The effects of high-velocity supernova kicks on the orbital properties and sky distributions of neutron-star binaries

Abstract

We systematically investigate the effects of high supernova kick velocities on the orbital parameters of post-supernova neutron-star binaries. Using Monte Carlo simulations, we determine the post-supernova distributions of orbital parameters (orbital period, eccentricity, system velocity, spin inclination, ratio of spin to orbital angular momentum) for progenitors of high-mass X-ray binaries (HMXBs) and low-mass X-ray binaries (LMXBs). With the recent distribution of pulsar birth velocities by Lyne & Lorimer, only about 27 per cent of massive systems remain bound after the supernova, of which ∼ 26 per cent immediately experience dynamical mass transfer and possibly merge to become Thorne-Żytkow objects. The correlations between various orbital parameters can be compared with observational samples to yield information about supernova kick velocities and pre-supernova orbital-period distributions. After the supernova, the spins of most stars in massive systems have large inclinations with respect to their orbital axes, and a significant fraction of systems (∼ 20 per cent) contain stars with retrograde spins. This may have important implications for the interpretation of those HMXBs that seem to have tilted, ‘precessing’ accretion discs. We estimate that the spin angular momentum in the massive components of most HMXBs is a significant fraction (0.1–0.4) of the total orbital angular momentum. Therefore spin-orbit coupling effects may be important in many HMXBs.

Locations

• Monthly Notices of the Royal Astronomical Society - View - PDF
• arXiv (Cornell University) - View - PDF