[Mesa-users] pre-main sequence boundary conditions

[TUCHOW, NOAH WOLFE]

Hello everyone,

I have a question about atmospheric boundary conditions for pre-main sequence models. I want to initialize a pre-main sequence model (setting  create_pre_main_sequence_model = .true.), save a model file after Deuterium depletion, and then load this model file for the rest of the star's evolution. Previously, I had been using the 'simple_photosphere'  boundary condition until the deuterium birthline and then changing the atmosphere to Eddington grey after loading the model file. However, looking at the evolutionary tracks on the HR diagram, I can see that changing the boundary condition upon loading a model causes a pretty large discontinuity in T and L (see attached image where I load a model file made with the simple_photosphere boundary condition and change to Eddington_grey). I've noticed that this discontinuity disappears if I keep the same boundary condition for both the initialization and the evolution inlists.

What I would like to do is have the same boundary condition to initialize the model and evolve it through the pre-main sequence and main sequence, so that I can get rid of the discontinuity upon loading. However, I'm having a problem in that I can only get the 'simple_photosphere' and 'photosphere_tables' boundary conditions working for the initialization prior to the deuterium birthline, whereas I would like to get a Grey atmosphere working, such as 'Eddington_grey'. When I try to use the Eddington grey boundary condition in my birthline inlist, MESA exits during the initial relaxation, saying "stopping because of problems dt < min_timestep_limit". I was wondering if there was anything that I could do to get a grey atmosphere working for my birthline model. Are there any tweaks to my inlists which I could do to prevent MESA from exiting during the initial relaxation? Alternatively, are there any ways to reduce the discontinuity upon loading a model with a different boundary condition?

I've attached my inlist_birthline which I've been using with MESA r11701.

Thanks for your assistance,
Noah Tuchow


Noah Tuchow
Penn State University
Department of Astronomy and Astrophysics
532C Davey Lab
University Park, PA 16802
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