Particle acceleration in the vacuum gaps in black hole magnetospheres

We consider particle acceleration in vacuum gaps in magnetospheres of black holes powered through Blandford-Znajek mechanism and embedded into radiatively-inefficient accretion flow (RIAF) environment. In such situation the gap height is limited by the onset of gamma-gamma pair production on the infrared photons originating from the RIAF. We numerically calculate acceleration and propagation of charged particles taking into account the detailed structure of electric and magnetic field in the gap and in the entire black hole magnetosphere, radiative energy losses and interactions of gamma rays produced by the propagated charged particles with the background radiation field of RIAF. We show that the presence of the vacuum gap has clear observational signatures. The spectra of emission from gaps embedded into a relatively high luminosity RIAF are dominated by the inverse Compton emission with a sharp, super-exponential cut-off in the very-high-energy gamma-ray band. The cut-off energy is determined by the properties of the RIAF and is largely independent of the structure of magnetosphere and geometry of the gap.The spectra of the gap residing in low-luminosity RIAFs are dominated by synchrotron / curvature emission with the spectra extending into 1-100 GeV energy range. We also consider the effect of possible acceleration of protons in the gap and find that proton energies could reach the ultra-high-energy cosmic ray (UHECR) range only in extremely low luminosity RIAFs.Comment: 10 pages, 15 figure

A rotating hollow cone anisotropy of TeV emission from binary systems

We show that TeV gamma-ray emission produced via interactions of high-energy particles with anisotropic radiation field of a massive star in binary systems should have a characteristic rotating hollow cone anisotropy pattern. The hollow cone, whose axis is directed away from the massive star, rotates with the period equal to the orbital period of the system. We note that the two maxima pattern of the TeV energy band lightcurve of the gamma-ray loud binary LS 5039 can be interpreted in terms of this rotating hollow cone model. Adopting such an interpretation, we are able to constrain the geometry of the system - either the inclination angle of the binary orbit, or the elevation of the gamma-ray emission region above the orbital plane.Comment: Ap.J.Lett., accepte

IceCube Sensitivity for Neutrino Flux from Fermi Blazars in Quiescent States

We investigate the IceCube detection potential of very high energy neutrinos from blazars, for different classes of "hadronic" models, taking into account the limits imposed on the neutrino flux by the recent Fermi telescope observations. Assuming the observed gamma-ray emission is produced by the decay of neutral pions from proton-proton interactions, the measurement of the time-averaged spectral characteristics of blazars in the GeV energy band imposes upper limits on the time-averaged neutrino flux. Comparing these upper limits to the 5 sigma discovery threshold of IceCube for different neutrino spectra and different source locations in the sky, we find that several BL Lacs with hard spectra in the GeV band are within the detection potential of IceCube. If the gamma-ray emission is dominated by the neutral pion decay flux, none of the flat-spectrum radio quasars are detectable with IceCube. If the primary high energy proton spectrum is very hard and/or neutrinos are produced in proton-photon, rather than proton-proton reactions, the upper limit on the neutrino flux imposed by the measured gamma-ray spectra is relaxed and gamma-ray observations impose only lower bounds on the neutrino flux. We investigate whether these lower bounds guarantee the detection of blazars with very hard neutrino spectra, expected in the latter type model. We show that all the "hadronic" models of activity of blazars are falsifiable with IceCube. Furthermore, we show that models with gamma-ray emission produced by the decay of neutral pions from proton-proton interactions can be readily distinguished from the models based on proton-gamma interactions and/or models predicting very hard high energy proton spectra via a study of the distribution of spectral indices of gamma-ray spectra of sources detected with IceCube.Comment: 10 pages, 5 figure

Quantum cosmology of the brane universe

We canonically quantize the dynamics of the brane universe embedded into the five-dimensional Schwarzschild-anti-deSitter bulk space-time. We show that in the brane-world settings the formulation of the quantum cosmology, including the problem of initial conditions, is conceptually more simple than in the 3+1-dimensional case. The Wheeler-deWitt equation is a finite-difference equation. It is exactly solvable in the case of a flat universe and we find the ground state of the system. The closed brane universe can be created as a result of decay of the bulk black hole.Comment: 4 pages, revte

Evidence for the Galactic contribution to the IceCube astrophysical neutrino flux

We show that the Galactic latitude distribution of IceCube astrophysical neutrino events with energies above 100~TeV is inconsistent with the isotropic model of the astrophysical neutrino flux. Namely, the Galactic latitude distribution of the events shows an excess at low latitudes |b|<10 degrees and a deficit at high Galactic latitude |b|> 50 degrees. We use Monte-Carlo simulations to show that the inconsistency of the isotropic signal model with the data is at > 3 sigma level, after the account of trial factors related to the choice of the low-energy threshold and Galactic latitude binning in our analysis.Comment: 4 pages, 2 figures, accepted to Astroparticle Physic