Volume 569, September 2014
|Number of page(s)||14|
|Section||Stellar structure and evolution|
|Published online||10 September 2014|
Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D,
2 Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
3 Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65804, USA
4 Uniwersytet Pedagogiczny w Krakowie, ul. Podchora¸żych 2, 30-084 Kraków, Poland
5 Dr. Karl Remeis-Observatory & ECAP, Astronomisches Inst., FAU Erlangen-Nuremberg, 96049 Bamberg, Germany
Accepted: 10 June 2014
The subdwarf-B pulsator, KIC 10553698A, is one of 16 such objects observed with a one-minute sampling rate for most of the duration of the Kepler mission. Like most of these stars, it displays a rich g-mode pulsation spectrum with several clear multiplets that maintain regular frequency splitting. We identify these pulsation modes as components of rotationally split multiplets in a star rotating with a period of ~41 d. From 162 clearly significant periodicities, we are able to identify 156 as likely components of ℓ = 1 or ℓ = 2 multiplets. For the first time we are able to detect ℓ = 1 modes that interpose in the asymptotic period sequences and that provide a clear indication of mode trapping in a stratified envelope, as predicted by theoretical models. A clear signal is also present in the Kepler photometry at 3.387 d. Spectroscopic observations reveal a radial-velocity amplitude of 64.8 km s-1. We find that the radial-velocity variations and the photometric signal have phase and amplitude that are perfectly consistent with a Doppler-beaming effect and conclude that the unseen companion, KIC 10553698B, must be a white dwarf most likely with a mass close to 0.6 M⊙.
Key words: subdwarfs / binaries: close / stars: oscillations / stars: individual: KIC 10553698
Based on observations obtained by the Kepler spacecraft, the Kitt Peak Mayall Telescope, the Nordic Optical Telescope, and the William Herschel Telescope.
Appendices A and B are available in electronic form at http://www.aanda.org
Tables A.1 and B.1 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A15
© ESO, 2014
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