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

TL;DR

This work proposes two novel channels for neutron-star formation inside planetary nebulae: (1) accretion-induced collapse of ONeMg white dwarfs in symbiotic nebulae formed by WD–giant binaries, demonstrated with MESA simulations showing mass transfer can drive a WD to $M_{\rm Ch} = 1.44\,M_\odot$ and produce a surrounding nebula, and (2) core-merger-induced collapse during common-envelope evolution, explored with binary population synthesis to identify systems where a WD merges with a giant core and forms a NS inside a PN. The study combines detailed 1D stellar evolution modeling of WD–RG binaries with rapid binary evolution simulations to map viable parameter spaces and predict observational manifestations, such as NS–WD binaries in the Milky Way and PN-embedded NS or pulsar-wind nebula signatures. The findings expand the landscape of NS formation scenarios and offer new avenues for detecting and studying rare WD explosions and collapses within planetary nebulae. The work has implications for binary evolution theory, PN formation, and the interpretation of peculiar nebulae hosting compact objects.

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.

Figures (4)

• Figure 1: Evolutionary pathways of WD binaries to form PNe (symbiotic nebulae) and the newborn neutron star. Abbreviations: MS: main sequence (star); RG: red giant; AGB: asymptotic giant branch; RLOF MT: Roche lobe overflow Mass transfer; WD: white dwarf; NS: neutron star.
• Figure 2: Evolution of a WD - RG binary which may form PN (symbiotic nebula) and the newborn NS. Results are derived from a 1D MESA simulation of a binary consisting of a $1.2 M_\odot$ WD and a $1.5 M_\odot$ RG star in the 120 day orbit. Upper figure shows the RLOF mass transfer rate and wind mass loss rate of the RG star, and lower figure shows the mass evolution of the RG star and WD.
• Figure 3: A typical evolutionary pathway to form neutron stars inside PNe via the core-merger-induced collapse (CMIC). CE: common envelope; see the text and Figure 1 for other abbreviations.
• Figure 4: A jointplot: distributions of masses of CE and total core from ONeMg WD binaries during the CE phase. Total cores are the addition of the WDs and core of companion giant stars. WD binaries which lead to the merger of WD and RG's core inside the CE are selected with a condition of total core masses being larger than $1.44 M_\odot$, and these systems are expected to form neutron stars inside PNe via the CMIC.