[Mesa-users] Trying to model a possible progenitor for type Ib Supernova

[Jared Goldberg]

Hi Amar,

First of all, I notice you have
steps_to_take_before_terminate = 2 ! if not removing anything
in the &star_job section of your inlist_remove, as such, the model is only
taking 2 timesteps when removing and not removing any hydrogen in the
working directory you sent.

Commenting out
! required_termination_code_string = 'max_model_number'
! steps_to_take_before_terminate = 2 ! if not removing anything
in star_job and
! max_number_backups = 1
! max_number_retries = 3
in the controls section allows the model to strip more as it evolves,
although the core evolution continues to proceed.

When running the inlists with these modifications, I find that the
evolution is failing at a similar evolutionary point while the model is
still stripping, during core oxygen burning, with complicated shell
burning. I find staring at pgstar plots near the crash helpful; see
especially the region between 2-2.5 Msun:

[image: image.png]


[image: image.png]
Notice also the little blips in the velocity around 2-2.5 solar masses,
where some of that shell burning is taking place.


12 Solar mass stars are challenging to model, with problems often arising
during complicated stages of shell burning. If you just want a working
model of a type Ib progenitor, an easy fix would be going to a higher
progenitor mass (15 - 18Msun, for example), which should make it through
these complicated stages of evolution with much less trouble.

If you do want to get a 12Mzams progenitor model through this stage of
evolution, other solutions may exist, but they are less simple, and I can't
as easily point you to "the answer."
Turning off Thermohaline mixing (setting thermohaline_coeff = 0 in &
controls), for example, gets the model through core O burning. I did not
run the model beyond that, so similar issues may still appear in subsequent
shell burning episodes. There are great suggestions in Rob Farmer's 2016
supernova progenitor models paper (
https://ui.adsabs.harvard.edu/abs/2016ApJS..227...22F/abstract) and the
related inlists (https://zenodo.org/record/2641723) on mesastar.org.
Although the inlists are somewhat out of date for current revisions of
MESA, the concepts therein can be very helpful.

Also, if you want to tighten the time resolution, perhaps try changing the
tolerances in the central abundances (e.g. delta_XNe_cntr_limit,
delta_XO_cntr_limit), temperature (delta_lgT_cntr_limit), and density
(delta_lgRho_cntr_limit), rather than just changing varcontrol, since these
seem to be what set the timesteps in the first place (when looking at the
terminal output for dt_limit).

Hope this is helpful, and definitely let us know if you have any more
questions or if any other issues arise!

Cheers,
~Jared


On Tue, Jan 21, 2020 at 8:36 AM Amar Aryan via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi,
> Using mesa version-11701, I am trying to model a possible progenitor for a
> type Ib supernova (SN). For this purpose, I am evolving a 12 solar mass
> zero-age main-sequence star, considering initial metallicity (Z) of 0.02.
> After evolving the model until the exhaustion of helium, I am imposing an
> artificial mass-loss rate of 10^(-4) solar masses per year until the total
> hydrogen mass of the star goes down to 0.01 solar masses. After the
> hydrogen mass reaches the specified limit, I switch off the artificial mass
> loss and evolve the model until the onset of core-collapse. For this
> purpose, I have used *example_make_pre_ccsn* directory of test_suit with
> some changes in the inlist files and in *rn* executable. I am attaching
> here my entire working directory.  The evolution starts smoothly but
> terminates by giving the following errors :
>
>
>                                                                  dt
> 3.1322685072350174D-13
>
>                                       min_timestep_limit
> 9.9999999999999998D-13
>
>                                                  stopping because of
> problems dt < min_timestep_limit
>
>
> I have tried a few solutions myself :
>
>     a) Varied* min_timestep_limit* in inlist_massive_default in the range
> (10^-6 to 10^-14), but these did not work, still got same error.
>     b) Then tried with changing *varcontrol_target* in the range (10^-2
> to 10^-5) with different min_timestep_limit, but still, we get the same
> error.
>
> I am looking for your guidance and suggestions.
> Thank you in advance for any suggestions.
>
> Regards,
> Amar.
>
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> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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