C. Inserra, S. J. Smartt, R. Scalzo, M. Fraser, A. Pastorello, M. Childress, G. Pignata, A. Jerkstrand, R. Kotak, S. Benetti, M. Della Valle, A. Gal-Yam, P. Mazzali, K. Smith, M. Sullivan, S. Valenti, O. Yaron, D. Young
We report optical and near-infrared observations of SN 2012ca with PESSTO, spread over one year since discovery. The SN bears many similarities to SN 1997cy and to other events classified as Type IIn but which have been suggested to have a thermonuclear origin with narrow hydrogen lines produced when the ejecta impact a hydrogen-rich circumstellar medium (CSM). Our analysis, especially in the nebular phase, reveals the presence of strong oxygen, magnesium and carbon features. The broad ejecta lines resemble those seen in Type Ic SNe. This suggests a core collapse explanation for this event, in contrast to the thermonuclear interpretation proposed for some members of this group. We suggest that the data can be explained with a hydrogen and helium deficient SN ejecta (Type I) interacting with a hydrogen-rich CSM, but that the explosion was more likely a Ic core-collapse explosion than a Type Ia thermonuclear explosion. This suggests two channels (both thermonuclear and stripped envelope core-collapse) are responsible for these SN 1997cy-like explosions.
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http://arxiv.org/abs/1307.1791
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