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

Abstract

We investigate the final collapse of rotating and non-rotating pulsational pair-instability supernova progenitors with zero-age-main-sequence masses of 60, 80, and 115 M and iron cores between 2.37 M and 2.72 M by 2D hydrodynamics simulations. Using the general relativistic NADA-FLD code with energy-dependent three-flavor neutrino transport by fluxlimited diffusion allows us to follow the evolution beyond the moment when the transiently forming neutron star (NS) collapses to a black hole (BH), which happens within 350-580 ms after bounce in all cases. Because of high neutrino luminosities and mean energies, neutrino heating leads to shock revival within 250 ms post bounce in all cases except the rapidly rotating 60 M model. In the latter case, centrifugal effects support a 10% higher NS mass but reduce the radiated neutrino luminosities and mean energies by ∼20% and ∼10%, respectively, and the neutrino-heating rate by roughly a factor of two compared to the non-rotating counterpart. After BH formation, the neutrino luminosities drop steeply but continue on a 1-2 orders of magnitude lower level for several 100 ms because of aspherical accretion of neutrino and shock-heated matter, before the ultimately spherical collapse of the outer progenitor shells suppresses the neutrino emission to negligible values. In all shock-reviving models BH accretion swallows the entire neutrino-heated matter and the explosion energies decrease from maxima around 1.5 × 10 51 erg to zero within a few seconds latest. Nevertheless, the shock or a sonic pulse moves outward and may trigger mass loss, which we estimate by long-time simulations with the P code. We also provide gravitational-wave signals.

Luminous Fast Blue Optical Transients and Type Ibn/Icn SNe from Wolf-Rayet/Black Hole Mergers

“…Furthermore, multiple PPI eruptions may be required to generate the large CSM mass covering radii ∼ 10 14 − 10 16 cm (potentially requiring a finetuned progenitor star mass), despite a broadly similar CSM density field now inferred to characterize multiple members of the LFBOT class (Ho et al 2019;Bright (Margutti et al 2019), is also in tension with the large ejecta masses predicted from the successful explosion of a ∼ 40M PPISN progenitor. The core collapse of stars which undergo PPI may not give rise to successful energetic SN explosions due to their massive Fe cores and the large gravitational binding energy of their envelopes (e.g., Powell et al 2021;Rahman et al 2021). An alternative, potentially more promising PPISN scenario for LFBOTs would therefore invoke an initially failed neutrino-driven explosion giving rise to prompt BH formation, followed by a delayed wind-driven explosion once the outer stellar layers form an accretion disk around the BH (similar to the scenario explored in Siegel et al 2021 in the context of even more massive stars above the pair-instability mass gap).…”

Observing neutrinos from failed Supernovae at LNGS

“…This term, usually called response time of the detector [66] cannot be deduced by the neutrino data-stream without any assumption on the emission model. Concerning the emission model that we are assuming, we are neglecting possible mechanisms providing neutrinos arriving subsequent to BH formation, such as delay due to the presence of neutrino mass, the possible neutrino emission after the BH formation [67], or also neutrino echos around the black hole [68]. All these effects are below the sensitivity of the detectors considered in this work or produce deviations smaller than the provided temporal uncertainty.…”

The Spin of a Newborn Black Hole: Swift J1728.9-3613

“…This configuration may be natural in binary systems, where tidal interactions with the companion star must influence the rotation rate and structure of the progenitor (Fuller & Lu 2022). There may even be important secondary effects: rotation within the progenitor star serves to increase the maximum supported mass of the PNS before collapse to a BH, influencing the neutrino flux before collapse (Rahman et al 2021) and driving up the natal spin of the black hole.…”