Mass Ejection in Failed Supernovae: Equation of State and Neutrino Loss Dependence

A failed core-collapse supernova from a nonrotating progenitor can eject mass due to a weakening of gravity associated with neutrino emission from the protoneutron star. This mechanism yields observable transients and sets an upper limit on the mass of the black hole (BH) remnant. Previous global simulations of this mechanism have included neutrino losses parametrically, however, with direct implications for the ejecta mass and energy. Here we evolve the inner supernova core with a spherically symmetric, general-relativistic neutrino radiation-hydrodynamic code until BH formation. We then use the result in a Newtonian code that follows the response of the outer layers of the star to the change in gravity and resolves the surface pressure scale height. We find that the dense-matter equation of state (EOS) can introduce a factor of similar to 2 variation in gravitational mass lost to neutrinos, with a stiff EOS matching previous parametric results and a soft EOS yielding lower ejecta masses and energies by a factor of several. This difference is caused primarily by the longer time to BH formation in stiffer EOSs. With a soft EOS, our red and yellow supergiant progenitors fail to unbind mass if hydrogen recombination energy is not included. Using a linear ramp in time for mass-energy lost to neutrinos (with suitable parameters) yields a stellar response within similar to 10% of that obtained using the detailed history of neutrino losses. Our results imply quantitative but not qualitative modifications to previous predictions for shock breakout, plateau emission, and final BH masses from these events.

Automated summary

This study investigates failed core-collapse supernovae from nonrotating progenitors and finds that the dense-matter equation of state (EOS) can introduce a factor of similar to 2 variation in gravitational mass lost to neutrinos, with stiffer EOS leading to higher ejecta masses and energies. The research also indicates that a soft EOS leads to lower ejecta masses and energies, primarily due to the longer time to black hole (BH) formation. Furthermore, it is discovered that red and yellow supergiant progenitors fail to unbind mass if hydrogen recombination energy is not considered.