The Thermal X‐Ray–emitting Shell of Large Magellanic Cloud Supernova Remnant 0540−69.3

We use data from the Advanced CCD Imaging Spectrometer (ACIS) on the ChandraX-ray Observatory to image the shell surrounding the pulsar B0540-69, and tomeasure its spectral properties. Weak emission line features, notably of Fe, Mgand Si, indicate that the shell is composed primarily of ambient materialheated by the blast wave. The shell emission in the east is faint and circularin appearance, with a temperature and ionization age of approximately 5 keV and10^10 cm^-3 s, respectively. The emission in the west is brighter and has amore complex, distorted morphology, and is fitted with significantly loweraverage temperatures and higher ionization ages. An image with photon energiesabove 2 keV shows two hard arcs of emission located diametrically opposite eachother at the outer boundary of the remnant shell; the spectra from theseregions could include a substantial nonthermal component.Comment: ApJ, in press; 12 LaTeX pages with 3 postscript figure