First Kepler results on compact pulsators - III. Subdwarf B stars with V1093 Her and hybrid (DW Lyn) type pulsations
Reed, M. D × Kawaler, S. D Ostensen, Roy Bloemen, Steven Baran, A Telting, J. H Silvotti, R Charpinet, S Quint, A. C Handler, G Gilliland, R. L Borucki, W. J Koch, D. G Kjeldsen, H Christensen-Dalsgaard, J #
Priestley and Weale
Monthly Notices of the Royal Astronomical Society vol:409 issue:4 pages:1496-1508
We present the discovery of non-radial pulsations in five hot subdwarf B (sdB) stars based on 27 d of nearly continuous time series photometry using the Kepler spacecraft. We find that every sdB star cooler than approximate to 27 500 K that Kepler has observed (seven so far) is a long-period pulsator of the V1093 Her (PG 1716) class or a hybrid star with both short and long periods. The apparently non-binary long-period and hybrid pulsators are described here. The V1093 Her periods range from 1 to 4.5 h and are associated with g-mode pulsations. Three stars also exhibit short periods indicative of p-modes with periods of 2-5 min and in addition, these stars exhibit periodicities between both classes from 15 to 45 min. We detect the coolest and longest-period V1093 Her-type pulsator to date, KIC010670103 (T-eff approximate to 20 900 K, P-max approximate to 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool (T-eff approximate to 23 900 K) and for the first time hybrid pulsators which have larger g-mode amplitudes than p-mode ones. All of these pulsators are quite rich with many frequencies and we are able to apply asymptotic relationships to associate periodicities with modes for KIC010670103. Kepler data are particularly well suited for these studies as they are long duration, extremely high duty cycle observations with well-behaved noise properties.