[Mesa-users] STELLA calculation fail to converge for massive stars

Mon Dec 14 06:05:42 EST 2020

Dear Jared,

Many thanks for your prompt response. I am really overwhelmed. Before going
to the references suggested by you, I wish to mention that a similar
situation arose for a 300M_sun case, but  lgT = 9.61  in
inlist_to_lgT9.9  and remove_initial_center_by_entropy = 18.0  in
inlist_to_lgT9.9 worked nicely, that's why I am troubled with the very slow
STELLA calculations for the case of 400M_sun. The STELLA produced
lightcurve and FeII line velocity evolution with these settings for
300M_sun progenitor are inscribed below.
[image: luminosity.png][image: FeII5169_vel_300M.png]
a) In  inlist_to_lgT9.9, If the lgT=9.85, then the Fe core infall limit is
reached before the lgT=9.85 condition satisfied (I missed to mention this
in previous mail), and the calculation stops. Is it possible to delay the
Fe core infall so that lgT=9.85 is achieved or vice-versa? I had tried
the  *T_function1_weight
*but still failed to reach the prescribed temperature limit before the Fe
core infall limit reached.

b) With remove_initial_center_by_entropy set less than 18.0, the following
error message (for the case when remove_initial_center_by_entropy =4) is
displayed in the terminal:
[image: terminal_err.png]
So, I do not know how to proceed further. Please suggest.

With best regards,
Amar

On Mon, Dec 14, 2020 at 12:29 PM Jared Goldberg <goldberg at physics.ucsb.edu>
wrote:

> Hi Amar,
>>
>>
>> a) I could notice that after finishing the *inlist_to_si_burn* stage in
>> the *example_make_pre_ccsn* directory, the model fails to achieve the
>> prescribed temperature (lgT) of 9.85 while running *inlist_to_lgT9.9*,
>> so I decreased the limit to 9.61 and rerun the calculation. This time the
>> evolution successfully proceeded. Please note that even a lgT of 9.62 was
>> not achieved so I tried 9.61.
>>
> Sounds like the model never made it to the end of Si burning/the
> generation of the Fe core, which should happen around log(Tcenter) = 9.9.
>
>
>> b) Thereafter, the shock is evolved using the *example_ccsn_IIp* directory
>> with few changes like, in *inlist_infall*, we required to change the *remove_initial_center_by_entropy
>> = 19.6*   (default value is 4). Few timestep adjustments were also done.
>> Then the calculation proceeded nicely and the *mesa.abn* and *mesa.hyd* (please
>> see attached ) files were successfully created. Please take a look to
>> *inlist_shock_part5* also.
>>
>
> This makes sense, given point (a). The entropy profile tells you where the
> various core boundaries are, and the Fe core boundary crosses an entropy
> value of 4. So by going up in entropy you're effectively removing more than
> what would have been the Fe core, likely closer to the CO boundary.
>
> c) These two files were then used as input for STELLA calculations. The
>> STELLA calculation started nicely but seems that it fails to converge. On a
>> 16GB RAM and octa-core processor machine, the calculations ran up to a
>> period of more than 24hours but the light curve only up to 7days was
>> produced with the calculation still going on.
>
> Since this is a fundamentally STELLA issue, I'm happy to discuss as a
> MESA+STELLA user but note that it seems like everything you're doing in
> actual MESA is working.
> It might just be the case that more runtime is simply what STELLA needs.
> Ultimately, you are solving radiation transport through a lot of
> slow-moving, dense material, with an order of magnitude more mass than a
> normal IIP calculation. Things to consider: What are the velocities you
> get? What explosion energy do you use? What do you set for the innermost
> velocity (your fallback cut)? Do you get any fallback (see Appendix D of MESA
> instrument paper V
> <https://ui.adsabs.harvard.edu/abs/2019ApJS..243...10P/abstract> and
> appendix A of this paper
> <https://ui.adsabs.harvard.edu/abs/2019ApJ...879....3G/abstract>)? For a
> 400 Msun star, the inner ejecta definitely could be causing the
> computational slowdown.
>
> Cheers,
> ~Jared
>
> On Sun, Dec 13, 2020 at 10:37 PM <amar at aries.res.in> wrote:
>
>> Dear MESA team,
>>
>> MESA Version : 11701
>>                   OS : ubuntu 20.04
>>
>> I am trying to study the evolution of very massive stars (in particular
>> 400M_sun without any rotation and mass loss) with the help of MESA. I could
>> evolve the star up to the stage of core-collapse. Here, I wish to discuss
>> and understand few points :
>>
>> a) I could notice that after finishing the *inlist_to_si_burn* stage in
>> the *example_make_pre_ccsn* directory, the model fails to achieve the
>> prescribed temperature (lgT) of 9.85 while running *inlist_to_lgT9.9*,
>> so I decreased the limit to 9.61 and rerun the calculation. This time the
>> evolution successfully proceeded. Please note that even a lgT of 9.62 was
>> not achieved so I tried 9.61.
>>
>> b) Thereafter, the shock is evolved using the *example_ccsn_IIp*
>> directory with few changes like, in *inlist_infall*, we required to
>> change the *remove_initial_center_by_entropy = 19.6*   (default value is
>> 4). Few timestep adjustments were also done. Then the calculation proceeded
>> nicely and the *mesa.abn* and *mesa.hyd* (please see attached ) files
>> were successfully created. Please take a look to *inlist_shock_part5*
>> also.
>>
>> c) These two files were then used as input for STELLA calculations. The
>> STELLA calculation started nicely but seems that it fails to converge. On a
>> 16GB RAM and octa-core processor machine, the calculations ran up to a
>> period of more than 24hours but the light curve only up to 7days was
>> produced with the calculation still going on.
>>
>> Please suggest me some possible methods to get convergence of STELLA
>> calculation. Also, suggest if I am doing something wrong.
>>
>> With thanks and best regards,
>> Amar
>>
>>
>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
>>
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