Model of ASCA X-ray spectrum of Kepler's SNR

Abstract

We report the results of Kepler's supernova remnant (SNR) observed with ASCA. We obtained the X-ray spectrum of Kepler's SNR in the energy range between 0.5 keV and 10 keV, clearly detected many emission lines from the heavy elements. The spectrum was not reproduced by a single temperature CIE and NEI model. Therefore, we constructed a realistic spectral model considering the SNR evolution; the Sedov and the Chevalier model. The X-ray spectrum of Kepler's SNR was not reproduced by the Sedov model, but well by the Chevalier model, except the Fe-K line blends. The emission from the ejecta heated by the reverse shock dominates that from the ISM heated by the blast wave. Kepler's SNR is not in the Sedov phase, but in the free-expansion phase. The abundance of the ejecta strongly suggests that Kepler's SN is a SN Ia. However, since the Fe-K line blends could not be reproduced well, another component producing the Fe-K line blends is needed. The Fe-K line emission is well produced by the additional iron component. This component must have a relatively higher temperature and a lower ionization timescale than these of the main ejecta. The iron component must be an iron dominant plasma which is a fossil of the iron ejecta of the SN Ia explosion.