0 Assuming assigned ID: 855 ----- Attempting Submission 1 (Fri Mar 06 21:50:57 GMT 2020) ----- ----- Attempting Submission 2 (Fri Mar 06 22:53:05 GMT 2020) ----- Recent studies cast doubt on whether the most massive red supergiants can successfully explode as Type II supernovae. However, these studies rely on populations of red supergiants that do not include pre-explosion constraints on recently discovered Type II supernovae or the full volume of such imaging in which distant red supergiant progenitor stars might be detectable. We want to address this problem by conducting a complete, volume-limited analysis of all Type II supernovae within 60 Mpc that have pre-explosion HST imaging, totaling 68 sources. This analysis will more than double the current sample of such supernova progenitor constraints, leading to much larger statistical sample with which we can better analyze the possibility of "missing" red supergiants. In particular, recent work suggests that if red supergiants are missing due to implosion as "failed supernovae", then red supergiants in other mass ranges should also be underrepresented relative to a typical Salpeter initial mass function. With better statistics, we can test this hypothesis and better understand the evolutionary pathways and final fates of massive stars. Dr. Charles Kilpatrick has significant experience in reduction and analysis of HST/WFC3, ACS, and WFPC2 imaging data. Dr. Kilpatrick is also an expert in explosive transient progenitor star studies and has 5 refereed publications on this topic in the past 4 years, including a publication on the proposed target of these observations. Prof. Ryan Foley is an expert in transient surveys and follow up of all types of explosive transients. He has 2 refereed publications on the progenitor stars of explosive transients in the past 10 years. Dr. Jones is an expert in transient surveys and follow up. Mr. Rojas-Bravo and Mr. Siebert are experts in transient follow up and data analysis. Stellar Physics and Stellar Types Stellar Physics and Stellar Types 0 Regular false false false false false SUPPORTED