[mesa-users] central hydrogen sudden increase

Bill Paxton paxton at kitp.ucsb.edu
Tue May 1 11:30:50 EDT 2012

Check to see what the central convection zone is doing.
I expect that the jump in center H is because convection
has reached outward to a fresh supply of H and brought
it down to the center.  So now your question becomes
why do convection zones grow and shrink.  Is it a bug?
Is it physical?  Have fun.


On May 1, 2012, at 12:50 AM, andres suarez wrote:

> Hi all,
> I noticed that the fraction of central hydrogen during the main sequence in very standard runs of massive stars sometimes shows a couple sudden jumps, which then considerably lengthens the duration of the star's central hydrogen, as compared to a stellar model with just one more or one less solar mass.
> I repeated the run, saving a model before the sudden jump and restarting from it, and still keep getting the same results.
> As an example, I attach a plot comparing the evolution of a 77 and 78 solar mass models where you can see a jump in the central hydrogen fraction around 1.6 Myr for both models and one around 3Myr that only appears in the 77 solar mass model. I notice that the jump that only shows in the 77 solar mass model makes its main sequence last significantly longer. I could not find the reason behind any of these two jumps.
> My question is if you guys would have some insight as to what is causing this jump.
> I also attach the inlist file for the 77 solar mass model (which shows two jumps).
> Regards,
> a.
> &star_job
>       mesa_data_dir = '/home/andres/Arbeit/mesa/data'
>       create_pre_main_sequence_model = .false.
>       change_net = .true. ! switch nuclear reaction network
>       new_net_name = 'o18_and_ne22.net'
> / !end of star_job
> &controls
>      ! starting specifications
>          initial_mass = 77 ! in Msun units
>          initial_Z = 0.02
>          initial_Y = -1
>      ! mass gain or loss
>          RGB_wind_scheme = 'Reimers'
>          Reimers_wind_eta = 0.4
>      ! when to stop
>          xa_central_lower_limit_species(1) = 'h1'
>          xa_central_lower_limit(1) = 1d-10
>             ! stop when the center abundance by mass of h1 drops below this limit.
> /
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