[Mesa-users] MESA convective boundary not matching up with element abundance profile

[Matteo Cantiello]

What Warrick said.
You're seeing the maximum extension of the first dredge-up, which has
homogenized the composition down to r/R~0.05.

-M

--
Matteo Cantiello - https://www.stellarphysics.org/
Associate Research Scientist,  CCA, Flatiron Institute
Visiting Associate Researcher, Princeton University


On Wed, Sep 8, 2021 at 9:15 AM Warrick Ball via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Hi Christopher,
>
> You mention that these models are before the RGB bump, so the convection
> zone has already reached its greatest depth and started become *smaller* in
> terms of mass.  So my guess is that you're seeing the region that was mixed
> by convection that has since "receded".
>
> There's no reason a radiative region can't have uniform composition.  If,
> however, a convective region has a non-uniform composition, I'd be
> surprised!
>
> Cheers,
> Warrick
>
> ___________
>
> Warrick Ball
> Postdoc, School of Physics and Astronomy
> University of Birmingham, Edgbaston, Birmingham B15 2TT
> W.H.Ball at bham.ac.uk
> +44 (0)121 414 4552
>
> On Wed, 8 Sep 2021, mesa-users at lists.mesastar.org wrote:
>
> > Hi All,
> >
> > I've been looking at elemental abundance and temperature gradient
> profiles for red giant stellar models before the red giant luminosity bump
> and I've noticed that for a period before the luminosity bump, the point
> where the element abundance profile
> > goes from being steady (in the convection zone) to being
> variant (outside the convection zone) doesn't match up with the position of
> the convection zone according to the temperature gradient (nabla -
> nabla_adiabatic) profile.
> >
> > Here is a figure showing what I'm talking about with the Hydrogen
> abundance plotted in the dot-dashed line and the temperature gradient
> profile (nabla - nabla_ad) plotted in a dotted line. The cz_bot_radius line
> in the history.data output seems to
> > line up with the temperature gradient profile so I wanted to know if
> anyone could point me to the code which shifts the elemental abundance
> profile turning point with respect to the convection zone position.
> >
> > I would expect that the fully mixed portion of the elemental abundance
> profile would only extend as deep as the convection zone bottom. I made
> sure that all overshoot options and element diffusion were off. This plot
> was made with MESA version r12778
> > but the same thing happens in r15140.
> >
> > Screen Shot 2021-09-06 at 1.12.29 PM.png
> > Thanks!
> > Christopher Lindsay.
> >
> >
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>
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