X-ray spectra of young type I supernova remnants: Exploded white dwarfs

We argue that the X-ray spectra of young Type I supernova remnants can be understood consistently in terms of thermal emission mainly from a reverse shock into initially uniform density ejecta. The inferred mass of ejecta is then consistent with 1.4 M/sub sun/ in SN 1006, Tycho, and Kepler. A substantial mass of iron, perhaps approx.0.8 M/sub sun/, may be present provided that the ejecta are chemically inhomogeneous, with iron confined to inner layers of ejecta. The marked difference between the X-ray spectra of SN 1006 and Tycho is explained by the lower interstellar density around SN 1006