X-Ray Spectra of Supernova Remnants

Abstract

High quality X-ray spectra for the brightest remnants are now available from several satellites. The data for Tycho’s remnant, Cas A, and Kepler’s remnant have been used to derive elemental abundances which appear mostly larger than average interstellar values and increase with respect to those values as one progresses from Mg to Ca. Iron appears low. All the abundances appear particularly high in Tycho. Spectral observations above 20 keV for Cas A and Tycho show that electron-ion equilibration proceeds faster than the Coulomb rate. Ionization-recombination equilibration, however, is almost certainly not attained in these young remnants, and this may account for the two temperature components found to fit the spectra best by most X-ray observers. Spectral evidence, coupled with optical evidence that Tycho’s remnant is in the Sedov phase of evolution, indicate that the ejecta were not primarily iron. The older remnant in Puppis has been well studied by a crystal spectrometer and shows many informative line features.