The Discovery of a Spatially-Resolved Supernova Remnant in M31 with Chandra

Chandra observations of M31 allow the first spatially resolved X-ray image of a supernova remnant (SNR) in an external spiral galaxy. CXOM31 J004327.7 + 411829 is a slightly elongated ring-shaped object with a diameter of similar to11" (42 pc). In addition, the X-ray image hints that the chemical composition of the SNR is spatial dependent. The X-ray spectrum of the SNR can be well fitted with a Raymond-Smith model or a nonequilibrium ionization model. Depending on the spectral model, the 0.3-7 keV luminosity is between and 3.2 x 10(36) and 4.5 x 10(37) ergs s(-1). The age of the SNR is estimated to be 3210-22,300 yr, and the number density of ambient gas is similar to0.003-0.3 cm(-3). This suggests that the local interstellar medium around the SNR is low.