[Mesa-users] Creating a Highly Irradiated Super-Earth

[Brian Jackson]

I've conducted additional experiments, and I think I'm starting to see
what the issues might be.

I've attached inlists and a model for a slightly different approach.
The model calculation behaves fine until about 4 Gyrs out, when the
timestep suddenly plunges and the code fails to complete the run. For
some reason, the central degeneracy parameter goes haywire shortly
before the run ends -- see attached History_Plot.png.

Looking at the 2011 MESA instrument
(https://ui.adsabs.harvard.edu/abs/2011ApJS..192....3P/abstract), it
seems the model core may be nearing a transition in the equation of
state (log(density) = -0.19, log(temp) = 3.79 -- see attached Figure
1). Is there a reason why that transition would severely and abruptly
modify the degeneracy parameter? Is there a way to smooth this
evolutionary phase?

Or have I completely misunderstood what's going on?

Thanks,
Brian

On Wed, Jan 22, 2020 at 5:58 PM Brian Jackson <bjackson at boisestate.edu> wrote:
>
> Dear MESA Users,
> I am still struggling to create highly-irradiated super-Earths using MESA.
>
> I have attached the inlists and saved models I'm using to create a
> 20-Earth mass planet with an envelope mass fraction of 20% (i.e., a
> core mass of 16 Earth masses) and an irradiation 20 times Earth's
> (i.e., 2.72e7 ergs/s/cm^2).
>
> I attempt to create the planet by irradiating a gas giant planet and
> then relaxing the mass down to my desired mass. (I've found doing it
> the other way around leads to badness.) I've tried tweaking lots of
> settings, but nothing seems to work. In the end, I wind up with a
> timestep below the suggested minimum of 9.9999999999999995D-07.
>
> I am using Mac OS 10.13.1, MESA 11701, and the most recent version of
> the SDK (August 30 2019).
>
> Please forgive me if I forgot any required information.
>
> Thanks,
> Brian
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