Models of asymptotic-giant-branch stars

The static structure and dynamical behavior of the envelopes of four 0.9 M0 asymptotic-giant-branch stars are described. It is found that in a model of luminosity log LIL0 = 3.42 the envelope pulsates steadily in the first-overtone mode. The full-amplitude pulsational properties of this model agree well with those of a Mira variable of the same period. Three more-luminous models (log LIL0 = 3.60, 3.85, and 4.14) all pulsate in the fundamental mode while simultaneously undergoing violent relaxation oscillations. Mass loss occurs from the models of luminosity log LIL0 = 3.60 and 4.14. The models which execute envelope relaxation oscillations have properties which resemble those of some of the symbiotic stars. A distinct outward-moving shell which forms in the two most luminous models suggests a connection with planetary-nebula ejection. Subject headings:combination spectra - interiors, stellar - late-type stars - long-period variables - mass loss - pulsation