First Kepler results on compact pulsators - III. Subdwarf B stars with V1093 Her and hybrid (DW Lyn) type pulsations

Abstract

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 ≈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 (Teff≈ 20 900 K, Pmax≈ 4.5 h) as well as a suspected hybrid pulsator, KIC002697388, which is extremely cool (Teff≈ 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.

Asteroseismology revealing trapped modes in KIC 10553698A

“…In the first four quarters of the Kepler mission, a survey for pulsating stars was made, and a total of 113 compact-pulsator candidates were checked for variability by Østensen et al (Østensen et al 2010b;2011 = Paper I). This very successful survey revealed one clear V361-Hya pulsator (Kawaler et al 2010b) and one other transient short-period pulsator, and a total of thirteen V1093-Her stars (Reed et al 2010;Kawaler et al 2010a;Baran et al 2011, Paper II), including an sdB+dM eclipsing binary in which the hot primary shows an exceptionally rich pulsation spectrum (Østensen et al 2010a). Another three V1093-Her pulsators have been identified in the open cluster NGC 6791 (Pablo et al 2011;Reed et al 2012a), bringing the total number of sdBV stars in the Kepler field to eighteen.…”

Stellar hydrodynamics caught in the act: Asteroseismology with CoRoT and Kepler

“…Here Reed et al (2010) detected 21 modes, with periods between 0.7 and 2.5 h, and in addition three modes in the p-mode region. Similar observational results were obtained by Van Grootel et al (2010a), who in addition carried out a fit of the g-mode periods to models of the star.…”

Keplerdetection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC 10001893

“…With a Kepler magnitude of 15.85, KIC 10001893 is one out of 19 subdwarf B (sdB) pulsators observed by the Kepler spacecraft in its primary mission , 2011, 2012Kawaler et al 2010a,b;Reed et al 2010Reed et al , 2011Reed et al , 2012Van Grootel et al 2010;Baran et al 2011Baran et al , 2012Charpinet et al 2011b). The spectroscopic atmospheric parameters of KIC 10001893, T eff = 26 700 ± 300 K, log g = 5.30 ± 0.04, and log (N He /N H ) = −2.09±0.1 are very compatible with the g-mode instability strip (Østensen et al 2011).…”