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1. Precise determination of stellar parameters of the ZZ Ceti and DAZ white dwarf GD 133 through asteroseismology

Author: C. Li, Hubiao Niu, N. Dolez, L. Fox Machado, Jian-Ning Fu, Hui-Fang Xue, Yan Li, G. Vauclair, S. L. Kim, Ali Esamdin, Jie Su, Raul Michel, Lu Ma, M. Alvarez, Jinzhong Liu, T. Q. Cang, François Colas, Xiao-Jun Jiang, Institut de recherche en astrophysique et planétologie (IRAP), 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), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Rotation period, Physics, Planetesimal, 010308 nuclear & particles physics, FOS: Physical sciences, stars:evolution, White dwarf, Astronomy and Astrophysics, Gravitational interaction, Astrophysics, 01 natural sciences, Asteroseismology, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Planet, 0103 physical sciences, Tidal force, stars: individual: GD 133, stars: oscillations, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), white dwarfs
Abstract: An increasing number of white dwarf stars show atmospheric chemical composition polluted by heavy elements accreted from debris disk material. The existence of such debris disks strongly suggests the presence of one or more planet(s) whose gravitational interaction with rocky planetesimals is responsible for their disruption by tidal effect. The ZZ Ceti pulsator and polluted DAZ white dwarf GD 133 is a good candidate for searching for such a potential planet. We started in 2011 a photometric follow-up of its pulsations. As a result of this work in progress, we used the data gathered from 2011 to 2015 to make an asteroseismological analysis of GD 133, providing the star parameters from a best fit model with $M$/$M_{\odot}$ = 0.630 $\pm$ 0.002, $T_{\rm eff}$ = 12400 K $\pm$ 70 K, log($M_{\rm He}/M$) = -2.00 $\pm$ 0.02, log($M_{\rm H}/M$) = -4.50 $\pm$ 0.02 and determining a rotation period of $\approx$ 7 days., 10 pages, 13 figures, accepted by MNRAS
Published: 2019
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2. Asteroseismology of the ZZ Ceti star KUV 08368+4026

Author: Jian-Ning Fu, Raul Michel, L. Fox-Machado, Emanuele Bertone, Miguel Chavez, Chunhui Li, G. Vauclair, and N. Dolez
Subjects: Physics, Rotation period, Stellar mass, White dwarf, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Star (graph theory), Asteroseismology, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Instability strip, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Data reduction
Abstract: Asteroseismology is a unique tool to explore the internal structure of stars through both observational and theoretical research. The internal structure of pulsating hydrogen shell white dwarfs (ZZ Ceti stars) detected by asteroseismology is regarded as the representative of all DA white dwarfs. Observations for KUV~08368+4026, which locates in the middle of the ZZ Ceti instability strip, have been carried out in 1999 and from 2009 to 2012 with either single-site runs or multisite campaigns. Time-series photometric data of about 300 hours were collected in total. Through data reduction and analysis, 30 frequencies were extracted, including four triplets, two doublets, one single mode and further signals. The independent modes are identified as either l=1 or l=2 modes. Hence, a rotation period of $5.52\pm 0.22$ days was deduced from the period spacing in the multiplets. Theoretical static models were built and a best fit model for KUV~08368+4026 was obtained with $0.692\pm0.002$ solar mass, $(2.92\pm0.02)\times 10^{-3}$ solar luminosity and the hydrogen mass fraction of $10^{-4}$ stellar mass., 9 pages, 7 figures
Published: 2017

3. Importance of fingering convection for accreting white dwarfs in the framework of full evolutionary calculations: the case of the hydrogen-rich white dwarfs GD133 and G29-38

Author: F. C. Wachlin, G. Vauclair, Sylvie Vauclair, Leandro Gabriel Althaus, Institut de recherche en astrophysique et planétologie (IRAP), 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), 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, Planetesimal, Ciencias Astronómicas, stars: abundances, Ciencias Físicas, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: interiors, 01 natural sciences, Instability, Evolution of stars, purl.org/becyt/ford/1 [https], accretion, Mixing length model, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, Abundances, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, white dwarfs, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, accretion disks, White dwarf, White dwarfs, Astronomy and Astrophysics, purl.org/becyt/ford/1.3 [https], Accretion (astrophysics), Astronomía, Interior stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, instabilities, [SDU]Sciences of the Universe [physics], Instabilities, Accretion disks, Astrophysics::Earth and Planetary Astrophysics, CIENCIAS NATURALES Y EXACTAS
Abstract: Context. A large fraction of white dwarfs show photospheric chemical composition that is polluted by heavy elements accreted from a debris disk. Such debris disks result from the tidal disruption of rocky planetesimals that have survived to whole stellar evolution from the main sequence to the final white dwarf stage. Determining the accretion rate of this material is an important step toward estimating the mass of the planetesimals and understanding the ultimate fate of the planetary systems. Aims. The accretion of heavy material with a mean molecular weight, μ, higher than the mean molecular weight of the white dwarf outer layers, induces a double-diffusive instability producing the fingering convection and an extra-mixing. As a result, the accreted material is diluted deep into the star. We explore the effect of this extra-mixing on the abundance evolution of Mg, O, Ca, Fe and Si in the cases of the two well-studied polluted DAZ white dwarfs: GD 133 and G 29-38. Methods. We performed numerical simulations of the accretion of material that has a chemical composition similar to the bulk Earth composition. We assumed a continuous and uniform accretion and considered a range of accretion rates from 104 g/s to 1010 g/s. Two cases are simulated, one using the standard mixing length theory (MLT) and one including the double-diffusive instability (fingering convection). Results. The double-diffusive instability develops on a very short timescale. The surface abundance rapidly reaches a stationary value while the depth of the zone mixed by the fingering convection increases. In the case of GD 133, the accretion rate needed to reproduce the observed abundances exceeds by more than two orders of magnitude the rate estimated by neglecting the fingering convection. In the case of G 29-38 the needed accretion rate is increased by approximately 1.7 dex. Conclusions. Our numerical simulations of the accretion of heavy elements on the hydrogen-rich white dwarf GD 133 and G 29-38 show that fingering convection is an efficient mechanism to mix the accreted material deeply. We find that when fingering convection is taken into account, accretion rates higher by 1.7 to 2 dex than those inferred from the standard MLT are needed to reproduce the abundances observed in G 29-38 and GD 133., Instituto de Astrofísica de La Plata
Published: 2017
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4. Asteroseismology of the exoplanet-host F-type star 94 Ceti: Impact of atomic diffusion on the stellar parameters

Author: M. E. Escobar, Olivier Richard, Morgan Deal, A. Hui-Bon-Hoa, G. Vauclair, Sylvie Vauclair, Laboratoire Univers et Particules de Montpellier (LUPM), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), Comisión Nacional de Investigación Científica y Tecnológica [CONICYT], Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), 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), 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: FOS: Physical sciences, Context (language use), Astrophysics, asteroseismology, Star (graph theory), 01 natural sciences, Asteroseismology, Planet, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, stars: evolution, 010306 general physics, 010303 astronomy & astrophysics, planetary systems, Solar and Stellar Astrophysics (astro-ph.SR), Earth and Planetary Astrophysics (astro-ph.EP), Physics, diffusion, Astronomy and Astrophysics, Exoplanet, Radial velocity, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, instabilities, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Earth and Planetary Astrophysics
Abstract: A precision of order one percent is needed on the parameters of exoplanet-hosts stars in order to correctly characterize the planets themselves. This will be achieved by asteroseismology. It is important in this context to test the influence on the derived parameters of introducing atomic diffusion with radiative accelerations in the models. In this paper, we begin this study with the case of the star 94 Ceti A. We performed a complete asteroseismic analysis of the exoplanet-host F-type star 94 Ceti A, from the first radial-velocity observations with HARPS up to the final computed best models. This star is hot enough to suffer from important effects of atomic diffusion, including radiative accelerations. We tested the influence of such effects on the computed frequencies and on the determined stellar parameters. We also tested the effect of including a complete atmosphere in the stellar models. The radial velocity observations were done with HARPS in 2007. The low degree modes were derived and identified using classical methods and compared with the results obtained from stellar models computed with the Toulouse Geneva Evolution Code (TGEC). We obtained precise parameters for the star 94 Ceti A. We showed that including atomic diffusion with radiative accelerations can modify the age by a few percents, whereas adding a complete atmosphere does not change the results by more than one percent., 7 pages, 6 figures, accepted for publication in A&A
Published: 2017
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5. Asteroseismology of the ZZ Ceti and DAZ GD133

Author: Jie Su, Jian-Ning Fu, and G. Vauclair
Subjects: Physics, Debris disk, Planetesimal, 010504 meteorology & atmospheric sciences, QC1-999, White dwarf, Astrophysics, Radius, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, Planet, 0103 physical sciences, Orbital motion, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Instability strip, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract: GD 133 is a DAZ white dwarf with an atmosphere polluted by heavy elements accreted from a debris disk, which is formed by the disruption of rocky planetesimals with orbits bringing them at the white dwarf tidal radius. To reach such orbits implies the potential presence of a perturbing planet. GD 133 is a ZZ Ceti pulsator close to the blue edge of the instability strip. The presence of a planet could be revealed by the periodical variation of the observed pulsation periods induced by the orbital motion of the white dwarf around the barycenter of the system. We started a multi-site photometric follow-up aimed at detecting the signature of this potential planet. As a preliminary result of this work in progress, we give the parameters of the GD 133 best-fit model derived from asteroseismology.
Published: 2017

6. Amplitude and frequency variations of oscillation modes in the pulsating DB white dwarf star KIC~08626021: The likely signature of nonlinear resonant mode coupling

Author: Weikai Zong, N. Giammichele, Stéphane Charpinet, G. Vauclair, Valérie Van Grootel, Institut de recherche en astrophysique et planétologie (IRAP), 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), 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: FOS: Physical sciences, Astrophysics, 01 natural sciences, techniques: photometric, stars: individual: KIC 08626021, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), white dwarfs, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Oscillation, Stellar rotation, Resonance, White dwarf, Astronomy and Astrophysics, Nonlinear system, Amplitude, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Mode coupling, Astrophysics::Earth and Planetary Astrophysics, Stellar pulsation
Abstract: Aims. We use the Kepler data accumulated on the pulsating DB white dwarf KIC 08626021 to explore in detail the stability of its oscillation modes, searching in particular for evidences of nonlinear behaviors. Methods. We analyse nearly two years of uninterrupted short cadence data, concentrating in particular on identified triplets due to stellar rotation that show intriguing behaviors during the course of the observations. Results. We find clear signatures of nonlinear effects attributed to resonant mode coupling mechanisms. We find that a triplet at 4310 {\mu}Hz and this doublet at 3681 {\mu}Hz (most likely the two visible components of an incomplete triplet) have clear periodic frequency and amplitude modulations typical of the so-called intermediate regime of the resonance, with time scales consistent with theoretical expectations. Another triplet at 5073 {\mu}Hz is likely in a narrow transitory regime in which the amplitudes are modulated while the frequencies are locked. Using nonadiabatic pulsation calculations based on a model representative of KIC 08626021 to evaluate the linear growth rates of the modes in the triplets, we also provide quantitative information that could be useful for future comparisons with numerical solutions of the amplitude equations. Conclusions. The identified modulations are the first clear-cut signatures of nonlinear resonant couplings occurring in white dwarf stars. These should resonate as a warning to projects aiming at measuring the evolutionary cooling rate of KIC 08626021, and of white dwarf stars in general. Nonlinear modulations of the frequencies can potentially jeopardize any attempt to measure reliably such rates, unless they could be corrected beforehand. These results should motivate further theoretical work to develop nonlinear stellar pulsation theory., Comment: 14 pages, 13 Figures, 2 Tables, accepted to A&A
Published: 2015
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7. Wet Observations of GD 358 in 2000

Author: J. E. Solheim, T. Sullivan, Paul A. Bradley, J. M. Gonzalez Perez, E. G. Meištas, Encarni Romero-Colmenero, E. W. Klumpe, Thorsten Nagel, G. Vauclair, Stefan Dreizler, Waldemar Ogloza, J. Xiaojun, P. Martinez, F. Johannessen, M. Chevreton, Antonio Kanaan, Matt A. Wood, Sonja Schuh, Martha L. Boyer, Nicole M. Silvestri, J. N. Fu, A. Ulla, Donald E Winget, Kazuhiro Sekiguchi, Staszek Zola, Denis J. Sullivan, T. S. Metcalfe, Jam Shaw, R. L. Riddle, Atsuko Nitta, E. R. Nather, J. L. Deetjen, Donal O'Donoghue, Souza Oliveira Kepler, A. F. Murillo Costa, S. D. Kawaler, J. E. S. Costa, Anjum S. Mukadam, J. Larrison, T. J. Ahrens, A. Kyle Jones, J. KrzesiŃski, S. J. Kleinman, R. Kalytis, R. Janulis, and A. E. Collins
Subjects: Physics, stars, lcsh:QB1-991, Stars, Space and Planetary Science, lcsh:Astronomy, evolution, Astronomy, Astronomy and Astrophysics, individual, GD 358 - stars, Astrobiology
Abstract: We report on the 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23 to June 8, 2000. We acquired more than 232 000 independent measurements and 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 796 s. 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.
Published: 2003

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

Author: Weikai Zong, G. Vauclair, and Stéphane Charpinet
Subjects: Physics, Spacecraft, business.industry, Oscillation, QC1-999, Astrophysics, Star (graph theory), Subdwarf, Nonlinear system, Stars, Amplitude, Mode coupling, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, business
Abstract: The Kepler spacecraft provides new opportinuties to observe long term frequency and amplitude modulations of oscillation modes in pulsating stars. We analyzed more than three years of uninterrupted data obtained with this instrument on the hot B subdwarf (sdB) star KIC 10139564 and found clear signatures of nonlinear resonant mode coupling affecting several multiplets. The observed periodic frequency and amplitude modulations may allow for new asteroseismic diagnostics, providing in particular ways to measure linear growth rates of pulsation modes in hot subdwarf stars for the first time.
Published: 2015

9. Preliminary Results from XCOV 17: PG 1336-018

Author: T. S. Metcalfe, Jérôme Perez, G. Vauclair, R. H. Østensen, E. G. Meištas, B. Shobbrook, B. N. Ashoka, H. Mendelson, Steven D. Kawaler, Matthew R. Burleigh, Stefan Dreizler, Waldemar Ogloza, Adalberto Piccioni, Denis J. Sullivan, F. van Wyk, R. Kalytis, Freddy Marang, J. Krzesinski, R. S. Stobie, O. Giovannini, J. L. Deetjen, Anjum S. Mukadam, A. Nitta-Kleinman, S. Seetha, T. K. Watson, S. J. Kleinman, P. Martinez, P. Mosaklik, Michael D. Reed, Sonja Schuh, Ana Ulla, D. O'Donoghue, M. Chevreton, Staszek Zola, D. Ališauskas, Antonio Kanaan, Martin A. Barstow, Judith L. Provencal, T. Sullivan, Roberto Silvotti, J. E. Solheim, Souza Oliveira Kepler, Olga Suarez, P. Ibbetson, J. Rene-Fremy, D. Kilkenny, Elia M. Leibowitz, Xiao-Jun Jiang, N. Dolez, and Minia Manteiga
Subjects: Physics, Space and Planetary Science, Astronomy, Astronomy and Astrophysics, QB1-991, Astrobiology
Published: 2000

10. PG 1541+650: A new ZZ Ceti white dwarf

Author: D. Homeier, Detlev Koester, J. N. Fu, S. Roques, N. Dolez, M. Chevreton, and G. Vauclair
Subjects: Physics, Space and Planetary Science, Astronomy, White dwarf, Astronomy and Astrophysics, QB1-991, Astrophysics
Published: 2000

11. White Dwarfs

Author: G. Vauclair, Edward Sion, G. Vauclair, and Edward Sion
Subjects: White dwarf stars--Congresses
Abstract: The European Workshop on White Dwarfs was initiated by Prof. V. Weidemann, with the first meeting organized in Kiel (FRG) in 1974. Almost every two years, an increasing number of astronomers met to share their results and projects in the subsequent workshops: Frascati (1976), Tel Aviv (1978), Paris (1981), Kiel (1984), Frascati (1986). In the mean time, two major IAU colloquia (No. 53 in Rochester, NY, 1979; and No. 114 in Hanover, NH, 1988) emphasized the importance of these stars for our understanding of stellar evolution. The informal organization of the white dwarf community has been the starting point for large cooperative projects of which the Hubble Space Telescope'White Dwarf Consortium'and the'Whole Earth Telescope'are the most spectacular examples. But many other successful collaborations have also been born during the very exciting discussions conducted in the last 16 years on the occasion of our regular meetings. The 7th European Workshop on White Dwarfs took place the year of the seventieth birthday of Prof. Evry Schatzman, whose pioneering work has been the inspiration for many of the new ideas in the white dwarf community. The Scientific Organizing Committee has agreed to dedicate the workshop to him on this occasion. We are pleased to publish as an introduction to the workshop, the text of the talk delivered by Prof. Schatzman at the workshop's banquet.
Published: 2012

12. Asteroseismology of RXJ 2117+3412

Author: Donald E Winget, E. G. Meištas, J. Krzesinski, A. V. Chernyshev, T. Matzeh, J. E. Solheim, G. Vauclair, Judith L. Provencal, B. N. Ashoka, S. J. Kleinman, T. M. K. Marar, N. Dolez, J. C. Clemens, Antonio Kanaan, Anne E. Sansom, Pawel Moskalik, B. Pfeiffer, R. E. Nather, Souza Oliveira Kepler, Paul A. Bradley, Juan Antonio Belmonte, Staszek Zola, B. Serre, M. Chevreton, Elia M. Leibowitz, Martin A. Barstow, T. K. Watson, Albert D. Grauer, G. Pajdosz, and Jian Shi Yang
Subjects: Physics, Space and Planetary Science, Astronomy, Astronomy and Astrophysics, QB1-991, Asteroseismology
Published: 1998

13. Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates

Author: Sylvie Vauclair, G. Vauclair, M. Deal, F. C. Wachlin, and S. Deheuvels
Subjects: Convection, Ciencias Astronómicas, Accretion, purl.org/becyt/ford/1.7 [https], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Instability, Gravitation, purl.org/becyt/ford/1 [https], Diffusion, Astrophysics::Solar and Stellar Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Infrared excess, Accretion (meteorology), accretion disks, Otras Ciencias Naturales y Exactas, White dwarf, White dwarfs, Astronomy and Astrophysics, Planetary system, Stars, Planetary systems, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Accretion disks, Hydrodynamics, Astrophysics::Earth and Planetary Astrophysics, CIENCIAS NATURALES Y EXACTAS
Abstract: Context. Recent observations of a large number of DA and DB white dwarfs show evidence of debris disks, which are the remnants of old planetary systems. The infrared excess detected with Spitzer and the lines of heavy elements observed in their atmospheres with high-resolution spectroscopy converge on the idea that planetary material accretes onto these stars. Accretion rates have been derived by several authors with the assumption of a steady state between accretion and gravitational settling. The results are unrealistically different for DA and DB white dwarfs. Aims. When heavy matter is accreted onto stars, it induces an inverse μ-gradient that leads to fingering (thermohaline) convection. The aim of this letter is to study the impact of this specific process on the derived accretion rates in white dwarfs and on the difference between DA and DB. Methods. We solve the diffusion equation for the accreted heavy elements with a time-dependent method. The models we use have been obtained both with the IRAP code, which computes static models, and the La Plata code, which computes evolutionary sequences. Computations with pure gravitational settling are compared with computations that include fingering convection. Results. The most important result is that fingering convection has very important effects on DAs but is inefficient in DBs. When only gravitational settling is taken into account, the time-dependent computations lead to a steady state, as postulated by previous authors. When fingering convection is added, this steady state occurs much later. Conclusions. The surprising difference found in the past for the accretion rates derived for DA and DB white dwarfs disappears. The derived accretion rates for DAs are increased when fingering convection is taken into account, whereas those for DBs are not modified. More precise and developed results will be given in a forthcoming paper., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
Published: 2013

14. Asteroseismology of the ZZ Ceti star HS 0507+0434B★

Author: László Molnár, S. L. Kim, M. Chevreton, N. Dolez, Y. P. Zhang, G. Vauclair, M. Alvarez, Yin-Bi Li, X. H. Yang, Stéphane Charpinet, Li Chen, C. Li, Emese Plachy, Jie Su, Jian-Ning Fu, Raul Michel, L. Fox Machado, 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), Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (LATT), Department of Electronic and Electrical Engineering, Pohang University of Science and Technology (POSTECH), 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), 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: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Rotation, 01 natural sciences, Asteroseismology, Luminosity, symbols.namesake, Sine wave, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Astronomy, White dwarf, Astronomy and Astrophysics, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Fourier analysis, symbols, Astrophysics::Earth and Planetary Astrophysics, Instability strip, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The pulsating DA white dwarfs (ZZ Ceti stars) are $g$-mode non-radial pulsators. Asteroseismology provides strong constraints on their global parameters and internal structure. Since all the DA white dwarfs falling in the ZZ Ceti instability strip do pulsate, the internal structure derived from asteroseismology brings knowledge for the DA white dwarfs as a whole group. HS 0507+0434B is one of the ZZ Ceti stars which lies approximately in the middle of the instability strip for which we have undertaken a detailed asteroseismological study. We carried out multisite observation campaigns in 2007 and from December 2009 to January 2010. In total, 206 hours of photometric time-series have been collected. They have been analysed by means of Fourier analysis and simultaneous multi-frequency sine-wave fitting. In total, 39 frequency values are resolved including 6 triplets and a number of linear combinations. We identify the triplets as $\ell$=1 $g$-modes split by rotation. We derived the period spacing, the rotational splitting and the rotation rate. From the comparison of the observed periods with the theoretical periods of a series of models we estimate the fundamental parameters of the star: its total mass M$_{*}$/M$_{\odot}$ = 0.675, its luminosity L/L$_{\odot}$=3.5$\times 10^{-3}$, and its hydrogen mass fraction M$_{H}$/M$_{*}$= 10$^{-8.5}$., Comment: 12 pages,8 figures, accepted for publication in MNRAS
Published: 2013
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15. Study of periodicities of the DAV white dwarf G 117-B15A with the Whole Earth Telescope

Author: Gilles Fontaine, Elia M. Leibowitz, Pierre Bergeron, B. N. Ashoka, R. E. Nather, Don Winget, S. Seetha, T. M. K. Marar, D. Dolez, J. E. Solheim, R. W. Tweedy, Albert D. Grauer, Matt A. Wood, F. Wesemael, B. P. Hine, J. C. Clemens, Antonio Kanaan, Chuck Claver, S. J. Kleinman, P. I. Emanuelsen, Tsevi Mazeh, Edward L. Robinson, G. Vauclair, Anne E. Sansom, Paul A. Bradley, M. Chevreton, Martin A. Barstow, Souza Oliveira Kepler, and Judith L. Provencal
Subjects: Telescope, Physics, Space and Planetary Science, law, Astronomy, White dwarf, Astronomy and Astrophysics, QB1-991, Astrophysics, Earth (classical element), law.invention
Published: 1995

16. Whole Earth Telescope observations and seismological analysis of the cool TIL Ceti star GD 154

Author: Chuck Claver, Judith L. Provencal, M. Chevreton, Martin A. Barstow, Tsevi Mazeh, J. A. Belmonte, J. R. Fremy, N. Dolez, Paul A. Bradley, Donald E Winget, S. J. Kleinman, O. Giovannini, Albert D. Grauer, T. K. Watson, J. S. Dixson, R. E. Nather, G. Vauclair, J. C. Clemens, Antonio Kanaan, Elia M. Leibowitz, B. Pfeiffer, F. Wesemael, Pierre Bergeron, Souza Oliveira Kepler, Pawel Moskalik, and Gilles Fontaine
Subjects: Rotation period, Physics, Hydrogen, Astronomy, Spectral density, chemistry.chemical_element, White dwarf, Astronomy and Astrophysics, QB1-991, Astrophysics, Star (graph theory), law.invention, Telescope, chemistry, Space and Planetary Science, law, Harmonics, Earth (classical element)
Abstract: This paper presents the results of high speed photo metric observations of the cool variable DA white dwarf (DAV) GD 154 obtained with the Whole Earth Telescope. GD 154 is one of the c;oolest pulsating DA white dwarfs and its study is important for understanding the red edge of the ZZ Ceti insta bility strip. Its power spectrum is dominated by three indepen dent modes (P 1 = 1186.5s, Pz = 1088.6s and P3 = 402.6s), and their harmonics and linear combinations. None of the half-integer harmonics reported in previous observations were present during the WET campaign. We propose that the ob served modes are trapped in the thin outer hydrogen layers. From the resulting identification of the pulsation modes, one derives an estimate of the rotation period (2.3 days) and of the mass ofthe outer hydrogen layer (2 X w-IO M *).
Published: 1995

17. EMPIRICAL DETERMINATION OF CONVECTION PARAMETERS IN WHITE DWARFS. I. WHOLE EARTH TELESCOPE OBSERVATIONS OF EC14012-1446

Author: Zsofia Bognar, J. R. Fremy, M. Yang, Agnès Bischoff-Kim, Wen Ping Chen, Margit Paparo, Harry L. Shipman, A. V. Sergeev, J. L. Provencal, Scot Kleinman, Su Wang, A. Maksim, Stephane Vennes, Matt A. Wood, Péter Pápics, Thorsten Nagel, N. Loaring, Gerald Handler, B. Walter, Timothy M. Brown, Kiran S. Baliyan, Souza Oliveira Kepler, David A. H. Buckley, P. Henrique, David Kilkenny, D. Childers, R. Rosen, Atsuko Nitta, Chia-You Shih, Jérôme Perez, J. M. Almenara, R. Janulis, Michael H. Montgomery, D. Chandler, W. Ogloza, S. L. Kim, J. C. Clemens, Andrzej S. Baran, Stanisław Zoła, Antonio Kanaan, N. Dolez, A. Kniazev, Xiao-Jun Jiang, R. Sefako, Péter Németh, Barbara G. Castanheira, W. Strickland, T. K. Watson, Roberto Silvotti, J. Dalessio, Denis J. Sullivan, Susan E. Thompson, M. Winiarski, G. Vauclair, Luciano Fraga, Hari Om Vats, S. Galleti, Michael D. Reed, Centre Hospitalier Métropole Savoie [Chambéry], Copernicus Astronomical Center of the Polish Academy of Sciences (CAMK), Polish Academy of Sciences (PAN), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Department of Electrical Engineering [Yale University], Yale University [New Haven], London South Bank University (LSBU), Department of Electronic and Electrical Engineering, Pohang University of Science and Technology (POSTECH), Laboratory of Behavioral Neuroscience, National Institutes of Health [Bethesda] (NIH), Qingdao Institute of Marine Geology, China Geological Survey, Qingdao 266071, China, Université Paris Diderot - Paris 7 (UPD7), Institute of Applied Physics of RAS, Russian Academy of Sciences [Moscow] (RAS), Mt. Suhora Observatory, Pedagogical University, Astronomy Department, South African Astronomical Observatory (SAAO), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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), 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), Escola de Odontologia, UNIVALE, 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), 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: oscillations [stars], Convection, FOS: Physical sciences, asteroseismology, Astrophysics, 01 natural sciences, law.invention, Photometry (optics), Telescope, symbols.namesake, law, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, white dwarfs, Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, White dwarf, Astronomy and Astrophysics, Light curve, Amplitude, Fourier transform, Astrophysics - Solar and Stellar Astrophysics, individual: EC14012-1446 [stars], 13. Climate action, Space and Planetary Science, evolution [stars], symbols, Instability strip, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We report on analysis of 308.3 hrs of high speed photometry targeting the pulsating DA white dwarf EC14012-1446. The data were acquired with the Whole Earth Telescope (WET) during the 2008 international observing run XCOV26. The Fourier transform of the light curve contains 19 independent frequencies and numerous combination frequencies. The dominant peaks are 1633.907, 1887.404, and 2504.897 microHz. Our analysis of the combination amplitudes reveals that the parent frequencies are consistent with modes of spherical degree l=1. The combination amplitudes also provide m identifications for the largest amplitude parent frequencies. Our seismology analysis, which includes 2004--2007 archival data, confirms these identifications, provides constraints on additional frequencies, and finds an average period spacing of 41 s. Building on this foundation, we present nonlinear fits to high signal-to-noise light curves from the SOAR 4.1m, McDonald 2.1m, and KPNO 2m telescopes. The fits indicate a time-averaged convective response timescale of 99.4 +/- 17 s, a temperature exponent 85 +/- 6.2 and an inclination angle of 32.9 +/- 3.2 degrees. We present our current empirical map of the convective response timescale across the DA instability strip., Comment: Accepted for publication in the Astrophysical Journal
Published: 2012
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18. Accurate p-mode measurements of the G0V metal-rich CoRoT target HD 52265

Author: T. Stahn, Savita Mathur, S. Deheuvels, K. H. Sato, Orlagh Creevey, Tiago L. Campante, Rafael A. García, David Salabert, Michael Bazot, Jérôme Ballot, Sylvie Vauclair, Claude Catala, William J. Chaplin, Hans Bruntt, Graham A. Verner, G. Vauclair, Benoit Mosser, Ian W. Roxburgh, Eric Michel, Frédéric Baudin, Othman Benomar, Patrick Gaulme, Thierry Appourchaux, Annie Baglin, Reza Samadi, C. Régulo, Michel Auvergne, Y. P. Elsworth, Laurent Gizon, N. Dolez, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 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, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and Laboratoire Hippolyte Fizeau (FIZEAU)
Subjects: Rotation period, Physics, 010504 meteorology & atmospheric sciences, Oscillation, FOS: Physical sciences, Astronomy and Astrophysics, Angular velocity, Astrophysics, Rotation, 01 natural sciences, 3. Good health, Amplitude, Spitzer Space Telescope, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], Space and Planetary Science, 0103 physical sciences, Differential rotation, Spectroscopy, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: The star HD 52265 is a G0V metal-rich exoplanet-host star observed in the seismology field of the CoRoT space telescope from November 2008 to March 2009. The satellite collected 117 days of high-precision photometric data on this star, showing that it presents solar-like oscillations. HD 52265 was also observed in spectroscopy with the Narval spectrograph at the same epoch. We characterise HD 52265 using both spectroscopic and seismic data. The fundamental stellar parameters of HD 52265 were derived with the semi-automatic software VWA, and the projected rotational velocity was estimated by fitting synthetic profiles to isolated lines in the observed spectrum. The parameters of the observed p modes were determined with a maximum-likelihood estimation. We performed a global fit of the oscillation spectrum, over about ten radial orders, for degrees l=0 to 2. We also derived the properties of the granulation, and analysed a signature of the rotation induced by the photospheric magnetic activity. Precise determinations of fundamental parameters have been obtained: Teff = 6100 +- 60 K, log g = 4.35 +- 0.09, [M/H] = 0.19 +- 0.05, as well as vsini = 3.6 +0.3 -1.0 km/s. We have measured a mean rotation period P_rot = 12.3 +- 0.15 days, and find a signature of differential rotation. The frequencies of 31 modes are reported in the range 1500-2550 micro-Hz. The large separation exhibits a clear modulation around the mean value = 98.3 +- 0.1 micro-Hz. Mode widths vary with frequency along an S-shape with a clear local maximum around 1800 micro-Hz. We deduce lifetimes ranging between 0.5 and 3 days for these modes. Finally, we find a maximal bolometric amplitude of about 3.96 +- 0.24 ppm for radial modes., Comment: published in A&A, 11 pages, 14 figures, 6 tables
Published: 2011
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19. The period and amplitude changes in the coolest GW Virginis variable star (PG 1159-type) PG 0122+200

Author: Alejandro H. Córsico, J.-E. Solheim, Li Chen, Matt A. Wood, N. Dolez, S. L. Kim, Isaac Silver, M. Chevreton, G. Vauclair, Zs. Bognár, M. Paparó, Jian-Ning Fu, 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), Department of Astronomy, Beijing Normal University, University of Oslo (UiO), Korea Astronomy and Space Science Institute (KASI), 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), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Department of Physics and Space Sciences and SARA Observatory, Florida Institute of Technology, Melbourne, Konkoly Observatory, Research Center for Astronomy and Earth Sciences, and Facultad de Ciencias Astronómicas y Geofísicas, Observatorio Astronómico & Instituto de Astrofísica de La Plata
Subjects: oscillations [stars], Ciencias Astronómicas, Ciencias Físicas, Astrophysics, stars: individual: PG 0122+200, Evolution of stars, purl.org/becyt/ford/1 [https], individual: PG 0122+200 [stars], Astrophysics::Solar and Stellar Astrophysics, stars: evolution, Stellar evolution, white dwarfs, Physics, PG 0122+200 (estrella), Stellar rotation, White dwarf, Astronomy, neutrinos, White dwarfs, Astronomy and Astrophysics, purl.org/becyt/ford/1.3 [https], Astronomía, Stars, Amplitude, Space and Planetary Science, [SDU]Sciences of the Universe [physics], evolution [stars], Star pulsations, stars: oscillations, Variable star, Neutrino, Instability strip, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], CIENCIAS NATURALES Y EXACTAS
Abstract: Context: The PG 1159 pre-white dwarf stars experiment a rapidly cooling phase with a time scale of a few 10 6 years. Theoretical models predict that the neutrinos produced in their core should play a dominant role in the cooling, mainly at the cool end of the PG 1159 sequence. Measuring the evolutionary time scale of the coolest PG 1159 stars could offer a unique opportunity to empirically constrain the neutrino emission rate. Aims. A subgroup of the PG 1159 stars are nonradial pulsators, the GW Vir type of variable stars. They exhibit g-mode pulsations with periods of a few hundred seconds. As the stars cool, the pulsation frequencies evolve according to the change in their internal structure. It was anticipated that the measurement of their rate of change would directly determine the evolution time scale and so constrain the neutrino emission rates. As PG 0122+200 (BB Psc) defines the red edge of the GW Vir instability strip, it is a good candidate for such a measurement. Methods. The pulsations of PG 0122+200 have been observed during 22 years from 1986 to 2008, through the fast photometry technique. We used those data to measure the rate of change of its frequencies and amplitudes. Results. Among the 24 identified ℓ = 1 modes, the frequency and amplitude variations have been obtained for the seven largest amplitude ones. We find changes of their frequency of much larger amplitudes and shorter time scales than the one predicted by theoretical models that assume that the cooling dominates the frequency variations. In the case of the largest amplitude mode at 2497 μHz (400 s), its variations are best fitted by a combination of two terms: one long term with a time scale of 5.4 × 10 4 years, which is significantly shorter than the predicted evolutionary time scale of 8 × 10 6 years; and one additional periodic term with a period of either 261 or 211 days. Some other mechanism(s) than the cooling must be responsible for such variations. We suggest that the resonant coupling induced within triplets by the star rotation could be such a mechanism. As a consequence, no useful constraints on the neutrino emission rate can presently be derived as long as the dominant mechanism is not properly understood. Conclusions. The temporal variations in the pulsation frequencies observed in PG 0122+200 cannot be simply attributed to the cooling of the star, regardless of the contribution of the neutrino losses. Our results suggest that the resonant coupling induced by the rotation plays a dominant role which must be further investigated., Facultad de Ciencias Astronómicas y Geofísicas
Published: 2011
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20. 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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21. 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

22. 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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23. 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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24. 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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25. 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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26. 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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27. 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

28. 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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29. 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

30. 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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31. 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

32. 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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33. 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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34. 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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35. 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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36. 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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37. 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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38. 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

39. Progress report on the analysis of the WET campaign on RXJ 2117+3412

Author: G. Vauclair
Subjects: Physics, Space and Planetary Science, Astronomy, Astronomy and Astrophysics, QB1-991
Published: 1993

40. A NEW ANALYSIS OF THE TWO CLASSICAL ZZ CETI WHITE DWARFS GD 165 AND ROSS 548. I. PHOTOMETRY AND SPECTROSCOPY.

Author: N. Giammichele, G. Fontaine, P. Bergeron, P. Brassard, S. Charpinet, B. Pfeiffer, and G. Vauclair
Subjects: DWARF stars, TIME series analysis, PHOTOMETRY, SPECTRUM analysis, ASTROPHYSICS research
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. [ABSTRACT FROM AUTHOR]
Published: 2015
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41. DISCOVERY OF MULTIPLE PULSATIONS IN THE NEW δ SCUTI STAR HD 92277: ASTEROSEISMOLOGY FROM DOME A, ANTARCTICA.

Author: Weikai Zong, Jian-Ning Fu, Jia-Shu Niu, S. Charpinet, G. Vauclair, Michael C. B. Ashley, Xiangqun Cui, Longlong Feng, Xuefei Gong, Jon S. Lawrence, Daniel Luong-Van, Qiang Liu, Carl R. Pennypacker, Lingzhi Wang, Lifan Wang, Xiangyan Yuan, Donald G. York, Xu Zhou, Zhenxi Zhu, and Zonghong Zhu
Published: 2015
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42. Seismic constraints on rotation of Sun-like star and mass of exoplanet.

Author: Gizon L, Ballot J, Michel E, Stahn T, Vauclair G, Bruntt H, Quirion PO, Benomar O, Vauclair S, Appourchaux T, Auvergne M, Baglin A, Barban C, Baudin F, Bazot M, Campante T, Catala C, Chaplin W, Creevey O, Deheuvels S, Dolez N, Elsworth Y, García R, Gaulme P, Mathis S, Mathur S, Mosser B, Régulo C, Roxburgh I, Salabert D, Samadi R, Sato K, Verner G, Hanasoge S, and Sreenivasan KR
Subjects: Astronomy, Models, Theoretical, Planets, Rotation, Stars, Celestial
Abstract: Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85(-0.42)(+0.52)M(Jupiter), which implies that it is a planet, not a brown dwarf.
Published: 2013
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43. A giant planet orbiting the 'extreme horizontal branch' star V 391 Pegasi.

Author: Silvotti R, Schuh S, Janulis R, Solheim JE, Bernabei S, Østensen R, Oswalt TD, Bruni I, Gualandi R, Bonanno A, Vauclair G, Reed M, Chen CW, Leibowitz E, Paparo M, Baran A, Charpinet S, Dolez N, Kawaler S, Kurtz D, Moskalik P, Riddle R, and Zola S
Abstract: After the initial discoveries fifteen years ago, over 200 extrasolar planets have now been detected. Most of them orbit main-sequence stars similar to our Sun, although a few planets orbiting red giant stars have been recently found. When the hydrogen in their cores runs out, main-sequence stars undergo an expansion into red-giant stars. This expansion can modify the orbits of planets and can easily reach and engulf the inner planets. The same will happen to the planets of our Solar System in about five billion years and the fate of the Earth is matter of debate. Here we report the discovery of a planetary-mass body (Msini = 3.2M(Jupiter)) orbiting the star V 391 Pegasi at a distance of about 1.7 astronomical units (au), with a period of 3.2 years. This star is on the extreme horizontal branch of the Hertzsprung-Russell diagram, burning helium in its core and pulsating. The maximum radius of the red-giant precursor of V 391 Pegasi may have reached 0.7 au, while the orbital distance of the planet during the stellar main-sequence phase is estimated to be about 1 au. This detection of a planet orbiting a post-red-giant star demonstrates that planets with orbital distances of less than 2 au can survive the red-giant expansion of their parent stars.
Published: 2007
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