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.lHowell D.A.Isern J.Leonini S.Pignata G.Turatto M.2022-08-222022-08-222018-04Monthly Notices of the Royal Astronomical Society Volume 475, Issue 2, Pages 2614 - 26311 April 201800358711https://repositorio.unab.cl/xmlui/handle/ria/23592Indexación ScopusSNhunt151 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. © 2017 The Author(s).enSupernovaeLight CurveWolf-Rayet StarsInfrared imagingSpace telescopesArtículoCC BY 4.010.1093/mnras/sty009