S. Geier, U. Heber, H. Edelmann, R. Napiwotzki, L. Morales-Rueda
We measured projected rotational velocities of more than a hundred apparently
single sdBs. A comparison is made with sdB stars in binary systems with orbits
so wide, that tidal interaction becomes negligible. All of these stars are slow
rotators (vsini<10 km/s) with EC 22081-1916 being the only exception. This
single star has the highest projected rotational velocity ever measured for an
sdB (vsini=163 km/s) and might have been formed by a merger event. The merger
of a red-giant core and a low-mass, main-sequence star or substellar object
during a common envelope phase fits particularly well with observations. The
implications of our results for hot subdwarf formation are briefly discussed.
View original:
http://arxiv.org/abs/1112.2925
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