XMM-Newton observation of Kepler's supernova remnant

¹ Service d'Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
² Department of Astronomy, University of Maryland, College Park, MD 20742
³ Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854-8109, USA
⁴ Laboratory for High Energy Astrophysics, Goddard Space Flight Center, Greenbelt, MD 20771

Corresponding author: G. Cassam-Chenaï, gcc@discovery.saclay.cea.fr

Received: 20 February 2003
Accepted: 30 September 2003

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.