XMM-Newton Observations 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 ≈ 48.6 ms, and its derivative \dot{P}\approx 8.6\times 10^{-14}, which is two times larger than previously reported values. The pulsar exhibits two very narrow (FWHM ~1.2 ms) X-ray pulses each rotation, separated by ≈0.48 of the period, with a pulsed fraction of ≈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 × 10¹² G. The pulsar spectrum is well modeled with a hard power-law (PL) model (photon index Γ = 0.9 ± 0.1, hydrogen column density n _H = (2.3 ± 0.3) × 10²² cm^-2). We detect a weak off-pulse emission, which can be modeled with a softer PL (Γ ≈ 1.7 ± 0.7), that is 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 _PSR= L_PSR/\dot{E} = 2 \times 10^{-4} (D/10\,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, Γ ≈ 0.9 ± 0.5, spectrum and a low efficiency, η_PWN ~ 2 × 10^-5(D/10 kpc)², for the compact pulsar wind nebula, unresolved in the XMM-Newton images.