A new X-ray census of rotation powered pulsars

TL;DR

This study compiles the largest X-ray counterpart sample of over 4000 pulsars, revealing new correlations between X-ray luminosity and pulsar properties, supporting the outer-gap emission model.

Contribution

It provides the first strong evidence of a correlation between X-ray luminosity and light cylinder magnetic field in millisecond pulsars, expanding understanding of pulsar emission mechanisms.

Findings

Established $L_{X} \,\propto \,\dot{E}^{0.85}$ correlation across the X-ray band.

Found a positive correlation between $L_{X}$ and $B_{lc}$ for MSPs.

Observed lower detection likelihood for Galactic Plane Pulsar Snapshot pulsars.

Abstract

To date, over 4000 pulsars have been detected. In this study, we identify 231 X-ray counterparts of Australia Telescope National Facility (ATNF) pulsars by performing a spatial cross match across the Chandra, XMM-Newton observational catalogs. This dataset represents the largest sample of X-ray counterparts ever compiled, including 98 normal pulsars (NPs) and 133 millisecond pulsars (MSPs). Based on this significantly expanded sample, we re-establish the correlation between X-ray luminosity and spin-down power, given by $L_{\rm X} \propto \dot{E}^{0.85\pm0.05}$ across the whole X-ray band. The strong correlation is also observed in hard X-ray band, while in soft X-ray band there is no significant correlation. Furthermore, $L_{\rm X}$ shows a strong correlation with spin period and characteristic age for NPs. For the first time, we observe a strongly positive correlation between $L_{\rm X}$ and the light cylinder magnetic field ($B_{\rm lc}$) for MSPs, with both NPs and MSPs following the relationship $L_{\rm X} \propto B_{\rm lc}^{1.14}$, consistent with the outer-gap model of pulsars that explains the mechanism of X-ray emission. Additionally, we investigate potential X-ray counterparts for Galactic Plane Pulsar Snapshot pulsars, finding a lower likelihood of detection compared to ATNF pulsars.