摘要：We report on the X-ray properties of four rotation-powered pulsars with characteristic ages in the range 0.3–5 Myr, derived from the analysis ofXMM–Newtonarchival observations. We found convincing evidence of thermal emission only in the phase-averaged spectrum of PSR B0114+58, which is well fitted by a blackbody with temperaturekT= 0.17 ± 0.02 keV and emitting radiusR= 405+110−90m, consistent with the size of its polar cap. The three other considered pulsars, PSR B0628−28, PSR B0919+06, and PSR B1133+16, have phase-averaged spectra that can be described well by single power laws with photon index Γ ~ 3. The 3σupper limits on the bolometric luminosity of a possible thermal component with temperatures in the range ~0.05−2 keV areLbol≲ 3.2 × 1028erg s−1andLbol≲ 2.4 × 1029erg s−1, for PSR B0628−28 and PSR B0919+06, respectively. On the other hand, we found possible evidence that the pulsed emission of PSR B0628−28 is thermal. Two absorption lines at ~0.22 keV and ~0.44 keV are detected in the spectrum of PSR B1133+16. They are best interpreted as proton cyclotron features, implying the presence of multipolar components with a field of a few 1013G at the neutron star polar caps. We discuss our results in the context of high-energy emission models of old rotation-powered pulsars.
关键词：Key wordsenpulsars: generalstars: neutronpulsars: individual: PSR B0628−28pulsars: individual: PSR B0919+06pulsars: individual: PSR B0114+58pulsars: individual: PSR B1133+16
