Sternberg Astronomical Institute, Moscow University,
119899 Moscow, Russia
1e-mail: lipunov@sai.msu.su
2e-mail: ozernoy@hubble.gmu.edu; ozernoy@stars.gsfc.nasa.gov
Dept. of Physics & Astron. and Inst. for Comput. Sci. &
Inform., George Mason Univ.,
also Laboratory for Astronomy
& Solar Physics, NASA/GSFC
We are exploring the evolution of massive binary star populations for a nuclear starburst occuring in the conditions similar to the Milky Way galaxy, in its central part, on a time scale of 10 Myr. A computer code is applied allowing for computing, by using Monte Carlo simulations, the evolution of a large ensemble of binary systems, with proper accounting for spin evolution of magnetized neutron stars (NSs). Our results include the number of X-ray transients (NS + main sequence star), super-accreting black holes (BHs), and binaries consisting of a BH + supergiant, all as functions of time.
We find that by 7 Myr after such a starburst one expects 1 X-ray source with a BH (Cyg X-1 type), 1 SS 433-like source (BH in the regime of superaccretion), and 37 transient sources with a NS, all to be within the central 1 kpc or so. An interesting result that can be considered as a specific starburst feature, is that the ratio of the number of systems like SS 433 to the number of X-ray transients is about 1:100, compared to 1:1000, characteristic to the average ratio in the galactic field. The ratio of the total number of X-ray sources containing a BH (of Cyg X-1 + SS 433 types) to the number of X-ray transients with NSs turns out to be a sensitive function of the age of the starburst, and its computed value 0.04 is consistent with observations.
Subject headings: Galaxy: center - stars: neutron stars: evolution - stars: formation - stars: statistics - X-rays: stars