On the Progenitor of SN 2005gl and the Nature of Type IIn Supernovae

We present a study of the type IIn supernova (SN) 2005gl, in the relatively\nnearby (d~66 Mpc) galaxy NGC 266. Photometry and spectroscopy of the SN\nindicate it is a typical member of its class. Pre-explosion Hubble Space\nTelescope (HST) imaging of the location of the SN, along with a precise\nlocalization of this event using the Laser-Guide-Star assisted Adaptive Optics\n(LGS-AO) system at Keck Observatory, are combined to identify a luminous\n(M_V=-10.3) point source as the possible progenitor of SN 2005gl. If the source\nis indeed a single star, it was likely a member of the class of luminous blue\nvariable stars (LBVs). This finding leads us to consider the possible general\nassociation of SNe IIn with LBV progenitors. We find this is indeed supported\nby observations of other SNe, and the known properties of LBV stars. For\nexample, we argue that should the prototypical Galactic LBV eta Carina explode\nin a phase similar to its current state, it will likely produce a type IIn SN.\nWe discuss our findings in the context of current ideas about the evolution of\nmassive stars, and review the census of SNe with identified progenitors. We\nintroduce the concept of the progenitor-SN map as a convenient means to discuss\nthe present status and future prospects of direct searches for SN progenitors.\nWe conclude that this field has matured considerably in recent years, and the\ntransition from anecdotal information about rare single events to robust\nassociations of progenitor classes with specific SN types has already begun.\n