[Mesa-users] Evolution of binaries, problem

[Josiah Schwab]

Hi Gökhan,

> I have a weird problem about evolution of the binaries. I have been
> trying to see the evolution of a resolved binary system that consists
> of two main-sequence stars. I would like to see what will happen on
> this system after mass transfer. But MESA stuck in a time and
> producing new models for that time over and over. I attached the
> "age-model number" diagram. What could cause this problem?

When the MESA timestep gets small, it is important to think a little
about what is happening physically (i.e. when is MESA getting stuck).
That helps in thinking through what might be going wrong.

In your history files (or on the terminal), you can see that the
timestep starts falling when star 1 starts to fill its Roche lobe for
the first time.  So for some reason mass transfer is having trouble
getting started.

> Also, I attached the inlist files.

Thank you for attaching everything to reproduce your problem.

That showed you were using

   mdot_scheme = "roche_lobe"

and if you search the docs about that scheme, you will see that there
are a couple of options that control how that scheme gets started.

You will find that it has an initial guess for mdot for the first
overflowing step.  By default that is 1d-12.  I know the mass transfer
rate here is going to be several orders of magnitude higher than that.
So I tried upping the guess a bit to

  starting_mdot = 1d-10

and then mass transfer started up smoothly.

Josiah