Chandra X-Ray Observations of G11.2–0.3: Implications for Pulsar Ages

We present Chandra X-Ray Observatory imaging observations of the young Galactic 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^h11^m2922, decl. -19°25'276, with 1 σ error radius of 06. This is within 8'' of the geometric center of the shell. This provides strong confirming evidence that the system is younger, by a factor of ~12, than the characteristic age of the pulsar. The age discrepancy suggests that pulsar characteristic ages can be poor age estimators for young pulsars. Assuming 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 the pulsar was born with a spin period of ~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 aspherical pulsar wind nebulae and argues that such structures are common around young pulsars.