[Mesa-users] Questions about (step)Overshooting

[Matheus Bernini]

Hello,

I'm an undergraduate student and I'm studying evolution of massive stars
using MESA.

I was "playing around" with step overshooting initial values (
overshoot_f0_...) for hydrogen helium and nonburn core/shell and I noticed
that slightly changes on f0 (but always keeping f - f0 = 0.1) caused great
changes on the post-MS phases [figure].


    overshoot_f0_above_burn_h_core = 0.035
    step_overshoot_f_above_burn_h_core = 0.135

vs.

    overshoot_f0_above_burn_h_core = 0.030
    step_overshoot_f_above_burn_h_core = 0.130

*For completeness, there was also an exponential overshooting on all of the
models of 0.001 on helium and hydrogen core/shell

If I understood correctly, the f0 is the starting point for the overshoot
inward the region (core or shell) because the mixing coefficient is 0 on
the edge of the region, not allowing the computations to happen. So, if f0
is just a "trick" to allow the computation of the overshoot, why changing
it a little causes important changes on the evolution?

Thanks :)

-----------------------------------------------------------------
*Matheus Bernini Peron*


* Undergraduate student Observatório do Valongo,Universidade Federal do Rio
de Janeiro*



*Ladeira do Pedro Antônio, 43 - SaúdeRio de Janeiro - RJ - CEP
20080-090Brasil*
___________________________________________________________
Evolution 32Msun, no rotation, Z_init = 0.014, Y_init = 0.266
red: 0.135 - 0.035
blue: 0.130 - 0.030
gray: GENEC (Ekstrom+2012)
[image: image.png]
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