Evolution of close binaries after the burst of starformation for different IMFs

Popov, S. B.; Lipunov, V. M.; Prokhorov, M. E.; Postnov, K. A.

Evolution of close binaries after the burst of starformation for different IMFs

Authors

Description

We use "Scenario Machine" -- the population synthesis simulator -- to calculate the evolution of populations of selected types of X-ray sources after a starformation burst with the total mass in binaries (1--1.5) \cdot 10^6 M_{\odot}$ during the first 20 Myr after a burst. We present here the results of two sets of runs of the program. In the first set we examined the following types of close binaries: transient sources-- neutron stars with Be- stars; ``X-ray pulsars''-- neutron stars in pairs with supergiants; Cyg X-1-like sources-- black holes with supergiants; ``SS443-like sources''-- superaccreting black holes. We used two values of the exponent $α$ in the initial mass function: 2.35 (Salpeter's function) and 1 (``flat spectrum''). The calculations were made for the folowing values of the upper limit of the mass function: 120 and 30 $M_{\odot}$. For the ``flat spectrum'', suggested in (Contini et al, 1995), the number of sources of all types significantly increased. With the ``flat spectrum'' and with the upper mass limit 120 $M_{\odot}$ we obtained hundreds of sources of all calculated types. Decreasing of the upper mass limit below the critical mass of a black hole formation increase the number of transient sources with neutron stars up to $\approx 300$. In the second set we examined the evolution of of 12 other types of X-ray sources for $α=1$, $α=1.35$ and $α=2.35$ and for three upper mass limits: 120 $M_{\odot}$, 60 $M_{\odot}$, 40 $M_{\odot}$ (see Perez-Olia & Colina 1995 for the reasons for such upper limits) on the same time scale 20 Myr after a star formation burst.
12 pages, 4 PostScript figures, to be presented as a poster at the conference "Cosmology: from COBE to galaxy formation", 1-7 December 1997, Copenhagen