XMM-Newton observation of Kepler's supernova remnant

TL;DR

This study presents XMM-Newton observations of Kepler's supernova remnant, revealing detailed spatial distributions of emission lines and continuum, and providing insights into the ejecta structure, temperature distribution, and environmental interactions.

Contribution

First detailed X-ray imaging and spectral analysis of Kepler's supernova remnant using XMM-Newton, highlighting ejecta layering, temperature gradients, and environmental effects.

Findings

Si K emission extends farther than Fe L, indicating no inversion of ejecta layers.

Fe K emission peaks inward of Fe L, suggesting increasing temperature inward.

North brightening likely due to circumstellar medium overdensities.

Abstract

We present the first results coming from the observation of Kepler's supernova remnant obtained with the EPIC instruments on board the XMM-Newton satellite. We focus on the images and radial profiles of the emission lines (Si K, Fe L, Fe K) and of the high energy continuum. Chiefly, the Fe L and Si K emission-line images are generally consistent with each other and the radial profiles show that the Si K emission extends to a larger radius than the Fe L emission (distinctly in the southern part of the remnant). Therefore, in contrast to Cas A, no inversion of the Si- and Fe-rich ejecta layers is observed in Kepler. Moreover, the Fe K emission peaks at a smaller radius than the Fe L emission, which implies that the temperature increases inwards in the ejecta. The 4-6 keV high energy continuum map shows the same distribution as the asymmetric emission-line images except in the southeast where there is a strong additional emission. A two color image of the 4-6 keV and 8-10 keV high energy continuum illustrates that the hardness variations of the continuum are weak all along the remnant except in a few knots. The asymmetry in the Fe K emission-line is not associated with any asymmetry in the Fe K equivalent width map. The Si K maps lead to the same conclusions. Hence, abundance variations do not cause the north-south brightness asymmetry. The strong emission in the north may be due to overdensities in the circumstellar medium. In the southeastern region of the remnant, the lines have a very low equivalent width and the X-ray emission is largely nonthermal.