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Luminous Blue Variables have been suggested to be the direct progenitors ofsupernova types IIb and IIn, with enhanced mass loss prior to explosion.However, the mechanism of this mass loss is not yet known. Here, we investigatethe qualitative behaviour of theoretical stellar wind mass-loss as a functionof Teff across two bi-stability jumps in blue supergiant regime and also inproximity to the Eddington limit, relevant for LBVs. To investigate thephysical ingredients that play a role in the radiative acceleration wecalculate blue supergiant wind models with the CMFGEN non-LTE model atmospherecode over an effective temperature range between 30000 and 8800 K. Although ouraim is not to provide new mass-loss rates for BA supergiants, we study andconfirm the existence of two bi-stability jumps in mass-loss rates predicted byVink, de Koter, & Lamers (1999). However, they are found to occur at somewhatlower Teff (20000 and 9000 K, respectively) than found previously, which wouldimply that stars may evolve towards lower Teff before strong mass-loss isinduced by the bi-stability jumps. When the combined effects of the secondbi-stability jump and the proximity to Eddington limit are accounted for, wefind a dramatic increase in the mass-loss rate by up to a factor of 30. Furtherinvestigation of both bi-stability jumps is expected to lead to a betterunderstanding of discrepancies between empirical modelling and theoreticalmass-loss rates reported in the literature, and to provide key inputs for theevolution of both normal AB supergiants and LBVs, as well as their subsequentsupernova type II explosions.

Two bi-stability jumps in theoretical wind models for massive stars and the implications for Luminous Blue Variable supernovae