[mesa-users] Scratchy surface metallicity profile with diffusion in 1.3Msun star

[Warrick Ball]

Oops!  Forgot to attach the initial model.

W

On Tue, 25 Nov 2014, Warrick Ball wrote:

> Hi,
>
> I've just been debugging some asteroseismic runs, and I've found that I'm 
> getting some scratchy surface metallicities in hotter stars.  Attached is a 
> plot of [Fe/H] vs age for a 1.3 Msun star (inlist attached), from revision 
> 7184.  As you can see, it gets quite scratchy around 2 Gyr.
>
> I've taken a look at the abundance and diffusion velocity profiles, and it 
> appears that the outermost meshpoint swaps between higher and lower values, 
> as seen in the history plot, even though the underlying abundance (i.e. the 
> abundance just below the surface) is more stable.
>
> I know diffusion is a bit iffy in hotter stars, like this one, which peaks 
> around 6400K.  But I wouldn't mind seeing the metals drained from the surface 
> completely as much as I'm perturbed by this kind of behaviour. This star has 
> a thin convective shell by mass (~0.002 Msun at core H exhaustion), and the 
> diffusion velocities reach a few times 10^-7 cm/s in the outermost layers by 
> the end.
>
> I'm gradually going through all the parameters in the diffusion controls, but 
> any pro tips would be appreciated.  I'm mainly hoping to smooth out the 
> outermost meshpoints so that the fluctuations are suppressed and the surface 
> abundance matches the underlying layers.
>
> Cheers,
> Warrick
>
>
> ------------
> Warrick Ball
> Postdoc, Institut für Astrophysik Göttingen
> wball at astro.physik.uni-goettingen.de
> +49 (0) 551 39 5069


------------
Warrick Ball
Postdoc, Institut für Astrophysik Göttingen
wball at astro.physik.uni-goettingen.de
+49 (0) 551 39 5069
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