2003ApJ...587..221P

An analysis of a 29 ks Chandra ACIS-S observation of the young, Cassiopeia A-like 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 a N_H=1x10²¹.cm^–2 and an X-ray temperature of T~9x10⁶ K. A nonequilibrium 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 with other oxygen-rich remnants.