High energy neutrinos from merging black holes such as blazars

Lunch Colloquium
Prof. Dr. Peter L. Biermann
MPI für Radioastronomie

High energy (HE) neutrinos are expected from interaction of high energy protons and nuclei. (A) Here we review first the sources of high energy protons and nuclei: i) Blue Super Giant star (BSG) supernovae exploding into their own wind give about $3 \cdot 10^{17} \, Z$ eV. ii) Gamma Ray Bursts (GRBs) can give a factor of a few hundred more energy per particle. iii) Radio galaxies can yield a few $10^{20}$ eV, and iv) blazars, basically radio galaxies with their relativistic jet pointed at us may reach the same energy. The cut-off spectra of hot spots in radio lobes, radio jet knots and compact nuclei of AGN, and the double-hump spectrum of blazars can all be understood with this approach: all present observational evidence for the presence of ultra high energy particles (UHECRs). (B) Second we review the source 41.9+58 in the starburst galaxy M82: It may be a mis-directed Gamma Ray Burst resulting from the merger of two stellar mass black holes: The open conal structure around it can be interpreted as resulting from the conal sweep of the dominant jet during a spin-flip. This in turn is caused by the orbital spin winning over intrinsic spin. 41.9+58 can be expected to have produced ultra high energy protons (perhaps also nuclei), high energy gammas, high energy neutrinos, and gravitational waves. (C) Third we consider the neutrino events of IceCube. Six of these events can be associated with relativistic jets pointing at us from blazars; one of them shows evidence for several neutrino events (TXS 0506+056 = PMN J0509+0541), and also coincident $\gamma$-ray flaring, while the other events are too old to allow a full check in the earlier data. All of these six sources allow interpretation as an ongoing merger of two super-massive black holes with an associated spin-flip; interaction is increased while the dominant jet sweeps around, allowing strong injection, acceleration and interaction. So flat radio spectra extending to far beyond GHz can be understood, very high energy protons and nuclei, high energy gammas and neutrinos, and in the actual merger gravitational waves. Future observations at IceCube and other observatories will check this picture. As the particle energies go much higher than at CERN, we can hope for new discoveries.