[mesa-users] Fixed Time Steps

[Ehsan Moravveji]

Dear Jeremy,
While I do not fully comprehend your problem, but as you know, taking
large timesteps leads to less precise results as explained e.g. in Table 7
in the instrument paper. Certainly, some epochs of evolution need be
solved with fine timesteps. So, if I would be you, I will set the upper
limit for the time step by either of
         max_timestep = 0  ! in seconds.  max_timestep <= 0 means no upper
limit.
         max_years_for_timestep = 0  ! max_years_for_timestep <= 0 means
no upper limit.
to make sure mesa steps does not exceed your desired upper limit. Then,
choose a very fine time step size by
         varcontrol_target = 1d-4
and have mesa evolve your model.

At the end of the run, you can compare your observable based on its
cumulative age (co-adding all fixed time steps taken) with the age
calculated by mesa.

In pre-4411 releases, the other options that I never played around with
can be found in star/public/star_defaults.dek in section: "controls for
timesteps".

Let us know how well things proceed.
Ehsan.


> Hi All,
>
> I have some data that I would like to feed into MESA and it comes at
> discreet time-steps. Even more annoyingly, they are spaced in delta log
> and
> not t. I was wondering, is there anyway to force MESA to evaluate each
> model using a fixed time step in delta log t?
>
> Cheers,
>
> Jeremy
>
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