[mesa-users] Finer control of mass change in star for binary evolution

[Pablo Marchant]

Hi! While working on implementing the binary evolution part of MESA I've
come across something that I don't know if it's possible to implement right
now. In mixing the effect of winds and mass transfer, I would expect to do
the following for each star in the system:

- For the donor, set as mdot the result of max(abs(wind_mdot),
abs(rlof_mdot)), with the appropiate sign of course. This is already done,
but the problem is that the calculation of the wind is completely contained
in the do_wind routine, for which the end result is the setting of mdot
that will be used to adjust the mass as said above. However there is no way
to differentiate (as far as I can see) what part of the final mdot is due
to winds and which is due to mass transfer. This is important because I
need to update the total angular momentum of the system accordingly.

- For the accretor, I would like to add up the mdot from the wind, and the
one from mass accretion.This is not done right now, and the criteria to set
the wind is the same as described above, max(abs(wind_mdot),
abs(rlof_mdot)), which doesn't really make sense  for the accretor. And
once again, I need to know precisely in the end what corresponds to mass
accretion and what to winds, in order not just to update the total angular
momentum of the system, but also to properly set the composition of the
accreted material.

I don't know really if there is a proper way to do this right now. I guess
the most natural way I can imagine, would be to have a user defined
function to specify mass accretion, which is called right after do_winds.
In this way I could do what I describe above by modifying mstar_dot in an
appropiate way. Any suggestions?

Cheers!

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