2006ApJ...648.1037G

We present a deep observation with the Chandra X-Ray Observatory of the neutron star bow shock G189.22+2.90 in the supernova remnant (SNR) IC 443. Our data confirm the cometary morphology and central point source seen previously, but also reveal considerable new structure. Specifically, we find that the X-ray nebula consists of two distinct components: a ``tongue'' of bright emission close to the neutron star, enveloped by a larger, fainter ``tail.'' We interpret the tongue and tail as delineating the termination shock and the postshock flow, respectively, as previously identified also in the pulsar bow shock G359.23-0.82 (``the Mouse''). However, for G189.22+2.90 the tongue is much less elongated than for the Mouse, while the tail is much broader. These differences are consistent with the low Mach number, M≲2, expected for a neutron star moving through the hot gas in a SNR's interior, supporting the case for a physical association between G189.22+2.90 and IC 443. We resolve the standoff distance between the star and the head of the bow shock, which allows us to estimate a space velocity for the neutron star of ∼230 km/s, independent of distance. We detect thermal emission from the neutron star surface at a temperature of 102±22 eV, which is consistent with the age of SNR IC 443 for standard neutron star cooling models. We also identify two compact knots of hard emission located 1"-2" north and south of the neutron star.