Janusz Ziolkowski, Krzysztof Belczynski
In the Galaxy and in the Magellanic Clouds there are 170 Be X-ray binaries
known to-date. Out of those, 111 host a neutron star, and for the reminder the
nature of a companion is not known. None, so far, is known to host a black
hole. This disparity is referred to as a missing Be -- black hole X-ray binary
problem. The stellar population synthesis calculations following the formation
of Be X-ray binaries in the Galaxy (Belczynski and Ziolkowski 2009) demonstrate
that there is no problem of the missing Be+BH X-ray binaries for the Galaxy
(the expected number of Be -- black hole X-ray binaries is 0 to 2, which is
entirely consistent with the observed Galactic sample). However, the
preliminary calculations for Magellanic Clouds indicate that there is a problem
of the missing Be+BH X-ray binaries for the Clouds (the expected number is
about 6, while none is observed). We believe, that to remove the discrepancy,
one has to take into account a different history of the star formation rate in
the Magellanic Clouds, with the respect to the Galaxy. New stellar population
synthesis calculations are currently being carried out. An updated (as of
November 2011) list of all 170 Be X-ray binaries known presently in the Galaxy
and in the Magellanic Clouds is included.
View original:
http://arxiv.org/abs/1111.2330
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