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: http://xray.sai.msu.ru/~mystery/articles/review/node72.html
Дата изменения: Sat Mar 1 20:50:55 1997 Дата индексирования: Tue Oct 2 14:52:22 2012 Кодировка: Поисковые слова: hydrogen |
In this section, we study the evolution of stellar
populations on a time-scale of 10
Myr for a starburst occurring under conditions similar to those
in the Galactic Center (see Lipunov et al. (1995d)[126]).
We estimate the expected number of
X-ray transient sources (NS + MS star),
super accreting BH, and BH + supergiant binaries,
all as functions of time elapsed after the burst.
The results are normalized so as to give the number
of OB stars with masses greater than 
in agreement with the
results of Tamblyn and Rieke (1993[186]).
Recently, Leitherer and Heckman (1995[96]) have
made a detailed investigation
of star formation for elliptical and spiral galaxies, but
only for single stars.
X-ray observations of the Galactic Center have revealed a number of energetic X-ray sources located in the innermost regions of the Galaxy (Pavlinsky et al., 1994[158], Churazov et al., 1994[33]), with some of them being considered, due to their spectral characteristics, as BH candidates. These observations demonstrate an enhanced spatial density of X-ray binary systems in the central region of the Galaxy in comparison with the average galactic value.
We show that this situation is a natural consequence of binary stellar evolution, if a star formation burst occurred a few millions years ago at the Galactic Center. The evidence for such a starburst was put forward by Sofue (1994[184]) who studied the North Polar Spur data, and by Ozernoy (1994[148]) who studied the data on the 10 KeV emitting gas in the central 200 pc of the Galaxy. A recently discovered possible WR-star in the Galactic Center (Blum et al., 1995[20]) provides a very strong direct argument for recent star formation in the Galactic Center.
Specifically, we focus on the most prominent, from the observational point of view, representatives of the late stages of massive binary evolution, such as X-ray transients (NS in a highly eccentric orbit around a main-sequence star, like A0535+26), super accreting BH (observationally seen as SS 433 if in pair a with a Roche lobe filling secondary component), and BH + supergiant binaries (like Cyg X-1, with an evolved supergiant underfilling its Roche lobe).