We report on extended photometry of two pulsating subdwarf B (sdB) stars in close binaries. For both cases, we use rotational splitting of the pulsation frequencies to show that the sdB component rotates much too slowly to be in synchronous rotation. We use a theory of tidal interaction in binary stars to place limits on the mass ratios that are independent of estimates based on the radial velocity curves. The companions have masses below 0.26 M⊙. The pulsation spectra show the signature of high-overtone g-mode pulsation. One star, KIC 11179657, has a clear sequence of g modes with equal period spacings as well as several periodicities that depart from that trend. KIC 02991403 shows a similar sequence, but has many more modes that do not fit the simple pattern.
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2012 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
binaries close, stars horizontal branch, stars oscillations, stars rotation, subdwarfs
Pablo, Herbert, Steven D. Kawaler, M. D. Reed, Steven Bloemen, S. Charpinet, Hao Hu, J. Telting et al. "Seismic evidence for non-synchronization in two close sdb+ dM binaries from Kepler photometry." Monthly Notices of the Royal Astronomical Society 422, no. 2 (2012): 1343-1351.
Monthly Notices of the Royal Astronomical Society