[Mesa-users] Type I X-ray bursts using ns_he test case

[Triantafyllos Kormpakis]

Hi everyone,

I'm quite a new user of MESA, and I'm trying to create a minimal working case of Helium type I X-ray bursts using MESA. I'm using mesa-r24.03.1.

I haven't created my own inlists, I'm just using the ns_he test case, and trying to modify it in order to follow the evolution of multiple bursts in time. The only modification I have done to the test case is to remove the lines:

required_termination_code_string = 'power_nuc_burn_upper_limit'
power_nuc_burn_upper_limit = 1d6

in the 'inlist_to_flash' inlist file. This in principle allows the model to evolve. The problem is that after some time, the hydro solver fails (using more iterations than the limit), and even if I increase the allowed iterations, the timestep starts getting smaller and smaller, until the hydro solver fails again. I have tried using the debugging options, saw that the 'equL' seems to be the limiting timestep factor, but when comparing the analytical and numerical derivatives following the MESA debugging principles, I find no apparent problem.

What I want to ask is, how should I modify the ns_he test case in order to have a minimal working simulation setup, on which I can afterwards build on? Before experimenting with different mass accretion, base luminosity etc. I want to achieve a stable setup.

Before anyone suggests, I have also looked into the inlists provided in the instrument paper of Paxton et al 2015, and other inlists from the MESA summer school for X-ray bursts, as well as Meisel 2018. I can make these inlists work, after looking into the changelog and fixing the backwards incompatibility issues, but even in these cases the simulations don't run as intended and I haven't figured out why.

Any help/suggestion would be appreciated. Thank you.

Triantafyllos Kormpakis
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