XMM-Newton and Chandra observations of G272.2-3.2. Evidence of stellar ejecta in the central region

Abstract

Aims. We aim to study the spatial distribution of the physical and chemical properties of the X-ray emitting plasma of the supernova remnant G272.2−3.2 in order to obtain important constraints on its ionization stage, the progenitor supernova explosion, and the age of the remnant. Methods. We report on combined XMM-Newton and Chandra images, median photon energy maps, silicon and sulfur equivalent width maps, and a spatially resolved spectral analysis for a set of regions of the remnant. Complementary radio and Hα observations, available in the literature, are also used to study the multi-wavelength connection of all detected emissions. Results. The X-ray morphology of the remnant displays an overall structure with an almost circular appearance and a centrally brightened hard region with a peculiar elongated hard structure oriented along the northwest-southeast direction of the central part. The X-ray spectral study of the regions shows distinct Kα emission-line features of metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by an absorbed variable abundance non-equilibrium ionization thermal plasma model, which produces elevated abundances of Si, S, and Fe in the circular central region, typical of ejecta material. The values of abundances found in the central region of the supernova remnant favor a Type Ia progenitor for this remnant. The outer region shows abundances below the solar value, to be expected if the emission arises from the shocked interstellar medium. The relatively low ionization timescales suggest non-equilibrium ionization. We identify the location of the contact discontinuity. Its distance to the outer shock is higher than expected for expansion in a uniform media, which suggests that the remnant spent most of its time in more dense medium.