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

Abstract

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 ∼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 ∼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.

Numerical Simulations of the Random Angular Momentum in Convection: Implications for Supergiant Collapse to Form Black Holes

“…A known limitation of Lovegrove & Woosley (2013) and Fernández et al (2018)'s calculations of how much neutrino losses occur prior to BH formation was the use of analytic functions to model the neutrino emission. Ivanov & Fernández (2021) improves on this earlier work by using generalrelativistic neutrino radiation-hydrodynamic simulations to model the evolution of the inner core of each progenitor to BH-formation using three different equations-of-state (EOSs) for the PNS. Self-consistently modeling the core collapse for a given progenitor is important because the neutrino-loss function and time to BH formation set the amount of neutrino energy radiated and thus the energy of the outgoing weak shock.…”

Pulsational pair-instability supernovae: gravitational collapse, black-hole formation, and beyond

“…the PNSs (they collapse to BHs within less than ∼0.6 s after bounce at the latest; Table 3), the mass equivalent of the total energy radiated in neutrinos is less than ∼0.1 M 𝑐 2 in all models (see Table 4). The maximum kinetic energy of the acoustic pulse triggered by this decrement of the gravitational mass was found to be at most a few 10 46 erg in the models of Ivanov & Fernández (2021). This is orders of magnitude lower than the energy of the revived bounce shock or its relic sonic pulse, as discussed in the following section.…”

Revisiting the explodability of single massive star progenitors of stripped-envelope supernovae

“…While other explosion mechanisms have been proposed (e.g., MacFadyen & Woosley 1999;Janka 2012;Gilkis et al 2016;Soker 2019), no criterion to assess the outcome across a large range of initial masses exists to our knowledge. We also note that possible faint electromagnetic transients in the case of a "failed SN" and BH formation due to the loss of gravitational mass to neutrinos (Fernández et al 2018;Ivanov & Fernández 2021) seem quite improbable for compact, stripped-envelope stars, for which little to no ejection is expected.…”

“…Self-consistent simulations that model the core-collapse process, within the neutrino-driven explosion paradigm, have suggested the possibility that the SN shock might stall and be reverted by the infalling material, failing to unbind the outer layers of the star (Herant et al 1994;Burrows et al 1995;Fryer & Heger 2000;Janka 2013;Müller 2019;Vartanyan et al 2021). In this case, in the absence of an extended H-rich envelope (e.g., Quataert et al 2019;Antoni & Quataert 2021), the expected outcome is the implosion of the collapsing star into a black hole (BH), with only a weak transient (e.g., Nadezhin 1980;Fernández et al 2018;Ivanov & Fernández 2021) or possibly no transient at all. There have been observational efforts to identify the disappearance of evolved stars without a SN, and thus far there are two potential candidates of red supergiant stars that have been reported missing (Gerke et al 2015;Adams et al 2017a,b;Neustadt et al 2021).…”