2009ApJ...695L.163Q -
Astrophys. J., 695, L163-L165 (2009/April-3)
Detection of a tertiary brown dwarf companion in the sdB-type eclipsing binary HS 0705+6700.
QIAN S.-B., ZHU L.-Y., ZOLA S., LIAO W.-P., LIU L., LI L.-J., WINIARSKI M., KULIGOWSKA E. and KREINER J.M.
Abstract (from CDS):
HS 0705+6700 is a short-period (P = 2.3 hr), close binary containing a hot sdB-type primary and a fully convective secondary. We have monitored this eclipsing binary for more than two years and as a result, 32 times of light minimum were obtained. Based on our new eclipse times together with these compiled from the literature, it is discovered that the observed-calculated curve of HS 0705+6700 shows a cyclic variation with a period of 7.15 years and a semiamplitude of 92.4 s. The periodic change was analyzed for the light-travel time effect that may be due to the presence of a tertiary companion. The mass of the third body is determined to be M3 sin i' = 0.0377(±0.0043) M☉ when a total mass of 0.617 M☉for HS 0705+6700 is adopted. For orbital inclinations i' ≥ 32°.8, the mass of the tertiary component would be below the stable hydrogen-burning limit of M3∼ 0.072 M☉, and thus it would be a brown dwarf. The third body is orbiting the sdB-type binary at a distance shorter than 3.6 AU. HS 0705+6700 was formed through the evolution of a common envelope after the primary becomes a red giant. The detection of a substellar companion in HS 0705+6700 system at this distance from the binary could give some constraints on stellar evolution in such systems and the interactions between red giants and their companions.
Abstract Copyright:
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Journal keyword(s):
binaries: close - binaries: eclipsing - stars: individual: HS 0705+6700 - stars: low-mass, brown dwarfs - subdwarfs
Simbad objects:
3
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