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        Spectroscopic Analysis of Subluminous B Stars in Binaries with Compact Companions

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        902255.pdf (PDF, 228Kb)
        Author
        Geier, S.
        Karl, C.
        Edelmann, H.
        Heber, U.
        Napiwotzki, R.
        Attention
        2299/2143
        Abstract
        The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with unseen compact companions to derive their masses and clarify their nature. Radial velocity curves were obtained from time resolved spectroscopy. The atmospheric parameters were determined in a quantitative spectral analysis. Based on high resolution spectra we were able to measure the projected rotational velocity of the stars with high accuracy. The assumption of orbital synchronisation makes it possible to constrain inclination angle and companion mass of the binaries. Five invisible companions have masses that are compatible with that of normal white dwarfs or late type main sequence stars. But four sdBs have very massive companions like heavy white dwarfs (> 1M⊙), neutron stars or even black holes. Such a high fraction of massive compact companions is not expected from current models of binary evolution.
        Publication date
        2007
        Published in
        In: Procs of the 15th European Workshop on White Dwarfs - ASP Conf Series 372
        Other links
        http://hdl.handle.net/2299/2143
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