Do all millisecond pulsars share a common heritage?

TL;DR

This paper investigates whether all millisecond radio pulsars originate from low mass X-ray binaries by comparing observed pulsar properties with predictions from the standard evolutionary model, finding some pulsars cannot be explained by it.

Contribution

The study provides a quantitative analysis and probability map showing that certain fast-spinning millisecond pulsars are inconsistent with the standard evolutionary model from LMXBs.

Findings

Fastest millisecond pulsars with high magnetic fields cannot be produced by the standard model.

The standard evolutionary process constrains the joint distribution of pulsar periods and spin-down rates.

More than 95% confidence that some pulsars are not descendants of observed millisecond X-ray pulsars.

Abstract

The discovery of millisecond pulsations from neutron stars in low mass X-ray binary (LMXB) systems has substantiated the theoretical prediction that links millisecond radio pulsars (MSRPs) and LMXBs. Since then, the process that produces millisecond radio pulsars from LMXBs, followed by spin-down due to dipole radiation has been conceived as the 'standard evolution' of millisecond pulsars. However, the question whether all the observed millisecond radio pulsars could be produced by LMXBs has not been quantitatively addressed until now. The standard evolutionary process produces millisecond pulsars with periods (P) and spin-down rates (Pdot) that are not entirely independent. The possible P-Pdot values that millisecond radio pulsars can attain are jointly constrained. In order to test whether the observed millisecond radio pulsars are the unequivocal descendants of millisecond X-ray pulsars (MSXP), we have produced a probability map that represents the expected distribution of millisecond radio pulsars for the standard model. We show with more than 95 % confidence that the fastest spinning millisecond radio pulsars with high magnetic fields, e.g. PSR B1937+21, cannot be produced by the observed millisecond X-ray pulsars within the framework of the standard model.