[Mesa-users] Full FeII line velocity evolution is not saved in STELLA

[Jared Goldberg]

Hi Amar,

The Fe II velocities are somewhat different than other
reported near-photosphere processes. They are calculated in post-processing
in the stella/res/stella_extras.f90 script, following the sobolev optical
depth prescription described in S6.5 of MESA IV
<https://ui.adsabs.harvard.edu/abs/2018ApJS..234...34P/abstract> (Paxton et
al 2018, see eq. 53).

[image: image.png]
These are only reported when the calculation finds a location where tau_sob
= (.1, 1, 10 for low, mid, hi), which typically means the Fe II velocities
are only reported where this is outside the photosphere location. Looking
at your plot, I think this is likely what is happening.

Best,
~Jared

On Tue, May 27, 2025 at 1:37 AM Amar Aryan via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Dear MESA users,
>
> I am using mesa-r24.03.1 on MacOS Sequoia with M2 Chip.
>
> In recent versions of MESA, I find that the entire FeII velocities are not
> properly saved in the "*mesa.vel_feII*" when running STELLA; however, the
> photospheric velocities are properly saved in the "*mesa.swd.ph
> <http://mesa.swd.ph>*" file. Please see the attached figure from these
> two files.
>
> [image: velocity.png]
>
>
> Could someone please suggest any possible diagnosis to properly save the
> "FeII" line velocities in the "*mesa.vel_feII*" file? I would highly
> appreciate any suggestions.
>
>
> With best regards,
>
> Amar
>
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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