[Mesa-users] Planet Radius and EOS question

Isaac Malsky isaacmalsky at gmail.com
Mon May 11 13:12:00 EDT 2020

Hi all,

Thanks! I've run some tests with the logQ_limit control much stricter, and
at the very least that lets me know when the model is reaching the limit of
what the eos tables are happy with.

I'll work some more with finding out how to model these planets with MESA
in a stable way, and I'd be happy to share what I find if anyone is
interested in the future. It's good to know the source at least. I really
appreciate all the help!


On Mon, May 11, 2020 at 12:59 PM Bill Paxton <paxton at kitp.ucsb.edu> wrote:

> > On May 11, 2020, at 9:48 AM, Josiah Schwab via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
> >
> > Hi Isaac,
> >
> > I looked at this briefly and my sense is that you're just off the EOS.
> You've taken off the logQ_limit safety barrier and this is sort of
> at-your-own-risk territory.  When we fall off SCVH we go do the (bad)
> approximation of an ideal gas -- this is the "dragons" area in Fig 50 of
> Paxton et al. 2019.  I think the radius change just reflects that change in
> the EOS.  I'd be surprised if there's much you can do here in current MESA
> versions.
> Hi Isaac,
> Josiah is ahead of me on this one, and I agree with his assessment.  You
> may be driving the system off a cliff and it cannot just fly away.  ;-)
> We have not tried to put up sufficient guard rails to keep this from ever
> happening - so it is left to the explorations of the user to find the
> limits in cases like this.   As you say, you are pushing the system into
> extreme territory, places no one has dared go before.   If you want to keep
> trying, I suggest the usual approach of finding a simpler case that works
> and then gradually modifying it in the direction you want so you can see
> where things finally break or perhaps find a work around.   It is rarely
> possible to work backwards from a badly broken system to restore something
> working unless it is a very simple bug.  this one doesn’t look simple.
> good luck,
> bill
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