X-ray emission from SN 2012ca: A Type Ia-CSM supernova explosion in a dense surrounding medium. Issue 1 (23rd August 2017)

• Record Type: Journal Article
• Authors: Bochenek, Christopher D.; Dwarkadas, Vikram V.; Silverman, Jeffrey M.; Fox, Ori D.; Chevalier, Roger A.; Smith, Nathan; Filippenko, Alexei V.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 473:Issue 1(2018)
• Page Start: 336
• Page End: 344
• Publication Date: 2017-08-23
• Subjects: shock waves – circumstellar matter – stars: mass-loss – supernovae: general – supernovae: individual: SN 2012ca – X-rays: individual: SN 2012ca; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx2029
• Languages: English
• ISSNs: 0035-8711

Abstract

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 d 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 favours 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 disc, 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.