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

[Marc Pinsonneault]

Thanks much.  Is there a location for the tables (as we can also supply
some new ones), and a listing of the current recognized mixtures /
prefixes? If we already have alpha-enhanced for A09 and GS98, I will focus
on parallel ones for the new mixtures (but having those tables for
comparison will be quite useful).

cheers

Marc

On Thu, Sep 15, 2022 at 12:13 PM Aaron Dotter <aaron.dotter at gmail.com>
wrote:

> 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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