The influence of turbulent pressure on the late stages of evolution of low- and intermediate-mass star. (II). The effect of turbulent pressure on the internal structure and evolution.

The authors' study of the evolution of a star with 7 M_sun from the main sequence to the AGB stage shows that the effect of turbulent pressure on its internal structure and evolution is significant. Turbulent pressure makes the H-burning shell thicker during the early AGB stage and vanish early; the central temperature of the star becomes lower, the evolutionary track in the HR diagram moves to the region of lower temperature and lower luminosity. In the late AGB stage of a star of 7 M_sun turbulent pressure can cause a periodic oscillation in the luminosity, temperature and density in the H-burning shell, while the cycle of the thermal pulses of the He-burning shell becomes shorter. However, the evolution of a star with 2.8 M_sun is hardly affected by the presence of turbulent pressure.