[Mesa-users] Regarding some clarifications

[Nathali Perera]

Hello everyone,
I'm a beginner to MESA and I'm working with this software for my final year research project. I'm currently modeling detached binary star systems which have almost similar masses like 1.875 and 1.856 solar mass. Since the binary star system is detached and not assumed to be mass transferring, these two stars were modeled as single evolutionary stars. Then I tried to change their mass (starting from 1.75 to 1.9 with a step size of 0.05), chemical composition (changes 0.01, 0.014, 0.018), mixing length (change as 1.8 and 0.2), and overshooting (0.005, 0.01,0.015)to see the effect for their evolutionary tracks. My question is, if there is more than one evolutionary track that intersects the star's error box, how do we know the best suitable track for that star?

Secondly, I would like to clarify some other questions regarding the code which I used. How can we select when to use 'kap_file_prefix' or 'use_type2_opaities'? Should we use 'kap_file_prefix' for stars that are rich in hydrogen and 'use_type2_opacities' for stars that have heavy metals? If I use both of these two conditions at the same time will MESA select one condition among them?

And if anyone sees any mistake in my code, please let me know. I would like to learn and correct my mistakes.

And I'm using mesa release r22.11.1.I have attached a figure that I obtained from my work and in that figure, I have marked the binary star system with error bars and several evolutionary tracks.

Thank You
Nathali Perera
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&star_job
  ! see star/defaults/star_job.defaults

  ! begin with a pre-main sequence model
    relax_Y = .true.
    change_Y = .true.
    relax_initial_Y = .true
    change_initial_Y = .true
    new_Y = 0.2485
    
    relax_Z = .true.
    change_Z = .true.
    relax_initial_Z = .true.
    change_initial_Z = .true.
    new_Z = 0.014
    
  ! save a model at the end of the run
    save_model_when_terminate = .true.
    

  ! display on-screen plots
    pgstar_flag = .true.
    pause_before_terminate = .true.
    
    initial_zfracs = 6

/ ! end of star_job namelist

&kap
   
    kap_file_prefix = 'a09'
    kap_lowT_prefix = 'lowT_fa05_a09p'
    use_Type2_opacities = .true.
    Zbase = 0.014
    
/

&eos
  ! eos options
  ! see eos/defaults/eos.defaults

/ ! end of eos namelist

    
&net
    
    change_net = .true.
    change_initial_net = .true.
    new_net_name = 'pp_and_cno_extras.net'

/




&controls

  ! starting specifications
    initial_mass = 1.8 ! in Msun units
    
    
  ! see star/defaults/controls.defaults
    terminal_interval = 10
    photo_interval = 50
    photo_directory = 'photos'
    history_interval = 1
    star_history_name= 'z0.01_m1.8_fov0.005_ml2.data'
    star_history_header_name = 'none'
    write_profiles_flag = .true.
    profile_interval = 1

    
  ! mesh
    mesh_delta_coeff = 1

    
  ! mixing length
    mixing_length_alpha = 2
    MLT_option = 'Cox'
    
  ! using the Ledoux criterion 
    use_Ledoux_criterion  =.true.
    alpha_semiconvection = 0.01
    
  ! Defining a minimum diffusive mixing
    set_min_D_mix = .true.
    min_D_mix = 1.0
    
  !overshooting
  
   overshoot_scheme = 'exponential' ! ``exponential``, ``step``, ``other``
   overshoot_zone_type= 'burn_H' !  ``burn_H``, ``burn_He``, ``burn_Z``, ``nonburn``, ``any``
   overshoot_zone_loc= 'core' ! ``core``, ``shell``, ``any``
   overshoot_bdy_loc= 'top' ! ``bottom``, ``top``, ``any`
   
   overshoot_f = 0.005 
   overshoot_f0 = 0.001
   
   overshoot_D_min = 5d-2
    

  ! wind
   
  ! atmosphere

  ! rotation

  ! element diffusion
  
  ! when to stop
    max_model_number = 300
  
    
  ! asteroseismology
    write_pulse_data_with_profile = .true.
    add_atmosphere_to_pulse_data = .true.
    pulse_data_format = 'FGONG'

  ! output
  
    

/ ! end of controls namelist
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