The Rate and Spatial Distribution of Novae in M101 (NGC 5457)

A new multiepoch Hα imaging study of M101 (NGC 5457) has been carried out as part of a larger campaign to study the rate and stellar population of extragalactic novae. The survey yielded a total of 13 nova detections from 10 epochs of M101 observations spanning a 3 yr period. After correcting for the temporal coverage and survey completeness, a global nova rate of 11.7+ 1.9−1.5 yr−1 is found. This value corresponds to a luminosity-specific nova rate of 1.23 ± 0.27 novae per year per 1010 L☉ ,K when the K luminosity is derived from the B − K color, or 1.94 ± 0.42 novae per year per 1010 L☉ ,K when the K magnitude from the Two Micron All Sky Survey is used. These values are consistent with previous estimates by Shafter et al. that were based on more limited data. The spatial distribution of the combined nova sample from the present survey and from the earlier Shafter et al. survey shows that the specific frequency of novae closely follows the integrated background light of the galaxy.