Formation of millisecond pulsars with long orbital periods by accretion-induced collapse of white-dwarfs

TL;DR

This study demonstrates that accretion-induced collapse of white dwarfs can produce millisecond pulsars with long orbital periods, covering observed wide-orbit MSPs in the 50-1200 day range.

Contribution

It systematically explores the formation of MSPs via the RG donor channel using binary evolution calculations, extending the known orbital period range to 50-1200 days.

Findings

The RG donor channel can account for MSPs with orbital periods of 50-1200 days.

Most observed wide-orbit MSPs can be explained by this formation channel.

AIC of white dwarfs is a viable pathway for forming MSPs with long orbital periods.

Abstract

Accretion-induced collapse (AIC) of massive white-dwarfs (WDs) has been proposed as an important way for the formation of neutron star (NS) systems. An oxygen-neon (ONe) WD that accretes H-rich material from a red-giant (RG) star may experience the AIC process, eventually producing millisecond pulsars (MSPs), known as the RG donor channel. Previous studies indicate that this channel can only account for MSPs with orbital periods $>500\,\rm d$. It is worth noting that some more MSPs with wide orbits ($60-500\,\rm d$) have been detected by recent observations, but their origin is still highly uncertain. In the present work, by employing an adiabatic power-law assumptions for the mass-transfer process, we performed a large number of complete binary evolution calculations for the formation of MSPs through the RG donor channel in a systematic way. We found that this channel can contribute to the observed MSPs with orbital periods in the range of $50-1200\,{\rm d}$, and almost all the observed MSPs with wide orbits can be covered by this channel in the WD companion mass versus orbital period diagram. The present work indicates that the AIC process provides a viable way to form MSPs with wide orbits.