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

[Mathieu Renzo]

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
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>

-- 
Mathieu Renzo <https://users.flatironinstitute.org/~mrenzo/>
Flatiron Research Fellow
Center for Computational Astrophysics
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