RED SUPERGIANT VARIABLES IN THE LARGE MAGELLANIC CLOUD - THEIR EVOLUTION AND PULSATIONS

Evolution and pulsations of red supergiants in the LMC are investigated using realistic evolutionary models of 15M(circle dot), 20M(circle dot) and 30M(circle dot), including the up-to-date opacity, the mass loss through the stellar wind and the overshooting from the convective core. It is found that the mass loss has notable effect on the evolution of stars above 20M(circle dot), and that the evolution of all models during the core helium-burning stage is significantly influenced by the overshooting. The fundamental mode is found to be the pulsation mode of the observed variable stars, while the assumption of the first overtone turns out to be inconsistent with observations. The instability strip is cut off by the mass loss at the high luminosity and by the extremely small time scale during the crossing through the instability strip at the low luminosity. The ratio of the mixing length to the local pressure scale height has to increase along the RGB to fit the observation.