Direct Detection of Core-Collapse SN Progenitors: The Explosive Deaths of the Most Massive Stars

Direct observations of massive stars - before they explode - provide a model free identification of SN progenitors. A high-resolution image of the location of a SN, serendipitously obtained before it exploded, is combined with a precise localization of the SN (after it exploded) to enable us to select the correct progenitor from among the stars in the pre-explosion SN images.
After decades of effort, less than a dozen SN progenitors have so far been detected. Once or twice a year a SN is discovered in an area previously observed by the Hubble Space telescope (HST). Efforts to localize nearby SNe with post-explosion HST data are difficult. Furthermore, HST is ill-suited to observe bright point sources such as nearby SNe, requiring either the use of highly saturated images, or a forced long wait while the SN declines.
We have shown that laser-guide-star assisted adaptive optics systems (LGS-AO) are a superb alternative, providing deep, unsaturated, high resolution (HST-like or better) images of any bright SN within minutes, leading to precise localization of these SNe. We have already applied this approach in several cases (e.g., Gal-Yam et al. 2005; 2007; Leonard et al. 2008; see below) using the Keck and Palomar LGS systems with great success. More recently, we have been using the Gemini ALTAIR-LGS (in collaboration with the Smartt group at Queen's University, Belfast) with excellent results. The most prominent result from this program is the identification of a luminous and likely very massive hypergiant progenitor of the Type IIn supernova SN 2005gl (Nature paper).