Formation of neutron stars inside planetary nebulae via accretion-induced collapse and core-merger-induced collapse from white dwarf binaries

TL;DR

This paper explores two novel pathways for neutron star formation within planetary nebulae, involving accretion-induced collapse of white dwarfs and core-merger-induced collapse during binary evolution, supported by simulations and population modeling.

Contribution

It introduces two new formation channels for neutron stars inside planetary nebulae, supported by stellar evolution simulations and binary population synthesis.

Findings

Neutron stars can form via accretion-induced collapse in symbiotic nebulae.

Binary mergers during common envelope evolution can produce neutron stars within PNe.

Milky Way may host dozens of NS-WD binary systems formed through these channels.

Abstract

The formation of neutron stars (NSs) within planetary nebulae (PNe) has not been previously even mentioned in the literature. In this paper, I propose two possible formation channels for NSs inside PNe. First, using simulations performed with the MESA stellar evolution code, I present a scenario in which NSs form via the accretion-induced collapse (AIC) of oxygen-neon-magnesium (ONeMg) white dwarfs (WDs) inside PNe--referred to here as symbiotic nebulae. In the late evolutionary stages of ONeMg WD-red giant (or asymptotic giant branch) star binaries, substantial mass loss can occur through strong stellar winds or/and Roche-lobe overflow, potentially leading to the formation of nebulae surrounding central accreting WD binaries. These nebulae may be ionized by the hot cores of the giant stars or by the accreting WDs themselves. Under such conditions, the accreting WD may grow in mass to the Chandrasekhar limit and undergo collapse into a neutron star. NSs formed via this AIC channel are likely to retain WD companions, resulting in NS-WD binary systems, of which the Milky Way may host dozens. Second, through binary population synthesis modeling, I introduce another evolutionary pathway: the core-merger-induced collapse occurring during the common envelope evolution of ONeMg WD binaries. This process may result in the formation of a newborn NS within a PN-or, in some cases, a pulsar wind nebula.