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Galaxy clusters are being assembled today in the most energetic phase of hierarchical structure formation which manifests itself in powerful shocks that contribute to a substantial energy density of cosmic rays (CRs). Hence, clusters are expected to be luminous gamma-ray emitters since they also act as energy reservoirs for additional CR sources, such as active galactic nuclei and supernova-driven galactic winds. To detect the gamma-ray emission from CR interactions with the ambient cluster gas, we conducted the deepest to date observational campaign targeting a galaxy cluster at very high-energy gamma-rays and observed the Perseus cluster with the MAGIC Cherenkov telescopes for a total of similar to 85 h of effective observing time. This campaign resulted in the detection of the central radio galaxy NGC 1275 at energies E > 100 GeV with a very steep energy spectrum. Here, we restrict our analysis to energies E > 630 GeV and detect no significant gamma-ray excess. This constrains the average CR-to-thermal pressure ratio to be less than or similar to 1-2%, depending on assumptions and the model for CR emission. Comparing these gamma-ray upper limits to models inferred from cosmological cluster simulations that include CRs constrains the maximum CR acceleration efficiency at structure formation shocks to be <50%. Alternatively, this may argue for non-negligible CR transport processes such as CR streaming and diffusion into the outer cluster regions. Finally, we derive lower limits on the magnetic field distribution assuming that the Perseus radio mini-halo is generated by secondary electrons/positrons that are created in hadronic CR interactions: assuming a spectrum of E-2.2 around TeV energies as implied by cluster simulations, we limit the central magnetic field to be > 4-9 mu G, depending on the rate of decline of the magnetic field strength toward larger radii. This range is well below field strengths inferred from Faraday rotation measurements in cool cores. Henc

The W51 complex hosts the supernova remnant W51C which is known to interact with the molecular clouds in the star forming region W51B. In addition, a possible pulsar wind nebula CXO J192318.5+140305 was found likely associated with the supernova remnant. Gamma-ray emission from this region was discovered by Fermi/LAT (between 0.2 and 50 GeV) and H. E. S. S. (>1 TeV). The spatial distribution of the events could not be used to pinpoint the location of the emission among the pulsar wind nebula, the supernova remnant shell and/or the molecular cloud. However, the modeling of the spectral energy distribution presented by the Fermi/LAT collaboration suggests a hadronic emission mechanism. The possibility that the gamma-ray emission from such an object is of hadronic origin can contribute to solvingthe long-standing problem of the contribution to galactic cosmic rays by supernova remnants. Aims. Our aim is to determine the morphology of the very-high-energy gamma-ray emission of W51 and measure its spectral properties. Methods. We performed observations of the W51 complex with the MAGIC telescopes for more than 50 h. The energy range accessible with MAGIC extends from 50 GeV to several TeV, allowing for the first spectral measurement at these energies. In addition, the good angular resolution in the medium (few hundred GeV) to high (above 1 TeV) energies allow us to perform morphological studies. We look for underlying structures by means of detailed morphological studies. Multi-wavelength data from this source have been sampled to model the emission with both leptonic and hadronic processes. Results. We detect an extended emission of very-high-energy gamma rays, with a significance of 11 standard deviations. We extend the spectrum from the highest Fermi/LAT energies to similar to 5 TeV and find that it follows a single power law with an index of 2.58 +/- 0.07(stat) +/- 0.22(syst). The main part of the emission coincides with the shocked cloud region, while we find a feat

The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) x 10(9) M-circle dot) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of tau(rise)(d) = (1.69 +/- 0.30) days and tau(decay)(d) = (0.611 +/- 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (similar to day), peak fluxes (Phi(>0.35 TeV) similar or equal to (1-3) x 10(-11) photons cm(-2) s(-1)), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken similar to 3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core (flux increased by factor similar to 2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubb

MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma. Since autumn 2009 both telescopes have been working together in stereoscopic mode, providing a significant improvement with respect to the previous single-telescope observations. We use observations of the Crab Nebula taken at low zenith angles to assess the performance of the MAGIC stereo system. The trigger threshold of the MAGIC telescopes is 50 - 60 GeV. Advanced stereo analysis techniques allow MAGIC to achieve a sensitivity as good as (0.76 +/- 0.03)% of the Crab Nebula flux in 50 h of observations above 290 GeV. The angular resolution at those energies is better than similar to 0.07 degrees. We also perform a detailed study of possible systematic effects which may influence the analysis of the data taken with the MAGIC telescopes. (C) 2011 Elsevier B.V. All rights reserved.

We use 73 h of stereoscopic data taken with the MAGIC telescopes to investigate the very high-energy (VHE) gamma-ray emission of the Crab pulsar. Our data show a highly significant pulsed signal in the energy range from 50 to 400 GeV in both the main pulse (P1) and the interpulse (P2) phase regions. We provide the widest spectra to date of the VHE components of both peaks, and these spectra extend to the energy range of satellite-borne observatories. The good resolution and background rejection of the stereoscopic MAGIC system allows us to cross-check the correctness of each spectral point of the pulsar by comparison with the corresponding (strong and well-known) Crab nebula flux. The spectra of both P1 and P2 are compatible with power laws with photon indices of 4.0 +/- 0.8 (P1) and 3.42 +/- 0.26 (P2), respectively, and the ratio P1/P2 between the photon counts of the two pulses is 0.54 +/- 0.12. The VHE emission can be understood as an additional component produced by the inverse Compton scattering of secondary and tertiary e(+/-) pairs on IR-UV photons.

Las imágenes de todo el cielo han demostrado ser una potente herramienta para determinar la calidad astronómica del cielo, y su uso se está extendiendo hoy en día tanto ubicaciones de futuros observatorios como en los ya existentes. El observatorio astronómico de la Universidad Complutense de Madrid (Observatorio UCM) es un observatorio urbano situado en el Campus Universitario que constituye un excepcional laboratorio para estudiar efectos de la actividad humana como la contaminación lumínica, la contaminación del aire y la concentración de aerosoles en la calidad astronómica del cielo. Para estudiar estos efectos, instalamos hace dos años el monitor astronómico AstMon-UCM. Durante el pasado año hemos desarrollado un paquete de programas de código abierto para automatizar el análisis de las imágenes de cámaras de todo el cielo, caracterizando la calidad del cielo para observaciones astronómicas a través de parámetros como el Brillo de Fondo de Cielo o la Extinción Atmosférica. Este paquete se ha aplicado tanto en imágenes de AstMon-UCM como de otros monitores de todo el cielo y cámaras digitales equipadas con objetivos ojo de pez, comparando los resultados obtenidos con datos provenientes de fotómetros SQM. Estas herramientas abren la puerta a numerosas y excitantes posibilidades.[ABSTRACT] All-Sky images have proven to be a powerful tool for determining the astronomical sky quality, nowadays their use is spreading both for planned and existing observatories. The Universidad Complutense de Madrid’s astronomical observatory (Observatorio UCM) is an urban observatory located at Campus of the University. It provides an excepcional laboratory to study the effects of human activity such as light pollution, air pollutants and aerosol concentration in the astronomical quality of the sky. In order to study these effects, we set up two years ago the all-sky monitor AstMon-UCM. During the last year we have been developing an open-source software package to automate the analy

Astrophysics is the branch of Astronomy (from the Greek "the laws of the stars") that studies the physics of the Universe. Nearly all our information for the study of distant cosmic objects in our Universe comes from the observation of electromagnetic waves and particles that reach the Earth. In the history of Astronomy, all the discoveries have been accompanied hand-in-hand by technological developments sometimes to improve our perception of the Universe and at other times to open new as yet unexplored windows. This Thesis intends to introduce the reader to one of the windows, opened in the recent past, since 1989, to the most violent phenomena of the Universe that take place at high energies and which has given rise to a new branch in Astronomy: High Energy Astronomy. The new window of observation has improved thanks to the development of new instrumentation, which needs calibration and monitoring tasks and which sometimes has to face up to new intrinsic difficulties. This work is based on the ground-based telescopes used to observe the Universe at high energies, in particular the MAGIC Telescope. Specifically, this Thesis covers the MAGIC telescope monitoring, its detection capabilities, the new challenges opened up by the effect of the Earth's magnetic field at low energies and the first results for the physics of some members of a particular kind of star, called pulsars. It describes in detail the efforts to monitor the behaviour of the telescope, which has to be stable enough to guarantee a good understanding of the results. Finally, this work presents the upper limits of two of the most promising pulsar gamma-ray candidates: PSR J0205+6449 and PSR J0218+4232.

Astrophysics is the branch of Astronomy (from the Greek "the laws of the stars") that studies the physics of the Universe. Nearly all our information for the study of distant cosmic objects in our Universe comes from the observation of electromagnetic waves and particles that reach the Earth. In the history of Astronomy, all the discoveries have been accompanied hand-in-hand by technological developments sometimes to improve our perception of the Universe and at other times to open new as yet unexplored windows. This Thesis intends to introduce the reader to one of the windows, opened in the recent past, since 1989, to the most violent phenomena of the Universe that take place at high energies and which has given rise to a new branch in Astronomy: High Energy Astronomy. The new window of observation has improved thanks to the development of new instrumentation, which needs calibration and monitoring tasks and which sometimes has to face up to new intrinsic difficulties. This work is based on the ground-based telescopes used to observe the Universe at high energies, in particular the MAGIC Telescope. Specifically, this Thesis covers the MAGIC telescope monitoring, its detection capabilities, the new challenges opened up by the effect of the Earth's magnetic field at low energies and the first results for the physics of some members of a particular kind of star, called pulsars. It describes in detail the efforts to monitor the behaviour of the telescope, which has to be stable enough to guarantee a good understanding of the results. Finally, this work presents the upper limits of two of the most promising pulsar gamma-ray candidates: PSR J0205+6449 and PSR J0218+4232.