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

[Alak Ray]

Dear Jeremy,

You may find the Appendix A of the paper by M.J. Murphy useful.

https://ui.adsabs.harvard.edu/abs/1980ApJS...42..385M/abstract

- Alak

On Wed, May 6, 2020, 10:30 PM Josiah Schwab via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> 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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