Instead of just the internal (i.e. thermal plus degeneracy) energy, the total energy contains the relativistic energy of the nucleons, i.e. their rest-mass energies plus their internal energy, renormalized by subtracting 930.773 MeV per nucleon. The latter roughly corresponds to the rest mass of nucleons bound in iron-group nuclei.

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A very small remaining difference stems from the rest-mass contributions that are per definition included in the total energy but not in the explosion energy at a time when the recombination of nucleons and $\alpha$ -particles to nuclei in the ejecta is still incomplete.

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... values

This assessment is based on considering the effective net energy balance of some collapsing and ultimately ejected matter, which means that the initial, gravitationally bound state of the gas (composed of heavy nuclei) in the core of the progenitor star is compared with the final state of the gas after ejection. Our conclusions are valid independent of the exact moment and detailed reason of the nuclear photodisintegration, whether such dissociation happens as a consequence of the compressional heating during infall, due to shock heating, or because matter is bathed in the intense neutrino flux of the nascent neutron star. A small net gain of energy can in principle be obtained only when the recombination leads to more strongly bound nuclei than the undissociated matter started out from. This could account for at most ${\sim}10^{49}~$ erg per $10^{-2}~M_\odot$ of ejected matter if the pre-collapse material consisted for example of oxygen and carbon while the ejecta contained mostly iron-group nuclei (see the dashed magenta line in panel c of Fig. 5). Such a gain of energy could occur either through nuclear burning or less directly by photodisintegration and later recombination when the matter goes through NSE.

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