[mesa-users] Problem evolving a donor star

[Pablo Marchant]

Also, if you have a non-rotating model, do_jdot_ls and do_jdot_missing_wind
should always be zero (if not, thats a bug!).

On Thu, Dec 11, 2014 at 1:29 PM, Pablo Marchant <pamarca at gmail.com> wrote:

> Odette, effectively the problem is the timestep. The loaded model starts
> with a huge timestep (about a third of a Gyr), and using that timestep in a
> close system with magnetic braking results in a negative total angular
> momentum. To make your system run, force a smaller initial timestep by
> adding this to your star_job section of inlist1:
>
>       set_initial_dt = .true.
>       years_for_initial_dt = 1
>
> Also, maybe you want to create your initial models with a better time
> resolution. Might not be neccesary (maybe the model has achieved proper
> convergence already), but I'd recommend you to use a smaller
> varcontrol_target there.
>
> Cheers!
>
> On Wed, Dec 10, 2014 at 6:40 PM, Odette Toloza <odette.toloza at gmail.com>
> wrote:
>
>> Hola Pablo,
>>
>> Thanks for helping me.
>>
>> I've installed the latest version, 7184. Maybe having a look into the
>> time step could handle it, I mean constraining the maximun value. I do not
>> know.
>>
>> Find attached the files.
>>
>>
>> Cheers,
>> Odette.
>>
>>
>> 2014-12-10 17:11 GMT+00:00 Pablo Marchant <pamarca at gmail.com>:
>>
>>> Hola Odette!
>>>
>>> Usually that error message appears when angular momentum comes out
>>> negative. That can happen since we compute delta J = jdot*dt (just the
>>> Euler method). However it usually means something else is wrong. Could you
>>> provide me with your full set of inlists and saved models (together with
>>> your MESA version) to check wether this is a bug?
>>>
>>> Cheers!
>>>
>>> On Wed, Dec 10, 2014 at 5:47 PM, Odette Toloza <odette.toloza at gmail.com>
>>> wrote:
>>>
>>>> Hi Mesa-users
>>>>
>>>> I am relatively new with MESA, and I am having troubles with evolving a
>>>> binary system containing a evolved donor. Based on the
>>>> binary_donor_only_implicit_mdot suite test we have tried to evolve white
>>>> dwarf of 0.8 solar masses together with a donor star of 1 solar mass. But
>>>> first at all we created a model for the donor starting from the ZAMS and
>>>> stopping the evolution controlling the core composition.
>>>>
>>>>
>>>> xa_central_lower_limit_species(1) = 'h1'
>>>> xa_central_lower_limit(1) = 0.5  ! or less evolved 0.8
>>>>
>>>>
>>>> When we include this model on the binary_donor_only_implicit_mdot suite
>>>> test and we make sure that with an orbital period of 0.6d the system is out
>>>> of contact. It starts running but as soon as the mass transfer starts MESA
>>>> stops. The first amount of mass transferred is too high and MESA collapses
>>>> returning negatives values for angular momentum (STOP bad
>>>> angular_momentum_j).
>>>>
>>>> the orbit shrinks quite fast since the jump of (r-rl)/rl is too abrupt
>>>> before the last step is 6.421261633E-01 and in the last step is
>>>> -1.409570580E-02, as well as lg_mdot, from -2.062847169E+01 to
>>>> -9.900000000E+01
>>>>
>>>> We have considered all the mechanisms of jdot,
>>>>
>>>>    do_jdot_gr = .true.
>>>>    do_jdot_ml = .true.
>>>>    do_jdot_ls = .true.
>>>>    do_jdot_missing_wind = .true.
>>>>    do_jdot_mb = .true.
>>>>
>>>>
>>>>
>>>> For some reason MESA complains with the inclusion of an evolved donor.
>>>> To make sure that we are not making any mistake during the inclusion of the
>>>> model, we created another evolved model this time with 80% of hydrogen in
>>>> the core. When we include it, MESA runs without problems.
>>>>
>>>>
>>>> Does anyone have any idea why this could be happen?
>>>>
>>>> Cheers,
>>>> Odette Toloza
>>>>
>>>>
>>>>
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>>>>
>>>>
>>>
>>>
>>> --
>>> Pablo Marchant Campos
>>> M.Sc on Astrophysics, Universidad Católica de Chile
>>> PhD student, Argelander-Institut für Astronomie
>>>
>>
>>
>
>
> --
> Pablo Marchant Campos
> M.Sc on Astrophysics, Universidad Católica de Chile
> PhD student, Argelander-Institut für Astronomie
>



-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD student, Argelander-Institut für Astronomie
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