Rings and Jets around PSR J2021+3651: the `Dragonfly Nebula'

TL;DR

This paper presents detailed Chandra X-ray observations of the 'Dragonfly Nebula' around pulsar PSR J2021+3651, revealing complex jet and nebula structures, spectral properties, and a revised distance estimate, contributing to understanding pulsar wind nebulae morphology.

Contribution

It provides the first detailed imaging and spectral analysis of the nebula, identifying unique double torus structures and refining the pulsar's distance estimate.

Findings

Detection of axisymmetric nebula with jets and double torus

Spectral steepening indicating synchrotron burn-off

Revised distance estimate of 3-4 kpc instead of 12 kpc

Abstract

We describe recent Chandra ACIS observations of the Vela-like pulsar PSR J2021+3651 and its pulsar wind nebula (PWN). This `Dragonfly Nebula' displays an axisymmetric morphology, with bright inner jets, a double-ridged inner nebula, and a ~30" polar jet. The PWN is embedded in faint diffuse emission: a bow shock-like structure with standoff ~1' brackets the pulsar to the east and emission trails off westward for 3-4'. Thermal (kT=0.16 +/-0.02 keV) and power law emission are detected from the pulsar. The nebular X-rays show spectral steepening from Gamma=1.5 in the equatorial torus to Gamma=1.9 in the outer nebula, suggesting synchrotron burn-off. A fit to the `Dragonfly' structure suggests a large (86 +/-1 degree) inclination with a double equatorial torus. Vela is currently the only other PWN showing such double structure. The >12 kpc distance implied by the pulsar dispersion measure is not supported by the X-ray data; spectral, scale and efficiency arguments suggest a more modest 3-4 kpc.