[Mesa-users] relaxing entropy

[Rob Farmer]

Hi,

Retries and backups are telling you that mesa is struggling to make the
change requested for that step of the entropy relax process. If you look in
a T-rho plot with

show_TRho_Profile_eos_regions = .true.

enabled, does it look like the model is crossing any EOS boundaries when it
crashes?

How different is your new entropy profile compared with the starting one
for the wd? The bigger the difference the harder it will be.

How "close" is the EOS in mesa (for WD's) to what was used in the hydro
simulation? The bigger the difference the harder it will be. Remember
MESA's eos is a composite of several sources, different parts of a star may
be using different EOS's.

> tried using the one provided in the "relax_composition_j_entropy"
template to see what would happen.

The entropy profile for relax_composition_j_entropy describes a 10 solar
mass TAMS star so that is not going to look like a 0.6Msun WD. So i'm not
surprised that starting from a WD and trying to turn it into a 10Msun star
fails.

Rob



On Tue, 8 Sep 2020 at 13:36, Akaash Conhye via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi all,
>
> I've been trying to relax a white dwarf's entropy profile (obtained from
> hydrodynamic simulations). The template I used was wd_cool_0.6M. To the
> file inlist_wd_cool_0.6M I've added the following lines:
>
>       relax_initial_entropy = .true.
>       max_steps_to_relax_entropy = 1000
>       timescale_for_relax_entropy = 1d-9 ! in years
>       max_dt_for_relax_entropy = 1d-8 ! in years
>       num_timescales_for_relax_entropy = 100
>       relax_entropy_filename = 'entropy_unrlx.dat'
>
> Where entropy_unrlx.dat is my entropy profile. Upon running, here is the
> output on my terminal:
>
> read inlist_wd_cool_0.6M
>  set_eos_PC_parameters
>                              mass_fraction_limit_for_PC
>  1.0000000000000000D-03
>                                        logRho1_PC_limit
>  2.9990000000000001D+00
>                                        logRho2_PC_limit
>  2.7999999999999998D+00
>                                      log_Gamma_all_HELM
>  1.0000000000000000D+00
>                                        log_Gamma_all_PC
>  1.3010299956000000D+00
>                                  PC_Gamma_start_crystal
>  1.7400000000000000D+02
>                                   PC_Gamma_full_crystal
>  1.7600000000000000D+02
>                                                PC_min_Z
>  9.9900000000000000D-01
> load saved model wd_0.6.mod
>
>                     WARNING -- inlist initial_z ignored
>  1.0000000000000000D-02
>                           using saved initial_z instead
>  2.0000000000000000D-02
>
>
>                                   relax_initial_entropy
>  relax_entropy: max_steps_to_use        1000
>  retry     129
>  retry     129
> backup     129
>  retry     129
>  retry     129
> backup     129
>  retry     129
>  retry     129
>                                                     dt
>  7.7046264609375010D-11
>                                      min_timestep_limit
>  1.0000000000000001D-09
>
>  stopping because of problems dt < min_timestep_limit
>
>  do_relax_initial_entropy ierr          -1
>  do_star_job_controls_after ierr          -1
>  before_evolve_loop ierr          -1
> DATE: 2020-09-08
> TIME: 11:00:31
>
> Some things Ive tried to do to fix this problem:
>
>    1.  decreasing min_timestep_limit (by setting it to a smaller value in
>    the controls section of my inlist) so that i don't get the inequality
>    dt<min_timestep_limit. But this doesn't solve the problem as dt continues
>    to get smaller.
>    2. using a different entropy profile. Initially I'd thought that there
>    was something wrong with my entropy profile, so I tried using the one
>    provided in the "relax_composition_j_entropy" template to see what would
>    happen. I got the same error message.
>
>
> the version of MESA im using is 12115. My operating system is Ubuntu
> 20.04.1 LTS 64 bit. Im running MESA on a cluster (eureka).
>
> Thanks,
>
> Akaash
>
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