[Mesa-users] Problems converging low mass stars because of min_timestep_limit

[Francis Timmes]

hi inma,

i ran your inlist in r24.03.1. while i didn't investigate every opacity/net experiment, i found that increasing the mass resolution from ~300 cells in your original inlist to ~1700 cells via

! mesh controls
      mesh_delta_coeff = 1
      max_dq  = 1d-3

allows the model to run smoothly to completion:

stop because star_age >= max_age
    0.2000000000E+10    0.2000000000E+10

you could also explore the inlists from farag et al 2024 at

https://doi.org/10.5281/zenodo.8327401

especially example_1Msun_solar_Z for setups and settings.

fxt




> On Mar 12, 2024, at 5:43 AM, Inma Moyano via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Dear MESA Users,
> 
> My name is Inma, a master's student. I am using MESA's version 23.05.1 on Ubuntu 23.10.
> 
> I am working on models for low mass stars (0.1, 0.35 and 0.6 Msun), testing different sets of opacity tables for low temperatures (kap_lowT_prefix = 'lowT_fa05_a09' , 'lowT_Freedman11') and also experimenting with the nuclear reaction networks (options 'basic.net', 'h_burn.net' and 'mesa_49.net'). 
> 
> I had no issues using the net 'basic.net', but when I use 'h_burn.net' and 'mesa_49.net' some models of 0.35 and 0.6 Msun do not converge due to the following error:
> 
>                                                      dt    6.9699513407705602D-09
>                                      min_timestep_limit    1.0000000000000000D-08
>  stopping because of problems dt < min_timestep_limit
> terminated evolution: cannot find acceptable model
> termination code: min_timestep_limit
> 
> None of my 0.35Msun models converge using any of the two nets or opacities. WIth regard to 0.6Msun models, they only converge using 'lowT_fa05_a09' opacity, for both nets, but when I change the opacity to Freedman11 they don't anymore. 
> Has anyone had this problem before or knows why this is happening? Here I attach my inlist_project file and also the net files.
> 
> Best regards,
> Inma
> 
> 
> 
> <h_burn.net><inlist_lowmass_nets><mesa_49.net>_______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>