Hubble Space Telescope WFPC2 imaging of SN 1979C and its environment

The locations of supernovae in the local stellar and gaseous environment in galaxies contain important clues to their progenitor stars. As part of a p rogram to study the environments of supernovae using Hubble Space Telescope imaging data, we have examined the environment of the Type II-L supernova SN 1979C in NGC 4321 (M100). We place rigorous constraints on the mass of t he SN progenitor, based on photometry of the stellar populations in its env ironment. The progenitor may have had an initial mass M approximate to 17-1 8(+/-3) M.. Moreover, 17 years after explosion we have recovered and measur ed the brightness of SN 1979C in several bands, e.g., m = 23.37 in F439W [s imilar to B; for comparison, m(B)(max) = 11.6].