2025RAA....25a5012W

We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey. Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10. By comparing their radial velocities with those predicted from the rotation curve of M31, as well as utilizing Gaia astrometric measurements to exclude foreground contaminations, 199 supergiant members in M31, including 168 “Rank1” and 31 “Rank2,” have been successfully identified. This sample contains 62 blue supergiants (BSGs, all “Rank1”), 134 yellow supergiants (YSGs, 103 “Rank1” and 31 “Rank2”) and three red supergiants (RSGs, all “Rank1”). For M33, we identify 84 supergiant members (56 “Rank1” and 28 “Rank2”), which include 28 BSGs (all “Rank1”), 53 YSGs (25 “Rank1” and 28 “Rank2”) and three RSGs (all “Rank1”). So far, this is one of the largest supergiant samples of M31/M33 with full optical wavelength coverage (3700 < λ < 9100 Å). This sample is valuable for understanding star formation and stellar evolution under different environments.