Finding that almos two-thirds of contact binaries are members of multiple stellar systems.
Authors:
T. Pribulla, S.M. Rucinski
Image & caption:
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Image caption::
Ratio of the rentgen and bolometric flux for contact binary stars as an indicator of additional components. The thick solid line indicates an approximate lower limit of the ratio; the dashed lines correspond to 10 and 100-times larger ratios. The flux ratios correspond to the measurements (circles) and to the upper limit estimates (triangles) in the RASS catalogue (ROSAT All Sky Survey). In case that the companion is a late-type M dwarf the ratio is enhanced. If the companion is an early-type A/F star, the ratio is reduced. The filled circles and asterisks represent known (or suspected) triple systems (shown with their catalogue designations).
Description:
Contact binary stars are systems with the lowest angular momentum among close binaries with non-degenerate components. Therefore, their origin requires substantial angular momentum loses. The present study of multiplicity of contact binaries uses all available observations such as: high-dispersion spectroscopy, direct observations using speckle interferometry and adaptive optics, astrometric observations (parallax and proper-motion errors), spectral-energy-distribution peculiarity (including x-ray radiation), so-called light-time effect caused by the finite speed of light, binary orbit precession etc. Several techniques were combined for individual objects. The final result is that in the sample of 138 contact binaries (brighter that V=10 in the maximum) the lower limit of the multiple stellar systems incidence is 42±5%, while in the much better studied Northern-hemisphere sample it is as much as 56±8%. Adding all suspicious cases for northern objects would increase the incidence to 68±9%. The detected high incidence of multiplicity supports the hypothesis that all contact binaries were formed in the multiple systems.
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