mesa-users] creating high Z pre main sequence model

[Bill Paxton]

Hi,

I'm glad you are using mesa.

The "create pre-main sequence" operation sometimes runs into cases
that are too hard for it to do -- and it looks like the Z=0.1 is such a case.

I'd suggest that you try creating what you want in a series of steps.
First, create a pre-main sequence star of the desired mass but lower Z.
Experiment to find a Z that is small enough to work.
Let the lower Z model run for 10 or 20 steps and then save it.

Now increase Z by using one of the "stellar engineering" operations
that are provided as options in the &star_job part of the inlist.
You might start by trying 
      change_Z = .true. ! simply changes abundances; doesn't reconverge the model.
      new_Z = 0.1
That just goes into the model and changes Z in a single operation.
Give it a try.  If it your model can absorb the change and keep running, great.
But if your model cannot converge when Z is changed so abruptly, try using
	relax_Z = .true. ! gradually change abundances, reconverging at each step.

Hopefully one or the other of those will do the trick.  
Save the new model and remove the inlist commands for changing Z.

I hope that works for you.  Let me know!

Cheers,
Bill




On Jul 20, 2010, at 2:47 AM, Masanobu Kunitomo wrote:

> Dear Dr. Paxton,
> 
> Hello, My name is Masanobu Kunitomo, a graduate student at Tokyo
> Institute of Technology.
> 
> First, I thank you for providing the great code MESA.
> 
> Today I am writing to ask you about the problem for high metallicity.
> While running the case of Z=0.1 with 'pre-main-sequence model', the
> following message was displayed;
> 
> *********************************************************************************
> Revision: 2258
> Tue Jul 20 17:30:20 JST 2010
> read extra star_job inlist1 from inlist--mine
> loading eos data
> loading kap data
> finished loading
> read extra controls inlist1 from inlist--mine
> 
> 
> The terminal output contains the following information
> 
>      'step' is the number of steps since the start of the run,
>      'lg_dt_yr' is log10 timestep in years,
>      'age_yr' is the simulated years since the start run,
>      'lg_Tcntr' is log10 center temperature (K),
>      'lg_Dcntr' is log10 center density (g/cm^3),
>      'lg_Pcntr' is log10 center pressure (ergs/cm^3),
>      'lg_Teff' is log10 surface temperature (K),
>      'lg_R' is log10 surface radius (Rsun),
>      'lg_L' is log10 surface luminosity (Lsun),
>      'lg_LH' is log10 total PP and CNO hydrogen burning power (Lsun),
>      'lg_L3a' is log10 total triple-alpha helium burning power (Lsun),
>      'lg_LZ' is log10 total burning power excluding LH and L3a and
> photodisintegrations (Lsun),
>      'lg_LNuc' is log10 nuclear power excluding photodisintegration (Lsun),
>      'lg_LNeu' is log10 total neutrino power (Lsun),
>      'lg_Psurf' is log10 surface pressure (gas + radiation),
>      'Mass' is the total stellar mass (Msun),
>      'lg_Mdot' is log10 magnitude of rate of change of mass (Msun/year),
>      'lg_Dsurf' is log10 surface density (g/cm^3),
>      'H_rich' is the remaining mass outside of the hydrogen poor core,
>      'H_poor' is the core mass where hydrogen abundance is <= 0.10E-03
>      'He_poor' is the core mass where helium abundance is <= 0.10E-03
>      'H_cntr' is the center H1 mass fraction,
>      'He_cntr' is the center He4 mass fraction,
>      'C_cntr' is the center C12 mass fraction,
>      'N_cntr' is the center N14 mass fraction,
>      'O_cntr' is the center O16 mass fraction,
>      'Ne_cntr' is the center Ne20 mass fraction,
>      'X_avg' is the star average hydrogen mass fraction,
>      'Y_avg' is the star average helium mass fraction,
>      'Z_avg' is the star average metallicity,
>      'gam_cntr' is the center plasma interaction parameter,
>      'eta_cntr' is the center electron degeneracy parameter,
>      'pts' is the number of grid points in the current model,
>      'jacs' is the number of jacobians created in the current step,
>      'retry' is the number of step retries required during the run,
>      'bckup' is the number of step backups required during the run,
>      'dt_limit' is an indication of what limited the timestep.
> 
> All this and more are saved in 'LOGS/star.log' during the run.
> 
> create pre-main-sequence model
> done build_pre_ms_model
> set_initial_model_number           0
> v_flag = F
> kappa_file_prefix gn93
>   eos_file_prefix mesa
> 
> 
> __________________________________________________________________________________________________________________________________________________
> 
>       step    lg_Tcntr    lg_Teff    lg_LH     lg_Lnuc     Mass
> H_rich     H_cntr     N_cntr     Y_surf     X_avg     eta_cntr   pts  retry
>   lg_dt_yr    lg_Dcntr    lg_Rsurf   lg_L3a    lg_Lneu     lg_Mdot
> H_poor     He_cntr    O_cntr     Z_surf     Y_avg     gam_cntr  jacs  bckup
>     age_yr    lg_Pcntr    lg_L       lg_LZ     lg_Psurf    lg_Dsurf
> He_poor    C_cntr     Ne_cntr    Z_cntr     Z_avg     v_div_cs     dt_limit
> __________________________________________________________________________________________________________________________________________________
> 
> stopping because of too many backups in a row          16
> 
> 
> 
> terminated evolution because hydro_failed_to_converge
> 
> Tue Jul 20 17:39:55 JST 2010
> *********************************************************************************
> 
> Would you let me know what I should do?
> 
> Sincerely,
> 
> Masanobu Kunitomo
> 
> ----------------------------------------------
> Masanobu Kunitomo
> master's student
> Department of Earth and Planetary Sciences
> Tokyo Institute of Technology
> Email: kunitomo at geo.titech.ac.jp
> ----------------------------------------------
>