Newly Discovered Wolf–Rayet Stars in M31

Abstract

Abstract The evolved massive star populations of the Local Group galaxies are generally thought to be well understood. However, recent work has suggested that the Wolf–Rayet (WR) content of M31 may have been underestimated. We therefore began a pilot project to search for new WRs in M31 and to reexamine the completeness of our previous WR survey, finished almost a decade prior. Our improved imaging data and spectroscopic follow-up confirmed 19 new WRs across three small fields in M31. These newly discovered WRs are generally fainter than the previously known sample due to slightly increased reddening as opposed to intrinsic faintness. From these findings, we estimate that there are another ∼60 WRs left to be discovered in M31; however, the overall ratio of WN-type (nitrogen-rich) to WC-type (carbon-rich) WRs remains unchanged with our latest additions to the M31 WR census. We are in the process of extending this pilot WR survey to include the rest of M31, and a more complete population will be detailed in our future work.