2008ApJ...684.1336K

Extragalactic transient searches have historically been limited to looking for the appearance of new sources such as supernovae. It is now possible to carry out a new kind of survey that will do the opposite, that is, search for the disappearance of massive stars. This will entail the systematic observation of galaxies within a distance of 10 Mpc in order to watch ∼10⁶ supergiants. Reaching this critical number ensures that something will occur yearly, since these massive stars must end their lives with a core collapse within ∼10^ 6^ yr. Using deep imaging and image subtraction, it is possible to determine the fates of these stars, whether they end with a bang (supernova) or a whimper (fall out of sight). Such a survey would place completely new limits on the total rate of all core collapses, which is critical for determining the validity of supernova models. It would also determine the properties of supernova progenitors, better characterize poorly understood optical transients (such as η Carina-like mass ejections), find and characterize large numbers of Cepheids, luminous blue variables, and eclipsing binaries, and allow the discovery of any new phenomena that inhabit this relatively unexplored parameter space.