[Mesa-users] Opacity tables for new and different mixtures.

[Aaron Dotter]

Hi Marc,

Good points all around.

There is a set of low- and high-T opacities based on GS98 for [a/Fe]=-0.2
to +0.8 in steps of 0.2 dex that already ship with MESA.  These are based
on OPAL + Ferguson et al. opacity tables and are originally from my
Thesis.  Beyond that, I believe that on Jason Ferguson's webpage there is a
set of alpha-enhanced low-T opacity tables for the Asplund 2009 mixture.
Not aware of anything like that for the most recent / higher-Z solar
abundances.

I am also aware of a couple of python scripts that automate, to some
extent, the process of generating opacity tables using online forms.

Cheers,
Aaron

On Thu, Sep 15, 2022 at 11:27 AM Marc Pinsonneault via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hello all.  I’d like to talk about opacity tables.
>
> Large stellar surveys have really transformed our ideas about how
> abundance patterns change in stars;
>
> there has also been interesting new work on the base solar mixture.
>
>
>
> In the former case, at minimum we now know that abundances in stars are
> (at least) a 2-dimensional family, usually given as [Fe/H] and {alpha/Fe].
>
> For example, see Weinberg et al. 2022,
>
>
>
> https://ui.adsabs.harvard.edu/abs/2022ApJS..260...32W/abstract
>
>
>
> The default mesa cases assume solar [alpha/Fe], and include two “older”
> solar mixtures – Asplund 2009 and Grevesse+Sauval 1998.
>
> There are two recently published solar mixtures.  The “low metallicity”
> solution, which builds on Asplund 2021, is Amarsi et al. 2021
>
>
>
> https://ui.adsabs.harvard.edu/abs/2021A%26A...656A.113A/abstract
>
>
>
> The “high metallicity” solution, also 3D NLTE, is Magg et al. 2022,
>
>
>
> https://www.aanda.org/articles/aa/pdf/2022/05/aa42971-21.pdf
>
>
>
> Note that the latter is fully consistent with helioseismology, and in my
> view it should be the default recommended base mixture.
>
>
> For full self-consistency, one should use high temperature opacities, low
> temperature (molecular) opacities, and model atmospheres with the
> appropriate mixtures.
>
> There are public websites that can be used to generate custom opacities –
> for example, here is the web interface for the opacity project.
>
> https://opserver.obspm.fr/rmos.shtml
>
> and here is the one for the Marigo low temperature opacities
>
> http://stev.oapd.inaf.it/cgi-bin/aesopus
>
> However, in practice these do not immediately make tables in formats
> suitable for stellar interiors calculations. The standard interiors opacity
> tables for MESA (and other evolution codes) use 126 different x / y/ z
> combinations, for example, and online resources are one at a time. This
> makes quick calculation of new tables challenging.
>
> Given this, I’m reaching out to the atomic physicists to see if we can get
> a more general set of opacity tables for community usage, and this would
> include updating the MESA documentation to indicate a more general set of
> options / resources. One place where I am stymied, however, and the reason
> for this email, is whether this is “already done” in part – e.g. are there
> already general tables available for, say, alpha to iron enhancement that
> we could point to? Or is this something that we need to make available as a
> community resource?
>
>
>
> Cheers
>
>
>
> Marc Pinsonneault
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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