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1. The pulsations of PG 1351+489

Author

Carl J. Hansen, Judith L. Provencal, D. A. H. Buckley, Waldemar Ogloza, Michael D. Reed, M. M. Brewer, Hari Om Vats, Mary E. Oksala, Jian-Ning Fu, R. E. Nather, Denis J. Sullivan, Luciano Fraga, Ramotholo Sefako, Ivan Bruni, J. E. S. Costa, Matt A. Wood, Wen Ping Chen, W. Strickland, Fergal Mullally, Roberto Silvotti, B. N. Ashoka, B. Walter, Timothy M. Brown, S. Hemar, R. Rosen, E. G. Meištas, P. Henrique, M. Andreev, X. Zhang, T. K. Watson, Kiran S. Baliyan, P. Ibbetson, Chuck Claver, Rimvydas Janulis, Harry L. Shipman, Michael H. Montgomery, Gerald Handler, J. C. Clemens, Antonio Kanaan, M. Chevreton, J. Dalessio, J.-E. Solheim, Thorsten Nagel, S. L. Kim, B. Pfeiffer, A. V. Chernyshev, Susan E. Thompson, Martin A. Barstow, S. Seetha, M. Redaelli, Donald E Winget, Atsuko Nitta, T. M. K. Marar, G. Vauclair, Michal Siwak, M. Yang, Xiao-Jun Jiang, Orlagh Creevey, Pawel Moskalik, Elia M. Leibowitz, A. V. Sergeev, J. R. Fremy, G. Pajdosz, M. Winiarski, S. J. Kleinman, D. Chandler, Andrzej S. Baran, Souza Oliveira Kepler, B. G. Castanheira, Chia-You Shih, Staszek Zola, O. Giovannini, D. Childers, Agnès Bischoff-Kim, Zs. Bognár, Donal O'Donoghue, N. Dolez, and Steven D. Kawaler

Subjects
Physics, Rotation period, Stellar rotation, White dwarf, Astronomy, Spectral density, Astronomy and Astrophysics, Astrophysics, law.invention, Telescope, Amplitude, Space and Planetary Science, Normal mode, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Stellar evolution
Abstract

PG 1351+489 is one of the 20 DBVs ― pulsating helium-atmosphere white dwarf stars ― known and has the simplest power spectrum for this class of star, making it a good candidate to study cooling rates. We report accurate period determinations for the main peak at 489.334 48 s and two other normal modes using data from the Whole Earth Telescope (WET) observations of 1995 and 2009. In 2009, we detected a new pulsation mode and the main pulsation mode exhibited substantial change in its amplitude compared to all previous observations. We were able to estimate the star's rotation period, of 8.9 h, and discuss a possible determination of the rate of period change of (2.0 ± 0.9) x 10 ―13 s s ―1 , the first such estimate for a DBV.

Published
2011
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2. Pulsational frequencies of the eclipsing δ Scuti star HD 172189. Results of the STEPHI XIII campaign

Author

F. Perez Hernendez, J. E. S. Costa, L. Parrao, Roi Alonso, O. L. Creevey, E. Michel, S. Pau, Zhongmu Li, João Luiz Pena, Juan Antonio Belmonte, M. Alvarez, J. R. Fremy, M. Chevreton, L. Fox Machado, A. Fernandez, 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, Ingénieurs, Techniciens et Administratifs, Instituto de Astronomia, Universidad Nacional Autonomica de Mexico, Instituto de Astrofísica de Canarias (IAC), and National Astronomical Observatoires-CAS

Subjects
Physics, Orbital elements, Frequency analysis, Astronomy and Astrophysics, Astrophysics, Star (graph theory), Orbital period, law.invention, Space and Planetary Science, law, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Binary system, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Open cluster
Abstract

International audience; Context: The eclipsing delta Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. Aims: The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. Methods: We performed a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign. Results: We have identified six pulsation frequencies with a confidence level of 99% and a seventh with a 65% confidence level of 65%, in the range between 100-300 muHz. In addiction, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system.

Published
2007
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3. New δ Scuti variable in the Pleiades: HD 23628

Author

E. Michel, B. Servan, Caroline Barban, M. Chevreton, M. M. Hernandez, S. Y. Jiang, Zhongmu Li, A. Fernandez, Juan Antonio Belmonte, F. Pérez Hernández, M. Alvarez, Z. L. Liu, O. Ringot, Juan Carlos Suárez, L. Fox Machado, N. Dolez, Ye Xu, S. Pau, J. R. Fremy, A.-Y. Zhou, 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, and Ingénieurs, Techniciens et Administratifs

Subjects
Physics, K-type main-sequence star, Astronomy, Astronomy and Astrophysics, Astrophysics, Light curve, Spectral line, Stars, Quality (physics), Amplitude, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Pleiades, Open cluster
Abstract

We report here the discovery of very low amplitude oscillations in the Pleiades star HD 23628. The 14-nights high quality light curve designates HD 23628 as a new member of the Scuti stars class. Amplitude spectra indicate a multi-periodic pulsation behaviour, and four pulsation frequencies have been detected so far. The frequency distribution suggests the presence of nonradial modes. Pulsation constant values of the four modes are distributed in the range corresponding to fundamental f to p4 radial modes.

Published
2002
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4. 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

5. 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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6. Observation of a Variable, ZZ Ceti White Dwarf: GD154

Author

Gilles Fontaine, Juan Antonio Belmonte, B. Pfeiffer, Pierre Bergeron, M. Chevreton, O. Giovannini, G. Herpe, R. E. Nather, S. J. Kleinman, Judith L. Provencal, Pawel Moskalik, Elia M. Leibowitz, F. Wesemael, Souza Oliveira Kepler, T. K. Watson, A. D. Grauer, J. S. Dixson, N. Dolez, G. Vauclair, J. R. Fremy, Martin A. Barstow, Paul A. Bradley, J. C. Clemens, Antonio Kanaan, T. Matzeh, Chuck Claver, and Don Winget

Subjects
Physics, Stellar atmosphere, Astronomy, White dwarf, Astronomy and Astrophysics, Astrophysics, Effective temperature, Light curve, Stars, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Variable star, Instability strip
Abstract

The ZZ Ceti stars form a class of variable white dwarfs: the hydrogen dominated atmosphere ones, which do pulsate in an instability strip in the effective temperature range 13000K-11500K. We know 22 such ZZ Ceti white dwarfs. Their variations are caused by nonradial g-mode pulsations with periods are in the range 100-1000 seconds.A subsample of the ZZ Ceti stars shows amplitude variations on time scales of the order of one month. These variations could be driven by nonlinear phenomena.

Published
1993
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7. 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

8. Observation of a Variable, ZZ Ceti White Dwarf: GD154

Author

B. Pfeiffer, G. Vauclair, N. Dolez, M. Chevreton, J. R. Fremy, G. Herpe, M. Barstow, S. J. Kleinman, T. K. Watson, J. A. Belmonte, S. O. Kepler, A. Kan-Aan, O. Giovannini, R. E. Nather, D. E. Winget, J. Provencal, J. C. Clemens, P. Bradley, J. Dixson, A. D. Grauer, G. Fontaine, P. Bergeron, F. Wesemael, C. F. Claver, T. Matzeh, E. Leibowitz, and P. Moskalik

Published
1993
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9. Whole Earth Telescope Observations of the DBV White Dwarf PG1115+158: Preliminary Results

Author

D. Sullivan, T. M. K. Marar, Elia M. Leibowitz, B. N. Ashoka, Don Winget, Lilia Ferrario, A. Chen, S. Seetha, S. J. Kleinman, D. A. H. Buckley, J. S. Dixon, H. Mendelson, J. C. Clemens, Matt A. Wood, Antonio Kanaan, J. R. Fremy, Dayal Wickramasinghe, Souza Oliveira Kepler, Paul A. Bradley, G. Vauclair, R. E. Nather, D. O'Donoghue, Judith L. Provencal, M. Chevreton, Staszek Zola, Martin A. Barstow, J. Krzesinski, G. Odilon, Pawel Moskalik, and Chuck Claver

Subjects
Physics, Period (periodic table), White dwarf, chemistry.chemical_element, Astronomy, Astrophysics, Rotation, law.invention, Telescope, symbols.namesake, Fourier transform, chemistry, law, symbols, Astrophysics::Earth and Planetary Astrophysics, Multiplet, Helium, Earth (classical element)
Abstract

We present preliminary results from Whole Earth Telescope (WET) data on the DBV star PG1115+158. In the Fourier Transform of this data, we have tentatively identified peaks arranged in multiplets with common frequency splitting. The average period spacing between these multiplets is ~ 40s, very similar to the multiplet spacing found in the DBV GD358. Theoretical models show l = 1 modes with ~ 40s period spacing between modes of consecutive k for white dwarfs with niasses near 0.6M ⊙. If we assume the identified multiplets are l = 1 modes, then the rotation rate of the star is 0.45 days. Furthermore, the deviations of the period spacing between modes from the mean period spacing indicates that, like GD358, the surface Helium layer is thin, less than 10-4 M *.

Published
1993
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10. Whole Earth Telescope Observations of the DAV White Dwarf G226-29

Author

O. Giovannini, S. Seetha, Staszek Zola, Matt A. Wood, J. E. Solheim, T. M. K. Marar, G. Vauclair, R. E. Nather, P. I. Emanuelsen, S. J. Kleinman, Lilia Ferrario, Tsevi Mazeh, Chuck Claver, B. N. Ashoka, Denis J. Sullivan, Martin A. Barstow, K. Yanagida, A. L. Chen, T. K. Watson, H. Mendelson, Kevin Krisciunas, David A. H. Buckley, G. Pajdosz, Judith L. Provencal, J. R. Fremy, N. Dolez, R. W. Tweedy, Jurek Krzesinski, M. Chevreton, Anne E. Sansom, J. C. Clemens, Antonio Kanaan, A. van der Peet, Donald E Winget, Souza Oliveira Kepler, Paul A. Bradley, P. Moskalik, Elia M. Leibowitz, and Dayal Wickramasinghe

Subjects
Physics, Telescope, Stars, Space and Planetary Science, law, White dwarf, Astronomy, Astronomy and Astrophysics, Spectral analysis, Astrophysics, Rotation, Earth (classical element), law.invention
Published
1995
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