[mesa-users] Angular momentum loss from mass loss clarification

Pablo Marchant pamarca at gmail.com
Mon Apr 3 18:32:11 EDT 2017

```Hi Kenny. mdot_system_transfer contains the amount of mass lost from mass
transfer, in terms of the mass_transfer_alpha and mass_transfer_beta
parameters (check the explanation for these in the defaults
http://mesa.sourceforge.net/binary_controls_defaults.html). So, barring
Eddington limited mass transfer, you have that

b% mdot_system_transfer(b% d_i) = b% mtransfer_rate * b% mass_transfer_alpha
b% mdot_system_transfer(b% a_i) = b% mtransfer_rate * b% mass_transfer_beta

In the case where mass accretion is limited by the Eddington rate, then b%
mdot_system_transfer(b% a_i) includes the amount of mass lost due to that
as well.

Cheers

On Mon, Apr 3, 2017 at 5:21 PM, Kenny Van <kvan at ualberta.ca> wrote:

> Hi,
>
> A question for clarity, in the binary_jdot.f90 the subroutine that
> describes angular momentum loss from mass loss in the system is calculated
> using:
>
>          !mass lost from vicinity of donor
>
>          b% jdot_ml = (b% mdot_system_transfer(b% d_i) + b%
> mdot_system_wind(b% d_i))*&
>              (b% m(b% a_i)/(b% m(b% a_i)+b% m(b% d_i))*b%
> separation)**2*2*pi/b% period *&
>              sqrt(1 - b% eccentricity**2)
>          !mass lost from vicinity of accretor
>
>          b% jdot_ml = b% jdot_ml + (b% mdot_system_transfer(b% a_i) + b%
> mdot_system_wind(b% a_i))*&
>              (b% m(b% d_i)/(b% m(b% a_i)+b% m(b% d_i))*b%
> separation)**2*2*pi/b% period *&
>              sqrt(1 - b% eccentricity**2)
>
> ignoring the cct term.
>
> I have a bit of confusion with the two mdot_system_transfer values. From
> going through the code in the binary_mdot.f90 file it looks like
>
> mdot_system_transfer(b% d_i)
> describes the mass loss from the donor, where some percentage of this mass
> (1- alpha) is just lost from the system.
>
> mdot_system_transfer(b% a_i)
> describes the mass that is lost from the donor and some percentage of this
> is not accreted by the compact object and thus lost from the system.
>
> Could someone verify this?
>
> Thanks
>
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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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