[mesa-users] central hydrogen sudden increase

andres suarez asuarezm at ucsc.edu
Tue May 1 03:50:15 EDT 2012

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



      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

     ! 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

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