Formation and coalescence of relativistic binary stars: effect of kick velocity

For the first time, using Monte-Carlo calculations of the modern scenario for binary stellar evolution with account for spin evolution of magnetized compact stars (the “Scenario Machine”), we compute the amount of galactic binary pulsars with different companion types (OB-star, white dwarf (WD), neutron star (NS), black hole (BH), or planet) assuming various phenomenological distributions for kick velocities of newborn NS. We demonstrate a strong dependence of the binary pulsar population fractions relative to single pulsars on the mean kick velocity and found an optimal kick velocity of 150-200 km/s. We also investigate how the merging rates of relativistic binary stars (NS+NS, NS+BH, BH+BH) depend on the kick velocity. We show that the BH+BH merging may occur, depending on parameters of BH formation, at a rate of one per 200,000 – 500,000 years in a Milky Way type galaxy. The NS+NS merging rate Rns is found to be 1 per ∼ 3, 000 years for zero recoil, and decrease to one per 10, 000 years even for the highest kick velocities of 400 km/s. That the merging rates derived from evolutionary calculations are by two order of magnitude higher than those based on binary pulsar statistics only, is suggested to be due to the fact that the observable binary pulsars in pairs with NS form only a fraction of the total number of binary NS systems. The merging rates obtained imply the expected detection rate of binary BH by a LIGO-type gravitational wave detector comparable with and even higher than the binary NS merging rate for a wide range of parameters. Detecting the final frequency of a merging event at about 100 Hz and the shaping of the waveforms would bring a firm evidence of BH existence in nature.