[Mesa-users] On the decreasing timestep of He star+WD binary (AM CVns) evolution

[Francis Timmes]

hi wei-min,

there is not enough information provided for anyone to potentially offer suggestions. 
there can be many reasons, physical and/or numerical, why the timestep is eventually reduced below the minimum.

mesa's terminal output will show what variable is controlling the timstep.
in broad terms, one can look at this output well before the model gets into trouble 
and use this outout as guidance on what to experiment with.

fxt




> On Apr 21, 2021, at 8:15 AM, Liu,Wei-Min via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Hi everyone,
> 
>   Does anyone met one case that, in the He star +WD binary which are evolving into AM CVns. If the He star has evolved into He WD, then the timesteps are subject to become smaller and smaller until "dt < min_timestep_limit" and stop. An example is M_He star_initial=0.4Msun, M_wd=0.8Msun, Period_initial=120mins (for reproducing this case, the factor beta =0.5 can be used, but test calculation show this issue seem not reltated to the accretion efficiency). My question is anyone know in what cases the condition "dt < min_timestep_limit" can happen? How to deal with this situation? Thanks to all!
> 
> Best wishes,
> 
> Wei-Min Liu
> 
> --
>   Department of Physics,
> Shangqiu Normal University,　
> 
> Wenhua Road 298, Shangqiu 476000, Henan, China
> 
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