ASCA Observations of the Twin Supernova Remnants in the Large Magellanic Cloud, DEM L316

We report results from an ASCA X-ray study of DEM L316, an emission nebula inthe Large Magellanic Cloud (LMC) consisting of two closely-spaced supernovaremnants (SNRs). The SIS image shows separate X-ray sources located at thepositions of the two radio- and optically-emitting SNR shells, 0547$-$69.7A and0547$-$69.7B (hereafter, shell A and B). The individual X-ray spectrum of eachshell is well described by optically-thin thermal emission, although thecharacteristics of the emission differ in important details between them. ShellA exhibits strong iron L emission, which we attribute to the presence ofiron-rich ejecta leading to the suggestion that this SNR originates from a TypeIa SN, an explosion of a moderate mass progenitor. Shell B, on the other hand,has a chemical composition similar to that of the interstellar medium of theLMC and so its X-ray emission is dominated by swept-up matter. The differentspectral features strongly disfavor the hypothesis that the two shells are dueto one supernova explosion into an interconnected bubble. We could not obtainthe evidence which positively supports the collision between two SNRs.