Red supergiants in M31: the Humphreys–Davidson limit at high metallicity

ABSTRACT The empirical upper limit to red supergiant (RSG) luminosity, known as the Humphreys–Davidson (HD) limit, has been commonly explained being caused by stripping of stellar envelopes metallicity-dependent line-driven winds. As such, theoretical expectation is that HD should be higher at lower metallicity, where weaker mass-loss rates mean initial masses are required for an envelope stripped. In this paper, we test prediction measuring luminosity function RSGs in M31 and comparing it those LMC SMC. We find log (Lmax/L?) = 5.53 ± 0.03 (Z ? Z?), consistent with found both ? 0.5 Z?) SMC 0.25 while RSG distributions these three galaxies within 1?. therefore no evidence a metallicity dependence on function, conclude winds main sequence not cause limit.