SNhunt151: an explosive event inside a dense cocoon

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

Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 2, p.2614-2631

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4
2018
Number of authors
23
IAC number of authors
1
Citations
11
Refereed citations
11
Description
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 MV ≈ -18 mag. No source is detected to MV ≳ -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 analysed 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 SN 2009ip. 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 ≤ 104 K). We suggest that SNhunt151 is the result of an outburst, or an SN explosion, within a dense circumstellar nebula, similar to those embedding some luminous blue variables like η Carinae and originating from past mass-loss events.
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