We present a statistical study of the non-thermal X-ray emission of 27 young rotation powered pulsars ( RPPs ) and 24 pulsar wind nebulae ( PWNe ) by using the Chandra and the XMM-Newton observations , which with the high spatial resolutions enable us to spatially 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 the relation with the pulsar rotational parameters .
In the pair-correlation analysis we find that : ( 1 ) the X-ray ( 2-10 keV ) luminosities of both pulsar and PWN ( L _ { X,psr } and L _ { X,pwn } ) display a strong correlation with pulsar spin down power \dot { E } and characteristic age \tau , and the scalings resulting from a simple linear fit to the data are L _ { X,psr } \propto \dot { E } ^ { 0.92 \pm 0.04 } and L _ { X,pwn } \propto \dot { E } ^ { 1.45 \pm 0.08 } ( 68 % confidence level ) , respectively , however , both the fits are not statistically acceptable ; ( 2 ) L _ { X,psr } also shows a possible weak correlation with pulsar period P and period derivative \dot { P } , whereas L _ { X,pwn } manifests a similar weak correlation with \dot { P } only ; ( 3 ) The PWN photon index \Gamma _ { pwn } is positively correlated with L _ { X,pwn } and L _ { X,pwn } / \dot { E } .
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 \lesssim \Gamma _ { pwn } \lesssim 2 .
The statistic study of PWN spectral properties supports the particle wind model in which the X-ray emitting electrons are accelerated by the termination shock of the wind .