2021MNRAS.504..667L

We present stellar evolution calculations from the asymptotic giant branch (AGB) to the planetary nebula (PN) phase for models of initial mass 1.2 and 2.0 M_☉ that experience a late thermal pulse (LTP), a helium shell flash that occurs following the AGB and causes a rapid looping evolution between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, V839 Ara (SAO 244567). The central star has been observed to be rapidly evolving (heating) over the last 50-60 yr and rapidly dimming over the past 20-30 yr. It has been reported to belong to the youngest known PN, now rapidly fading in brightness. In this paper, we show that the observed time-scales, sudden dimming, and increasing Log(g), can all be explained by LTP models of a specific variety. We provide a possible explanation for the nebular ionization, the 1980s sudden mass-loss episode, the sudden decline in mass-loss, and the nebular recombination and fading.