Chandra Observation of the Large Magellanic Cloud Supernova Remnant J0550-6823

Radio, optical, and X-ray observations of this rather faint, old, LMC supernova remnant are described. The [OIII] emission forms a distinct shell, the remnant of the Outer Shock, which encloses the radio and X-ray emission and gives an estimate of age and explosion energy. Because of a collision with an LMC Hα filament, radio and X-ray emission are concentrated in the northern half of the remnant. The X-ray spectrum is almost solely lines from O, Ne, Mg, and Fe. The known distance, low extinction, and low ISM metallicity, allow derivation of masses of several elements produced by the star and in the explosion. Masses of O, Ne, and Fe point to a Type II Supernova from the explosion of a 20-25 M star. The mass of Mg, however, is higher than that of almost all predictions. In the background, a radio-bright AGN appears just outside the shell of the remnant.