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Paper: The Secondary Companions in Short-Period sdB Binaries
Volume: 334, 14th European Workshop on White Dwarfs
Page: 363
Authors: Green, E.M.; For, B.-Q.; Hyde, E.A.
Abstract: We have determined the distributions of orbital periods and minimum secondary masses in an unbiased sample of 25 short-period, post-common envelope sdB binaries, and distinguished between main sequence (MS) and white dwarf (WD) companions in most cases. Precise light curves were used to search for reflection effects produced by MS companions in sdB binaries with orbital periods shorter than 0.5−2.0 days. V−J vs. J−H colors were used to identify MS companions with longer periods and larger masses. The two-color plot shows that sdB stars are split into two groups, with a striking dichotomy between the long-period sdB+MS binaries whose secondaries can be detected in optical spectra, and sdB stars showing spectral lines from only the hot star. The latter group includes all short period sdB binaries as well as apparently single sdB stars. The distribution of main sequence secondary masses over all sdB+MS binaries shows a large deficit between 0.3 and 0.6MSolar.
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