Nonthermal transient phenomena around rotating black holes
by van Putten, Maurice H. P. M.
Invited review, in Orleans School On The Sciences Of The Universe: Mass Motion (Springer-Verlag), to appear
Ultra-high energy cosmic rays (UHECRs) and gamma-ray bursts (GRBs) are the most exceptional nonthermal transient events, that appear to be associated with black holes. Here, we describe radiation mechanisms induced by turbulent flows around rapidly rotating black holes: high-energy emissions from a relativistic capillary effect along the black hole spin-axis and low-energy emissions by catalytic conversion of spin-energy. High-energy emissions arise, concurrently, in photons and, upstream of an outgoing Alfv\’en front, in ionic contaminants by linear acceleration. The latter develop into ultra-high energy cosmic rays (UHECRs) about the Greisen-Zatsepin-Kuzmin (GZK) threshold in low-luminosity, intermittent active galactic nuclei. These may include Seyfert galaxies and Cen A suggested by detections of UHECRs by the Pierre Auger Observatory and, for the latter, also of Very High Energy (VHE) gamma-rays by the High Energy Stereoscopic System (HESS). Nearly complete spin-down of stellar mass black holes is common to collapsars and mergers of neutron stars with another neutron star or companion black hole. Thus, long GRBs from rotating black holes explain events with and without supernovae and a diversity in their X-ray afterglows. Their intrinsic exponential decay is remarkably consistent with the average of 600 light curves of long GRBs, whose total output agrees with observed peak and true energies in gamma-rays. We conclude that long GRBs are spin-powered. Gravitational radiation from turbulent flows in SgrA* might be of interest to the planned Laser Interferometric Space Antenna (LISA) and, for stellar mass black holes in GRBs, should be detectable by LIGO-Virgo. Long GRBs from naked inner engines produced in mergers produce long-duration radio-burst that may be seen in all-sky surveys by the Low Frequency Array (LOFAR).