[Mesa-users] Question about calculating electron densities for high mass stars

[Josiah Schwab]

Hi Jeremy,

I have a quick question about calculating electron/positron densities using
> MESA.
>
> For low mass stars this is just [image: Y_e\frac{\rho}{m_u}] (I don't
> need to distinguish between free and bound) but am I correct in that this
> doesn't include electron-positron pairs?
>
> I am interested in high-mass stars where pair production could occur. If [image:
> Y_e] does not include these ep pairs, can someone give me a suggestion
> for how to calculate the extra contribution?
>

The EOS returns lnfree_e (ln # of free electrons per nucleon).  When you're
on HELM (which covers where pair production is important), I think this
value is actually the combined number of e^- & e^+ per nucleon.

I'm a little hazy on this, but you should be able to inspect at that value
and pretty quickly see if it is giving sensible answers that mesh with my
half-remembered interpretation.

Josiah
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