Nonthermal X‐Ray Properties of Rotation‐powered Pulsars and Their Wind Nebulae

Abstract

We present a statistical study of the nonthermal X-ray emission of 27 young rotation-powered pulsars (RPPs) and 24 pulsar wind nebulae (PWNe) using the Chandra and XMM-Newton observations, whose high spatial resolutions enable us to resolve pulsars from their surrounding PWNe. We obtain the X-ray luminosities and spectra separately for RPPs and PWNe, and then investigate their distribution and relation to each other, as well as their relation to the pulsar rotational parameters. In pair-correlation analysis we find that (1) the X-ray (2-10 keV) luminosities of both pulsar and PWN (LX,psr and LX,pwn) display a strong correlation with the pulsar spin-down power Ė and characteristic age τ. The scalings resulting from a simple linear fit to the data are LX,psr~Ė0.92+/-0.04 and LX,pwn~Ė1.45+/-0.08 (68% confidence level), respectively; however, neither fit is statistically acceptable. (2) LX,psr also shows a possible weak correlation with the pulsar period P and period derivative Ṗ, whereas LX,pwn manifests a similar weak correlation with Ṗ only. (3) The PWN photon index Γpwn is positively correlated with LX,pwn and LX,pwn/Ė. We also found that the PWN X-ray luminosity is typically 1 to 10 times larger than that from the underlying pulsar, and the PWN photon indices span a range of 1.5