[mesa-users] Unexpected metallicity profiles, possibly caused by diffusion

Francis Timmes fxt44 at mac.com
Wed Oct 8 08:02:59 EDT 2014

thanks anna.


On Oct 3, 2014, at 8:52 AM, Anna V. Oreshina <avo at sai.msu.ru> wrote:

> Hi, Warrick and all,
> The profiles of heavy elements under the convective zone were studied in 
> the paper by
> A. B. Gorshkov, V. A. Baturin
> Astronomy Reports
> September 2008, Volume 52, Issue 9, pp 760-771
> http://link.springer.com/article/10.1134%2FS1063772908090072
> A short version is also available in
> A. B. Gorshkov and V. A. Baturin
> "Diffusion segregation of heavy elements in the Sun"
> Journal of Physics: Conference Series 271 (2011) 012041
> doi:10.1088/1742-6596/271/1/012041
> http://iopscience.iop.org/1742-6596/271/1/012041/pdf/1742-6596_271_1_012041.pdf
> The local maximum of the heavy element profiles are caused by 
> thermodiffusion. It appears in any case of ion-charge profile (constant or 
> variable). See as example the Model-S as well.
> If your have questions, please do not hesitate and write to us.
> With best wishes,
> Anna Oreshina
> Scientific researcher
> Sternberg Astronomical Institute
> Moscow State University
> Russia
> ______________________________________________________________
> Message: 6
> Date: Wed, 1 Oct 2014 16:09:44 +0200 (CEST)
> From: Warrick Ball <wball at astro.physik.uni-goettingen.de>
> Subject: [mesa-users] Unexpected metallicity profiles,  possibly caused
>         by diffusion
> To: mesa-users at lists.sourceforge.net
> Message-ID:
> <alpine.LNX.2.00.1410011536360.19230 at astro84.astro.physik.uni-goettingen.de>
> Content-Type: text/plain; charset="iso-8859-15"
> Hi all,
> I've been looking more closely at the output of some models I've been
> fitting.  There was one case I looked at closely (for a different, but
> also interesting reason), and I found that the model has an unexpectedly
> bumpy the metallicity profile.  I've attached an appropriate inlist, and
> the results are taken from the final model of that run, at TAMS.  This is
> a somewhat metal rich star with M=1.17 Msun, Z=0.042, Y=0.3 and 
> alpha=1.91.
> I copied the diffusion parameters out of the solar calibration test case,
> but I think they're basically the same as the defaults anyway.
> Note that this is a revision 6022.  Obviously, a first thing to try
> (downloading now!) is to check out the most recent release...
> The plot shows metallicity Z as a function of logT for a series of models
> along the main sequence.  As you can see, around logT=6.5, there's a
> certain bumpiness to the profile.  I immediately suspected the diffusion
> was to blame, so I added in the diffusion velocities, plotted in the
> second file.  There, I've plotted the magnitude of the diffusion velocity
> for O16 as a function of logT.  The diffusion is also bumpy, but I a
> closer look seems to show that this is in the convection zone where it'd
> be totally overwhelmed.  The only structural feature that I think is of
> interest is the fact that this region is consistently just below the base
> of the outer convection zone, though I don't use overshooting or
> semiconvection.
> Anyway, any help on what's going on and what I'm doing wrong here would be
> greatly appreciated.  Or, advice on why this effect is real.
> Cheers,
> Warrick
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