Chandra X-ray observations of G11.2-0.3: Implications for pulsar ages

We present Chandra X-Ray Observatory imaging observations of the young Gala ctic supernova remnant G11.2-0.3. The image shows that the previously known young 65 ms X-ray pulsar is at position (J2000) R.A. 18(h)11(m)29(s).22, d ecl. -19 degrees 25'27 " .6, with 1 sigma error radius of 0."6. This is wit hin 8 " of the geometric center of the shell. This provides strong confirmi ng evidence that the system is younger, by a factor of similar to 12, than the characteristic age of the pulsar. The age discrepancy suggests that pul sar characteristic ages can be poor age estimators for young pulsars. Assum ing conventional spin-down with constant magnetic field and braking index, the most likely explanation for the age discrepancy in G11.2-0.3 is that th e pulsar was born with a spin period of similar to 62 ms. The Chandra image also reveals, for the first time, the morphology of the pulsar wind nebula . The elongated hard X-ray structure can be interpreted as either a jet or a Crab-like torus seen edge-on. This adds to the growing list of highly asp herical pulsar wind nebulae and argues that such structures are common arou nd young pulsars.