S. Geier, L. Classen, P. Bruenner, K. Nagel, V. Schaffenroth, C. Heuser, U. Heber, H. Drechsel, H. Edelmann, C. Koen, S. J. O'Toole, L. Morales-Rueda
It has been suggested that besides stellar companions, substellar objects in
close orbits may be able to trigger mass loss in a common envelope phase and
form hot subdwarfs. In an ongoing project we search for close substellar
companions combining time resolved high resolution spectroscopy with
photometry. We determine the fraction of as yet undetected radial velocity
variable systems from a sample of 27 apparently single sdB stars to be 16%. We
discovered low-mass stellar companions to the He-sdB CPD-20 1123 and the
pulsator KPD 0629-0016. The brown dwarf reported to orbit the eclipsing binary
SDSS J0820+0008 could be confirmed by an analysis of high resolution spectra
taken with UVES. Reflection effects have been detected in the light curves of
the known sdB binaries CPD-64 481 and BPS CS 22169-0001. The inclinations of
these systems must be much higher than expected and the most likely companion
masses are in the substellar regime. Finally, we determined the orbit of the
sdB binary PHL 457, which has a very small radial velocity amplitude and may
host the lowest mass substellar companion known. The implications of these new
results for the open question of sdB formation are discussed.
View original:
http://arxiv.org/abs/1112.2929
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