Issue |
A&A
Volume 534, October 2011
|
|
---|---|---|
Article Number | A125 | |
Number of page(s) | 70 | |
Section | Catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361/201117368 | |
Published online | 19 October 2011 |
The Kepler characterization of the variability among A- and F-type stars
I. General overview
1
Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, Centre de Saclay,
91191
Gif-sur-Yvette
France
2
Kiepenheuer-Institut für Sonnenphysik,
Schöneckstraße 6, 79104
Freiburg im Breisgau,
Germany
3
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife,
Spain ; Departamento de Astrofísica, Universidad de La Laguna,
38205 La Laguna, Tenerife, Spain
e-mail: katrien@iac.es
4
Laboratorio de Astrofísica Estelar y Exoplanetas, LAEX-CAB (INTA-CSIC),
PO BOX 78, 28691 Villanueva de la Cañada, Madrid, Spain
5
Centro de Astrofísica, Faculdade de Ciências, 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 Astrofísica de Andalucía (CSIC),
Apartado 3004, 18080
Granada,
Spain
8
LESIA, Observatoire de Paris, CNRS, UPMC, Université
Paris-Diderot, 92195
Meudon,
France
9
Valentian International University, Prolongación C/ José Pradas Gallen, s/n
12006
Castellón de la Plana,
Spain
10
Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
11
Institut für Astronomie, Türkenschanzstraße 17, 1180
Wien,
Austria
12
Nicolaus Copernicus Astronomical Center,
Bartycka 18, 00-716
Warsaw,
Poland
13
South African Astronomical Observatory,
PO Box 9, Observatory
7935, South
Africa
14
Instytut Astronomiczny, Uniwersytet Wrocławski,
Kopernika 11, 51-622
Wrocław,
Poland
15
Observatorio Astronómico Nacional, Instituto de
Astronomía, 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
21
INAF - Osservatorio Astronomico di Capodimonte,
via Moiariello 16, 80131
Napoli,
Italy
22
Lab. d’Astrophysique de Toulouse-Tarbes, Université de Toulouse,
CNRS, 57 avenue
d’Azereix, 65000
Tarbes,
France
23
Thüringer 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 Genève, Université de Genève,
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
PR1 2HE,
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, TX
78712,
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
Received: 30 May 2011
Accepted: 29 June 2011
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 γ Doradus (γ Dor), δ Scuti (δ 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 pulsating A-F type stars: γ Dor, δ Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the γ Dor and δ Sct range, also between 5 and 10 d-1, which is a challenge for the current models. We find indications for the existence of δ Sct and γ Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the δ Sct and γ Dor instability strips and beyond. Non-variable stars seem to exist within the instability strips. The location of γ Dor and δ Sct classes in the (Teff, log g)-diagram has been extended. We investigate two newly constructed variables, “efficiency” and “energy”, as a means to explore the relation between γ Dor and δ Sct stars.
Conclusions. Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ mechanism and convective blocking effect to drive hybrid pulsations. Accurate physical parameters for all stars are needed to confirm these findings.
Key words: stars: oscillations / stars: fundamental parameters / binaries: general / asteroseismology / stars: variables:δScuti / stars: statistics
© ESO, 2011
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