Assessing the nature of SNR candidates in M 101.

We are conducting a study of SNR candidates in M 101 that have been identified in ground-based optical surveys. We have used archival HST WFPC2 Hα and continuum images, complemented by ground-based high-dispersion spectra. In this study, we determine the physical properties of the remnants, and use the continuum images to examine the stellar environment of the SNR candidates in order to determine whether the large candidates are superbubbles and to infer whether each remnant has a massive progenitor. Our study of the M 101 SNRs will aid our understanding of the distribution and environment of SNRs in a giant-spiral galaxy, and allow us to search for unusual SNRs in an enlarged sample. Here, we present preliminary results of this study. [ABSTRACT FROM AUTHOR]