[mesa-users] AGB convergence problem

[LAURA A. BOYLE]

Dear all,


I have a problem regarding the evolution of low and intermediate mass stars through the AGB phase. For example in a 2Msun star what I have done is create a pre-main sequence model in order to use metallicity, Z = 0.01 and then evolve the star with default parameters through the main sequence through to the end of the horizontal branch, at which point I stop the model. Using the final point of this model I begin to run from end of horizontal branch with the aim of going to the end of the AGB. I am only interested in retrieving the history.data file for the AGB output.... and I am most importantly interested in the AGB tip luminosity.


The problem I am having is that the model seems to get stuck somewhere possibly near the AGB tip, and I am not even sure if it ever really reaches it. At this point I either stop the model manually or wait until it eventually (after about 12 hours!) stops due to a "convergence" error because the timesteps have gotten too small.


Is there a stopping control to have MESA stop at the AGB-tip or before it gets stuck in this slow low-timestep phase? I have read that increasing the mass-loss rate near this point can help MESA remove the envelope, but I think in that case the evolution has surpassed the point I need to look at, I would like to stop before the problem arises.





________________________________
Laura Boyle (Ph.D. Student)
Room 139,
Centre for Astronomy,
School of Physics,
NUI Galway


Telephone: +353 91492992


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