ASCA observation of Kepler's supernova remnant

Abstract

We report the results of Kepler's supernova remnant (SNR) observed with ASCA. We clearly detected many emission lines from heavy elements on the SIS spectrum. Since we could not fit the data with a simple non-equilibrium ionization (NEI) hot-plasma model, we applied realistic SNR models employing either the Sedov model or the Chevalier model. As a result, the spectrum was not reproduced by the Sedov model, but was well-reproduced by the Chevalier model, except for the Fe-K line blends. The emission from the ejecta heated by reverse shock dominates that from the interstellar matter heated by the fore shock. The relative abundances of the ejecta strongly suggest that Kepler's SN is a SN Ia. However, the Fe-K line blends could not be reproduced well by only the Chevalier model from an astrophysical point of view. We found that the Fe-K line emission was well produced by an additional iron component. This component must have a relatively higher temperature and a lower ionization time scale than those of the ejecta component. This additional iron component may result from mixing of the inner region. This must be an iron-dominant plasma which is a fossil of the SN Ia explosion.