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MESAHub / mesa

Modules for Experiments in Stellar Astrophysics
http://mesastar.org
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Extend EOS coverage to lower densities #329

Closed evbauer closed 2 years ago

evbauer commented 3 years ago

The EOS currently provides almost no coverage for logRho < -12. It returns NaN in the green region labeled "none" on this plot:

image

Some stellar models can have envelopes that extend out to these low densities at logT ~ 5. Providing EOS coverage for this region may solve some of our convergence issues for hot stars with extended envelopes (e.g. post-AGB stars).

A possible solution is to generate a new HELM table that covers these lower densities, extending out to at least logRho = -15, or perhaps lower if possible.

(The "none" regions for logT < 3 are less of a concern. I'm not aware of stellar models that end up in this territory.)

fxt44 commented 3 years ago

a new helm table can be made with as low a density as needed. its the upper left where some subtractions get nasty, but then i don't know of stellar models that have rho=1e-20 g/cc and T=1e10 k.

adamjermyn commented 3 years ago

I don't think we're worried about the top-left. I think it's more T ~ 1e5K where stars sometimes have low densities...

-Adam

On Tue, Sep 28, 2021 at 4:49 PM, fxt @.***> wrote:

a new helm table can be made with as low a density as needed. its the upper left where some subtractions get nasty, but then i don't know of stellar models that have rho=1e-20 g/cc and T=1e10 k.

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fxt44 commented 3 years ago

should be no issues at 1e5 k for a helm approach. and for the record, the eos that makes the tables has no such subtraction issues, so it should not be an issue there either. 40 or 100 points per decade in rho and T? and how low in rho?

evbauer commented 3 years ago

Thanks! I think we should be fine with whatever we have now as far as points per decade and T range, just extending density down to logRho = -20.

fxt44 commented 3 years ago

was 40/decade for a long time, then 100/decade last year or so but i can't recall if that was used. i'll look.

evbauer commented 3 years ago

It looks like MESA is currently using the 100/decade version.

integer, parameter :: imax = 2701, jmax = 1001 ! dimensions of large version of helm table; 100 points per decade

adamjermyn commented 3 years ago

This is potentially resolved by PR #333 once merged.

adamjermyn commented 2 years ago

Resolved with #333

rjfarmer commented 2 years ago

Could we get a changelog entry?

adamjermyn commented 2 years ago

Sure, on it.

-Adam

On Mon, Oct 25, 2021 at 12:59 PM, Robert Farmer @.***> wrote:

Could we get a changelog entry?

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adamjermyn commented 2 years ago

Done.

-Adam

On Mon, Oct 25, 2021 at 1:22 PM, Adam Jermyn @.***> wrote:

Sure, on it.

-Adam

On Mon, Oct 25, 2021 at 12:59 PM, Robert Farmer @.***> wrote:

Could we get a changelog entry?

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