[Mesa-users] Doubts from a master's student about MESA

[francandon]

  Dear MESA members,

  I’m a master student at the university of Zaragoza, currently finishing 
my master thesis. I have just started using MESA to run stellar 
simulations, and I read the documentation and tutorials.

  For my project, I need to calculate the abundance of some isotopes in 
the Sun. For example, I want to know the abundance of Fe57. What I did 
was the following: I used te documentation example 
(https://docs.mesastar.org/en/latest/using_mesa/running.html) and 
changed some parameters. In addition, I used the nuclear network 
“http://aprox21.net” and I added Fe57 to consider all the possible 
reactions that can produce it.
  However, my problem arises at the first step of the simulation. The 
abundance rate of Fe57 is 10 times larger than I expected, because the 
presence of the Fe57 isotope in nature is just 2% of that of Fe. I even 
tried changing the set_uniform_initial_composition with the 
initial_zfracs = 3, corresponding to GS98. I obtain the following for 
the first step:

  total_mass_fe56                                       total_mass_fe57
  1.4142415754937801E-003                 3.0840908076103230E-004
  which means that Fe57 is the 21.43% if we assume Fe56 to be the 98%.

  I would appreciate it if someone could clarify this for me. You can 
find attached to this email the inlist and the nuclear network files 
that I’m using.
  Thank you for your attention.

  Best regards,
  Fran