ASCAX‐Ray Spectroscopy of Large Magellanic Cloud Supernova Remnants and the Metal Abundances of the Large Magellanic Cloud

We present the results of X-ray spectroscopy of a flux-limited sample ofseven middle-aged supernova remnants (SNRs) in the Large Magellanic Cloud (LMC)(N23, N49, N63A, DEM71, N132D, 0453-68.5, and N49B), using nonequilibriumionization Sedov-phase SNR models. All the remnants were well described by themodel, allowing us to derive accurate values for their ages, densities, initialexplosion energies, and metal abundances. Four SNRs are fully consistent withthe Sedov model and yield a mean value of the initial SN explosion energy of(1.1+/-0.5)x10^51 erg. We show that it is likely that the other three remnantsexploded within preexisting cavities in the interstellar medium. The limits onhigh energy X-ray emission (>3 keV) that we present indicate that these SNRs donot contain very luminous pulsar-powered synchrotron nebulae. We findstatistical evidence for enrichment by supernova ejecta in the sense thatsmaller remnants show a somewhat higher mean metallicity than the larger ones.For DEM71, the remnant of a SN Ia, the derived Fe abundance is about a factorof two larger than the other remnants in the sample. These things being said,however, the derived abundances are in general dominated by swept-upinterstellar material and so we use the SNR sample to estimate the mean LMCgas-phase abundances. We find that the astrophysically common elements from Oto Fe are less abundant than the solar values by factors of 2--4. Overall theseresults are consistent with previous ones based on optical and UV data, but donot show the anomalous overabundance of Mg and Si seen by others.Comment: 45 pages, including 12 postscript figs, LaTeX. Submitted to Ap