Rings and Jets around PSR J2021+3651: The "Dragonfly Nebula"

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 of ~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 Γ = 1.5 in the equatorial torus to Γ = 1.9 in the outer nebula, suggesting synchrotron burnoff. A fit to the Dragonfly structure suggests a large (86°± 1°) 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.