The Role of Helium Stars in the Formation of Double Neutron Stars

Preprint
Publisher Website
Google Scholar
  • 11 October 2002
Abstract
We have calculated the evolution of 60 model binary systems consisting of helium stars in the mass range of M_He=2.5-6Msun with a 1.4Msun neutron star (NS) companion to investigate the formation of double neutron star systems (DNS). Orbital periods ranging from 0.09 to 2 days are considered, corresponding to Roche lobe overflow on starting anywhere from the helium main sequence to after the ignition of core-C burning. We have also examined the evolution into a common envelope (CE) phase via secular instability, delayed dynamical instability, and the consequence of matter filling the NS Roche lobe. The survival of some close He-star NS binaries through this last mass transfer (MT) episode (either dynamically stable or unstable MT phase) leads to the formation of extremely short-period DNS systems (with P<0.1 days). In addition, we find that systems throughout the entire calculated mass range can evolve into a CE phase, depending on the orbital period at the onset of MT. The critical orbital period below which CE evolution occurs generally increases with M_He. In addition, a CE phase may occur during a short time for systems characterized by orbital periods of 0.1-0.5 days at low He-star masses (2.6-3.3Msun). The existence of a short-period population of DNS increases the predicted detection rate of inspiral events by ground-based gravitational-wave detectors and impacts their merger location in host galaxies and their possible role as gamma-ray burst progenitors. We use a set of population synthesis calculations and investigate the implications of the MT results for the orbital properties of DNS populations.

This publication has 0 references indexed in Scilit: