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arXiv · 1801.03040

SNhunt151: an explosive event inside a dense cocoon

N. Elias-Rosa·S. Benetti·E. Cappellaro·A. Pastorello·G. Terreran·A. Morales-Garoffolo·S. C. Howerton·S. Valenti·E. Kankare·A. J. Drake·S. G. Djorgovski·L. Tomasella·L. Tartaglia·T. Kangas·P. Ochner·A. V. Filippenko·F. Ciabattari·S. Geier·D. A. Howell·J. Isern·S. Leonini·G. Pignata·M. Turatto
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Abstract

SNhunt151 was initially classified as a supernova (SN) impostor (nonterminal outburst of a massive star). It exhibited a slow increase in luminosity, lasting about 450 d, followed by a major brightening that reaches M_V ~ -18 mag. No source is detected to M_V > -13 mag in archival images at the position of SNhunt151 before the slow rise. Low-to-mid-resolution optical spectra obtained during the pronounced brightening show very little evolution, being dominated at all times by multicomponent Balmer emission lines, a signature of interaction between the material ejected in the new outburst and the pre-existing circumstellar medium. We also analyzed mid-infrared images from the Spitzer Space Telescope, detecting a source at the transient position in 2014 and 2015. Overall, SNhunt151 is spectroscopically a Type IIn SN, somewhat similar to SN2009ip. However, there are also some differences, such as a slow pre-discovery rise, a relatively broad light-curve peak showing a longer rise time (~ 50 d) and a slower decline, along with a negligible change in the temperature around the peak (T < 10^4 K). We suggest that SNhunt151 is the result of an outburst, or a SN explosion, within a dense circumstellar nebula, similar to those embedding some luminous blue variables like Eta Carinae and originating from past mass-loss events.

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N. Elias-Rosa, S. Benetti, E. Cappellaro, A. Pastorello, G. Terreran, A. Morales-Garoffolo, S. C. Howerton, S. Valenti, E. Kankare, A. J. Drake, S. G. Djorgovski, L. Tomasella, L. Tartaglia, T. Kangas, P. Ochner, A. V. Filippenko, F. Ciabattari, S. Geier, D. A. Howell, J. Isern, S. Leonini, G. Pignata, M. Turatto. 2018-01-09. SNhunt151: an explosive event inside a dense cocoon. https://doi.org/10.1093/mnras/sty009

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