Formation and evolution of compact binaries in globular clusters: II. Binaries with neutron stars.

In this paper, the second of a series, we study the stellar dynamical and evolutionary processes leading to the formation of compact binaries containing neutron stars in dense globular clus-ters. For this study, 70 dense clusters were simulated independently, with a total stellar mass ∼ 2 × 107 M⊙, well exceeding the mass of all dense globular clusters in our Galaxy. We find that, in order to reproduce the empirically derived formation rate of low-mass X-ray bina-ries (LMXBs), we must assume that NSs can be formed via electron-capture supernovae with typical natal kicks smaller than in core-collapse supernovae. Our results explain the observed dependence of the number of LMXBs on “collision number ” as well as the large scatter ob-served between different globular clusters. We predict that the number of quiescent LMXBs should not have a strong metallicity dependence. For millisecond pulsars (MSPs), we distin-guish high-magnetic-field (short-lived) and low-magnetic-field (long-lived) populations. With this distinction, we obtain good agreement of our models with the numbers and characteris-tics of observed MSPs in 47 Tuc and Terzan 5, as well as with the cumulative statistics for MSPs detected in globular clusters of different dynamical properties. We find that significant production of merging double neutron stars potentially detectable as short γ-ray bursts occurs only in very dense, most likely core-collapse clusters