[mesa-users] Sound-speed discontinuity in solar-like main sequence model

[Bellinger, Earl]

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Hello everyone,

I'm a new Ph.D. student at the Max-Planck-Institut für Sonnensystemforschung in Göttingen, Germany, and this is my first post on this mailing list. So, hello!

I am using MESA r7623 to generate models of solar-like stars on the main sequence. I use an Eddington atmosphere, enable atomic diffusion, and disable rotation. All of my model tracks are varied by mixing length, initial helium, initial metallicity, and mass. I start each track on the PMS and begin collecting profiles once it hits the ZAMS. I also changed pre_ms_T_c from 3e5 to 9e5 to get the models on the PMS to converge. Other than those things, my inlist is basically the same as the 1M-pms-to-wd in the test suite.

In some (around 3%) of my model tracks, I notice a sound-speed discontinuity that is present in all the models in the track. I haven't noticed anything in the output logs that indicate anything being amiss.

I have (I hope) attached a plot of one such model with M=1.290625, Y=0.259375, Z=0.002055, alpha_MLT=1.8125 at an age of t=2.2E-005 (just after hitting ZAMS). The discontinuity in this model happens very near the boundary of the star at a radius of 99.235% of the total radius. I have also attached the inlist for this track as well as the output log and the profile file corresponding to the plot.

I am wondering the source of this discontinuity, and whether it is possible to eliminate it?

Thanks in advance for any assistance.

Best regards,
Earl Bellinger
Stellar Ages & Galactic Evolution Group
Max-Planck-Institut für Sonnensystemforschung 
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