The expansion of G11.2-0.3, A radio composite supernova remnant

We compare recent observations of the supernova remnant G11.2-0.3 taken with the Very Large Array (VLA) during 2001-2002 with images from VLA archives (1984-1985) to detect and measure the amount of expansion that has occurred during 17 years. The bright, circular outer shell shows a mean expansion of 0.71% ± 0.15% and 0.50% ± 0.17%, from 20 and 6 cm data, respectively, which corresponds to a rate of 0″.057 ± 0″.012 yr^-1 at 20 cm and 0″.040 ± 0″.013 yr^-1 at 6 cm. From this result, we estimate the age of the remnant to be roughly between 960 and 3400 yr old, according to theoretical models of supernova evolution. This is highly inconsistent with the 24,000 yr characteristic age of PSR J1811-1925, located at the remnant's center, but rather is consistent with the time that has passed since the observation of the historical supernova of A.D. 386. We also predict that G11.2-0.3 is currently in a pre-Sedov evolutionary state and set constraints on the distance to the remnant based on Chandra X-ray spectral results.