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

[Amar Aryan]

Hi Jared, 

Thank you very much for your suggestions. I will surely get back to you after applying your suggestions. 

Thank you once again for your suggestions. 
Best Regards, 
Amar 

From: "Jared Goldberg" <goldberg at physics.ucsb.edu> 
To: "Amar Aryan" <amar at aries.res.in> 
Cc: "mesa-users" <mesa-users at lists.mesastar.org>, "Abhay" <abhay at aries.res.in> 
Sent: Wednesday, January 22, 2020 2:41:12 AM 
Subject: Re: [Mesa-users] Trying to model a possible progenitor for type Ib Supernova 

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: 




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 | https://ui.adsabs.harvard.edu/abs/2016ApJS..227...22F/abstract ] ) and the related inlists ( [ https://zenodo.org/record/2641723 | https://zenodo.org/record/2641723 ] ) on [ http://mesastar.org/ | 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 < [ mailto:mesa-users at lists.mesastar.org | 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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