[Mesa-users] irradiated AGB mass loss

[Sergei Nayakshin]

Dear all,

I’m investigating how mass loss from AGB stars might respond to a very strong irradiation, and I came across some very strange results.

I would assume that resolving the atmosphere better (to smaller tau) is a good idea in this problem, so I set 

relax_to_this_tau_factor = 1d-3

However, with this setting I get the mass loss rate *decreasing* with increasing irradiation flux! That surely should not be the case, and indeed with the default atmosphere depth (relax_to_this_tau_factor = 1), I get an increasing Mdot as the irradiation flux increases. 

I would really appreciate any ideas on why this is happening. Is there a contradiction in using the ‘Blocker’ mass loss prescription and resolving atmosphere to smaller depths?

The detail of my inlist are given below.

Thanks in advance,
Sergei.

——————————————————-

I am using the ‘agb’ problem from the test_suite of mesa-r10108, and the most relevant lines that I added to the inlist_agb are

&star_job

relax_to_this_tau_factor = 1d-3
dlogtau_factor = 0.1
relax_initial_tau_factor = .true.
relax_tau_factor = .true.

&controls

column_depth_for_irradiation = 1e0
irradiation_flux = 1.d10



—————— Full inlist just in case it’s needed: —————————————

! inlist_agb


&star_job
      show_log_description_at_start = .false.
      !list_net_reactions = .true.

      load_saved_model = .true.
      saved_model_name = '2m_z1m2_agb.mod'

      save_model_when_terminate = .true.
      save_model_filename = 'final.mod'
      
      write_profile_when_terminate = .true.
      filename_for_profile_when_terminate = 'final_profile.data'

      change_initial_net = .true.      
      new_net_name = 'o18_and_ne22.net'  ! 10 species
      !new_net_name = 'agb.net' ! 18 species
      !new_net_name = 'sagb_NeNa.net' ! 24 species
      !new_net_name = 'sagb_NeNa_MgAl.net' ! 29 species

      relax_to_this_tau_factor = 1d-3
      dlogtau_factor = 0.1
      relax_initial_tau_factor = .true.
      relax_tau_factor = .true.

      set_initial_dt = .true.
      years_for_initial_dt = 1d-1

      pgstar_flag = .true.


/ ! end of star_job namelist

&controls


      !okay_to_reduce_gradT_excess = .false.
      !mixing_length_alpha= 1.89
      varcontrol_target = 1.d-3


      ! check for retries and backups as part of test_suite
      ! you can/should delete this for use outside of test_suite
         max_number_backups = 10
         max_number_retries = 80

      max_model_number = 9000

      initial_mass = 2.0
      initial_z = 0.01d0

      ! surface heating
      column_depth_for_irradiation = 1.e0
      irradiation_flux = 1.d11     ! day side flux!!! Bill puts in 1/4 by hand

      star_mass_min_limit = 1.4

      !xa_surface_upper_limit_species(1) = 'c12'
      !xa_surface_upper_limit(1) = 0.0013

      cool_wind_RGB_scheme = 'Reimers'
      Reimers_scaling_factor = 0.5
      cool_wind_AGB_scheme = 'Blocker'
      Blocker_scaling_factor = 0.5
      RGB_to_AGB_wind_switch = 1d-4

   !  only use the cool_wind_scheme
      !cool_wind_full_on_T = 1d8    !K
      !cool_wind_full_off_T = 1.1d8 !K
      hot_wind_scheme = ''

      photo_interval = 50
      profile_interval = 50
      history_interval = 1
      terminal_interval = 10
      write_header_frequency = 10
         
 
      mesh_dlog_pp_dlogP_extra = 0.25
      mesh_dlog_cno_dlogP_extra = 0.25
      
      mesh_dlog_3alf_dlogP_extra = 0.225
      mesh_dlog_burn_c_dlogP_extra = 0.225
      mesh_dlog_burn_n_dlogP_extra = 0.225
      mesh_dlog_burn_o_dlogP_extra = 0.225
      
      
      mesh_logX_species(1) = 'h1'
      mesh_logX_min_for_extra(1) = -6
      mesh_dlogX_dlogP_extra(1) = 0.25
      
      mesh_logX_species(1) = 'he4'
      mesh_logX_min_for_extra(1) = -6
      mesh_dlogX_dlogP_extra(1) = 0.25

      xtra_coef_os_above_nonburn = 0.5
      xtra_coef_os_below_nonburn = 0.25
   
      xtra_coef_os_above_burn_h = 0.25
      xtra_coef_os_below_burn_h = 0.15
   
      xtra_coef_os_above_burn_he = 0.25
      xtra_coef_os_below_burn_he = 0.25
   
      xtra_coef_os_above_burn_z = 0.25
      xtra_coef_os_below_burn_z = 0.25

      xtra_dist_os_above_nonburn = 0.1
      xtra_dist_os_below_nonburn = 0.2
   
      xtra_dist_os_above_burn_h = 0.2
      xtra_dist_os_below_burn_h = 0.2
   
      xtra_dist_os_above_burn_he = 0.2
      xtra_dist_os_below_burn_he = 0.2
   
      xtra_dist_os_above_burn_z = 0.2
      xtra_dist_os_below_burn_z = 0.2

      overshoot_f_above_nonburn_core = 0.014
      overshoot_f_above_nonburn_shell = 0.014
      overshoot_f_below_nonburn_shell = 0.014
      overshoot_f_above_burn_h_core = 0.014
      overshoot_f_above_burn_h_shell = 0.014
      overshoot_f_below_burn_h_shell = 0.014
      overshoot_f_above_burn_he_core = 0.014
      overshoot_f_above_burn_he_shell = 0.014
      overshoot_f_below_burn_he_shell = 0.014
      overshoot_f_above_burn_z_core = 0.014
      overshoot_f_above_burn_z_shell = 0.014
      overshoot_f_below_burn_z_shell = 0.014

      overshoot_f0_above_nonburn_core = 0.004
      overshoot_f0_above_nonburn_shell = 0.004
      overshoot_f0_below_nonburn_shell = 0.004
      overshoot_f0_above_burn_h_core = 0.004
      overshoot_f0_above_burn_h_shell = 0.004
      overshoot_f0_below_burn_h_shell = 0.004
      overshoot_f0_above_burn_he_core = 0.004
      overshoot_f0_above_burn_he_shell = 0.004
      overshoot_f0_below_burn_he_shell = 0.004
      overshoot_f0_above_burn_z_core = 0.004
      overshoot_f0_above_burn_z_shell = 0.004
      overshoot_f0_below_burn_z_shell = 0.004
      
      overshoot_below_noburn_shell_factor = 10
      
      use_Type2_opacities = .true.
      Zbase = 0.01d0
      
      T_mix_limit = 1d4

      ! FOR DEBUGGING

      !report_hydro_solver_progress = .true. ! set true to see info about newton iterations
      !report_ierr = .true. ! if true, produce terminal output when have some internal error
      !hydro_show_correction_info = .true.
      
      !max_years_for_timestep = 3.67628942044319d-05



/ ! end of controls namelist



&pgstar

      Grid4_win_flag = .true.
      Kipp_mass_min = 0.565 ! (Msun units) negative means use default
      Kipp_mass_max = 0.575 ! (Msun units) negative means use default
      ! set window size (aspect_ratio = height/width)
      TRho_Profile_win_width = 8
      TRho_Profile_win_aspect_ratio = 0.75

/ ! end of pgstar namelist