[Mesa-users] Question about MESA EOS

[Francis Timmes]

hi tu,

unfortunately the analysis has a few issues. among them are

1) the version of mesa being used is not given.

2) a stellar equation of state depends on the composition; 
here the composition is not given. 

3) the y-axis of figure 1 indicates temperatures of log(T) ~ 20. 
i'm unaware of any stellar model that reaches a temperature 1e20 K.
so the plotting of the mesa temperature profile has gone off-track.

4) the "mesa eos" label of figure 1 is a misnomer. the label should be 
"my extraction and interpolation of a tabulated table".

5) the mesa temperature profile shown in red is smooth. 
i cannot answer why your extraction and interpolation blue curve shows a kink.

6) the plot showing the number density of free electrons n_e indicates 
an n_e range of 1e-20 1/cm^3 to 1e-120 1/cm^3. fully ionized hydrogen 
at 1 g/cm^3 has n_e ~ rho / mass of proton ~ 1e24 1/cm^3. this suggests 
that something has gone wrong, by ~ 40 orders of magnitude or more, with the 
extraction, interpolation, and/or plotting.

fxt






> On May 8, 2020, at 1:33 PM, Yisheng Tu via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> 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
> 
> <Figure_1.png><Figure_3.png><Figure_2.png><Figure_2_zoom.png>_______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>