XMM-Newton observations of young and energetic pulsar J2022+3842

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 P-dot ≈8.6×10⁻¹⁴, 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 P-dot , we calculate the pulsar's spin-down power E-dot =3.0×10³⁷ 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, η_PSR=L_PSR/ E-dot =2×10⁻⁴(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.