A study of the oscillations of medium-mass metal-rich AGB long-period variable stars

Abstract We combine calculations of stellar evolution and stellar oscillation in a study of the oscillation properties as medium-mass, metal-rich stars evolve along the asymptotic giant branch. We found theoretically that such stars are oscillating at the first harmonic and that the oscillation is excited through the combined action of three factors operating in the zones of ionized hydrogen and twice ionized helium. We point out that the AGB long-period variables of very long periods can only come from medium-mass stars. Our calculation is favorable to the view that huge mass loss through wind exists at the top of the AGB and that such mass loss is probably related to the oscillations.