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Paper: The Mass of the sdB Primary of the Binary HS 2333+3927
Volume: 334, 14th European Workshop on White Dwarfs
Page: 357
Authors: Heber, U.; Drechsel, H.; Karl, C.; Ostensen, R.; Folkes, S.; Napiwotzki, R.; Altmann, M.; Cordes, O.; Solheim, J.-E.; Voss, B.; Koester, D.
Abstract: Short period sdB binaries with cool companions are crucial to understand pre-CV evolution, because they will evolve into cataclysmic variables, when the sdB will have left the extended horizontal branch. Recently we discovered the sixth such system, HS 2333+3927, consisting of an sdB star and an M dwarf (period: 0.172 d) with a very strong reflection effect, but no eclipses. The reflection is stronger than in any of the other similar systems which renders a quantitative spectral analysis very difficult because the Balmer line profiles may be disturbed by the reflected light. A spectroscopic analysis results in Teff = 36,500 K, log g = 5.70, and log(nHe=nH) = −2.15. Mass-radius relations were derived from the results of the analysis of light and radial-velocity curves. Comparison with the mass-radius relation derived from the surface gravity of the sdB star favours a rather low mass of 0.38 MSolar for the primary. The mass of the companion is 0.29 MSolar. HS 2333+3927 is the only known sdB+dM system with a period above the CV period gap.
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