[Mesa-users] Ni56 getting converted to Fe isotopes during SN shock breakout

Wed Apr 8 15:49:20 UTC 2026

Dear MESA users,

I have been trying to model core collapse and eventual shock breakout in a massive star, using the 'ccsn_IIp' problem in star/test_suite as a template. The pre core-collapse star is a partially stripped massive star of solar metallicity, with M_ZAMS = 16Msun, and M_env (at core collapse) = 1.27Msun. The eventual goal is to handoff these models to STELLA and produce lightcurves.

STELLA crashes early and produces erroneous lightcurves. Upon investigating the shock breakout phase and looking for sharp abundance changes in the profiles, I find that Ni56 abundances in the model profiles suddenly drop dramatically between inlist_shock_part4 and inlist_shock_part5. This is accompanied by sudden increase in Fe52 and Fe54 abundances. The temperature profile remains around log T[K] ~ 5.5, which rules out nuclear burning. I do not understand (i) why all the Ni56 is getting converted into Fe isotopes, and (ii) if this is related to numerical issues encountered by STELLA.

I'd greatly appreciate if someone is aware of/encountered similar issues with shock breakout in MESA and could chime in! The inlists and a snapshot of the profile abundances for shock_part4 and shock_part5 are attached to the email. Thanks for your attention! Please let me know if more information is required.

Best,
Dr. Soham Mandal
VITA postdoctoral research fellow
Department of Astronomy
University of Virginia
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