Iron-rich Ejecta in the Supernova Remnant DEM L71

Chandra X-ray observations of DEM L71, a supernova remnant (SNR) in the LargeMagellanic Cloud (LMC), reveal a clear double shock morphology consisting of anouter blast wave shock surrounding a central bright region of reverse-shockheated ejecta. The abundances of the outer shock are consistent with LMCvalues, while the ejecta region shows enhanced abundances of Si, Fe, and otherspecies. However, oxygen is not enhanced in the ejecta; the Fe/O abundanceratio there is more than 5 times the solar ratio. Based on the relativepositions of the blast wave shock and the contact discontinuity in the contextof SNR evolutionary models, we determine a total ejecta mass of approximately1.5 solar masses. Ejecta mass estimates based on emission measures derived fromspectral fits are subject to considerable uncertainty due to lack of knowledgeof the true contribution of hydrogen continuum emission. Maximal massestimates, i.e., assuming no hydrogen, result in 1.5 solar masses of Fe and0.24 solar masses of Si. Under the assumption that an equal quantity ofhydrogen has been mixed into the ejecta, we estimate 0.8 solar masses of Fe and0.12 solar masses of Si. These characteristics support the view that in DEM L71we see Fe-rich ejecta from a Type Ia SN several thousand years after explosion.Comment: 5 pages, including 3 postscript figs, LaTeX, to appear in ApJ Letters 2003 Jan 1