[mesa-users] Problem evolving a donor star

[Pablo Marchant]

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
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