Can eccentric binary millisecond pulsars form by accretion induced collapse of white dwarfs?

TL;DR

This study investigates whether accretion-induced collapse of white dwarfs can produce eccentric binary millisecond pulsars, concluding that it is unlikely under typical conditions and thus cannot explain certain observed pulsars.

Contribution

The paper uses population synthesis modeling to assess the AIC channel's ability to form eccentric BMSPs, providing new constraints on pulsar formation scenarios.

Findings

AIC can produce eccentric BMSPs only with high natal kicks.

Most eccentric BMSPs formed via AIC are with helium star companions.

AIC is unlikely to form BMSPs with orbital periods over 20 days.

Abstract

Binary radio pulsars are generally believed to have been spun up to millisecond periods (i.e. recycling) via mass accretion from their donor stars, and they are the descendants of neutron star low-mass X-ray binaries. However, some studies indicate that the formation of pulsars from the accretion-induced collapse (AIC) of accreting white dwarfs (WDs) cannot be excluded. In this work, we use a population synthesis code to examine if the AIC channel can produce eccentric binary millisecond pulsars (BMSPs) in the Galaxy. Our simulated results indicate that, only when the natal MSPs receive a relatively strong kick ($\ga100\rm km\,s^{-1}$), can the AIC channel produce $\sim 10-180$ eccentric ($e>0.1$) BMSPs in the Galaxy, most of which are accompanied by a Helium star. Such a kick seems to be highly unlikely in the conventional AIC process, hence the probability of forming eccentric BMSPs via the AIC channel can be ruled out. Even if a high kick is allowed, the AIC channel cannot produce eccentric BMSPs with an orbital period of $\ga 20$ days. Therefore, we propose that the peculiar BMSP PSR J1903+0327 cannot be formed by the AIC channel. However, the AIC evolutionary channel may produce some fraction of isolated millisecond pulsars, and even sub-millisecond pulsars if they really exist.