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

[Jeremy Sakstein]

Yes, thank you!

Does the definition of lnfee_e depend on which EOS table is being called?

I ran some tests for a 1 solar mass model and found that exp(lnfree_e) is
around unity at the center of the model. I was expecting 10^(25-27), which
I get by calculating [image: \langle Z\rangle][image: \rho/(\langle
A\rangle m_u)].

Strangely, if I divide exp(lnfree_e) by the electron mass I get a number I
expect. Could this be the electron density rather than the mass?

Cheers,

Jeremy

On Wed, May 6, 2020 at 4:50 PM Francis Timmes <fxt44 at mac.com> wrote:

> the charge neutrality equation
>
> n_{electrons,matter} = n_{electrons,fermi_integral} -
> n_{positrons,fermi_integral}
>
> determines the electron and positron chemical potentials in their fermi
> integrals,
> hence all other thermodynamic quantities. here, each number density n is
> in 1/cm^3.
>
> the helm table tabulates n_{electrons,fermi_integral} +
> n_{positrons,fermi_integral}
> and its first and second derivatives with respect to temperature and
> density.
>
> clearer?
>
> fxt
>
>
>
>
> > On May 6, 2020, at 1:36 PM, Jeremy Sakstein <sakstein at hawaii.edu> wrote:
> >
> > Thanks Frank.
> >
> > Just to clarify, exp(lnfree_e) is the number density of all electrons
> and positrons in ?
> >
> > On Wed, May 6, 2020 at 4:34 PM Francis Timmes <fxt44 at mac.com> wrote:
> > the straight sum of the electron and positron number densities, not per
> nucleon.
> >
> > fxt
> >
> >
> >
> > > On May 6, 2020, at 1:24 PM, Josiah Schwab via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
> > >
> > > Final question: does lnfree_e include positrons too?
> > >
> > > My memory was that when on HELM this is the combined number of e^- &
> e^+ per nucleon, but you should probably check that before relying on it.
> > >
> > > Josiah
> > > _______________________________________________
> > > mesa-users at lists.mesastar.org
> > > https://lists.mesastar.org/mailman/listinfo/mesa-users
> > >
> >
>
>
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