High Spatial Resolution X-Ray Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

TL;DR

Deep Chandra observations of the IC443 pulsar wind nebula reveal detailed structures, confirming the pulsar nature, nebula morphology, and thermal emission, while constraining the pulsar's proper motion.

Contribution

This study provides high-resolution X-ray imaging of the IC443 pulsar wind nebula, revealing its structure, spectrum, and motion constraints for the first time.

Findings

Identification of a ring-like structure around the pulsar

Confirmation of a pulsar wind nebula with non-thermal emission

Upper limit on pulsar proper motion less than 44 mas/yr

Abstract

Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222127, in the supernova remnant IC443 reveal an ~5$^{\prime\prime}$-radius ring-like structure surrounding the pulsar and a jet-like feature oriented roughly north-south across the ring and through the pulsar's location at 06$^{\rm h}$17$^{\rm m}$5.200$^{\rm s}$ +22$^{\circ}$21$^{\prime}$27.52$^{\prime\prime}$ (J2000.0 coordinates). The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar, (2) the non-thermal spectrum and morphology of the surrounding nebula are consistent with a pulsar wind and, (3) the spectrum at greater distances is consistent with thermal emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic: There is no evidence either spectrally or morphologically for a bow shock or contact discontinuity; the nearly circular ring is not distorted by motion through the ambient medium; and the shape near the apex of the nebula is narrow. Comparing this observation with previous observations of the same target, we set a 99% confidence upper limit to the proper motion of CXOU J061705.3+222127 to be less than 44 mas/yr (310 km/s for a distance of 1.5 kpc), with the best-fit (but not statistically significant) projected direction toward the west.