[Mesa-users] Warnings with additional energy sink and rel_E_err

[Josiah Schwab]

Hi Adrián,

I tried to compute a 1 solar mass model at r12778, implementing an
> extension in run_star_extras, to account for an additional sink in the star
> energy budget.
>
> I got a value of rel_E_err of 10^-1, which is, in my views, too much.
>
> The point is that the error remains, which the same order of magnitude,
> even when I turned off the additional energy sink, running a simple 1 solar
> mass, solar metallicity model.
>
> Please, find the inlists attached.
>
>
Thank you for starting a new thread.  I recommend you carefully read Bill's
message about whan run_E_err means (
https://lists.mesastar.org/pipermail/mesa-users/2020-May/011334.html).

>From glancing at your inlist, I suspect you are encountering something I
mentioned in the same thread (
https://lists.mesastar.org/pipermail/mesa-users/2020-May/011359.html)

if you run a 1M MESA model with the eps_grav form out of
the box, you get poor energy conservation during the MS.  The deeper reason
is not numerical, rather it is a result of the default implementation of
eps_grav dropping the term associated with composition changes.

This assumption is well justified in terms of the total energy budget of
the star.  The energy associated with the change in mean molecular weight
is dwarfed by the energy release from nuclear reactions that cause it.
However, our reference point for checking energy conservation is not the
time-integrated radiated energy of the star, but is the instantaneous total
energy of the star (excluding rest mass).  Relative to that, the energy
change is not negligible.

If you turn on the eps_grav composition terms (setting
"include_composition_in_eps_grav = .true.), you should see an improvement
in reported energy conservation.

Josiah
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