mesa-users] Massive star runs end before planetary nebula stage

[Bill Paxton]

Hi Eric,

Here's some more information about the convergence problems for large stars at the tip of the AGB.

It appears that there is a very narrow zone at the base of the envelope where Pgas/Ptotal gets very small (6% or so).
The model is on the brink of physical instability there, and the code is having a very hard time coping.
I checked, and the convergence issues are arising in exactly the area where Pgas/Ptotal gets small.
In order to deal with the situation, the code needs to keep the timesteps small, hence the extremely slow progress.

Here are some plots from the 4 Msun run I'm using to study this porblem.   Note the huge jump in opacity at the trouble spot.
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You might want to check your 5 Msun case to see if you find a similar pattern.

-Bill