Observations of the Luminous , O - Rich SNR in the Irregular Galaxy NGC 4449

An analysis of a 29 ksec Chandra ACIS-S observations of the young, Cas-siopeia Alike supernova remnant in the irregular galaxy NGC 4449 is presented. The observed 0.5 − 2.1 keV spectrum reveals the likely presence of several emission lines including O VIII at 0.65 and 0.77 keV, Ne X at 1.05 keV, Mg XI at 1.5 keV, and Si XIII at 1.85 keV. From the observed spectrum, we derive an N H = 1 × 10 21 cm −2 and an X-ray temperature of T ≈ 9 × 10 6 K. A non-equilibrium ionization fit to the spectrum suggests an overabundance of oxygen around 20 times solar, consistent with the remnant's UV and optical emission-line properties. We discuss the remnant's approximate X-ray derived elemental abundances and compare its X-ray spectrum and luminosity to other oxygen-rich remnants.