Observations of PSR J2021+3651 and its X-ray pulsar wind nebula G75.2+0.1

Abstract

We present the results from X-ray and radio observations of the recently discovered young Vela-like pulsar PSR J2021+3651, which is coincident with the EGRET γ-ray source GeV 2020+3658. A 19.0 ks Chandra ACIS-S observation has revealed a ∼20″ × 10″ pulsar wind nebula that is reminiscent of the equatorial tori seen around some young pulsars, along with thermal emission from an embedded point source (kT ∞ = 0.15 ± 0.02 keV). We have named the nebula G75.2+0.1. Its spectrum is well fitted by an absorbed power-law model with a photon index of Γ = 1.7 -0.2 -0.3, a hydrogen column density of N H = (7.8 -1.4 +1.7) × 10 21 cm -2, and an unabsorbed 0.5-10.0 keV flux of (1.7 ± 0.1) × 10 -12 ergs cm -2 s -1. We have spatially fitted G75.2+0.1 with a model that assumes a toroidal morphology, and from this we infer that the axis of the torus is highly inclined to the line of sight. A 20.8 ks Chandra observation in continuous-clocking mode reveals a possible pulse detection, with a pulsed fraction of ∼65% and an H-test probability of occurring by chance of 8.9 × 10 -5. Timing observations with the Arecibo radio telescope spanning 2 yr show that PSR J2021+3651 glitched sometime between MJD 52,616 and 52,645 with parameters Δν/ν = (2.587 ± 0.002) × 10 -6 and Δν̇/ν̇ = (6.2 ± 0.3) × 10 -3, similar to those of the largest glitches observed in the Vela pulsar. PSR J2021+3651 is heavily scattered (τ scsc = 17.7 ± 0.9 ms at 1 GHz) and exhibits a significant amount of timing noise.