The accretion rate and minimum spin period of accreting pulsars

TL;DR

This paper investigates how magnetic field decay during accretion limits the minimum spin period of neutron stars, explaining the observed discrepancy between the shortest detected and theoretically possible spin periods.

Contribution

It introduces a mechanism where magnetic field decay during accretion prevents neutron stars from spinning up beyond a certain limit, refining understanding of pulsar spin evolution.

Findings

Magnetic field decay reduces angular momentum transfer efficiency.

Neutron stars cannot spin faster than a certain limit despite prolonged accretion.

The mechanism explains the gap between observed shortest and theoretical minimum spin periods.

Abstract

We consider combined rotational, magnetic, and thermal evolution of the neutron star during the accretion phase in a binary system. A rapid accretion-driven decay of the magnetic field decreases substantially the efficiency of angular momentum transfer. As a result, the neutron star cannot spin up to periods shorter than some limiting value even if accretion is very long and accretion rate is high. The proposed mechanism can explain a discrepancy between the shortest detected period and minimal possible spin period of neutron stars.