Constraints on Pulsar Evolution: The Joint Period-Spindown Distribution of Millisecond Pulsars

TL;DR

This study examines the period and spindown distributions of millisecond pulsars to test their evolutionary origins, revealing inconsistencies with the standard model and suggesting multiple progenitor populations.

Contribution

It provides a detailed analysis of the joint period-spindown distribution, challenging the standard evolutionary model for millisecond pulsars and proposing the need for alternative explanations.

Findings

Overabundance of young/high magnetic field MSRPs inconsistent with standard model

Fastest millisecond pulsars cannot originate from observed MSXPs under current model

Statistically significant evidence against a single progenitor population

Abstract

We calculate the joint period-spindown (P-Pdot) distributions of millisecond radio pulsars (MSRP) for the standard evolutionary model in order to test whether the observed MSRPs are the unequivocal descendants of millisecond X-ray pulsars (MSXP). The P-Pdot densities implied by the standard evolutionary model compared with observations suggest that there is a statistically significant overabundance of young/high magnetic field MSRPs. Taking biases due to observational selection effects into account, it is unlikely that MSRPs have evolved from a single coherent progenitor population that loses energy via magnetic dipole radiation after the onset of radio emission. By producing the P-Pdot probability map, we show with more than 95% confidence that the fastest spinning millisecond pulsars with high magnetic fields, e.g. PSR B1937+21, cannot be produced by the observed MSXPs within the framework of the standard model.