[mesa-users] sdB

Jan-Torge Schindler jtschindler at email.arizona.edu
Mon May 22 14:12:10 EDT 2017


Dear Rahou,

I have simulated sdB stars with an older version of MESA.

I am not aware that MESA currently has capabilities to simulate the 
complicated two star evolution that produces sdB stars.
However my approach was 'mimicking' it by

1.) Start a single star evolution with the initial mass of your sdB 
progenitor star.
2.) Run the evolution and then write out a model at the point in time 
where you would like the mass transfer to happen. (Somewhat close to but 
before the He-flash.
3.) Start the saved model but specify a M_new and let MESA take mass off 
from the outside of the star. But beware, you must be careful not too 
take off too much mass. Physically, the mass transfer will quench the 
H-shell burning and then the mass transfer will stop as well. So never 
let MESA take off mass below the H-shell burning zone.

Unfortunately, I am currently travelling and I don't have much time to 
elaborate. I did find the old inlists I used with version 7184. Be aware 
much has changed since then, but they should give you a head start.

One more advice, turn off wind for the sdB evolution. This let's you 
control the total mass better in the beginning and you can turn them on 
later for a more 'realistic' simulation ( not sure how realistic the 
wind parameters are constraint for sdBs).

At last have a look at our paper from 2015, where I describe how we 
modelled sdB stars.

Cheers,
Jan-Torge

On 05/21/2017 08:56 PM, kaoutar lahlou wrote:
> Hi mesa users:
>
> I am traying to figure out the EHB or sdB. I read in an article that 
> we need to make simulation between two stars: M _ initial and M _new.
>
> On mesa -binary, what i should make for initial condition ie for M1 
> and M2.
>
> Who will be the donor and accretor ?
>
> Thanks
>
> Rahou
>
>
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! inlist_pre_sdB 

! contains the parameters controlling this job

! This inlist contains the minimum of information to create a pre_sdB model



&star_job  ! this is the star_job namelist
      
      mesa_dir = '/home/jtschindler/MESA/mesa-r7184' ! serenity
      
      create_pre_main_sequence_model = .true.

      change_net = .true. ! switch nuclear reaction network
      new_net_name = 'pp_cno_extras_o18_ne22.net' ! including all possible processes for hydrogen and helium burning

      eos_file_prefix = 'mesa' !equation of state combining HELM,OPAL and SCVH
      kappa_file_prefix = 'gs98' ! opacity mix, Grevesse & Sauval 1998
      
      
      save_model_number = 16700
      save_model_filename = '1.0_progenitor_16700.data'
     
      pgstar_flag = .true. !show the pg plots

/ !end of star_job

&controls

      max_model_number = 27000
   
  ! starting specifications
      initial_mass = 1.0d0 ! in Msun units
      
      !using defaults for initial abundances z=0.02,y=0.30,x=68
      initial_z = 0.02  ! 
   
   ! output to files and terminal
      photostep = 100
      profile_interval = 250
      history_interval = 1
      terminal_interval = 10
      write_header_frequency = 10
      star_history_name = 'progenitor_history.data'

  ! mass gain or loss
      RGB_wind_scheme = 'Reimers'
      AGB_wind_scheme = 'Blocker'
      RGB_to_AGB_wind_switch = 1d-4 ! this is the default value
      Reimers_wind_eta = 0.5d0  
      Blocker_wind_eta = 0.5d0  
      
  !opacity controls
     use_Type2_opacities = .true.
     Zbase = 0.02
     kap_Type2_full_off_X = 0.71d0
     kap_Type2_full_on_X = 0.70d0
      
  ! mesh
      max_allowed_nz = 64000
      mesh_delta_coeff = 1   
      
  !MLT
      mixing_length_alpha = 2
  
  !overshooting
      min_overshoot_q = 1d-3
      D_mix_ov_limit = 1d2
      
      overshoot_f_above_nonburn = 0.0
      overshoot_f_below_nonburn = 0.0
      overshoot_f_above_burn_h = 0.0
      overshoot_f_below_burn_h = 0.0
      overshoot_f_above_burn_he = 0.0
      overshoot_f_below_burn_he = 0.0
      overshoot_f_above_burn_z = 0.0
      overshoot_f_below_burn_z = 0.0
      
  !Ledoux criterion & semiconvection, thermohaline and semiconvection only applies if ledoux is true
      use_Ledoux_criterion = .false.
      alpha_semiconvection = 0
      thermohaline_option = 'Kippenhahn'      

  !element diffusion 
      show_diffusion_info = .true.
      do_element_diffusion = .true.
      diffusion_calculates_ionization = .true.
  
  

 
 
/

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! inlist_pre_sdB 

! contains the parameters controlling this job

! This inlist contains the minimum of information to create a pre_sdB model



&star_job  ! this is the star_job namelist
      
      mesa_dir = '/home/jtschindler/MESA/mesa-r7184' ! serenity
      
      create_pre_main_sequence_model = .false.

      change_net = .true. ! switch nuclear reaction network
      new_net_name = 'pp_cno_extras_o18_ne22.net' ! including all possible processes for hydrogen and helium burning

      eos_file_prefix = 'mesa' !equation of state combining HELM,OPAL and SCVH
      kappa_file_prefix = 'gs98' ! opacity mix, Grevesse & Sauval 1998
      
       
      load_saved_model=.true.
      saved_model_name='1.0_Msun_16700_progenitor.data'
      
      relax_mass=.true.
      new_mass=0.48
      
      !save_model_number = 
      !save_model_filename = ''
     
      pgstar_flag = .true. !show the pg plots

/ !end of star_job

&controls

      max_model_number = 35000
   
  ! starting specifications
      initial_mass = 1.0d0 ! in Msun units
      
      !using defaults for initial abundances z=0.02,y=0.30,x=68
      initial_z = 0.02  ! solar metallicity
   
   ! output to files and terminal
      photostep = 100
      profile_interval = 100
      history_interval = 1
      terminal_interval = 10
      write_header_frequency = 10
      star_history_name = 'sdB_history.data'

  ! mass gain or loss
      RGB_wind_scheme = 'Reimers'
      AGB_wind_scheme = 'Blocker'
      RGB_to_AGB_wind_switch = 1d-4 ! this is the default value
      Reimers_wind_eta = 0.5d0  
      Blocker_wind_eta = 0.5d0  
      
  ! mesh
      max_allowed_nz = 64000
      mesh_delta_coeff = 1   
  
  !opacity controlling
      use_Type2_opacities = .true.
      Zbase = 0.02
      kap_Type2_full_off_X = 0.71d0
      kap_Type2_full_on_X = 0.70d0
  
  !MLT
      mixing_length_alpha = 2
  
  !overshooting
      min_overshoot_q = 1d-3
      D_mix_ov_limit = 1d2
      
      overshoot_f_above_nonburn = 0.0
      overshoot_f_below_nonburn = 0.0
      overshoot_f_above_burn_h = 0.0
      overshoot_f_below_burn_h = 0.0
      overshoot_f_above_burn_he = 0.0
      overshoot_f_below_burn_he = 0.0
      overshoot_f_above_burn_z = 0.0
      overshoot_f_below_burn_z = 0.0
      
  !Ledoux criterion & semiconvection, thermohaline and semiconvection only applies if ledoux is true
      use_Ledoux_criterion = .false.
      alpha_semiconvection = 0
      thermohaline_option = 'Kippenhahn'      

  !element diffusion 
      show_diffusion_info = .true.
      do_element_diffusion = .true.
      diffusion_calculates_ionization = .true.
  

 
 
/

 
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