[Mesa-users] Definition of eta (electron degeneracy parameter)

diogo.capelo at tecnico.ulisboa.pt diogo.capelo at tecnico.ulisboa.pt
Sat Dec 10 16:47:02 UTC 2022

Thank you for the clarification. I did find both definitions - one in the
equation of state and one in the opacity routine - but pasted the wrong one.
I assumed the one on the equation of state (as described in the MESA
instrument papers) was the correct one I should use. 


I believe my initial mistake (that caused me to miss the definition in all
manner of places) was assuming that there had to be a log somewhere to
explain the negative values. I should have known better (and now I do).



Best regards,



From: Evan Bauer <evan.bauer.astro at gmail.com> 
Sent: 10 de dezembro de 2022 01:48
To: diogo.capelo at tecnico.ulisboa.pt
Cc: mesa-users <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Definition of eta (electron degeneracy parameter)


To help avoid confusion, I'd also like to clarify that the eta assignment
you found earlier is misleading:


eta = (efermi - me*clight*clight)/(kerg*T)


This code snippet is coming from an assignment that is internal to the
compton opacity routine in the kap module, and is distinct from the EOS code
that sets the value of eta that is used in the star module.




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