Novel Model of an Ultra-stripped Supernova Progenitor of a Double Neutron Star

Abstract

Recent discoveries of double neutron star (DNS) mergers and ultra-stripped supernovae (SNe) raise the questions of their origin and connection. We present the first 1D~model of a DNS progenitor system which is calculated self-consistently until an ultra-stripped iron core collapse. We apply the \texttt{MESA} code starting from a post-common envelope binary consisting of a $1.35M_{\odot }$ NS and a $3.20M_{\odot }$ zero-age main-sequence helium star and continue the modelling via Case~BB Roche-lobe overflow until the infall velocity of the collapsing iron core exceeds $1000{\mathrm{km}\mathrm{s}}^{-1}$. The exploding star has a total mass of $\sim 1.90M_{\odot }$, consisting of a $\sim 0.29M_{\odot }$ He-rich envelope embedding a CO core of $\sim 1.61M_{\odot }$ and an iron-rich core of $\sim 1.50M_{\odot }$. The resulting second-born NS has an estimated mass of $\sim 1.44M_{\odot }$ and we discuss the fate of the post-SN system, as well as the mild recycling of the first-born NS. Depending on the initial conditions, this family of systems is anticipated to reproduce the DNS mergers detected by the LIGO-network.

8 pages, 5 figures, ApJL in press