[mesa-users] MESA opacities

[Manos Chatzopoulos]

Aaron,

This is exactly the information I needed, thanks a bunch!

Manos

On 6/9/15 3:50 PM, Aaron Dotter wrote:
> Hi Manos,
>
>     1) Does "X" in the file names (like x00, x10...etc) represent the
>     Hydrogen abundance? Is that a mass fraction representative of the
>     shell or the overall abundance?
>
>
> Yes, X is hydrogen mass fraction.  Opacity is a local quantity, called 
> microphysics in the MESA instrument papers.  In MESA, opacity is 
> evaluated in every shell using the local values of X and Z.  In a 
> stellar model in which any degree of nuclear burning has occurred 
> you'll want to interpolate to the appropriate composition (as much as 
> possible).
>
>     2) I look at three variants of solar metallicity (z0.02, z2m2)
>     data with X = 0.0000 attached (OP_gs98_z2m2_x00.data,
>     gs98_z2m2_x00.data and lowT_Freedman11_z0.02). I notice that there
>     is some overlap both in terms of logR = logRho - 3*logT + 18
>     and in terms of logT itself between the Freedman and the gs98
>     tables. For the overlapped values I see significant differences
>     in the opacity. For example, for logR = -6 and logT = 4.25 the
>     lowT_Freedman table yields a value of -4.229 and the
>     gs98 table a value of -0.870 (-0.863 for the OP_gs98 table). What
>     values are correct in the over-lapping regime?
>
>
> You can find references to the relevant papers in the MESA instrument 
> papers.  Maybe Freedman et al only comes into Paper II.  The "fa05" 
> tables are from Ferguson et al and are more appropriate for stellar 
> conditions.  The Freedman et al tables are designed for the planetary 
> regime.
>
> I hope that helps!
>
> Aaron
>
>

-- 
Dr. Emmanouil Chatzopoulos
Enrico Fermi Postdoctoral Fellow
Department of Astronomy & Astrophysics
FLASH Center for Computational Science
University of Chicago
https://www.linkedin.com/pub/manos-chatzopoulos/a1/688/a03
https://astro.uchicago.edu/people/manos-chatzopoulos.php

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