Detalles de publicación
PP 011038
The Kepler characterization of the variability among A- and F-type stars I. general overview
(1) Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot; CEA, IRFU, SAp, Centre de Saclay, 91191, Gif-sur-Yvette, France , (2) Kiepenheuer-Institut fur Sonnenphysik, Schoneckstrasse 6, 79104 Freiburg im Breisgau, Germany, (3) Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain; Departamento de Astrofisica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain, (4) Laboratorio de Astrofisica Estelar y Exoplanetas, LAEX-CAB , (INTA-CSIC), PO BOX 78, 28691 Villanueva de la Canada, Madrid, Spain, (5) Centro de Astrofisica, Faculdade de Ciencias, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal, (6) Los Alamos National Laboratory, XTD-2, Los Alamos, NM 87545-2345, USA, (7) Instituto de Astrofisica de Andalucia , (CSIC), Apartado 3004, 18080 Granada, Spain, (8) LESIA, Observatoire de Paris, CNRS, UPMC, Universite Paris-Diderot, 92195 Meudon, France, (9) Valentian International University, Prolongacion C/ Jose Pradas Gallen, s/n 12006 Castellon de la Plana - Spain, (10) Astrophysics Group, Keele University, Staffordshire, ST5 5BG, United Kingdom, (11) Institut fur Astronomie, Turkenschanzstrasse 17, 1180 Wien, Austria, (12) Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland, (13) South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa, (14) Instytut Astronomiczny, Uniwersytet Wroclawski, Kopernika 11, 51-622 Wroclaw, Poland, (15) Observatorio Astronomico Nacional, Instituto de Astronomia, UNAM, Ensenada B.C., Apdo. Postal 877, Mexico , (16) CISAS, Padova University, Via Venezia 15, 35131 Padova, Italy, (17) INAF - Astronomical Observatory of Padova, Vicolo Osservatorio 5, 35122 Padova, Italy, (18) UMR 6525 H. Fizeau, UNS, CNRS, OCA, Campus Valrose, 06108 Nice Cedex 2, France, (19) Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium, (20) Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest PO Box 67, Hungary, (201) INAF - Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy, (22) Lab. d'Astrophysique de Toulouse-Tarbes, Universite de Toulouse, CNRS, 57 avenue d'Azereix, 65000 Tarbes, France , (23) Thuringer Landessternwarte Tautenburg, 07778 Tautenburg, Germany , (24) Department of Astronomy, New Mexico State University, Las Cruces, NM 88001, USA , (25) Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands, (26) University of Birmingham, School of Physics and Astronomy, Edgbaston, Birmingham B15 2TT, UK , (27) Department of Astronomy and Physics, Saint Marys University, Halifax, NS B3H 3C3, Canada , (28) Observatoire de Geneve, Universite de Geneve, 51 ch. des Maillettes, 1290 Sauverny, Switzerland , (29) Los Alamos National Laboratory, XCP-6, MS T-087, Los Alamos, NM 87545-2345, USA , (30) Jeremiah Horrocks Institute of Astrophysics, University of Central Lancashire, Preston PR12HE, UK , (31) Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium , (32) Department of Physics and Astronomy, University of Aarhus, bygn. 1520, Ny Munkegade, 8000 Aarhus C., Denmark , (33) Department of Astronomy, University of Texas, Austin, TX78712, USA , (34) Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney, NSW, 2006, Australia , (35) Bay Area Environmental Research Inst./NASA Ames Research Center, Moffett Field, CA 94035, USA , (36) SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
Context: The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars.
Aims: We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between gamma Dor, delta Sct, and hybrid stars.
Methods: We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, 'energy' and 'efficiency', related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively.
Results: We propose three main groups to describe the observed variety in A-F type stars: gamma Dor, delta Sct, and hybrid stars. We assign 64% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars with a different spectral type than A or F, or stars that show no clear periodic variability. 23% of the stars are hybrid stars, which is a much larger fraction than what has been observed before based on solely ground-based observations. We characterize for the first time a large number of A-F type stars (468 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show a continuous frequency spectrum, which cannot be explained by the current models. We find that delta Sct stars exist beyond the red edge of the current observational instability strip, while gamma Dor pulsations appear in both hotter and cooler stars than expected. The hybrid stars occupy the entire region within the delta Sct, and gamma Dor instability strips and beyond. We find indications for the presence of non-variable stars within the instability strips. The previous apparently significant separation between gamma Dor and delta Sct classes in the (Teff, logg)-diagram has disappeared. Instead, we propose to investigate two newly constructed variables 'efficiency' and 'energy' that are directly related to the internal physics of the stars, as a new means to differentiate between gamma Dor and delta Sct stars.
Conclusions: Our results suggest a revision of the current observational instability strips of delta Sct and gamma Dor stars, and imply an investigation of other pulsation mechanisms to supplement the kappa mechanism and convective blocking effect to drive hybrid pulsations.
Aims: We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between gamma Dor, delta Sct, and hybrid stars.
Methods: We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, 'energy' and 'efficiency', related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively.
Results: We propose three main groups to describe the observed variety in A-F type stars: gamma Dor, delta Sct, and hybrid stars. We assign 64% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars with a different spectral type than A or F, or stars that show no clear periodic variability. 23% of the stars are hybrid stars, which is a much larger fraction than what has been observed before based on solely ground-based observations. We characterize for the first time a large number of A-F type stars (468 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show a continuous frequency spectrum, which cannot be explained by the current models. We find that delta Sct stars exist beyond the red edge of the current observational instability strip, while gamma Dor pulsations appear in both hotter and cooler stars than expected. The hybrid stars occupy the entire region within the delta Sct, and gamma Dor instability strips and beyond. We find indications for the presence of non-variable stars within the instability strips. The previous apparently significant separation between gamma Dor and delta Sct classes in the (Teff, logg)-diagram has disappeared. Instead, we propose to investigate two newly constructed variables 'efficiency' and 'energy' that are directly related to the internal physics of the stars, as a new means to differentiate between gamma Dor and delta Sct stars.
Conclusions: Our results suggest a revision of the current observational instability strips of delta Sct and gamma Dor stars, and imply an investigation of other pulsation mechanisms to supplement the kappa mechanism and convective blocking effect to drive hybrid pulsations.