[mesa-users] ionization fraction or kap table ?

[Jing Luan]

Thank you very much, Rich. It is very useful :-) :-)

Sincerely,
Jing

On Mon, Jun 26, 2017 at 9:27 PM, RICHARD H D TOWNSEND <
townsend at astro.wisc.edu> wrote:

> Hi Jing —
>
> > On Jun 24, 2017, at 9:55 AM, Jing Luan <jingluan.xw at gmail.com> wrote:
> >
> > Dear mesa users,
> >
> > 1, Are there parameters in mesa that tells the ionization fraction of
> (HI to HII) and of (HeI to HeII) please? I search around
> mesa/star/public/star_data.inc, but did not find any. But maybe I miss
> something there.
> >
>
> I would suspect not. Nowadays, with tabulated EOS’s, it is unusual to
> actually solve the Saha equation during a stellar evolution calculation.
> However, MESA *can* tell you the free electron number density, and so you
> could calculate the ionization fractions yourself, using the Saha equation
> (for this, I suggest you ignore excited states of the H/He).
>
> > 2, For calculating kappa mechanism due to H or He opacity bumps for
> driving stellar oscillation, which kappa table and eos table should be
> adopted please? The default in mesa-r8118 are
> >
> > kappa_file_prefix = 'gn93'
> >
> > eos_file_prefix = 'mesa'
> > eosDT_Z1_suffix = '_CO_1'
> > eosPT_Z1_suffix = ‘_
> > CO_1'
> >
>
> For the blue edges of the classical (Cepheid) instability strip, plotted
> in Fig. 14 of Paxton et al (2015), I used:
>
> initial_zfracs = 6 ! Asplund et al. (2009)
> kappa_file_prefix = 'a09' ! Asplund et al. (2009)
>
> …in the &star_job namelist, and
>
> initial_Y = 0.2703 ! Asplund et al. (2009) / proto-solar
> initial_Z = 0.0142 ! Asplund et al. (2009) / proto-solar
>
> …in the &controls namelist. I expect the metallicity is less important to
> driving classical Cepheid pulsations than the relative H/He abundances.
>
> cheers,
>
> Rich
>
> > Many thanks 😊😊😊😊
> >
> > Sincerely,
> > Jing
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