[Mesa-users] Question about MESA EOS

[Yisheng Tu]

Hi MESA community,

I'm working with MESA EOS and I encountered some problems when I tried to
put MESA EOS and MESA Profile together.

I got a tabulated EOS by hacking into eos/test/src/sample_eos.f. I exported
the region -18 <= log10(rho) <= -1, 0 <= log10(T) <= 8 using eosDT to get *P(D,
T) *(pressure as a function of density and temperature). Then I used the
P(D, T) eos table to reconstruct pressure of a MESA profile from density
and temperature, and compared with the original pressure profile (attached
figure 1). The area left of the dashed line is inconsistent since I
extrapolated everywhere beyond the region I carved out; But I don't
understand why I get a kink at the edge of the envelope at about 1.60
log10(R/Rsun) (also see the zoom-in within figure 1).

I've plotted the MESA profile on the density-temperature-pressure EOS
surface (figure 2 & figure 2_zoom). The profile lies on the EOS surface
until the kink, where it deviates. Why would the MESA profile different
from MESA EOS results?

I also exported free electrons as a function of density and temperature
(i_lnfree_e). There is a flat plateau starting af about log10(T) ~ 4.5 and
log10(rho) ~ -11.9. Why would there be such a sharp transition in
ionization and why does it stay constant as the temperature and density
goes higher?

Thank you,
Yisheng Tu
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