SIMBAD references

We present stellar evolution models of the final AGB phase, in which the star undergoes heavy and optically thick mass-loss (``superwind" phase). Our computations are based on consistent, pulsating wind models for carbon-rich stars and include a detailed treatment of dust formation, radiative transfer and wind acceleration (Fleischer et al., 1992A&A...266..321F). For a specific mass range, around 1.2M_☉ stellar mass at the foot-AGB and only about 0.2M_☉ wide, we find particularly pronounced episodic mass-loss which is consistent with all properties of the detached CO shells found by Olofsson et al. (1990A&A...230L..13O, 1993ApJS...87..267O, 1996A&A...311..587O) around bright carbon stars: kinematic ages of 1 to 2x10⁴yrs, masses of several 0.01M_☉, and a mass-loss duration of less than several thousand years. The physics, micro-physics, and chemistry of our dust-induced superwind is essential for understanding such details of the final stellar mass-loss history. Unlike other superwind models, our mass-loss rate depends very sensitively on the stellar temperature - about ∝T_eff^–8 - and our models require a minimum luminosity to be surmounted. Together, that yields a much pronounced mass-loss variation with the late thermal pulses. In particular, our models suggest the formation of CO shells in the final 2 to 6x10⁴yrs on the tip-AGB - if the stellar luminosity is close to the critical (Eddington-like) luminosity logL_c (around 3.5 to 3.7, depending on T_eff), while the star has only ≲0.2M_☉ left to lose towards the exposure of its hot core.