J0453+1559: a neutron star-white dwarf binary from a thermonuclear electron-capture supernova?

TL;DR

This paper proposes that the companion in the J0453+1559 binary system might be a white dwarf formed via a thermonuclear electron-capture supernova, challenging the previous neutron star interpretation.

Contribution

It introduces a novel scenario where the companion is a white dwarf from a tECSN, providing an alternative explanation for the system's properties.

Findings

White dwarf companion could explain the system's orbital characteristics.

Ejecta mass and kick velocity are consistent with a white dwarf formation scenario.

Further research on tECSNe is needed to confirm this hypothesis.

Abstract

The compact binary radio pulsar system J0453+1559 (Martinez et al. 2015) consists of a recycled pulsar as primary component of $1.559(5)\,M_\odot$ and an unseen companion star of $1.174(4)\,M_\odot$. Because of the relatively large orbital eccentricity of $e = 0.1125$, it was argued that the companion is a neutron star, making it the neutron star with the lowest accurately determined mass to date. However, a direct observational determination of the nature of the companion is currently not feasible. Moreover, state-of-the-art stellar evolution and supernova modeling are contradictive concerning the possibility to produce such a low-mass neutron star remnant. Here we challenge the neutron star interpretation by reasoning that the lower-mass component could instead be a white dwarf born in a thermonuclear electron-capture supernova (tECSN) event, in which oxygen-neon deflagration in the degenerate stellar core of an ultra-stripped progenitor ejects several $0.1\,M_\odot$ of matter and leaves a bound ONeFe white dwarf as the second-formed compact remnant. We determine the ejecta mass and remnant kick needed in this scenario to explain the properties of PSR~J0453+1559 by a neutron star--white dwarf system. More work on tECSNe is needed to assess the viability of this scenario.