Observational evidence for a spin-up line in the P-Pdot diagram of millisecond pulsars

TL;DR

This paper provides observational evidence for a theoretical spin-up line in the $P$-$\dot{P}$ diagram of millisecond pulsars, supporting models of their spin-up via accretion from companion stars.

Contribution

It presents the first observational confirmation of the spin-up line in the $P$-$\dot{P}$ diagram using a large pulsar sample and demonstrates Bayesian methods to constrain accretion physics.

Findings

Evidence for the spin-up line in the $P$-$\dot{P}$ diagram.

PSRs J1823$-$3021A and J1824$-$2452A are consistent with the spin-up line.

Bayesian inference constrains accretion rates and disk-magnetosphere interactions.

Abstract

It is believed that millisecond pulsars attain their fast spins by accreting matter and angular momentum from companion stars. Theoretical modelling of the accretion process suggests a spin-up line in the period-period derivative ($P$-$\dot{P}$) diagram of millisecond pulsars, which plays an important role in population studies of radio millisecond pulsars and accreting neutron stars in X-ray binaries. Here we present observational evidence for such a spin-up line using a sample of 143 radio pulsars with $P$ < 30 ms. We also find that PSRs~J1823$-$3021A and J1824$-$2452A, located near the classic spin-up line, are consistent with the broad population of millisecond pulsars. Finally, we show that our approach of Bayesian inference can probe accretion physics, allowing constraints to be placed on the accretion rate and the disk-magnetosphere interaction.