[mesa-users] AGB convergence problem

[Choi, Jieun]

Hi Laura,

As Héctor already mentioned, you can set your own stopping criterion in
run_star_extras.f. What is the physical definition of the AGB tip you're
working with here? Some Mdot threshold?

In terms of the built-in stopping criteria, there's a simple way to stop
the calculation after the occurrence of the first TP. But you probably want
to go a bit further than that?

         !### stop_at_TP

         ! If true, stop at next AGB thermal pulse.
         ! This is defined as having a convective zone with helium burning
         ! when central helium is depleted
         ! and `he_core_mass - c_core_mass <= TP_he_shell_max`.

      stop_at_TP = .false.

Cheers,
Jieun

On Thu, Jul 21, 2016 at 3:06 PM, Héctor MR <hector.mr at pitt.edu> wrote:

>   Hi Laura,
>
>   In general, convergence problems in MESA are difficult to diagnose.
>
>   I have been creating WDs for a long time and have frequently found the
> problem you mention: my stars were getting stuck in the middle of the AGB
> (mostly for high initial masses and metallicities), going back and forth
> without being able to get to higher effective temperatures.
>
>   After some useful interactions in this mailing list, I found that
> increasing the AGB mass loss, as you say, could help circumvent this (via
> Blocker_scaling_factor from r8118 on ahead). I do not fully understand why
> this should be a problem for your purposes; you can always implement your
> own stopping condition via extras_finish_step or extras_check_model under
> run_star_extras.f (http://mesa.sourceforge.net/run_star_extras.html#toc-2).
> On the other hand, I would not recommend you to modify the default value of
> min_timestep_limit or your results might get noisy (in case you were
> thinking about it).
>
>   When you say "the model seems to get stuck somewhere possibly near the
> AGB tip", have you actually checked it with an HR diagram using PGPLOT? I
> have found that this is one of the most powerful debugging tools in MESA
> and it could help you see what is occurring to your star in a better way.
>
>   Hope this helps.
>
>
>   --
>   Héctor
>
>
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