mesa-users] a question about MESA

Aaron Dotter aaron.dotter at
Thu Sep 16 09:33:13 EDT 2010

Dear Masanobu,

Thanks for your question.

Today I am writing to ask about adequate parameters of Overshooting like "
> overshoot_f_..." and "mass_for_overshoot_...".  I'm using version 2258 of
> MESA, but I don't know and couldn't find the parameters I should use.  Would
> you tell me generally adequate parameters for Overshooting?

My first suggestion would be that you read the MESA "instrument paper" that
recently appeared on astro-ph!

It contains a description of the overshoot mixing in MESA/star and plenty of
references on how the method is implemented and what values of the
overshoot_f_* are recommended for different boundaries (and evolutionary

> Moreover, I want to use same treatment for Overshooting with Girardi.
> If you know the parameters to do so, would you tell me also those?

There isn't a simple answer to this question.  MESA/star treats overshoot
mixing in a very different manner from the Padova group in a couple of ways:
(1) MESA/star treats convective mixing as a time-dependent, diffusive
process and (2) the overshoot diffusion coefficient is modeled as an
exponential decay of the diffusion coefficient at the convective boundary.
 Many (but not all) other codes treat convective regions as instantaneously
mixed and overshoot as an "all or nothing" approach, where the extent of the
overshoot region is fully mixed with the adjoining convective region.

Best wishes,
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