Stochastic pulsations in the subdwarf-B star KIC 2991276 (Ostensen et al.)

Vol. 564
In section 1. Letters

Stochastic pulsations in the subdwarf-B star KIC 2991276

The subdwarf-B star KIC2991276 was monitored with the Kepler spacecraft for nearly three years. Two pulsation modes with periods of 122 and 132 s, as well as a few weaker modes with periods ranging from 118 to 216 s were detected. The modes in KIC 2991276 do not display long-term coherency, in contrast to other subdwarf-B pulsators. Instead, the pulsations in KIC 2991276 lose coherence on timescales longer than ~60 days. Stochastic oscillations are commonly observed in the Sun and other cool stars, but this is the first unambiguous detection in a hot subdwarf. The authors discuss possible causes of this phenomenon.