[Mesa-users] Why does the orbital separation decrease

[Ali Pourmand]

Hello,

I have been trying to evolve a 1Msun star in a binary system with a
companion of 0.625, and an initial separation of 11.2Rsun.
I have shut off the tides in the inlists that I have attached below.

Up to this time that I evolve this star, no mass transfer happens in the
binary. I was wondering why the separation is decreasing when tidal
evolution is off. I have also attached the binary_history.data of this run.
I am not sure if I am switching off the tidal evolution correctly, or is
there something else going on that could cause this that I am missing?

I attached the plots of binary separation and Jdot versus time in case it
helps.
There isn't any eccentricity so no circulization should have happened as
well.
[image: separation of mesa binaries.png]
[image: Js_vs_age.png]
best
Ali Pourmand
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