wang, Zong-Hong Zhu, Michael C. B. Ashley, Long-Long Feng, Xiangqun Cui, Qiang Liu, C. R. Pennypacker, Daniel M. Luong-Van, G. Vauclair, Donald G. York, Zhenxi Zhu, Stéphane Charpinet, and Jon Lawrence
Subjects: Physics, Photometry (optics), Stars, Amplitude, Space and Planetary Science, Astronomy, Astronomy and Astrophysics, Astrophysics, Visible radiation, Effective temperature, Light curve, Linear combination, Asteroseismology
Abstract: We report the discovery of low-amplitude oscillations in the star HD 92277 from long, continuous observations in the r and g bands using the CSTAR telescopes in Antarctica. A total of more than 1950 hours of high-quality light curves were used to categorize HD 92277 as a new member of the delta Scuti class. We have detected 21 (20 frequencies are independent and one is the linear combination) and 14 (13 frequencies are independent and one is the linear combination) pulsation frequencies in the r and g bands, respectively, indicating a multi-periodic pulsation behavior. The primary frequency f(1) = 10.810 days(-1) corresponds to a period of 0.0925 days and is an l = 1 mode. We estimate a B - V index of 0.39 and derive an effective temperature of 6800 K for HD 92277. We conclude that long, continuous and uninterrupted time-series photometry can be performed from Dome A, Antarctica, and that this is especially valuable for asteroseismology where multi-color observations (often not available from space-based telescopes) assist with mode identification.
Published: 2015
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76. Time-frequency analysis and observation synthesis of non-radial oscillations of white dwarfs

Author: G. Vauclair, B. Pfeiffer, Pierre Maréchal, B. Serre, A. Lannes, and S. Rogues
Subjects: symbols.namesake, Fourier transform, Fourier analysis, symbols, Calculus, Deconvolution, Inverse problem, Regularization (mathematics), Algorithm, Matching pursuit, Complement (set theory), Mathematics, Interpolation
Abstract: We reconstruct temporal spectra obtained from incomplete light-curve records of white dwarfs. The regularization of the corresponding inverse problem refers to band-limited interpolation and matching pursuit. A crucial point is the choice of the frequency support of the deconvolution. We show that matching pursuit, used as a complement to Fourier analysis, is a powerful tool for discriminating these supports. We illustrate this study with an example and discuss its degree of confidence by comparing it with the CLEAN deconvolution technique and with results provided by a more complete set of observations. >
Published: 2002
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77. Asteroseismology of RXJ 2117+3412, the hottest pulsating PG 1159 star

Author: Carl J. Hansen, S. Y. Jiang, J. N. Fu, J. E. Solheim, Judith L. Provencal, Souza Oliveira Kepler, Elia M. Leibowitz, Pawel Moskalik, M. S. O'Brien, K. Yanagida, O. Giovannini, S. Hemar, Tsevi Mazeh, T. K. Watson, A. Bruvold, B. Pfeiffer, A. V. Chernyshev, E. W. Klumpe, N. Dolez, M. Chevreton, Anne E. Sansom, B. N. Ashoka, R. E. Nather, G. Pajdosz, J. S. Dixson, J. C. Clemens, Antonio Kanaan, T. M. K. Marar, G. Vauclair, E. G. Meištas, B. Serre, Albert D. Grauer, Donald E Winget, Martin A. Barstow, Steven D. Kawaler, Nicholas Achilleos, J. A. Belmonte, A. Nitta Kleinman, Paul A. Bradley, S. J. Kleinman, Staszek Zola, J. Krzesinski, Michael H. Montgomery, Matt A. Wood, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Physics, Nebulosas planetarias, individual (RXJ 2117+3412) [Stars], oscillations [Stars], Processos internos estelares, Astronomy, Astronomy and Astrophysics, Fotometria estelar, Astrophysics, Star (graph theory), Massa estelar, Asteroseismology, fundamental parameters [Stars], Estrelas variaveis, Rotacao estelar, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Pulsacoes estelares, Anãs brancas, Estrelas, Ventos estelares, Material circum-estelar, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The pulsating PG 1159 planetary nebula central star RXJ 2117+3412 has been observed over three successive seasons of a multisite photometric campaign. The asteroseismological analysis of the data, based on the 37 identified l = 1 modes among the 48 independent pulsation frequencies detected in the power spectrum, leads to the derivation of the rotational splitting, the period spacing and the mode trapping cycle and amplitude, from which a number of fundamental parameters can be deduced. The average rotation period is 1.16 ± 0.05 days. The trend for the rotational splitting to decrease with increasing periods is incompatible with a solid body rotation. The total mass is 0.56⁺⁰˙⁰²₋₀.₀₄ Mѳ and the He-rich envelope mass fraction is in the range 0.013–0.078 M*. The luminosity derived from asteroseismology is log(L/Lѳ) = 4.05⁺⁰˙²³₋₀.₃₂ and the distance 760⁺²³⁰₋₂₃₅ pc. At such a distance, the linear size of the planetary nebulae is 2.9 ± 0.9 pc. The role of mass loss on the excitation mechanism and its consequence on the amplitude variations is discussed.
Published: 2002
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78. Asteroseismology of the DBV White Dwarf GD 358 with the Whole Earth Telescope

Author: Judith L. Provencal, M. Candy, D.A. Buckleys, P. V. Birch, Pierre Bergeron, Carl J. Hansen, B. N. Ashoka, J. S. Dixson, S. J. Kleinman, G. Vauclair, Souza Oliveira Kepler, Matt A. Wood, A. D. Grauer, T. Augusteijn, Don Winget, D. O'Donoghue, M. Chevreton, Brian Warner, Paul A. Bradley, Chuck Claver, J. C. Clemens, Antonio Kanaan, T. M. K. Marar, R. E. Nather, P. Tripe, N. Doleza, Elia M. Leibowitz, B. P. Hine, and S. Seetha
Subjects: Physics, Stellar mass, Astronomy, White dwarf, Astrophysics, Light curve, Asteroseismology, law.invention, Telescope, symbols.namesake, Fourier transform, law, symbols, Stellar evolution, Earth (classical element)
Abstract: We report the analysis of 154 hours of nearly continuous high-speed photometric data on the pulsating DB white dwarf (DBV) GD 358 obtained during the Whole Earth Telescope (WET) run of May 1990. The Fourier transform (FT) of the light curve is dominated by power in the range from 1200 – 1700μHz with more than 180 significant peaks in the total transform. We also see significant power at the sums and differences of the dominant frequencies, indicating the importance of nonlinear behavior. We can use this data to obtain an accurate total stellar mass, and surface He layer mass. The implied surface He layer mass, if correct, provides a significant and surprising challenge to stellar evolution theory, as well as the theory of chemical mixing.
Published: 1993
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79. Nonradial Pulsations of the DA Type White Dwarf Star G 255-2

Author: J.-N. Fu, S. Y. Jiang, N. Dolez, M. Chevreton, G. Vauclair, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Subjects: Physics, Astronomy, White dwarf, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Blue dwarf
Abstract: Photometric data obtained on the DA type white dwarf star G255-2 between 1991 and 1997 were reduced and the pulsation spectrum was explored with the standard process. The further analysis provides 10 normal, probably l = 1, independent nonradial eigenmodes.
Published: 2001

80. Convection and the ZZ Ceti Instability Strip

Author: G. Vauclair and D. Koester
Subjects: Physics, Convection, Convection zone, Scale height, Mechanics, Edge (geometry), Instability strip, Surface gravity, Mixing (physics), Energy transport
Abstract: Theoretical predictions of the ZZ Ceti instability strip (Bradley and Winget 1994; Brassard et al. as cited in Bergeron et al. 1995 (B95)) have found a very strong dependence of the blue edge on the assumed efficiency of the convective energy transport. Convection is usually described within the framework of the mixing length approximation (MLT); in the following we will use the nomenclature introduced by Fontaine et al. (1981) and Koester et al. (1994), where ML1/α=1.5 stands for a specific choice of the parameters a,b,c and a ratio of mixing length over presure scale height of 1.5.
Published: 1997
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81. Asteroseismology of White Dwarf Stars

Author: G. Vauclair
Published: 1997
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82. Discovery of Two New ZZ Ceti Variables

Author: G. Vauclair, J. N. Fu, M. Chevreton, and N. Dolez
Subjects: Data mining, computer.software_genre, computer, Selection (genetic algorithm), Mathematics
Abstract: We report the discovery of two new pulsating DA variables. The candidates have been selected from the KISO survey (Nogushi et al. 1980). The selection has been based on the color indices of the objects.
Published: 1997
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83. The blue edge of the ZZ Ceti instability strip

Author: G. Vauclair, Nicole F. Allard, and Detlev Koester
Subjects: Physics, Synthetic spectrum, White dwarf, Astrophysics, Edge (geometry), Instability strip
Published: 1995
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84. From Planetary Nebulae to White Dwarfs: Constraints from the Asteroseismology of the Pulsating Planetary Nebula Central Star RXJ 2117+3412

Author: G. Vauclair and P. Moskalik
Subjects: Physics, Emission nebula, Reflection nebula, White dwarf, Astronomy, Astrophysics, Star (graph theory), Planetary nebula, Asteroseismology, Protoplanetary nebula
Abstract: We summarize the results of an asteroseismological study of the pulsating planetary nebula central star RXJ 2117+3412.
Published: 2002
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85. Observation of a Variable, ZZ Ceti White Dwarf: GD154

Author: B. Pfeiffer, G. Vauclair, N. Dolez, M. Chevreton, J. R. Fremy, G. Herpe, M. Barstow, S. J. Kleinman, T. K. Watson, J. A. Belmonte, S. O. Kepler, A. Kan-Aan, O. Giovannini, R. E. Nather, D. E. Winget, J. Provencal, J. C. Clemens, P. Bradley, J. Dixson, A. D. Grauer, G. Fontaine, P. Bergeron, F. Wesemael, C. F. Claver, T. Matzeh, E. Leibowitz, and P. Moskalik
Published: 1993
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86. Whole Earth Telescope Observations of the DBV White Dwarf PG1115+158: Preliminary Results

Author: D. Sullivan, T. M. K. Marar, Elia M. Leibowitz, B. N. Ashoka, Don Winget, Lilia Ferrario, A. Chen, S. Seetha, S. J. Kleinman, D. A. H. Buckley, J. S. Dixon, H. Mendelson, J. C. Clemens, Matt A. Wood, Antonio Kanaan, J. R. Fremy, Dayal Wickramasinghe, Souza Oliveira Kepler, Paul A. Bradley, G. Vauclair, R. E. Nather, D. O'Donoghue, Judith L. Provencal, M. Chevreton, Staszek Zola, Martin A. Barstow, J. Krzesinski, G. Odilon, Pawel Moskalik, and Chuck Claver
Subjects: Physics, Period (periodic table), White dwarf, chemistry.chemical_element, Astronomy, Astrophysics, Rotation, law.invention, Telescope, symbols.namesake, Fourier transform, chemistry, law, symbols, Astrophysics::Earth and Planetary Astrophysics, Multiplet, Helium, Earth (classical element)
Abstract: We present preliminary results from Whole Earth Telescope (WET) data on the DBV star PG1115+158. In the Fourier Transform of this data, we have tentatively identified peaks arranged in multiplets with common frequency splitting. The average period spacing between these multiplets is ~ 40s, very similar to the multiplet spacing found in the DBV GD358. Theoretical models show l = 1 modes with ~ 40s period spacing between modes of consecutive k for white dwarfs with niasses near 0.6M ⊙. If we assume the identified multiplets are l = 1 modes, then the rotation rate of the star is 0.45 days. Furthermore, the deviations of the period spacing between modes from the mean period spacing indicates that, like GD358, the surface Helium layer is thin, less than 10-4 M *.
Published: 1993
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87. Surveys and the Discovery of New Variable White Dwarfs

Author: D. Homeier, G. Vauclair, N. Dolez, Fu Jian Ning, Detlev Koester, and M. Chevreton
Subjects: Physics, Variable (computer science), Astronomy, White dwarf
Abstract: We report the discovery of a new variable DA white dwarf (ZZ Ceti): PG1541+650, identified as a potential ZZ Ceti candidate in the Hamburg Quasar Survey.
Published: 2000
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88. Frequency variations in the PG 1159 pulsator PG 0122+200

Author: G. Vauclair and Jian-Ning Fu
Subjects: Physics, History, Amplitude, Scale (descriptive set theory), Astrophysics, Time variations, Neutrino, Rotation, Nonlinear coupling, Cooling time, Computer Science Applications, Education
Abstract: PG 0122+200 is the coolest PG 1159 pulsator. On theoretical basis, its cooling time scale was predicted to be dominated by neutrino emission. The measurement of the frequency variation (or P) for a number of its pulsation modes would then provide an empirical estimate of the yet uncertain neutrino emission rate. To test this prediction, we reanalysed the time-series obtained during the seven observing campaigns spanning a time interval of 19 years. We determine the time variations for the seven largest amplitude modes. This includes two complete triplets and one component of a third triplet. We find that PG 0122+200 exhibits much larger frequency variations and on considerably shorter time scales than the ones predicted by cooling theory. We suggest that these variations are not dominated by the star cooling but instead by nonlinear coupling induced by rotation.
Published: 2009
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89. A Measurement of the Evolutionary Timescale of the Cool White Dwarf G117-B15A with Wet

Author: F. Wesemael, A. D. Grauer, Elia M. Leibowitz, J. C. Clemens, R. E. Nather, Antonio Kanaan, Matt A. Wood, J. E. Solheim, Souza Oliveira Kepler, Pierre Bergeron, N. Dolez, B. P. Hine, B. N. Ashoka, S. J. Kleinman, P.-I. Emanuelsen, Gilles Fontaine, S. Seetha, Don Winget, G. Vauclair, T. M. K. Marar, Chuck Claver, Judith L. Provencal, R. W. Tweedy, Tsevi Mazeh, M. Chevreton, Martin A. Barstow, Paul A. Bradley, and Anne E. Sansom
Subjects: Physics, White dwarf, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Light curve, law.invention, Telescope, Cooling rate, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Blue dwarf, Stellar evolution, Astrophysics::Galaxy Astrophysics
Abstract: We have measured the cooling rate of the 13,000K DA white dwarf G117-B15A by measuring the rate of period change with time for the main pulsation of this ZZ Ceti star, using the Whole Earth Telescope. The observed rate of period change is larger than the predictions of g-mode pulsation theory applied to C/O core white dwarf models.
Published: 1991
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90. Atmospheric Parameters for DA White Dwarfs in the Vicinity of the ZZ Ceti Instability Strip

Author: Detlev Koester, N. Dolez, and G. Vauclair
Subjects: Physics, Gravity (chemistry), medicine.diagnostic_test, Spectrophotometry, Convective mixing, medicine, White dwarf, Astronomy, Astrophysics, Effective temperature, Instability strip, Surface gravity
Abstract: A sample of DA white dwarfs whose high S/N spectrophotometry has been obtained at the Palomar 5m telescope is analysed with a grid of model atmospheres. Atmospheric parameters are derived for 38 DA. A tendancy to increased log g with decreasing temperature is found. This does support the conclusion that the apparent increase in gravity is due to the increased He abundance in cool DA produced by convective mixing. The presence of a few nonpulsating DA in the ZZ Ceti instability strip is discussed.
Published: 1991
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91. Whole Earth Telescope Observations of the Interacting White Dwarf Binary System AM CVn: First Results

Author: Pierre Bergeron, S. J. Kleinman, B. N. Ashoka, G. Vauclair, Chuck Claver, Tsevi Mazeh, Gilles Fontaine, P.-I. Emanuelsen, Elia M. Leibowitz, Albert D. Grauer, N. Dolez, Anne E. Sansom, Paul A. Bradley, J. E. Solheim, T. M. K. Marar, Souza Oliveira Kepler, Don Winget, Judith L. Provencal, R. E. Nather, R. W. Tweedy, S. Seetha, M. Chevreton, J. C. Clemens, Antonio Kanaan, Martin A. Barstow, and B. P. Hine
Subjects: Telescope, Physics, law, Harmonics, Astronomy, White dwarf, Astrophysics, Binary system, Fourier spectrum, Light curve, Earth (classical element), law.invention
Abstract: We report the first results of the Whole Earth Telescope observations of AM CVn in March/April 1990. The Fourier Spectrum of the light curve shows harmonically related peaks. High frequency sidebands with the fine-splitting of 21 µHz are observed for the fundamental period of 1051 s and its 4 lowest harmonics. These have not been observed before. The fundamental period itself is not detected.
Published: 1991
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92. Introduction

Author: G. Vauclair and E. G. Meištas
Subjects: Telescope, Engineering, Space and Planetary Science, law, business.industry, Astronomy, QB1-991, Astronomy and Astrophysics, Earth (chemistry), business, Archaeology, law.invention
Published: 2000
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93. 两颗新的DA型脉动白矮星的光度变化

Author: N., Dolez, primary, G., Vauclair, additional, 傅, 建宁, additional, and J., Fremy, additional
Published: 1997
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94. Whole Earth Telescope Observations and Seismological Analysis of the Pre--White Dwarf PG 2131+066

Author: J. S. Dixson, Souza Oliveira Kepler, G. Vauclair, A. Bruvold, Matt A. Wood, D. O'Donoghue, Martin A. Barstow, O. Giovannini, Staszek Zola, G. Pajdosz, Steven D. Kawaler, Carl J. Hansen, J. C. Clemens, Judith L. Provencal, Jurek Krzesinski, Antonio Kanaan, P. Moskalik, Elia M. Leibowitz, S. J. Kleinman, N. Dolez, J.-E. Solheim, M. Katz, K. Yanagida, Donald E Winget, E. G. Meištas, Paul A. Bradley, R. E. Nather, Denis J. Sullivan, M. Chevreton, M. S. O'Brien, and T. K. Watson
Subjects: Physics, Telescope, Stars, Space and Planetary Science, law, White dwarf, Astronomy, Astronomy and Astrophysics, Astrophysics, Earth (classical element), law.invention
Published: 1995
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95. Whole Earth Telescope Observations of the DAV White Dwarf G226-29

Author: O. Giovannini, S. Seetha, Staszek Zola, Matt A. Wood, J. E. Solheim, T. M. K. Marar, G. Vauclair, R. E. Nather, P. I. Emanuelsen, S. J. Kleinman, Lilia Ferrario, Tsevi Mazeh, Chuck Claver, B. N. Ashoka, Denis J. Sullivan, Martin A. Barstow, K. Yanagida, A. L. Chen, T. K. Watson, H. Mendelson, Kevin Krisciunas, David A. H. Buckley, G. Pajdosz, Judith L. Provencal, J. R. Fremy, N. Dolez, R. W. Tweedy, Jurek Krzesinski, M. Chevreton, Anne E. Sansom, J. C. Clemens, Antonio Kanaan, A. van der Peet, Donald E Winget, Souza Oliveira Kepler, Paul A. Bradley, P. Moskalik, Elia M. Leibowitz, and Dayal Wickramasinghe
Subjects: Physics, Telescope, Stars, Space and Planetary Science, law, White dwarf, Astronomy, Astronomy and Astrophysics, Spectral analysis, Astrophysics, Rotation, Earth (classical element), law.invention
Published: 1995
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96. The unusual helium variable AM Canum Venaticorum

Author: Matt A. Wood, Chuck Claver, S. Seetha, Carl J. Hansen, Judith L. Provencal, Elia M. Leibowitz, Martin A. Barstow, T. M. K. Marar, G. Vauclair, R. E. Nather, Gilles Fontaine, J. C. Clemens, Antonio Kanaan, Souza Oliveira Kepler, R. W. Tweedy, A. Bruvold, J.-E. Solheim, E. G. Meištas, Paul A. Bradley, Pierre Bergeron, B. N. Ashoka, Edward L. Robinson, S. J. Kleinman, N. Dolez, M. Chevreton, Anne E. Sansom, A. D. Grauer, and Donald E Winget
Subjects: Physics, Stars, Amplitude, Space and Planetary Science, Stellar atmosphere, White dwarf, Astronomy, Astronomy and Astrophysics, Stellar structure, Astrophysics, Variable star, Mass ratio, Stellar evolution
Abstract: The unusual variable star AM CVn has puzzled astronomers for over 40 years. This object, both a photometric and spectroscopic variable, is believed to contain a pair of hydrogen-deficient white dwarfs of extreme mass ratio, transferring material via an accretion disk. We examine the photometric properties of AM CVn, analyzing 289 hours of high-speed photometric data spanning 1976 to 1992. The power spectrum displays significant peaks at 988.7, 1248.8, 1902.5, 2853.8, 3805.2, 4756.5, and 5707.8 microHz (1011.4, 800.8, 525.6, 350.4, 262.8, 210.2, and 175.2 s). We find no detectable power at 951.3 microHz (1051 s), the previously reported main frequency. The 1902.5, 2853.9, and 3805.2 microHz peaks are multiplets, with frequency splitting in each case of 20.77 +/- 0.05 microHz. The 1902.5 microHz seasonal pulse shapes are identical, within measurement noise, and maintain the same amplitude and phase as a function of color. We have determined the dominant frequency to be 1902.50902 +/- 0.00001 microHz with dot P = +1.71 (+/- 0.04) x 10(exp -11) s/s. We discuss the implications of these findings on a model for AM CVn.
Published: 1995
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97. Photospheric, circumstellar, and interstellar features of HE, C, N. O, and SI in the HST spectra of four hot white dwarf stars

Author: Jay B. Holberg, Harry L. Shipman, Judith L. Provencal, R. W. Tweedy, Edward M. Sion, F. Wesemael, S. Roby, Gilles Fontaine, David S. Finley, Frederick C. Bruhweiler, J. A. Nousek, Martin A. Barstow, and G. Vauclair
Subjects: Physics, Photosphere, Stellar atmosphere, White dwarf, Astronomy, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Accretion (astrophysics), Spectral line, Radial velocity, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Emission spectrum, Astrophysics::Galaxy Astrophysics, Line (formation)
Abstract: This paper reports on the observations of four hot white dwarf stars with the spectrographs on the Hubble Space Telescope (HST). The higher resolving power and higher signal/noise, in comparison with IUE, reveals a very rich phenomomenology, including photospheric features from heavy elements, circumstellar features, and the first direct detection of accretion onto the white dwarf component of a binary system. Specific results include the following: Our observations of the ultrahot degenerate H1504+65 confirm that it has a photosphere which is depleted in both H and He, and reveals features of C IV and O VI. The spectrum fits previously published models extremely well. The intermediate-temperature DO star PG 1034+001 has an ultraviolet spectrum showing complex profiles of the well-known resonance doublets of C IV, N v, and Si IV. The O V 1371 line shows a clear separation into a photospheric and a circumstellar component, and it is likely that the same two components can explain the other lines as well. The cooler DA star GD 394 has an extensive system of heavy-element features, but their radial velocity is such that it is highly unlikely that they are formed in the stellar photosphere. Time-resolved spectra of the accreting white dwarf in the V 471 Tau binary system are briefly presented here; they do show the presence of C IV, Si IV, and He II. However, the C IV and He II lines are in emission, rather than in aborption as had been expected.
Published: 1995
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98. Observational limits on companions to G29-38

Author: Souza Oliveira Kepler, Matt A. Wood, N. Dolez, R. E. Nather, M. Chevreton, Carl J. Hansen, K. Yanagida, O. Giovannini, J. S. Dixson, Chuck Claver, T. K. Watson, G. Vauclair, Donald E Winget, E. G. Meištas, M. Katz, G. Pajdosz, Steven D. Kawaler, Jurek Krzesinski, Paul A. Bradley, J. C. Clemens, Antonio Kanaan, A. Bruvold, Denis J. Sullivan, Judith L. Provencal, J.-E. Solheim, P. Moskalik, Elia M. Leibowitz, S. J. Kleinman, Staszek Zola, D. O'Donoghue, and Martin A. Barstow
Subjects: Physics, Space and Planetary Science, Astronomy, Astronomy and Astrophysics, Observational study
Published: 1994
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99. Whole earth telescope observations of the DBV white dwarf GD 358

Author: Elia M. Leibowitz, Albert D. Grauer, B. N. Ashoka, R. E. Nather, Brian Warner, J. S. Dixson, T. M. K. Marar, G. Vauclair, Carl J. Hansen, P. Birch, P. Tripe, Donald E Winget, S. Seetha, Paul A. Bradley, N. Dolez, J. C. Clemens, Antonio Kanaan, Matt A. Wood, T. Serre, T. Augusteijn, M. Chevreton, Judith L. Provencal, Chuck Claver, M. Candy, Michael H. Montgomery, Souza Oliveira Kepler, Pierre Bergeron, S. J. Kleinman, B. P. Hine, R. Garrido, David A. H. Buckley, and D. O'Donoghue
Subjects: Physics, Solar mass, Stellar mass, Stellar rotation, Stellar atmosphere, White dwarf, Astronomy, Astronomy and Astrophysics, Astrophysics, Light curve, Astronomical spectroscopy, Photometry (optics), Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract: We report on the analysis of 154 hours of early continuous high-speed photometry on the pulsating DB white dwarf (DBV) GD 358, obtained during the Whole Earth Telescope (WET) run of 1990 May. The power spectrum of the light curve is dominated by power in the range from 1000 to 2400 microHz with more than 180 significant peaks in the total spectrum. We identify all of the triplet frequencies as degree l = 1, and from the details of their spacings we derive the total stellar mass as 0.61 + or - 0.03 solar mass, the mass of the outer helium envelope as 2.0 + or - 1.0 x 10(exp -6) M(sub *), the absolute luminosity as 0.050 + or - 0.012 solar luminosity and the distance as 42 + or - 3 pc. We find strong evidence for differential rotation in the radial direction -- the outer envelope is rotating at least 1.8 times faster than the core -- and we detect the presence of a weak magnetic field with a strength of 1300 + or - 300 G. We also find a significant power at the sums and differences of the dominant frequencies, indicating nonlinear processes are significant, but they have a richness and complexity that rules out resonant mode coupling as a major cause.
Published: 1994
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100. High-speed photometric observations of the pulsating DA white dwarf GD 165

Author: Chuck Claver, Judith L. Provencal, Pierre Brassard, M. Candy, P. Birch, Gilles Fontaine, R. E. Nather, D. A. H. Buckley, P. Tripe, Robert Lamontagne, John T. McGraw, G. Vauclair, Pierre Bergeron, Donald E Winget, T. Augusteijn, S. J. Kleinman, Souza Oliveira Kepler, J. C. Clemens, Antonio Kanaan, Paul A. Bradley, and F. Wesemael
Subjects: Physics, Astronomy, White dwarf, Astronomy and Astrophysics, Astrophysics, Light curve, law.invention, Telescope, Photometry (optics), symbols.namesake, Observacoes astronomicas, Slow rotation, Space and Planetary Science, law, Fourier analysis, Temporal resolution, symbols, Astrophysics::Solar and Stellar Astrophysics, Astrofisica estelar, Harmonic oscillator
Abstract: New high-speed photometric observations ofthe pulsating DA white dwarfGD 165 are presented. The Fourier spectrum ofthe light curve ofGD 165 exhibits two main regions ofpower at 120 and 193 s. The presence of a high-amplitude long period mode near ~1800 s reported by Bergeron and McGraw is not confirmed by these new observations. Light curves obtained with the Canada-France-Hawaii Telescope reveal previously undetected low-amplitude harmonic oscillations. Observations with the Whole Earth Telescope are used to resolve the two principal regions of power. The 120 and 193 s peaks are shown to be multiplets composed of at least three, and possibly tive frequency components. The most likely explanation is that these two peaks correspond to nonradial gravity modes with different values of the radial order k and with I= 1 or 2 split into 21+1 components by slow rotation. The frequency differences observed between the three dominant components of each peak are consistent with equal spacing, but a slight asymmetry in spacing cannot be totally ruled out at this stage. They suggest a rotation time scale of the order of 4.2 days. Within a peak, power is not distributed evenly or symmetrically among the three frequency components, particularly for the 193 s mode. Consequently, a simple interpretation in terms of geometric effects (inclination of the pulsation axis with respect to the line of sight) cannot be invoked here. The tentative identification of modes with l=1 or 2 is used to constrain the hydrogen layer mass in GD 165. In particular, the 120 s pulsation mode has a period sufficiently short that useful limits can be derived on this quantity. Using recent adiabatic pulsation calculations and new determinations of the atmospheric parameters of GD 165, it is found that ..(H)/*~>10-3.7 or~>10-6.4 if the 120 s pulsation is a mode with l=1 or 2, respectively.
Published: 1993
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