[Mesa-users] Problem with r12778. Bug?

[Josiah Schwab]

Hi Ian,


> you have found a good work around for the problem until the next release
> when this bug will be fixed.
> as you noticed, the treatment in basic.net avoids the problem, so it is
> only larger nets that will hit it when dealing with low temperatures.
>

To add a bit more, we noticed the rate chosen for li7 burning with a "soft"
net (where your net file only specifies isotopes) isn't behaving correctly
at low T.  (You might notice when you look closely the li7 profile looks
"funny" in your model.)  Nets like pp_and_cno_extras.net use a
different rate, which is probably why this had gone unnoticed.

As a workaround, you can swap out the rate for a better behaved version.
Aaron Dotter suggested doing

remove_reaction(r_h1_li7_to_he4_he4)
add_reaction(r_li7_pa_he4)

and when I added these lines to ian30r.net (after the
add_isos_and_reactions part) I no longer saw the issue.

I think the spikes in eps_nuc were associated with zones reaching logT > 7
and then having their li7 suddenly burn.  (Physically it should have burned
at lower T).

Thanks for the bug report!

Josiah
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