X-Ray Signatures of Type II Core-Collapse Supernovae

Abstract

Over the past few decades, there has been a lot of interest in studying supernovae (SNe) from the beginning of core collapse to an outer explosion. Core-collapse supernovae (CCSNe) occur when the iron core of a massive star exceeds the Chandrasekhar mass limit (~1.4 M_\(\odot\)), at which point electron degeneracy pressure is no longer sufficient to support the core, leading to collapse. This study examines X-ray emission from supernova ejecta-CSM interaction, primarily driven by thermal processes in shocks. Despite their cosmic significance, massive stars' mass loss and explosion mechanisms remain uncertain due to their rarity and short final stages. Recent wide-field surveys have increased supernova detections, offering new insights into late-stage evolution and the progenitors of CCSNe, whose explosion mechanisms remain a key astrophysical challenge.

Significant details about the interactions between the supernova ejecta and the surrounding circumstellar material (CSM) were obtained from the analysis of the X-ray emission from SN 2008ij. This interaction revealed key details about the density distribution, shock front size, and radiation mechanisms at play. Spectral analysis conducted in Photon Counting (PC) mode demonstrated that power-law, blackbody, and Astrophysical Plasma Emission Code (APEC) models offered strong fits to the data. The blackbody fitting yielded an effective temperature of 0.54 (+0.02, -0.03) keV, while the absorbed APEC model suggested a plasma temperature of 4.76 (+1.22, -0.83) keV. Additionally, the study examined the evolution of the X-ray luminosity, which exhibited a sharp increase in the early post-shock phase, followed by a gradual decline during the photospheric phase (days 7–30), from 8.4±0.3 to 6.8±0.24 × 10 ⁴¹ erg/s.