[Mesa-users] problem with small time-steps

[Rob Farmer]

MESA has a number of timestep controls
https://docs.mesastar.org/en/release-r21.12.1/reference/controls.html#timestep-controls
which also points out that the terminal output contains the output dt_limit
which will tell you why mesa is taking small time steps.

Rob

On Tue, 18 Jan 2022 at 10:36, Warrick Ball via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi Ebrahim,
>
> I haven't looked at your code but it will be easier for other users to
> help you if you could describe what at point in evolution the timesteps
> decrease.  MESA using small timesteps is a fairly generic problem.  Could
> you attach some plots of, say, an HR diagram?  And could you include the
> models that do finish?  What's the closest mass to 2 Msun that *does* reach
> the "final stages" of evolution?
>
> My instinct is that your 2 Msun star is struggling with the
> thermally-pulsing asymptotic giant branch (TP-AGB) more than the other
> models.  However, I've also noticed that your `inlist` doesn't include (or,
> rather, has commented out) the lines for mass loss, so I'm also curious
> about what are the "final stages" in the evolution of the 1 and 3 Msun
> models.  Normally the star would lose enough mass during the (TP) AGB to
> expose the central CO core.  I'm not sure what happens if you try to run
> without any mass loss and no other stopping condition.
>
> Cheers,
> Warrick
>
> ___________
>
> Warrick Ball
> Postdoc, School of Physics and Astronomy
> University of Birmingham, Edgbaston, Birmingham B15 2TT
> W.H.Ball at bham.ac.uk
> +44 (0)121 414 4552
>
> On Tue, 18 Jan 2022, mesa-users at lists.mesastar.org wrote:
>
> > Dear Mesa-users
> >
> > I edited the run_star_extras.f90 file of the ~/mesa-r21.12.1/star/work
> star to consider dark matter effects in stars (After copying the files of
> the star to the Home directory in Ubuntu 20.04). The edited code is working
> correctly for 1.0 and 3.0
> > M_Sun stars. But, when I want to run the code for 2.0 M_Sun, it takes so
> many steps (at least more than 40000) for the star to reach the final
> stages of its evolution. In fact, when 2.0 M_Sun star leaves the
> main-sequence, its time steps become very
> > small (~ 1 year and sometimes less than 1 year). And for this reason, it
> takes so many time-steps for the 2.0 M_Sun star to reach the final stages
> of its evolution.
> >
> > May I ask what might be the possible reasons for this problem? And how
> can I solve this problem? And also, why the same problem does not happen
> for the 1.0 and 3.0 M_Sun stars?
> >
> > The attached files are the codes that I used in my work.
> >
> > Best regards
> > Ebrahim Hassani
> >
> >
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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