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.
Physics, Astronomy, and Materials Science
Reproduced with permission from Astronomy & Astrophysics, © ESO
subdwarfs stars, oscillations stars
Baran, A. S., M. D. Reed, R. H. Østensen, J. H. Telting, and C. S. Jeffery. "EPIC 211779126: a rare hybrid pulsating subdwarf B star richly pulsating in both pressure and gravity modes." Astronomy & Astrophysics 597 (2017): A95.
Astronomy and Astrophysics