Supernova Discoveries 2010–2011: Statistics and Trends

Abstract

ABSTRACTWe have inspected all supernova discoveries reported during 2010 and 2011, a total of 538 events during 2010 and 926 events during 2011. This number includes a small number of supernova impostors (bright extragalactic eruptions) but not novae or events that turned out to be Galactic stars. We examine the statistics of all discovered objects, as well as those of the subset of spectroscopically-confirmed events. In these 2 years we see the rise of wide-field non-targeted supernova surveys to prominence, with the largest numbers of events reported by the CRTS and PTF surveys (572 and 393 events in total respectively, contributing together 74% of all reported discoveries in 2011), followed by the integrated contribution of numerous amateurs (184 events). Among spectroscopically-confirmed events the PTF (393 events) leads, followed by CRTS (170 events), and amateur discoveries (144 events). Traditional galaxy-targeted surveys, such as LOSS and CHASE, maintain a strong contribution (86 and 61 events, respectively) with high spectroscopic completeness (∼90%). It is interesting to note that the community managed to provide substantial spectroscopic follow-up for relatively brighter amateur discoveries (〈m〉 = 16.5 mag), but significant less help for fainter (and much more numerous) events promptly released by the CRTS (〈m〉 = 18.6 mag). Inspecting discovery magnitude and redshift distributions we find that PS1 discoveries have similar properties (〈m〉 = 21.6 mag, 〈z〉 = 0.23) to events found in previous seasons by cosmology-oriented projects (e.g., SDSS-II), while PTF (〈m〉 = 19.2 mag, 〈z〉 = 0.095) and CRTS (〈m〉 = 18.6 mag, 〈z〉 = 0.049) populate the relatively unexplored phase space of faint supernovae (SNe) (>19 mag) in nearby galaxies (mainly PTF), and events at 0.05 < z < 0.2 (CRTS and PTF). Examining the specific question of reporting channels over the previous dozen years, we find that traditional reports via CBET telegrams now account only for a minority of SN discoveries.