[Mesa-users] Question about tidal synchronization and circulization

Thu Jan 27 18:57:06 UTC 2022

Hi Pablo and Thanks for your help!

I am now evolving them, and the good news is that something has definitely
changed since they stop evolving at different timesteps.
The bad news is that all these cases I'm trying to evolve stop because they
start going lower than the minimum timestep limit at some point e.g.:

                                 dt    5.4850503805433365D-07
                                 min_timestep_limit
 9.9999999999999995D-07
                                 stopping because of problems dt <
min_timestep_limit

Their properties up to stopping do look a bit different from each other
though; so the physics has definitley changed somewhat; e.g. the left
figure doesn't include tidal sync, and the right one does (note that the
scales for the age plot are different):
[image: separation of mesa binaries.png][image: separation of mesa
binaries.png]

Do you suggest anything I could tweak in the inlists in order not to run
into minimum timestep errors? I might be wrong, but I don't think it's
reasonable to reduce the minimum timestep any more than the default value.

Thanks again,
Ali

On Thu, Jan 27, 2022 at 2:34 AM Pablo Marchant <pamarca at gmail.com> wrote:

> Thanks Ali,
>
> looking into your inlists I see two things:
>
> - you do not specify eccentricity. This means the system will be
> initialized with zero eccentricity so tidal circularisation is not expected
> to do anything to the model.
> - to model tidal synchronization, you need to include stellar rotation. In
> the star_job section of inlist1 (and inlist2 when you model both stars) you
> need to include (details here
> https://docs.mesastar.org/en/release-r21.12.1/reference/star_job.html#new-rotation-flag
> ):
>
> new_rotation_flag = .true.change_initial_rotation_flag = .true.
>
> Let me know how that works.
>
> Cheers!
>
> On Wed, Jan 26, 2022 at 7:53 PM Ali Pourmand <pourmand at ualberta.ca> wrote:
>
>> Hi Pablo,
>>
>> Sorry for not including any details. It's nothing complicated, just a
>> binary system, in which only one star evolves.
>> I am trying to evolve it, with a threshold for the maximum radius the
>> star could reach. I am trying to do it once by including the tidal
>> synchronization, and once without it.
>> I have attached the inlists I use below. Inlist 1 and 2 are the same for
>> both cases; but the inlist_project is different for the two cases where I
>> have switched tidal_sync on in one of them, and off in the other.
>>
>>
>> What has made me curious is that the orbital separation (and all other
>> properties) goes through the same evolution both with and without the tidal
>> sync switch module being on or off. For example, for a 3Msun donor with a
>> 1.875Msun companion and 9.47Rsun initial separation, the plots of angular
>> momentum, and photospheric radius and orbital separation as a function of
>> age looks like the plots below, with both inlist_project_with_tides, and
>> inlist_project_no_tides.
>>
>> Am I writing something wrong in my inlists that switching tidal
>> synchronization on and off makes no difference? (I had the same problem
>> with the
>>    "do_tidal_circ=.false." command, switching it from true to false
>> doesn't have any effect on the outcome)
>> [image: Js_vs_age.png]
>> [image: radiusvsage.png]
>> Best,
>> Ali
>>
>> On Wed, Jan 26, 2022 at 10:49 AM Pablo Marchant <pamarca at gmail.com>
>> wrote:
>>
>>> Hi Ali,
>>>
>>> it would be useful if you share your full inlists to understand your
>>> problem (both inlist_project as well as the individual inlists of each
>>> star). It's also useful if you provide a description of what type of system
>>> you're actually trying to model.
>>>
>>> Cheers
>>>
>>> On Wed, Jan 26, 2022 at 1:26 AM Ali Pourmand <pourmand at ualberta.ca>
>>> wrote:
>>>
>>>> Hello,
>>>>
>>>> I have been having a problem with the MESA binary package, namely on
>>>> the tidal synchronization and circulization switches; I can't seem to turn
>>>> these effects on or off.
>>>>
>>>> I have evolved my stars with two different inlists; the first one has:
>>>>
>>>>    do_tidal_sync = .true.
>>>>
>>>>    sync_type_1 = 'Hut_conv'
>>>>    sync_type_2 = 'None'
>>>>    sync_mode_1 = 'Uniform'
>>>>    sync_mode_2 = 'Uniform'
>>>>    do_initial_orbit_sync_1 = .true.
>>>> -----------------------------------------
>>>> The second one has:
>>>>
>>>>    do_tidal_sync = .false.
>>>>
>>>>    do_initial_orbit_sync_1 = .false.
>>>> ---------------------------------
>>>> I also tried evolved with both true and false for the following switch:
>>>>    do_tidal_circ = .true.
>>>> ------------------------------------
>>>>
>>>> None of these make a difference in the outcomes whatsoever.
>>>> I wanted to ask whether I am not including something in the inlists, or
>>>> is there another problem.
>>>>
>>>> More generally, Is the code's default to initiate tidal synchronization
>>>> or not? I am also wondering how there are two independent switches for
>>>> circulization and synchronization; namely, is it possible for one switch to
>>>> be off without the other?
>>>>
>>>> Best
>>>> Ali Pourmand
>>>> M.Sc. student,
>>>> University of Alberta
>>>>
>>>> _______________________________________________
>>>> mesa-users at lists.mesastar.org
>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>
>>>>
>>>
>>> --
>>> Pablo Marchant Campos
>>> M.Sc on Astrophysics, Universidad Católica de Chile
>>> PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
>>>
>>
>
> --
> Pablo Marchant Campos
> M.Sc on Astrophysics, Universidad Católica de Chile
> PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
>
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