[Mesa-users] Questions about (step)Overshooting

[RICHARD H D TOWNSEND]

Hi Matheus --

Your tracks in the HR diagram look rather jagged, and it may be that your calculations aren't properly converged. Have you tried running with shorter timesteps and/or a finer spatial grid?

cheers,

Rich

> On Sep 27, 2018, at 6:39 PM, Matheus Bernini via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> 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 - Saúde
> Rio de Janeiro - RJ - CEP 20080-090
> Brasil
> ___________________________________________________________
> 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.png>
> <inlist_massive_defaults><inlist_32M0><run_star_extras.f>_______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>