A deep Chandra observation of Kepler's supernova remnant:: A type IA event with circumstellar interaction

We present initial results of a 750 ks Chandra observation of the remnant of Kepler's supernova of AD 1604. The strength and prominence of iron emission, together with the absence of O-rich ejecta, demonstrate that Kepler resulted from a thermonuclear supernova, even though evidence for circumstellar interaction is also strong. We have analyzed spectra of over 100 small regions, and find that they fall into three classes. ( 1) The vast majority show Fe L emission between 0.7 and 1 keV and Si and S K alpha emission; we associate these with shocked ejecta. A few of these are found at or beyond the mean blast wave radius. (2) A very few regions show solar O/Fe abundance ratios; these we associate with shocked circumstellar medium ( CSM). Otherwise O is scarce. ( 3) A few regions are dominated by continuum, probably synchrotron radiation. Finally, we find no central point source, with a limit similar to 100 times fainter than the central object in Cas A. The evidence that the blast wave is interacting with CSM may indicate a Ia explosion in a more massive progenitor.