[Mesa-users] A very short timestep of the evolution of a He star appears during it towards an AGB star

[曾耀田]

Dear all MESA users,

I'm trying to evolve a He star with MESA-r12778. This He star has a mass of 1.23 solar mass and all the parameters to generate it showed by the inlist_start attached below). By using this initial He star model (i.e., he_start.mod), I'm trying to evolve it to a WD (all settings contained in the inlist_for_evo attached below). However, the timestep of the evolution of this star getting shorter (e.g., a few hundred years) when it close to the bottom of its AGB phase. This timestep becomes shorter and shorter (e.g., it can even less than 10^-8 years) when it towards the top of its AGB phase. I'm trying to understand what happened there. But I have no idea about processes that lead the timestep to get shorter and the way to figure it out. Any ideas, suggestions, or help would be greatly appreciated!

The attached files include all used inlists, a log file during the evolution, and four figures which show profiles and history of evolution at different star ages from the start of timestep getting shorter.

With best wishes!
Yaotian Zeng
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