XMM-NEWTONOBSERVATIONS OF YOUNG AND ENERGETIC PULSAR J2022+3842

Abstract

We report on $XMM-Newton$ EPIC observations of the young pulsar J2022+3842, with a characteristic age of 8.9 kyr. We detected X-ray pulsations and found the pulsation period $P\approx 48.6$ ms, and its derivative $\dot{P}\approx 8.6\times 10^{-14}$, twice larger than the previously reported values. The pulsar exhibits two very narrow (FWHM $\sim 1.2$ ms) X-ray pulses each rotation, separated by $\approx 0.48$ of the period, with a pulsed fraction of $\approx 0.8$. Using the correct values of $P$ and $\dot{P}$, we calculate the pulsar's spin-down power $\dot{E}=3.0 \times 10^{37}$ erg s$^{-1}$ and magnetic field $B=2.1\times 10^{12}$ G. The pulsar spectrum is well modeled with a hard power-law (PL) model (photon index $\Gamma = 0.9\pm0.1 $, hydrogen column density $n_H = (2.3\pm0.3) \times 10^{22}\,{\rm cm}^{-2}$). We detect a weak off-pulse emission which can be modeled with a softer PL ($\Gamma \approx 1.7\pm0.7$), poorly constrained because of contamination in the EPIC-pn timing mode data. The pulsar's X-ray efficiency in the $0.5-8$ keV energy band, $\eta_{\rm PSR}= L_{\rm PSR}/\dot{E} = 2 \times 10^{-4} (D/10\,{\rm kpc})^2$, is similar to those of other pulsars. The $XMM-Newton$ observation did not detect extended emission around the pulsar. Our re-analysis of $Chandra$ X-ray observatory archival data shows a hard, $\Gamma \approx 0.9 \pm 0.5$, spectrum and a low efficiency, $\eta_{\rm PWN}\sim 2\times 10^{-5} (D/10\,{\rm kpc})^2$, for the compact pulsar wind nebula, unresolved in the $XMM-Newton$ images.