[Mesa-users] Is it possible to fake a he wd with an envelope?

Chen DDan ChenDDan at outlook.com
Wed Mar 11 07:42:53 EDT 2020

Hi Josiah,

I try to evolve a binary from 1Msun ZAMS with the roche lobe wind as you suggested, but i do not evolve into the surface H flash and the final WD and H layer. So i write to ask when you turn on the roche lobe wind, whether i need to let the ZAMS evlove to certain stage and let the wind on?  I let the wind be there all the way.

This is my binary inlist:

   inlist_names(1) = 'inlist1'
   inlist_names(2) = 'inlist2'

   evolve_both_stars = .false.

/ ! end of binary_job namelist


   m1 = 1d0  ! donor mass in Msun
   m2 = 1.29d0 ! companion mass in Msun

   append_to_star_history = .true.
/ ! end of binary_controls namelist

And this is the star inlist:

      show_log_description_at_start = .false.
      save_model_when_terminate = .true.
      save_model_filename = '1zamsfinal.mod'

      pgstar_flag = .true.
      pause_before_terminate = .true.

    set_initial_model_number = .true.
    initial_model_number = 0
/ ! end of star_job namelist

      ! check for retries and backups as part of test_suite
      ! you can/should delete this for use outside of test_suite
         max_number_backups = -1
         max_number_retries = -1

      extra_terminal_output_file = 'log1'
      log_directory = 'LOGS1'

      profile_interval = 50
      history_interval = 10
      terminal_interval = 10
      write_header_frequency = 10

  ! wind options
      rlo_scaling_factor = 1
      rlo_wind_roche_lobe_radius = 10d0
      rlo_wind_base_mdot = 1d-5
      rlo_wind_scale_height = 1d0

/ ! end of controls namelist


      read_extra_pgstar_inlist1 = .true.
      extra_pgstar_inlist1_name = 'inlist_pgstar'
/ ! end of pgstar namelist

So you can see that i only use the basic parameters and i do not add any code into src/run_binary_extras.f and run_star_extras.f.  Is there any difference that cause the disagreement?

Best Wishes

Hi Chen,

I didn't quite understand your email.  But in addition to what Evan said, I would add that if you want to make a somewhat more realistic He WD, you are probably better off doing something other that using make_he_wd.  That test case takes a very "stellar engineering" approach to effectively make a very low mass (0.15Msun) degenerate He ball and has no H envelope.

You could do a real NS + MS evolution (e.g., https://ui.adsabs.harvard.edu/abs/2016A%26A...595A..35I/abstract).  But as an easier alternative, you can mock up the binary evolution.  For example, take a 1Msun star at ZAMS and put it in a fixed-size "Roche lobe".   I tried just tried that with the wind options

      rlo_scaling_factor = 1
      rlo_wind_roche_lobe_radius = 10d0
      rlo_wind_base_mdot = 1d-5
      rlo_wind_scale_height = 1d0

and after about 5000 steps (and a surface H flash or two) I had a 0.25-ish Msun He WD with a 1e-3-ish Msun H layer.  You can fiddle with the mass by either further relaxing that model, changing the Roche radius, etc.

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