Two New Ejecta‐dominated Galactic Supernova Remnants: G337.2−0.7 and G309.2−0.6

We present the analysis of new X-ray observations of two Galactic radiosupernova remnants (SNRs), G337.2-0.7 and G309.2-0.6. Both remnants exhibitline-rich thermal spectra that require highly non-solar elemental abundanceratios. In each case, Si and S are unequivocally overabundant compared to solarbased purely on the measured equivalent width of the K$\alpha$ line complex.Detailed nonequilibrium ionization spectral analysis of these remnants, using asingle temperature, single ionization age model, confirm the overabundances,yielding Si, S and Ar abundances many times their solar values: 3 to 5 timessolar for G337.2-0.7 and greater than 3 to 10 times solar for G309.2-0.6. Wealso find that for both remnants, Ne and Mg are underabundant relative to Si,and for G309.2-0.6, Ca and Fe as well are relatively underabundant. This is thefirst detection of metal-rich, non-solar abundance material in these remnants,identifying them as young ejecta-dominated SNRs. Further support for theiryouth comes from the distances that we estimate from the fitted columndensities (less than 15 kpc for G337.2-0.7, and $4 \pm 2$ kpc for G309.2-0.6). From the implied sizes of the remnants at these distances we infer relativelyyoung ages (2000 to 4500 years for G337.2-0.7, and 700 to 4000 years forG309.2-0.6). Finally we note that no compact object has yet been found withinG337.2-0.7, but an X-ray point source is evident within the radio shell ofG309.2-0.6, although its nature remains unknown.Comment: 23 pages, 8 figures, ApJ, accepte