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

TL;DR

This paper presents the first self-consistent 1D model of a double neutron star progenitor leading to an ultra-stripped supernova, providing insights into their formation and connection to observed DNS mergers.

Contribution

It introduces a novel, detailed model of a DNS progenitor system from binary evolution to core collapse, advancing understanding of ultra-stripped supernovae and DNS formation.

Findings

The model predicts a second-born neutron star of about 1.44 solar masses.

The progenitor's structure includes a 0.29 solar mass He-rich envelope and a 1.61 solar mass CO core.

The system's evolution can explain the properties of observed DNS mergers.

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 $1.35\;M_\odot$ NS and a $3.20\;M_\odot$ 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 $1000\;{\rm km\,s}^{-1}$. The exploding star has a total mass of $\sim 1.90\;M_\odot$, consisting of a $\sim 0.29\;M_\odot$ He-rich envelope embedding a CO core of $\sim 1.61\;M_\odot$ and an iron-rich core of $\sim 1.50\;M_\odot$. The resulting second-born NS has an estimated mass of $\sim 1.44\;M_\odot$ 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.