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Your search keyword '"J. R. Fremy"' showing total 6 results
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6 results on '"J. R. Fremy"'

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. 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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3. 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

4. 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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5. 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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6. 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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