The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved

We present numerical simulations of the axisymmetric accretion of a massive magnetized plasma torus on a rotating black hole. We use a realistic equation of state, which takes into account neutrino cooling and energy loss due to nucleus dissociations. We simulated various magnetic field configurations and torus models, both optically thick and thin for neutrinos. It is shown that the neutrino cooling does not significantly change either the structure of the accretion flow or the total energy release of the system. The calculations evidence heating of the wind surrounding the collapsar by the shock waves generated at the jet-wind border. This mechanism can give rise to a hot corona around the binary system like SS433.Angular momentum of the accreting matter defines the time scale of the accretion. Due to the absence of the magnetic dynamo in our calculations, the initial strength and topology of the magnetic field determines magnetization of the black hole, jet formation properties and the total energy yield. We estimated the total energy transformed to jets as 1.3 × 10 52 ergs which was sufficient to explain hypernova explosions like GRB 980425 or GRB 030329.

In this paper we consider dark matter particle annihilation in the gravitational field of black holes. We obtain exact distribution function of the infalling dark matter particles, and compute the resulting flux and spectra of gamma rays coming from the objects. It is shown that the dark matter density significantly increases near a black hole. Particle collision energy becomes very high affecting relative cross-sections of various annihilation channels. We also discuss possible experimental consequences of these effects.

The indirect detection of dark matter requires that dark matter annihilation products be discriminated from conventional astrophysical backgrounds. Here, we re-analyze GeV-band gamma-ray observations of the prominent Milky Way dwarf satellite galaxy Segue 1, for which the expected astrophysical background is minimal. We explicitly account for the angular extent of the conservatively expected gamma-ray signal and keep the uncertainty in the dark-matter profile external to the likelihood analysis of the gamma-ray data. PACS numbers: 95.35.+d; 95.85.Pw; 95.30.Cq

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