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 program 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 the SN progenitor, based on photometry of the stellar populations in its environment. The progenitor may have had an initial mass M ≈ 17–18(±3) M⊙. Moreover, 17 years after explosion we have recovered and measured the brightness of SN 1979C in several bands, e.g., m = 23.37 in F439W [∼B; for comparison,mB(max) = 11.6].