"Violent eruptive episodes, and consequently major mass loss, are a common feature of the so-called Luminous Blue Variable stars (LBVs). These outbursts can mimic the behaviour of genuine Type IIn supernovae (SNe), showing similar spectroscopic properties and are therefore frequently labelled with the name of ‘supernova impostors’.

Type IIn SN spectra are characterized by blue continua with prominent narrow Balmer lines in emission. In most cases, SNe IIn arise from massive stars (M>8Mo) exploding in a dense H-rich circumstellar medium, produced through strong winds or eruptive events prior to the SN explosion. While different physical mechanisms triggering these outbursts have been proposed, in the last few years we had direct proof of the connection between LBVs, their eruptions and SNe IIn.

The case of LSQ13zm is of interest since we observed an outburst only ~3 weeks before the terminal SN explosion, along with very high expansion velocities. This SN, along with a handful of other well-studied similar objects (e.g. SNe 2010mc, hunt151, hunt275 and the controversial 2009ip), suggests that SN impostors may herald real SN explosions.

On the other hand, the recent discovery of the SN impostor PSN J09132750+7627410, and the analysis of archival pre-outburst HST images of its field, revealed a 18-20 Mo yellow-white supergiant as viable candidate progenitor, suggesting that also moderate-mass stars can experience large outbursts and hence produce SN impostors."