Volume 597, January 2017
|Number of page(s)||12|
|Section||Stellar structure and evolution|
|Published online||10 January 2017|
EPIC 211779126: a rare hybrid pulsating subdwarf B star richly pulsating in both pressure and gravity modes
1 Uniwersytet Pedagogiczny, Obserwatorium na Suhorze, ul. Podchorążych 2, 30-084 Kraków, Poland
2 Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65804, USA
3 Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
4 Armagh Observatory, College Hill, Armagh BT61 9DG, UK
5 School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland
Received: 5 September 2016
Accepted: 11 October 2016
We present our analysis of EPIC 211779126, a pulsating subdwarf B star discovered with the Kepler spacecraft during K2 Campaign 5. We found 154 frequencies in the g-mode region as well as 29 frequencies in the p-mode region. This makes EPIC 211779126 a rare hybrid pulsator with a rich pulsation spectrum in both regions. We successfully identified modal degrees and relative radial orders of most of the g-modes using asymptotic period spacing, and modal degrees of some of the p-modes using rotational splitting. We detected trapped modes, which are a very important feature for constraining theoretical models. Our ground-based spectroscopic observations revealed no companion, therefore EPIC 211779126 is likely a single sdB star. Using p-mode multiplets, we derived a rotation period of approximately 16 days, making EPIC 211779126 the fastest rotating non-binary subdwarf B pulsator observed with Kepler. However, we do not find any resolved multiplets among the high-amplitude g-mode pulsations that correspond to the rotation rate inferred from the p-mode splittings. This may indicate that the star’s core is rotating more slowly than its envelope.
Key words: subdwarfs / stars: oscillations
© ESO, 2017
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