[mesa-users] finding ZAMS minimum mass

[Robert Farmer]

Hi
So star/work is not the best place to start from, it is the absolute
minimum you need to run a star but doesn't necessarily give you a good
star. MESA has many options to twiddle to change the physics and the
accuracy of the model, don't assume the default set will work for your star.

I would suggest you look at the star/test_suite folder and find one close
to your problem. The brown_dwarf and cool_brown_dwarf problems might be
more applicable for you case. If you look in the brown_dwarf case you see
it does things like set mixing_length_alpha=1.89 instead of the default of
2.0, which will probably help your test case get to the MS.

Rob

On Mon, Sep 26, 2016 at 12:28 AM, tahere parto <tahereparto at gmail.com>
wrote:

> Dear mesa users,
>
> I'm trying to implement MESA to find a minimum mass for ZAMS
> (the minimum mass for a star which can develop a hot core to be able
>  to burn hydrogen as the main source of energy and start main
> sequence stage). I started with running the code at MESA\star\work
> directory and try to reduce the initial_mass as much as I can and
> check whether the code can approach to the limit log_LH = log_L.
>  Then I did look for the critical mass where the code fail to
> satisfy the condition for initiation of main sequence stage.
>
> We found that as we decrease initial_mass down to 0.113155 solar mass the
> code stops with this error:
>
> hydro_newton_step failed to converge
> stopping because of convergence problems dt < min_timestep_limit
> terminated evolution: convergence problems “
>
>
> The first question is "is it a good idea at all?"
>
> Normally the code takes longer time to approach to the main
>  sequence stage as we reduce the initial_mass. Does this mean
> that for initial_masses less than the critical mass for
>  initiation of main sequence the code must take infinite
>  time to approach the limit log_LH = log_L?
>
> Thank you for your consideration,
>
> Tahere
>
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