0 Assigned ID: 215 ----- Attempting Submission 1 (Thu Apr 10 17:31:26 GMT 2014) ----- We propose to expand our previous successful archival program to constrain the progenitor masses of supernova remnants (SNRs) in M31. Our previous program has resulted in 2 papers that each significantly improve our knowledge of the mass distribution of stars that produce supernovae. However, a new and significantly improved SNR catalog has been released this year, which is more comprehensive and reliable that anything available at the time of our previous program. The amount of high-quality HST imaging has also increased. This new catalog provides 106 SNRs with HST coverage, 67 of which were not measured by our previous archival program. Furthermore, our technique for measuring uncertainties in our mass estimates has become more reliable. This expanded and updated program will increase the number of measurements SNRs by a factor of 2, while also producing a much cleaner, more homogeneous sample. RESOLVED STELLAR POPULATIONS Default Small false false false false false SUPPORTED