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

[Jeremy Sakstein]

Thanks Josiah,

Is lnfree_e called in the star pointer? I am using this in other_neu so I
was hoping not to have to call the EOS twice.

If not, does this info end up in s% ye(k) or does this only include
electrons from ions?

Cheers,

Jeremy

On Wed, May 6, 2020 at 12:58 PM Josiah Schwab <jwschwab at ucsc.edu> 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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