Time variation in the effective temperature of a 2.5 M_⊙ model star during the transition from the AGB to the post-AGB phase. Times are counted since the beginning of contraction. The black line indicates the standard result, obtained by adopting the prescription from Wachter et al. (2002, 2008) for mass loss. Coloured tracks refer to results obtained by assuming that Ṁ decreases as , with α = 2 (green), 3 (blue) and 4 (red). The dashed orange line indicates the effective temperature of J005803.08 given in K14 and K15.