[mesa-users] finding ZAMS minimum mass

[Bill Paxton]

Rob's advice is right on.  

I'd add that you should take a careful look at Figures 15-18 in the 1st mesa instrument paper (2011).  

Then read and run the cool_brown_dwarf test case as is -- it is based on the method used to create the data for figure 18.

You might be able to copy that test case and modify it to do your problem -- that's often a fast-track option to success!  ;)

-Bill



On Sep 26, 2016, at 10:02 AM, Robert Farmer wrote:

> 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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