[Mesa-users] Stellar wind & time step for massive helium core burning stars

[Jelena Petrović]

Hi Mathieu,

Thank you for your fast response!

For dt_limit in terminal output it stands "max_increase".

Considering your second point, I actually turn off the wind during core 
helium burning when time step becomes really low (not from the beginning 
of the evolution!) and this solves the problem with small time step. The 
lower the wind, larger the time step.
Do you have any idea why this might be happening?

Many thanks,
Jelena





On 2020-07-09 21:53, Mathieu Renzo via Mesa-users wrote:
> Hi Jelena,
> 
> it is difficult to diagnose with certainty what is the issue here
> without seeing your inlists and/or plots of your models.
> What is limiting the timestep in your models with winds on and scaling
> parameter 1? What is the timestep_limit string in the terminal output?
> Is the problem the same in the WR primary stars in binaries and in
> single stars, or are you facing different issues?
> 
> I suppose when you turn off the wind you do so from the beginning (not
> only after He ignition). Therefore, the difference in your models
> might be caused by the different chemical/density profile at the edge
> of the core when you have winds on/off. I would try to compare the
> TAMS density and chemical profiles, and in particular the core edge to
> see if something might be happening there.
> 
> Bests,
> Mathieu
> 
> On 7/9/20 3:32 PM, Jelena Petrović wrote:
> 
>> Dear all,
>> 
>> I am calculating evolution of massive stars, above 30Ms with an
>> option for stellar wind:
>> hot_wind_scheme = 'Dutch'
>> Dutch_scaling_factor = 1d0
>> 
>> I have noticed that time step drops drastically (even to 10^-2) once
>> the star enters helium core burning phase.
>> However, if I decrease scaling factor, time step increases and if I
>> fully switch off stellar wind (scaling_factor = 0d0), helium core
>> burning is calculated with time steps of 10^2-10^3.
>> 
>> I have the same problem with massive binaries, where the primary
>> becomes WR star, so helium core burning star with most of its
>> hydrogen envelope gone.
>> Also, if I switch of stellar wind, time steps goes from 10^-2 to
>> 10^2-10^3.
>> 
>> What can be the reason for this? How can I keep a reasonable time
>> step with stellar wind option on?
>> 
>> Many thanks,
>> Jelena
>> 
>> -------------------------------------
>> Dr. Jelena Petrovic
>> Senior Research Associate
>> Astronomical Observatory Belgrade
>> Serbia
>> -------------------------------------
>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
> 
> --
> Mathieu Renzo [1]
> Flatiron Research Fellow
> Center for Computational Astrophysics
> 
> 
> Links:
> ------
> [1] https://users.flatironinstitute.org/~mrenzo/
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