[mesa-users] resending - Questions about physical model and numericalimplementation of binary star evolution

[Bill Paxton]

my previous response said we don't do common envelope modeling in mesa.
that's true, but it is often possible to let the binary go through a period of extremely high mass loss caused by unstable transfer.
the timesteps get small during that period, but mesa/star manages to shed an envelope okay at rates over 1Msun/year.
once things have restabilized the mass loss rate will drop back down to normal levels again.

that is a very rough form of dealing with a common envelope, a "stellar engineering" solution to a very difficult problem.
in some situations it may be good enough -- at least it let's you get beyond the common envelope stage.
but the details of what comes out cannot be expected to be highly accurate.  it is just a work-around.

-bill





On Dec 11, 2014, at 8:33 AM, Bill Paxton wrote:

> 
> On Dec 11, 2014, at 7:34 AM, Dean Townsley wrote:
> 
>> I am unsure what the mesa binary module does once both stars touch their Roche lobes.  From your inlist, it appears that is a stopping condition, I don't know what might happen after that if it doesn't stop.
> 
> 
> Once both stars fill their Roche lobes you've entered the strange and wonderful world of common envelopes.
> 
> Lot's of very smart people have spent lots of time exploring that world, and continue to do so.
> 
> mesa/star deals with stars; mesa/binary deals with pairs of stars; a common envelope object is neither of those.
> 
> so we stop when we form one and hand the problem off to a specialist.
> 
> once the common envelope object settles down to form a new star, then we can work with it again.
> 
> -B
> 
> 
> 
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