[Mesa-users] WD + WD merger simulation
Amar Aryan
amararyan941 at gmail.com
Thu Jan 18 08:04:19 UTC 2024
Dear Pablo,
Thank you very much for the detailed response.
Initially, I was using the 'contact' mass loss scheme. Further, I utilized
all three other mass loss (Ritter, Kolb, and roche_lobe) schemes, one by
one. With the hydrodynamics on, the 'contact' mass loss scheme provided a
mass loss rate of 1d-7 m_sun/yr, while others offered only 1d-8. As you
pointed out, I did not get any significant enhancement in mass loss rate to
mimic the merger event. Both the WDs evolve (in the binary system) for a
period of around 0.433Myr before termination due to the timestep issue.
With a mass ratio of ~1, both the WDs have nearly similar surface
composition at the start of the binary evolution (as shown in the attached
figure).
As you indicated, it appears to be difficult to achieve a dynamical
timescale mass transfer rate to mimic the accretion scenario of two WDs
here.
I shall be highly grateful if anyone has any other ideas to mimic this
(WD+WD) merger scenario.
With best regards,
Amar
On Wed, Jan 10, 2024 at 8:47 PM Pablo Marchant <pamarca at gmail.com> wrote:
> Hi Amar,
>
> what mass transfer prescription are you using? In practice, MESA will not
> get you to the point where you have a dynamical timescale mass transfer
> rate, that is the realm of 3D hydrodynamics. In particular if you're using
> the roche_lobe scheme, which determines the mass transfer rate by requiring
> the donor to remain within its Roche lobe, the model might be failing
> simply because it does not find such a solution once RLOF starts. This
> would be indicative of the actual system becoming dynamically unstable. You
> can also try a more physical scheme like Kolb. The mass transfer scheme is
> controlled by the option `mdot_shceme`, which by default is set to
> `mdot_scheme = 'Ritter'`. If you don't have that option in your
> inlist_project, you are just using the default of Ritter.
>
> Also, your model appears to be very close to a mass ratio of unity. Such a
> system might physically evolve with a small mass transfer rate while
> becoming a contact system until you get overflow of L2. That is a much more
> complex process to follow, but you can try to do that by using the
> "contact" scheme which determines the mass transfer rate during contact
> phases by requiring the surface of the stars to live in the same Roche
> equipotentials. Anyhow, you will not get a model with a high mass loss rate
> through L2, as that is not implemented (nor trivial to implement in both
> physical and computational terms).
>
> Just one last extra idea, if the surface composition of your stars is
> significantly different, the solver might not be happy when trying to
> transfer mass from one to the other, potentially causing convergence issues.
>
> Cheers
>
> On Wed, Jan 10, 2024 at 12:12 PM Amar Aryan via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> Dear Ebraheem,
>>
>> Thank you very much for the suggestion. I turned the hydrodynamics on for
>> both models and saw an increase of an order (10^-8 ---> 10^-7) in mass
>> transfer rate. Nevertheless, the current mass transfer rate is still too
>> small to qualify as a merger event.
>>
>> I kindly request others also to provide their valuable suggestions in
>> this regard.
>>
>> With thanks and regards,
>> Amar
>>
>> On Mon, Jan 8, 2024 at 1:17 PM Ebraheem Farag <ekfarag at asu.edu> wrote:
>>
>>> (cc'd mesa-users again). Thanks for sharing the output Amar!
>>>
>>> I can't tell exactly what's tripping up the solver near timestep ~500,
>>> but perhaps try turning on "report_solver_progress = .true.", which
>>> should tell you which zones in the models have the largest residuals, and
>>> hence are causing solver retries.
>>>
>>> This might not help, but maybe try the run again but with hydrodynamics
>>> turned on (i.e. change_v_flag = .true. and new_v_flag = .true. in
>>> star_job).
>>>
>>> I'm not an expert when it comes to binaries, so I can't speculate any
>>> further without running your inlists for myself, but someone else in
>>> MESA-users might know!
>>>
>>> -EbF
>>>
>>> On Mon, Jan 8, 2024 at 1:31 AM Amar Aryan <amararyan941 at gmail.com>
>>> wrote:
>>>
>>>> Hi Ebraheem,
>>>>
>>>> I have copied the entire output of the evolution (from beginning to
>>>> termination) in the* diagnose.txt* file. Please take a look.
>>>>
>>>> P.S.: In my previous email, I missed to cc my reply to MESA users.
>>>> Please cc MESA users in your next reply.
>>>>
>>>> With regards,
>>>> Amar
>>>>
>>>> On Mon, Jan 8, 2024 at 12:51 PM Ebraheem Farag <ekfarag at asu.edu> wrote:
>>>>
>>>>> Can you attach a txt file of the whole output? I'd just like to take a
>>>>> peak if you don't mind!
>>>>>
>>>>> -EbF
>>>>>
>>>>> On Mon, Jan 8, 2024 at 1:16 AM Amar Aryan <amararyan941 at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hi Ebraheem,
>>>>>>
>>>>>> Here it is:
>>>>>>
>>>>>> retry: abs(dlogT) > hydro_mtx_max_allowed_abs_dlogT 1018
>>>>>> 3552
>>>>>> retry 3500
>>>>>> dt
>>>>>> 6.7177175109631907D-07
>>>>>> min_timestep_limit
>>>>>> 9.9999999999999995D-07
>>>>>> stopping because of problems dt < min_timestep_limit
>>>>>> retry: abs(dlogT) > hydro_mtx_max_allowed_abs_dlogT 1022
>>>>>> 3552
>>>>>> dt
>>>>>> 6.7177175109631907D-07
>>>>>> min_timestep_limit
>>>>>> 9.9999999999999995D-07
>>>>>> stopping because of problems dt < min_timestep_limit
>>>>>> bin 1286 0.658000 0.066633 0.002456 0.000E+00 1.037312
>>>>>> 0 1 -1.257E-08 1.000000 2.080E+50 -1.981E+37 0.000E+00
>>>>>> -4.942012 0.322975 0.025034 0.000000 0.000E+00 698.818212
>>>>>> 0.025038 -1.375E-04 -1.257E-08 1.000E+99 0.000E+00 -1.981E+37 0.000E+00
>>>>>> 4.3317E+05 0.335025 0.021527 0.000000 -3.080E+48 673.681683
>>>>>> 0.025460 -1.545E-01 1.257E-08 0.000E+00 0.000E+00 0.000E+00 0
>>>>>>
>>>>>> save photos/b_x286, photos/1_x286, photos/2_x286 for model
>>>>>> 1286
>>>>>>
>>>>>> runtime (minutes), retries, steps 26.24
>>>>>> 218 3500
>>>>>> terminated evolution: cannot find acceptable model
>>>>>> termination code: min_timestep_limit
>>>>>> terminated evolution: cannot find acceptable model
>>>>>> termination code: min_timestep_limit
>>>>>> DATE: 2024-01-08
>>>>>> TIME: 11:06:22
>>>>>> finished
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Jan 8, 2024 at 12:29 PM Ebraheem Farag <ekfarag at asu.edu>
>>>>>> wrote:
>>>>>>
>>>>>>> Hello Amar, Happy New Year!
>>>>>>>
>>>>>>> Can you share a little more of your terminal output preceding
>>>>>>> "terminated evolution: cannot find acceptable model"?
>>>>>>>
>>>>>>> -EbF
>>>>>>>
>>>>>>> On Mon, Jan 8, 2024 at 12:15 AM Amar Aryan via Mesa-users <
>>>>>>> mesa-users at lists.mesastar.org> wrote:
>>>>>>>
>>>>>>>> Dear MESA users,
>>>>>>>>
>>>>>>>> I wish you all a very happy, prosperous, and productive new year!
>>>>>>>> On that note, I am trying to perform the simulation of a binary white dwarf
>>>>>>>> merger event (WD1 + WD2). I followed the below-mentioned steps to start
>>>>>>>> with:
>>>>>>>>
>>>>>>>> 1) I build two WDs using the *make_he_wd *directory with the
>>>>>>>> desired final radii and temperatures. The final_wd1.mod and final_wd2.mod
>>>>>>>> files were produced for WD1 and WD2, respectively.
>>>>>>>>
>>>>>>>> 2) I utilized the *final_wd1.mod *and *final_wd2.mod *models as
>>>>>>>> input to the *evolve_both_stars *directory in the binary module of
>>>>>>>> MESA.
>>>>>>>>
>>>>>>>> 3) In evolve_both_star directory, I modified the *inlist_project *to
>>>>>>>> provide the desired orbital period.
>>>>>>>>
>>>>>>>> 4) The evolution starts; however, after an evolution of ~ 4.33d5
>>>>>>>> years, the simulation terminated, showing:
>>>>>>>>
>>>>>>>> terminated evolution: cannot find acceptable model
>>>>>>>> termination code: min_timestep_limit
>>>>>>>> terminated evolution: cannot find acceptable model
>>>>>>>> termination code: min_timestep_limit
>>>>>>>> DATE: 2024-01-08
>>>>>>>> TIME: 11:06:22
>>>>>>>> finished
>>>>>>>>
>>>>>>>> 5) At the time of termination, the mass transfer rate is too minute
>>>>>>>> (10^-8 M_sun/yr) to be called a merger (please see the attached PNG file
>>>>>>>> for details)!
>>>>>>>>
>>>>>>>>
>>>>>>>> I shall be highly thankful for any suggestion to simulate the
>>>>>>>> merger event. I am using MESA-r23.05.1 version with the corresponding
>>>>>>>> MESASDK.
>>>>>>>>
>>>>>>>> With best regards,
>>>>>>>> Amar
>>>>>>>> _______________________________________________
>>>>>>>> mesa-users at lists.mesastar.org
>>>>>>>>
>>>>>>>> https://urldefense.com/v3/__https://lists.mesastar.org/mailman/listinfo/mesa-users__;!!IKRxdwAv5BmarQ!drX2mQMmB31kDxMrH7oL1pZkxnDh3uCjuLyz2mUjhVJOlrhPr1cccuZcwLQWjAK0ymZ2MYSUZDCoBRv4vdUuDYaF$
>>>>>>>>
>>>>>>>> _______________________________________________
>> 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
>
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