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
  00:50:55.08 -07:46:00.98 ASASSN Ia 0.05 ATEL
SDSS J175740.70+5001 17:57:40.36 +50:02:19.72 ASASSN Ia Pec 0.017 ATEL
2MASX J14433925+1852 14:43:39.05 +18:52:12.65 ASASSN Ia Pec 0.031 ATEL
GALEXASC J114845.20- 11:48:45.10 -18:24:34.31 ASASSN Ia 0.07 ATEL
  09:41:10.63 +24:01:20.51 ASASSN Ia Pec 0.070 ATEL