THE SCENARIO MACHINE - RESTRICTIONS ON KEY PARAMETERS OF BINARY EVOLUTION

The ''Scenario Machine'' (Monte Carlo simulations of binary evolution) which permits to build up a complete picture of all possible evolutio nary stages of binaries in the Galaxy is used to study parameters of b inary evolution scenario. Ratios of different populations of binary sy stems turn out to be most sensitive to the initial binary mass ratio d istribution, f(q), (q = M(2)/M(1) < 1), the efficiency of angular mome ntum removal during common envelope (CE) stage alpha(CE), and value of additional kick velocity imparted to young pulsars during supernova e xplosions. We find that our model gives the best agreement with the ob servations (within a half-order-of-magnitude difference between the ob served (O) and calculated numbers (C) C/O + O/C similar or equal to 3. 3) if f(q) proportional to q(1.5), which is centered toward equal init ial masses. Common envelope efficiency alpha(CE) is found to less effe ct the results, allowing a range alpha(CE) similar to 0.1 - 10. The be st value of mean kick velocity w found by comparing the calculations w ith observational data on the galactic X-ray luminosity and binary rad iopulsars statistics is similar to 100-200 km/s; the currently popular high mean kick velocity of 450 km/s would give C/O + O/C similar or e qual to 6 - 10 depending on the assumed kick velocity distribution.