We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey sample and the various methods applied in its compilation are described, and spectroscopic observations are presented to separate the objects into accurate classes. From the Kepler photometry we clearly identify nine compact pulsators and a number of interesting binary stars. Of the pulsators, one shows the strong, rapid pulsations typical of a V361 Hya-type sdB variable (sdBV); seven show long-period pulsation characteristics of V1093 Her-type sdBVs; and one shows low-amplitude pulsations with both short and long periods. We derive effective temperatures and surface gravities for all the subdwarf B stars in the sample and demonstrate that below the boundary region where hybrid sdB pulsators are found, all our targets are pulsating. For the stars hotter than this boundary temperature a low fraction of strong pulsators (<10 per cent) is confirmed. Interestingly, the short-period pulsator also shows a low-amplitude mode in the long-period region, and several of the V1093 Her pulsators show low-amplitude modes in the short-period region, indicating that hybrid behaviour may be common in these stars, also outside the boundary temperature region where hybrid pulsators have hitherto been found.
Physics, Astronomy, and Materials Science
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2010 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
surveys, binaries close, stars oscillations, subdwarfs, white dwarfs
Østensen, Roy H., Roberto Silvotti, S. Charpinet, R. Oreiro, Gerald Handler, E. M. Green, Steven Bloemen et al. "First Kepler results on compact pulsators–I. Survey target selection and the first pulsators." Monthly Notices of the Royal Astronomical Society 409, no. 4 (2010): 1470-1486.
Monthly Notices of the Royal Astronomical Society