[Mesa-users] Changing reaction rate issu in PPISN

[Warrick Ball]

Hi Jeremy,

I just searched `controls.defaults` in r12778 and found the following near the end of "mixing parameters" (just before "rotation controls"):

     set_min_D_mix = .false.
     mass_lower_limit_for_min_D_mix = 0d0
     mass_upper_limit_for_min_D_mix = 1d99
     min_D_mix = 1d3

     set_min_D_mix_in_H_He = .false.
     min_D_mix_in_H_He = 1d3

     set_min_D_mix_below_Tmax = .false.
     min_D_mix_below_Tmax = 1d3

     min_center_Ye_for_min_D_mix = 0.47d0

They're all present in r15140 so you can see the HTML version here:

     https://docs.mesastar.org/en/r15140/reference/controls.html#set-min-d-mix

I think Mathieu's suggestions corresponds to

     set_min_D_mix = .false.
     min_D_mix = 1d-2

Cheers,
Warrick


___________

Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552

On Fri, 21 Jan 2022, Jeremy Sakstein wrote:

> Hi Mathieu,
> "Regarding running PPISN at low-Z: I would look at how sharp the core edges are in these models. Once wind-mass loss becomes too small, the cores become sharper and it is hard for pulses to get through them (as I found in models with no-winds at
> finite Z). If you really want low-Z model an idea could be add some small extra mixing (D_mix = 1d-2 for example) to smooth the edges a bit without messing up the stars too much. N.B: I have not tested this myself."
> 
> Thanks for this, I was not aware this could be an issue and am interested in testing it. I looked for D_mix in controls_defalts but couldn't find a verbatim control with that name. What's the control I should be looking for?
> 
> I am using MESA-r12778.
> 
> Cheers,
> 
> Jeremy
> 
> On Thu, Jan 20, 2022 at 9:52 AM Mathieu Renzo via Mesa-users <mesa-users at lists.mesastar.org> wrote:
>       Hi Vaishnav and Harshda,
>
>       I believe you want to set num_special_rate_factors=1 in your inlist.
>
>       The exact setup to reproduce Farmer et al. results is available on zenodo: https://zenodo.org/record/3346593
>       and https://zenodo.org/record/3559859 (and I believe https://ui.adsabs.harvard.edu/abs/2022ApJ...924...39M/abstract successfully used these).
>
>       Regarding running PPISN at low-Z: I would look at how sharp the core edges are in these models. Once wind-mass loss becomes too small, the cores become sharper and it is hard for pulses to get through them (as I found in models with
>       no-winds at finite Z). If you really want low-Z model an idea could be add some small extra mixing (D_mix = 1d-2 for example) to smooth the edges a bit without messing up the stars too much. N.B: I have not tested this myself.
>
>       Hope this helps!
>       Mathieu
>
>       On 1/20/22 2:17 PM, Vaishnav Rao via Mesa-users wrote:
>       Dear MESA users,
> 
> We have been playing around with the PPISN test suite for the past year in an attempt to understand and reproduce the black hole mass gap. We were facing difficulties in incorporating custom reaction rates for the C12-O16 reaction in
> our test suite. 
> 
> We have been attempting to reproduce the plots of the effect of CO reaction rates on the final BH mass as in Farmer et al., 2019 and Farmer et al., 2020 . Using the reaction rates from the files of the latter, we tried to run a modified
> test suite with recommended settings (which had already run for the default rates for us before). However, upon comparing the final BH masses for 0 sigma and -1 sigma rate tables, there was no major difference, even though there is an
> expected difference of 8M in the final BH masses. Clearly the lines 
> 
> num_special_rate_factors=0
> reaction_for_special_factor(1)='r_c12_ag_o16'
> special_rate_factor(1)=1.0d0 ! Used for linear scaling of rates
>   
> rate_tables_dir='rates/c12alpha/rate_tables-1s’
> 
> which specify the path to the modified rate tables do not seem to be having any major effect on the simulations. 
> 
> Our simulations are for metallicities of 1d-3 (in accordance with Farmer et al., 2019). We chose this metallicity because our simulations for 1d-5 ( as in Farmer et al., 2020) faced multiple convergence issues (mostly ‘hydro_failed’ or
> too many retries). According to the other posts we saw on the MESA mailing list archives, many others too faced convergence issues of this sort for such low metallicities. We are not sure whether using the same rate tables for different
> metallicities is correct. 
> 
> Our inlist, run_star_extras, and rate tables (zip file) have been attached for reference. Any advice on solving this issue would be appreciated.
> 
> Software details:
> MESA version: r12778
> SDK version: March 25, 2020
> OS: Cluster, 64-bit Linux 
> 
> Thanking you in advance,
> Vaishnav V. Rao & Harshda Saxena
> Department of Physics
> Indian Institute of Technology Bombay
> 
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
> 
> 
> --
> Mathieu Renzo
> Flatiron Research Fellow
> Center for Computational Astrophysics
> Columbia University
> _______________________________________________
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> 
> 
> 
> --
> Jeremy Sakstein (He/Him/His)
> Assistant Professor of Theoretical PhysicsDepartment of Physics & Astronomy
> University of Hawaiʻi at Mānoa
> Watanabe Hall
> 2505 Correa Road
> Honolulu, HI, 96822, USA
> http://www.jeremysakstein.com
> 
>