X-ray emission from SN 2012ca: A Type Ia-CSM supernova explosion in a dense surrounding medium

Abstract

X-ray emission is one of the signposts of circumstellar interaction in supernovae (SNe), but until now, it has been observed only in core-collapse SNe. The level of thermal X-ray emission is a direct measure of the density of the circumstellar medium (CSM), and the absence of X-ray emission from Type Ia SNe has been interpreted as a sign of a very low density CSM. In this paper, we report late-time (500-800 days after discovery) X-ray detections of SN 2012ca in Chandra data. The presence of hydrogen in the initial spectrum led to a classification of Type Ia-CSM, ostensibly making it the first SN Ia detected with X-rays. Our analysis of the X-ray data favors an asymmetric medium, with a high-density component which supplies the X-ray emission. The data suggest a number density > 10 8 cm −3 in the higher-density medium, which is consistent with the large observed Balmer decrement if it arises from collisional excitation. This is high compared to most core-collapse SNe, but it may be consistent with densities suggested for some Type IIn or superluminous SNe. If SN 2012ca is a thermonuclear SN, the large CSM density could imply clumps in the wind, or a dense torus or disk, consistent with the single-degenerate channel. A remote possibility for a core-degenerate channel involves a white dwarf merging with the degenerate core of an asymptotic giant branch star shortly before the explosion, leading to a common envelope around the SN.

The Deepest Radio Observations of Nearby SNe Ia: Constraining Progenitor Types and Optimizing Future Surveys

“…An immediate method to probe circumstellar gas is through X-ray observations, and the only SNIa detected in X-rays is SN2012ca (Bochenek et al 2017). This SN belongs to the class of SNIa Hα emitters, and the mass of the circumstellar shell is at least 0.1±0.05 M  .…”

Cosmic Ray Production in Supernovae

“…Until very recently no type Ia SN explosion has been confirmed in X-rays, but Bochenek et al (2018) have reported the detection in Chandra data of SN 2012c, a type Ia-CSM object, i.e., a type Ia SN surrounded by very dense material. On the other hand more than 60 core-collapse SNe have been detected in X-rays (see Ross & Dwarkadas 2017, and the SNaX database at http://kronos.uchicago.edu/snax/).…”

The Cold and Dusty Circumstellar Matter around Fast-expanding Type Ia Supernovae

“…Many progenitor classes have been proposed (Gilfanov et al 2010, Wang & Han 2012, Maoz 2014, but observational evidences have not yet reached definitive conclusions on particular progenitor systems. The SD scenario is favored by the possible detections of circumstellar materials (CSM) around some SNe Ia through detections of strong ejecta-CSM interaction (Hamuy et al 2003, Wang et al 2004, Aldering et al 2006, Taddia et al 2012, Silverman et al 2013, Bochenek et al 2018 or evolving narrow absorption lines possibly due to CSM (Patat et al 2007, Sternberg et al 2011, Dilday et al 2012, while there are also observational findings suggesting no companion signatures for some SNe Ia (Li et al 2011a, Gonzalez et al 2012, Schaefer et al 2012, Olling et al 2015. This may suggest that SNe Ia have multiple progenitor systems, as favored by the discovery that SNe Ia with different ejecta velocities originate from distinct birthplace environments .…”