Direct Black Hole Formation Research Articles

NEUTRINO SIGNAL OF COLLAPSE-INDUCED THERMONUCLEAR SUPERNOVAE: THE CASE FOR PROMPT BLACK HOLE FORMATION IN SN 1987A

ABSTRACT Collapse-induced thermonuclear explosion (CITE) may explain core-collapse supernovae (CCSNe). We analyze the neutrino signal in CITE and compare it to the neutrino burst of SN 1987A. For strong ( erg) CCSNe, such as SN 1987A, CITE predicts a proto-neutron star (PNS) accretion phase lasting up to a few seconds that is cut off by black hole (BH) formation. The neutrino luminosity can later be revived by accretion disk emission after a dead time of a few to a few tens of seconds. In contrast, the neutrino mechanism for CCSNe predicts a short (≲s) PNS accretion phase, followed by slowly declining PNS cooling luminosity. We repeat statistical analyses used in the literature to interpret the neutrino mechanism, and apply them to CITE. The first 1–2 s of the neutrino burst are equally compatible with CITE and with the neutrino mechanism. However, the data points toward a luminosity drop at t = 2–3 s, which is in some tension with the neutrino mechanism but can be naturally attributed to BH formation in CITE. The occurrence of neutrino signal events at 5 s suggests that, within CITE, the accretion disk formed by that time. We perform two-dimensional numerical simulations showing that CITE may be able to accommodate this disk formation time while reproducing the ejected 56Ni mass and ejecta kinetic energy within factors of 2–3 of observations. We estimate the accretion disk neutrino luminosity, finding it to be on the low side but compatible with the data to a factor of 10. Given comparable uncertainties in the disk luminosity simulation, we conclude that direct BH formation may have occurred in SN 1987A.

Revealing local failed supernovae with neutrino telescopes

We study the detectability of neutrino bursts from nearby direct black hole-forming collapses (failed supernovae) at Megaton detectors. Due to their high energetics, these bursts could be identified - by the time coincidence of N >= 2 or N >= 3 events within a ~ 1 s time window - from as far as ~ 4-5 Mpc away. This distance encloses several supernova-rich galaxies, so that failed supernova bursts could be detected at a rate of up to one per decade, comparable to the expected rate of the more common, but less energetic, neutron star-forming collapses. Thus, the detection of a failed supernova within the lifetime of a Mt detector is realistic. It might give the first evidence of direct black hole formation, with important implications on the physics of this phenomenon.

Diffuse Neutrino Flux from Failed Supernovae

I study the diffuse flux of electron antineutrinos from stellar collapses with direct black hole formation (failed supernovae). This flux is more energetic than that from successful supernovae, and therefore it might contribute substantially to the total diffuse flux above realistic detection thresholds. The total flux might be considerably higher than previously thought, and approach the sensitivity of Super-Kamiokande. For more conservative values of the parameters, the flux from failed supernovae dominates for antineutrino energies above 30-45 MeV, with potential to give an observable spectral distortion at megaton detectors.

Publisher's Note: New criterion for direct black hole formation in rapidly rotating stellar collapse [Phys. Rev. D70, 084005 (2004)

Publisher's Note: New criterion for direct black hole formation in rapidly rotating stellar collapse [Phys. Rev. D<b>70</b>, 084005 (2004)

New criterion for direct black hole formation in rapidly rotating stellar collapse

We study gravitational collapse of rapidly rotating relativistic polytropes of adiabatic indices $\ensuremath{\Gamma}=1.5$ and 2. The nondimensional spin parameter of the system $q\ensuremath{\equiv}J/{M}^{2}$ where $J$ and $M$ are the total angular momentum and the gravitational mass is set to be larger than unity. First, analyzing initial distributions of mass and spin parameters inside the stars, we predict the final outcome after the collapse proposing a new criterion for direct black hole formation as ${q}_{c}&lt;1$ where ${q}_{c}$ denotes an effective spin parameter of the stellar central region. To confirm our predictions, we then perform fully general relativistic simulations assuming axial and equatorial symmetries. It is found that in contrast with previous conclusions for the criterion of no black hole formation, a black hole is formed even from a star with $q&gt;1$ if the condition ${q}_{c}&lt;1$ is satisfied. For ${q}_{c}&lt;1$, a seed black hole is always formed first, and then, it grows as the ambient fluid elements accrete onto it. We also find that the time evolution of the relation between angular momentum and mass enclosed in the seed black hole can be approximately determined from the initial profiles of the density and the specific angular momentum.

Black hole formation preceded by a SN explosion or not: evidence from Galactic chemical evolution

We derive a constraint on direct black hole formation from the evolution of [O/Fe] as function of time, during the early evolution of the Galaxy in the solar neighbourhood. Since oxygen is dominantly produced by massive stars, the evolution of [O/Fe] is an indirect observable signature of the death of massive stars. We use a detailed Galactic code that computes as function of time the chemical composition of the interstellar gas, out of which successive generations of stars are formed. From our simulations we conclude, that to fit simultaneously the observed [O/Fe] evolution and other observational constraints: (i) all massive stars (single or binary) with M &gt; 40 M⊙ should form massive black holes with the ejection of at least 7 M⊙ of oxygen and little carbon and iron; and (ii) mass loss by stellar wind during the Luminous Blue Variable phase and/or helium burning phase is likely to be metallicity dependent.