[Mesa-users] runaway mass transfer in WD-WD binary

[Jim Fuller]

Hi Kareem,

It sounds like the mass transfer is becoming unstable. It should be stable
for conservative mass transfer, but you're using non-conservative mass
transfer, and I think that usually is unstable for white dwarfs. Have you
tried with conservative mass transfer, i.e., mass transfer beta = 0 ?

-Jim

On Wed, Sep 2, 2020 at 7:00 AM Kareem El-Badry <kelbadry at berkeley.edu>
wrote:

> Hello MESA users,
>
> I'm trying to simulate mass transfer from a low-mass He WD (0.13 Msun)
> onto a point mass that represents a massive WD (1.1 Msun). Mass transfer
> should be stable and the period should increase once mass transfer begins
> [I think] because (a) the orbit expands when the He WD loses mass, and (b)
> the radius of the He WD increases when it loses mass, reestablishing
> contact with the Roche lobe at a longer period.
>
> However, in the MESA calculations, Mdot gets very large as soon as the He
> WD overflows its Roche lobe, and the calculation grinds to a halt. I've
> attached inlists and a model.
>
> I am using version 12778.
>
> Some things I have tried:
> - decreasing varcontrol_target and mesh_delta_coeff
> - decreasing fm and fr
> - setting set_to_this_tau_factor = 30
> - turning off diffusion
>
>
> But none of these had an appreciable effect. Does anyone have relevant
> experience or an idea what the problem might be?
>
> Thanks,
> Kareem
>
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