[Mesa-users] degeneracy parameter

[Jason Wright]

How is eta, the degeneracy parameter, defined in MESA?

The first instrument paper claims (p.19) it is roughly eta = E_F/kT, but I
think the proper definition is something more like (in the non-relativistic
regime)

np.log ( 8/(3*pi) (E_F/(kT))^(3/2) )

Indeed, when I plot the above equation vs. eta I get pretty good agreement:
eta is <1 for most of my star, so there must be a logarithm in there.

But I'm also confused because I do not get *very* good agreement: I get
differences of factors of a few in the atmosphere of my star, where the
non-relativistic approximation should hold best!

Is there a good reference for how to interpret this parameter?

-- 
                                                -
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Jason T Wright
Professor of Astronomy & Astrophysics
Director, Penn State Extraterrestrial Intelligence Center
Acting Director, Center for Exoplanets and Habitable Worlds
NEID Instrument Team Project Scientist <http://neid.psu.edu/>
he/him/his
*https://sites.psu.edu/astrowright/ <https://sites.psu.edu/astrowright/>*
@Astro_Wright

<http://twitter.com/Astro_Wright>
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