[Mesa-users] Question regarding do_tidal_sync

[Bear Ealeal]

Dear Prof. MarchantThank youfor your reply, I apologize but I did not understand, can you point me to thechange caused by setting:
do_tidal_sync= .true. 

Where inthe code\which equation it effects? 

As youmentioned do_jdot_ls is at default (true).

Thanks,

Ealeal

 

Theinlist_project we used is:

&binary_job

   inlist_names(1) = 'inlist1' 

   inlist_names(2) = 'inlist2'

   evolve_both_stars = .false.

/ ! end ofbinary_job namelist

&binary_controls

   m1 = 1.32d0 !  Msun 

   m2 = 0.00063d0 ! companion mass in Msun  Try: 0.001

   initial_period_in_days = 3.66! Also tried 4, 3.5...

   initial_eccentricity =0 ! try 0,0.05,0.1

   fr = 0.05 ! default is 0.01

do_tidal_sync= .true.

!do_tidal_circ= .false. ! only apply if e>0

/ ! end ofbinary_controls namelist

 

The inlist1contains rotation:

&star_job

      mesa_dir = '../../..'

      show_log_description_at_start = .false.

      save_model_when_terminate = .true.

      save_model_filename = 'final.mod'

      new_rotation_flag = .true.

      change_rotation_flag = .true. 

      new_surface_rotation_v = 25.18 ! solar(km sec^1)

      set_surface_rotation_v = .true. 

      set_initial_surface_rotation_v = .true

      change_initial_Z = .true. ! also triedwith solar metallicity

      new_Z = 0.03  ! also tried with solar metallicity

 ! end of star_job namelist

&controls

      All regular things  as test suite, instabilities are set:

D_DSI_factor= 0

D_SH_factor= 1

D_SSI_factor= 1

D_ES_factor= 1

D_GSF_factor= 1

D_ST_factor= 1

/ ! end ofcontrols namelist

&pgstar

   / ! end of pgstar namelist


Thank you,Ealeal
    On Tuesday, October 26, 2021, 09:55:51 AM GMT+3, Pablo Marchant <pamarca at gmail.com> wrote:  
 
 Hi Bear,
Without more information it is unclear if the difference on the fifth digit you mention is incorrect. What kind of system are you modeling precisely (always better to share inlists and other input files)? What were you expecting from the model and why? Does the star evolve towards synchronicity?

there are two controls taking care of activating tides in MESA:
- do_tidal_sync, this is by defalt set to false. It determines whether there is a torque term applied to each star.- do_jdot_ls, which defaults to true. This determines if there is a sink term in the equation for the evolution of orbital angular momentum which accounts for the torque imparted on the stars.

One important thing is that these controls assume you have rotation included in your stellar models. do_jdot_ls only accounts for the torque applied through the star, and do_tidal_sync can only apply a torque if there is rotation included in the star. But you should beware of how tidal strength is actually computed (see various options in the documentation). I'd suggest you take a closer look at these as well.
Cheers

On Tue, Oct 26, 2021 at 8:08 AM Bear Ealeal via Mesa-users <mesa-users at lists.mesastar.org> wrote:


Dear MESA users,

I am trying to run MESAbinary+point mass, where the star is a MS and the point mass is a planet.

I turned on do_tidal_sync = .true.
I did itfor both MESA 10398 and MESA 15140.I amnot sure what "do_tidal_sync"  does, if it is true or false, tidal occurs and I see that the  binary separationdecreases.
In thedefaults it says:

! If true,apply tidal torque to the star
      do_tidal_sync = .false.But true or false, I get the same results up to the 5 digit...
Do  you know what it does and on which parameterit effects?

Thank you very much for you help,

Ealeal



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-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de ChilePhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn  
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