A1 Refereed original research article in a scientific journal
SNhunt151: an explosive event inside a dense cocoon
Authors: Elias-Rosa N, Benetti S, Cappellaro E, Pastorello A, Terreran G, Morales-Garoffolo A, Howerton SC, Valenti S, Kankare E, Drake AJ, Djorgovski SG, Tomasella L, Tartaglia L, Kangas T, Ochner P, Filippenko AV, Ciabattari F, Geier S, Howell DA, Isern J, Leonini S, Pignata G, Turatto M, Turatto M
Publisher: OXFORD UNIV PRESS
Publication year: 2018
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 475
Issue: 2
First page : 2614
Last page: 2631
Number of pages: 18
ISSN: 0035-8711
DOI: https://doi.org/10.1093/mnras/sty009
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/30673600
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 approximate to -18 mag. No source is detected to M-V greater than or similar to -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 (similar to 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 an 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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