Effect of irradiation on the spin of millisecond pulsars

TL;DR

This paper investigates how irradiation influences the spin evolution of millisecond pulsars during binary evolution, proposing it as a key factor in explaining high spin period derivatives observed in some MSPs.

Contribution

It introduces a model using MESA to show irradiation effects can alter MSP spin properties, providing a new explanation for high spin period derivatives.

Findings

Irradiation modifies MSP spin period and mass.

Irradiation can lead to higher spin period derivatives.

Binary evolution with irradiation explains observed MSP properties.

Abstract

A millisecond pulsar (MSP) is an old neutron star (NS) that has accreted material from its companion star, causing it to spin up, which is known as the recycling scenario. During the mass transfer phase, the system manifests itself as an X-ray binary. PSR J1402+13 is an MSP with a spin period of $5.89~{\rm ms}$ and a spin period derivative of $\log\dot{P}_{\rm spin}=-16.32$. These properties make it a notable object within the pulsar population, as MSPs typically exhibit low spin period derivatives. In this paper, we aim to explain how an MSP can posses high spin period derivative by binary evolution. By utilizing the stellar evolution code \textsc{MESA}, we examine the effects of irradiation on the companion star and the propeller effect on the NS during binary evolution. We demonstrate that irradiation can modify the spin period and mass of an MSP, resulting in a higher spin period derivative. These results suggest that the irradiation effect may serve as a key factor in explaining MSPs with high spin period derivatives.