Padova-Asiago Supernova Group

SNhunt151: an explosive event inside a dense cocoon
Elias-Rosa, N. et al. 2018, MNRAS 475, 2614
  (link to pdf)

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 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 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 <=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.

sn galaxy RA DEC discoverer type redshift ref class fits
galactic 20:42:41.717 +04:47:36.71 ASASSN CV 0 ATEL
UGC 04642 08:52:56.32 +42:24:47.02 ASASSN IIn 0.023863 ATEL
2MASS J09360855+0615 09:36:08.70 +06:15:27.72 ASASSN ? 0.008087 ATEL
UGC 3700 07:09:53.50 +54:58:07.46 ASASSN Ia 0.037136 ATEL
SDSS J092317.60+4222 09:23:17.76 +42:22:47.46 ASASSN II 0.009 ATEL