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El proyecto se ha centrado en evaluar las posibilidades de un sistema espectrométrico basado en monocromadores y cámaras CCD como detectores de luz, y en una placa Arduino como controlador automatizado del monocromador. El software necesario ha incluido la programación de una placa Arduino para controlar un motor paso a paso, y la creación de un programa para controlar todo el proceso de toma de datos (movimiento del motor, lectura de la cámara y registro de las medidas). Desde el punto de vista mecánico se ha resuelto la adaptación al monocromador, tanto de la cámara ccd como del motor de avance, mediante elementos sencillos disponibles en el laboratorio. El proyecto ha involucrado a dos estudiantes que han colaborado en esos diseños, como contribución a sus TFGs.

Esta tesis se enmarca en un contexto a caballo entre dos generaciones de telescopios Cherenkov terrestres de rayos gamma de muy alta energía. Los instrumentos actuales, en operación desde hace unos 15 años, se encuentran en un estado de gran madurez tanto operacionalmente como en términos de explotación científica. Los telescopios prototipos de la nueva generación que conformara el observatorio Cherenkov Telescope Array (CTA) se han construido recientemente y actualmente se encuentran en fase de puesta a punto, comenzando incluso a producir resultados científicos..., This thesis is framed in a context between two generations of ground-based Cherenkov telescopes for very high energy gamma rays (VHE, > 50 GeV). The current instruments, in operation for about 15 years, are in a shape of great maturity regarding operations and scientific exploitation. The prototype telescopes of the new generation that will be part of the Cherenkov Telescope Array (CTA) are currently in their commissioning phase. Some are even starting to produce scientific results...

Artículo firmado por 369 autores., Aims. Large-Sized Telescope 1 (LST-1), the prototype for the Large-Sized Telescope at the upcoming Cherenkov Telescope Array Observatory, is concluding its commissioning phase at the Observatorio del Roque de los Muchachos on the island of La Palma. The proximity of LST-1 to the two MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes makes it possible to carry out observations of the same gamma-ray events with both systems. Methods. We describe the joint LST-1+MAGIC analysis pipeline and used simultaneous Crab Nebula observations and Monte Carlo simulations to assess the performance of the three-telescope system. The addition of the LST-1 telescope allows for the recovery of events in which one of the MAGIC images is too dim to survive analysis quality cuts. Results. Thanks to the resulting increase in the collection area and stronger background rejection, we found a significant improvement in sensitivity, allowing for the detection of 30% weaker fluxes in the energy range between 200 GeV and 3 TeV. The spectrum of the Crab Nebula, reconstructed in the energy range between ∼60 GeV and ∼10 TeV, is in agreement with previous measurements., Spanish Ministry of Science and Innovation, Spanish Research State Agency (AEI), Centro de Excelencia Severo Ochoa program, Unidad de Excelencia María de Maeztu program, Juan de la Cierva Incorporación program, Programa Operativo FEDER 2014-2020, Consejería de Economía y Conocimiento de la Junta de Andalucía, PAIDI 2020, Universidad de Jaén, Programa Operativo de Crecimiento Inteligente FEDER 2014-2020, Consejería de Economía, Industria, Comercio y Conocimiento del Gobierno de Canarias, Generalitat de Catalunya-CERCA, European Union’s-Horizon 2020, Ramon y Cajal program, Next Generation EU, Spanish MCIN by State Secretariat for Education, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, Instituto de Física de Partículas y del Cosmos (IPARCOS), TRUE, pub

Firmado por 966 autores (MAGIC Collaboration), Neutrino emission from a flaring blazar Neutrinos interact only very weakly with matter, but giant detectors have succeeded in detecting small numbers of astrophysical neutrinos. Aside from a diffuse background, only two individual sources have been identified: the Sun and a nearby supernova in 1987. A multiteam collaboration detected a high-energy neutrino event whose arrival direction was consistent with a known blazar—a type of quasar with a relativistic jet oriented directly along our line of sight. The blazar, TXS 0506+056, was found to be undergoing a gamma-ray flare, prompting an extensive multiwavelength campaign. Motivated by this discovery, the IceCube collaboration examined lower-energy neutrinos detected over the previous several years, finding an excess emission at the location of the blazar. Thus, blazars are a source of astrophysical neutrinos., USA-U.S. National Science Foundation-Office of Polar Programs, National Science Foundation (NSF), Wisconsin Alumni Research Foundation, Center for High Throughput Computing (CHTC) at the University of Wisconsin-Madison, Open Science Grid (OSG), Extreme Science and Engineering Discovery Environment (XSEDE), United States Department of Energy (DOE), Particle astrophysics research computing center at the University of Maryland, Institute for Cyber-Enabled Research at Michigan State University, Astroparticle physics computational facility at Marquette University, Fonds de la Recherche Scientifique - FNRS, Belgium-Fund for Scientific Research (FWO), FWO Odysseus programme, Big Science programme, Belgian Federal Science Policy Office, Federal Ministry of Education & Research (BMBF), German Research Foundation (DFG), Helmholtz Alliance for Astroparticle Physics (HAP), Helmholtz Association, High Performance Computing cluster of the RWTH Aachen, Swedish Research Council, Swedish Polar Research Secretariat, Swedish National Infrastructure for Computing (SNIC), Knut & Alice Wallenberg Foundation, Australia-Australian Research Council, Natural Sciences and Engineering Research Council of Canada (NSERC), Calcul Quebec, Compute Ontario, Canada Foundation for Innovation CGIAR, Spanish Government, WestGrid, Compute Canada, Villum Fonden, Danmarks Grundforskningsfond, Royal Society of New Zealand Marsden Fund (NZ), Japan-Japan Society for Promotion of Science (JSPS), Institute for Global Prominent Research (IGPR) of Chiba University, National Research Foundation of Korea, Swiss National Science Foundation (SNSF), Istituto Nazionale Astrofisica (INAF), Centre National D'etudes Spatiales, United States Department of Energy (DOE), Federal Ministry of Education & Research (BMBF), Max Planck Society, Istituto Nazionale di Fisica Nucleare (INFN), Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT), Japan Society for the Promotion of Science, Unidad de Excelencia "Mara de Maeztu", Croatian Science Foundation (HrZZ) Project, University of Rijeka Project, German Research Foundation (DFG), Polish National Research Centre, Brazilian MCTIC, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ), Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ), Agenzia Spaziale Italiana (ASI), Gordon and Betty Moore Foundation, National Science Foundation (NSF), Mt. Cuba Astronomical Foundation, Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, Chinese Academy of Sciences South America Center for Astronomy (CASSACA), National Natural Science Foundation of China (NSFC), Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT), Ministry of Economy, Development, and Tourism's Millennium Science Initiative, Robert Martin Ayers Sciences Fund, Laboratory Directed Research and Development (LDRD) program of Los Alamos National Laboratory, Consejo Nacional de Ciencia y Tecnologia (CONACyT), Laboratorio Nacional HAWC de rayos gamma, L'Oreal Group, Red HAWC, Mexico, Universidad Nacional Autonoma de Mexico, VIEP-BUAP, PIFI, PROFOCIE, Royal Society, University of Wisconsin Alumni Research Foundation, Institute of Geophysics, Planetary Physics, and Signatures at Los Alamos National Laboratory, Polish Science Centre grant, Coordinacion de la Investigacion Cientfica de la Universidad Michoacana, Federal Ministry of Education & Research (BMBF), Max Planck Society Foundation CELLEX, German Research Foundation (DFG), Helmholtz Association, Alexander von Humboldt Foundation, French Ministry of Higher Education, Research and Innovation, Centre National de la Recherche Scientifique (CNRS/IN2P3), Centre National de la Recherche Scientifique (CNRS), French Atomic Energy Commission, UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC), National Science Centre, Poland, South African Department of Science and Technology, National Research Foundation, University of Namibia, National Commission on Research, Science AMP; Technology of Namibia (NCRST), Austrian Federal Ministry of Education, Science and Research, Austrian Science Fund (FWF), Australian Research Council, Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT), Japan Society for the Promotion of Science, University of Amsterdam, European Space Agency, French Atomic Energy Commission, Centre National D'etudes Spatiales, Helmholtz Association German Aerospace Centre (DLR), INTA, National Aeronautics & Space Administration (NASA), OSTC, European Union's Horizon 2020 Programme under the AHEAD project, German INTEGRAL, Optical and Near-infrared Astronomy Inter-University Cooperation Program, National Aeronautics and Space Administration Swift Guest Investigator Program, University of Leicester by the UK Space Agency, Smithsonian Institution, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

The Cherenkov Telescope Array (CTA) is a next-generation ground-based observatory for gamma-ray astronomy at very high energies. The Large-Sized Telescope prototype (LST-1) is located at the CTA-North site, on the Canary Island of La Palma. LSTs are designed to provide optimal performance in the lowest part of the energy range covered by CTA, down to ≃20 GeV. LST-1 started performing astronomical observations in 2019 November, during its commissioning phase, and it has been taking data ever since. We present the first LST-1 observations of the Crab Nebula, the standard candle of very-high-energy gamma-ray astronomy, and use them, together with simulations, to assess the performance of the telescope. LST-1 has reached the expected performance during its commissioning period—only a minor adjustment of the preexisting simulations was needed to match the telescope's behavior. The energy threshold at trigger level is around 20 GeV, rising to ≃30 GeV after data analysis. Performance parameters depend strongly on energy, and on the strength of the gamma-ray selection cuts in the analysis: angular resolution ranges from 0fdg12–0fdg40, and energy resolution from 15%–50%. Flux sensitivity is around 1.1% of the Crab Nebula flux above 250 GeV for a 50 hr observation (12% for 30 minutes). The spectral energy distribution (in the 0.03–30 TeV range) and the light curve obtained for the Crab Nebula agree with previous measurements, considering statistical and systematic uncertainties. A clear periodic signal is also detected from the pulsar at the center of the Nebula., Ministerio de Ciencia e Innovación (España), Comunidad de Madrid, Ministerio de Industria y Turismo (España), Fundación La Caixa, Junta de Andalucia, Gobierno de Canarias, Generalitat de Catalunya, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Artículo firmado por 183 autores. © ESO 2023. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish MINECO (FPA2017-87859-P, FPA2017-85668-P, FPA2017-82729-C6-2-R, FPA2017-82729-C6-6-R, FPA2017-82729-C6-5-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2017-87055-C2-2-P, FPA2017-90566-REDC); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-268/16.12.2019 and the Academy of Finland grant no. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia "Severo Ochoa" SEV-2016-0588 and SEV-2015-0548, the Unidad de Excelencia "María de Maeztu" MDM-2014-0369 and the "la Caixa" Foundation (fellowship LCF/BQ/PI18/11630012), by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energ, Context. Diffusive shock acceleration (DSA) is the most promising mechanism that accelerates Galactic cosmic rays (CRs) in the shocks of supernova remnants (SNRs). It is based on particles scattering caused by turbulence ahead and behind the shock. The turbulence upstream is supposedly generated by the CRs, but this process is not well understood. The dominant mechanism may depend on the evolutionary state of the shock and can be studied via the CRs escaping upstream into the interstellar medium (ISM). Aims. Previous observations of the gamma Cygni SNR showed a difference in morphology between GeV and TeV energies. Since this SNR has the right age and is at the evolutionary stage for a significant fraction of CRs to escape, our aim is to understand gamma-ray emission in the vicinity of the gamma Cygni SNR. Methods. We observed the region of the gamma Cygni SNR with the MAGIC Imaging Atmospheric Cherenkov telescopes between 2015 May and 2017 September recording 87 h of good-quality data. Additionally, we analysed Fermi-LAT data to study the energy dependence of the morphology as well as the energy spectrum in the GeV to TeV range. The energy spectra and morphology were compared against theoretical predictions, which include a detailed derivation of the CR escape process and their gamma-ray generation. Results. The MAGIC and Fermi-LAT data allowed us to identify three emission regions that can be associated with the SNR and that dominate at different energies. Our hadronic emission model accounts well for the morphology and energy spectrum of all source components. It constrains the time-dependence of the maximum energy of the CRs at the shock, the time-dependence of the level of turbulence, and the diffusion coefficient immediately outside the SNR shock. While in agreement with the standard picture of DSA, the time-dependence of the maximum energy was found to be steeper than predicted, and the level of turbulence was found to change over the lifetime of the SNR., German BMBF, German MPG, Italian INFN, Italian INAF, Swiss National Fund SNF, ERDF under the Spanish MINECO, Indian Department of Atomic Energy, Japanese ICRR, Japanese University of Tokyo, Japanese JSPS, Japanese MEXT, Bulgarian Ministry of Education and Science, National RI Roadmap Project, Academy of Finland, Centro de Excelencia "Severo Ochoa", Unidad de Excelencia "Maria de Maeztu", Fundación "la Caixa", Croatian Science Foundation (HrZZ) Project, University of Rijeka Project, DFG Collaborative Research Centers, Polish National Research Centre grant, Brazilian MCTIC, Brazilian CNPq, Brazilian FAPERJ, DOE, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

La astronomía de rayos “ ofrece una ventana a los fenómenos más energéticos del universo. Este campo de investigación ha sufrido un gran desarrollo a principios del siglo XXI gracias a telescopios como MAGIC (Major Atmospheric Gamma-rayImaging Cherenkov telescopes), los cuales han motivado la construcción del primer observatorio de rayos “ abierto a toda la comunidad científica, la Red de Telescopios Cherenkov CTA (Cherenkov Telescope Array).MAGIC es un sistema de dos telescopios Cherenkov de imagen atmosférica que opera en modo estereoscópico desde 2012. El telescopio LST-1 es el primer telescopio de gran tamaño LST (Large Size Telescope) del emplazamiento norte de CTA. Este se encuentra en su fase de puesta a punto desde octubre de 2018, habiendo tenido lugar su primera luz en diciembre del mismo año. Tanto los telescopios MAGIC como el LST-1 se encuentran instalados en el Observatorio del Roque delos Muchachos en la isla de La Palma, España. La presente tesis aborda fundamentalmente dos estudios. El primero es la caracterización del telescopio LST-1, y el segundo es el análisis de las observaciones ópticas realizadas con los píxeles centrales de los telescopios MAGIC.., Gamma-ray astronomy offers a window to the most energetic phenomena in the universe. This field of research has undergone a great development at the beginning of the 21th century thanks to telescopes such as MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov telescopes), which have motivated the construction of the first gamma-ray observatory open to the entire scientific community, the Cherenkov Telescope Array (CTA). MAGIC is a system of two Atmospheric Imaging Cherenkov telescopes operating in stereoscopic mode since 2012. The LST-1 telescope is the first Large-Size Telescope of the northern site of the CTA observatory. The LST-1 has began its commissioning phase in October 2018 and its first light took place in December of the same year. Both the MAGIC and LST-1 telescopes are installed on the Roque de los Muchachos Observatory on the Canary island of La Palma, Spain. This thesis mainly addresses two studies. The first is the characterization of the LST-1 telescope, and the second is the analysis of the optical observations made with the central pixels of the MAGIC telescopes...

© American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," and by the Polish MNiSzW Grant N N203 390834., The very high energy (VHE) gamma-ray source HESS J0632+057 has recently been confirmed to be a gamma-ray binary. The optical counterpart is the Be star MWC 148, and a compact object of unknown nature orbits it every similar to 321 days with a high eccentricity of similar to 0.8. We monitored HESS J0632+057 with the stereoscopic MAGIC telescopes from 2010 October to 2011 March and detected significant VHE gamma-ray emission during 2011 February, when the system exhibited an X-ray outburst. We find no gamma-ray signal in the other observation periods when the system did not show increased X-ray flux. Thus, HESS J0632+057 exhibits gamma-ray variability on timescales of the order of one to two months possibly linked to the X-ray outburst that takes place about 100 days after the periastron passage. Furthermore, our measurements provide for the first time the gamma-ray spectrum down to about 140 GeV and indicate no turnover of the spectrum at low energies. We compare the properties of HESS J0632+057 with the similar gamma-ray binary LS I +61 degrees 303 and discuss the possible origin of the multi-wavelength emission of the source., German BMBF, MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz G, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© Science. We thank the electronics division at the Max-Planck-Insitut, Munich, for their work in developing and producing the analog sum trigger system, especially O. Reimann, R. Maier, S. Tran, and T. Dettlaff. We also thank L. Stodolsky for comments. We acknowledge the Instituto de Astrofisica for providing all infrastructure on the Roque de los Muchachos in La Palma. The support of the German Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie and Max-Planck-Gesellschaft, the Italian INFN and INAF, the Swiss Schweizerische Nationalfonds, and Spanish Ministerio de Ciencia e Innovacion is acknowledged. This work was also supported by ETH research grant TH 34/043, by the Polish Ministertwo Nauki i Szkolnictwa Wyzszego grant N N203 390834, and by the Young Investigators Program of the Helmholtz Gemeinschaft., One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high- end region of a pulsar's spectrum would shed light on this question. By developing a new electronic trigger, we lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov (MAGIC) telescope to 25 giga-electron volts. In this configuration, we detected pulsed gamma-rays from the Crab pulsar that were greater than 25 giga-electron volts, revealing a relatively high cutoff energy in the phase- averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar- cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot- gap scenario., German Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie, Max-Planck-Gesellschaft, Italian INFN and INAF, Swiss Schweizerische Nationalfonds, Spanish Ministerio de Ciencia e Innovacion, ETH, Polish Ministertwo Nauki i Szkolnictwa Wyzszego, Young Investigators Program of the Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2013. We would like to thank the anonymous referee for constructive comments. The MAGIC Collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 127740 of the Academy of Finland, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0. The AGILE Mission is funded by the Italian Space Agency (ASI), with scientific and programmatic participation by the Italian Institute of Astrophysics (INAF) and the Italian Institute of Nuclear Physics (INFN). Research partially supported through the ASI grants no. I/089/06/2 and I/042/10/0. The Fermi-LAT Collaboration acknowledges support from a number of agencies and institutes for both development and the operation of the LAT as well as scientific data analysis. These include NASA and DOE in the United States, CEA/Irfu and IN2P3/CNRS in France, ASI and INFN in Italy, MEXT, KEK, and JAXA in Japan, and the K.A.Wallenberg Foundation, the Swedish Research Council and the National Space Board in Sweden. Additional support from INAF in Italy and CNES in France for science analysis during the operations phase is also gratefully acknowledged. We gratefully acknowledge the entire Swift team, the duty scientists and science planners for the dedicated support, making these observations possible. This research has made use of the XRT Data Analysis Software (XRTDAS) developed under the responsibility of the ASI Science Data Center (ASDC), Italy. This research is partly based on observations with the 100-m, Context. BL Lacertae objects are variable at all energy bands on time scales down to minutes. To construct and interpret their spectral energy distribution (SED), simultaneous broad-band observations are mandatory. Up to now, the number of objects studied during such campaigns is very limited and biased towards high flux states. Aims. We present the results of a dedicated multi-wavelength study of the high-frequency peaked BL Lacertae (HBL) object and known TeV emitter 1ES 2344+514 by means of a pre-organised campaign. Methods. The observations were conducted during simultaneous visibility windows of MAGIC and AGILE in late 2008. The measurements were complemented by Mets hovi, RATAN-600, KVA+Tuorla, Swift and VLBA pointings. Additional coverage was provided by the ongoing long-term F-GAMMA and MOJAVE programs, the OVRO 40-m and CrAO telescopes as well as the Fermi satellite. The obtained SEDs are modelled using a one-zone as well as a self-consistent two-zone synchrotron self-Compton model. Results. 1ES 2344+514 was found at very low flux states in both X-rays and very high energy gamma rays. Variability was detected in the low frequency radio and X-ray bands only, where for the latter a small flare was observed. The X-ray flare was possibly caused by shock acceleration characterised by similar cooling and acceleration time scales. MOJAVE VLBA monitoring reveals a static jet whose components are stable over time scales of eleven years, contrary to previous findings. There appears to be no significant correlation between the 15 GHz and R-band monitoring light curves. The observations presented here constitute the first multi-wavelength campaign on 1ES 2344+514 from radio to VHE energies and one of the few simultaneous SEDs during low activity states. The quasi-simultaneous Fermi-LAT data poses some challenges for SED modelling, but in general the SEDs are described well by both applied models. The resulting parameters are typical for TeV emitting HBLs. Consequently, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, CPAN, MultiDark, Academy of Finland, DFG Cluster of Excellence "Origin and Structure of the Universe", DFG Collaborative Research Centers, Polish MNiSzW, Italian Space Agency (ASI), Italian Institute of Astrophysics (INAF), Italian Institute of Nuclear Physics (INFN), ASI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2010. Supported by INFN Padova. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Polish MNiSzW Grant No. N203 390834, by the YIP of the Helmholtz Gemeinschaft, and by grant DO02-353 of the the Bulgarian National Science Fund., Context. Part of the very high energy gamma-ray radiation coming from extragalactic sources is absorbed through the pair production process on the extragalactic background light photons. Extragalactic magnetic fields alter the trajectories of these cascade pairs and, in turn, convert cosmic background photons to.-ray energies by inverse Compton scattering. These secondary photons can form an extended halo around bright VHE sources. Aims. We searched for an extended emission around the bright blazars Mrk 421 and Mrk 501 using the MAGIC telescope data. Methods. If extended emission is present, the angular distribution of reconstructed gamma-ray arrival directions around the source is broader than for a point-like source. In the analysis of a few tens of hours of observational data taken from Mrk 421 and Mrk 501 we used a newly developed method that provides better angular resolution. This method is based on the usage of multidimensional decision trees. Comparing the measured shapes of angular distributions with those expected from a point-like source one can detect or constrain possible extended emission around the source. We also studied the influence of different types of systematic errors on the shape of the distribution of reconstructed gamma-ray arrival directions for a point source. Results. We present upper limits for an extended emission calculated for both sources for various source extensions and emission profiles. We obtain upper limits on the extended emission around the Mrk 421 (Mrk 501) on the level of <5% (<4%) of the Crab Nebula flux above the energy threshold of 300 GeV. Using these results we discuss possible constraints on the extragalactic magnetic fields strength around a few times 10(-15) G., INFN Padova, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Polish MNiSzW, Helmholtz Gemeinschaft, Bulgarian National Science Fund, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the IAC for the excellent working conditions at the Observatory de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and the Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH 34/04 3 and the Polish MNiI grant 1P03D01028. This Letter is dedicated to the memory of Nicolaj Pavel., Recently, the HESS array has reported the detection of gamma-ray emission above a few hundred GeV from eight new sources located close to the Galactic plane. The source HESS J1834 - 087 is spatially coincident with the supernova remnant G23.3 - 0.3 (W41). Here we present MAGIC observations of this source, resulting in the detection of a differential gamma-ray flux consistent with a power law, described as dN(gamma)/(dA dt dE) = (3.7 +/- 0.6) x 10(-12) (E/TeV)(-2.5 +/- 0.2) cm(-2) s(-1) TeV-1. We confirm the extended character of this flux. We briefly discuss the observational technique used and the procedure implemented for the data analysis, and we put this detection in the perspective of the molecular environment found in the region of W41. We present (CO)-C-13 and (CO)-C-12 emission maps showing the existence of a massive molecular cloud in spatial superposition with the MAGIC detection., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish MNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. This research project has made use of data collected by NASA's RXTE. We thank the RXTE scheduling team for their help in coordinating the simultaneous observations. We also thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0., The acceleration of particles up to GeV or higher energies in microquasars has been the subject of considerable theoretical and observational efforts in the past few years. Sco X-1 is a microquasar from which evidence of highly energetic particles in the jet has been found when it is in the so-called Horizontal Branch (HB), a state when the radio and hard X-ray fluxes are higher and a powerful relativistic jet is present. Here we present the first very high energy gamma-ray observations of Sco X-1, obtained with the MAGIC telescopes. An analysis of the whole data set does not yield a significant signal, with 95% CL flux upper limits above 300 GeV at the level of 2.4 x 10(-12) cm(-2) s(-1). Simultaneous RXTE observations were conducted to provide the X-ray state of the source. A selection of the gamma-ray data obtained during the HB based on the X-ray colors did not yield a signal either, with an upper limit of 3.4 x 10(-12) cm(-2) s(-1). These upper limits place a constraint on the maximum TeV luminosity to non-thermal X-ray luminosity of L-VHE/L-ntX less than or similar to 0.02 that can be related to a maximum TeV luminosity to jet power ratio of L-VHE/L-j less than or similar to 10(-3). Our upper limits indicate that the underlying high-energy emission physics in Sco X-1 must be inherently different from that of the hitherto detected gamma-ray binaries., German BMBF, MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Spanish Consolider-Ingenio, Bulgarian NSF, Academy of Finland, Helmholtz Gemeinschaft, DFG, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the IAC for the excellent working conditions on the La Palma Observatory Roque de los Muchachos. We are grateful to the RXTE ASMteamfor their quick-look results. The support of the German BMBF andMPG, the Italian INFN, and the Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH-34/04-3 and by Polish grant MNiI 1P03D01028. In addition, the authors want to thank Deirdre Horan, Martin Tluczykont, and Fre´de´ric Piron for providing Mrk 501 data from WHIPPLE, HEGRA CT1, and HEGRA CT System and CAT, respectively, and for useful discussions., The blazar Mrk 501 was observed at energies above 0.10 TeV with the MAGIC Telescope from 2005 May through July. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude. Intranight flux variability with flux-doubling times down to 2 minutes was observed during the two most active nights, namely, June 30 and July 9. These are the fastest flux variations ever observed in Mrk 501. The similar to 20 minute long flare of July 9 showed an indication of a 4 +/- 1 minute time delay between the peaks of F(< 0.25 TeV) and F(> 1.2 TeV), which may indicate a progressive acceleration of electrons in the emitting plasma blob. The flux variability was quantified for several energy ranges and found to increase with the energy of the gamma-ray photons. The spectra hardened significantly with increasing flux, and during the two most active nights, a spectral peak was clearly detected at 0.43 +/- 0.06 and 0.25 +/- 0.07 TeV, respectively, for June 30 and July 9. There is no evidence of such a spectral feature for the other nights at energies down to 0.10 TeV, thus suggesting that the spectral peak is correlated with the source luminosity. These observed characteristics could be accommodated in a synchrotron self-Compton framework in which the increase in gamma-ray flux is produced by a freshly injected ( high energy) electron population., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish grant MNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. Supported by INFN Padova.We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN are gratefully acknowledged. This work was also supported by the Polish MNiSzW Grant N N203 390834, by the YIP of the Helmholtz Gemeinschaft, and by grant DO02-353 of the Bulgarian National Science Fund. S. T. is grateful for the support of the RATAN observations and the Russian Foundation for Basic Research, grant N08-02-00504-a., Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy. rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or transient ejections. Therefore, detecting such emission would improve the understanding of the jet physics. The imaging atmospheric Cherenkov telescope MAGIC observed Cygnus X-3 for about 70 hr between 2006 March and 2009 August in different X-ray/radio spectral states and also during a period of enhanced gamma-ray emission. MAGIC found no evidence for a VHE signal from the direction of the microquasar. An upper limit to the integral flux for energies higher than 250 GeV has been set to 2.2 x 10(-12) photons cm(-2) s(-1) (95% confidence level). This is the best limit so far to the VHE emission from this source. The non-detection of a VHE signal during the period of activity in the high-energy band sheds light on the location of the possible VHE radiation favoring the emission from the innermost region of the jets, where absorption is significant. The current and future generations of Cherenkov telescopes may detect a signal under precise spectral conditions., INFN Padova, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Polish MNiSzW, YIP of the Helmholtz Gemeinschaft, Bulgarian National Science Fund, RATAN observations, Russian Foundation for Basic Research, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 The Royal Astronomical Society. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF and the Spanish MICINN is gratefully acknowledged. This work was also supported by the CPANCSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the DFG Cluster of Excellence 'Origin and Structure of the Universe', by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3 and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0.The Fermi-LAT Collaboration acknowledges support from a number of agencies and institutes for both development and the operation of the LAT as well as scientific data analysis. These include NASA and DOE in the United States; CEA/Irfu and IN2P3/CNRS in France; ASI and INFN in Italy; MEXT, KEK and JAXA in Japan; and the K. A. Wallenberg Foundation, the Swedish Research Council and the National Space Board in Sweden. Additional support from INAF in Italy and CNES in France for science analysis during the operations phase is also gratefully acknowledged. This research is partially supported by NASA through the Fermi Guest Investigator Grants NNX09AT92G and NNX10AP22G. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester., Indications of a GeV component in the emission from gamma-ray bursts (GRBs) are known since the Energetic Gamma-Ray Experiment Telescope observations during the 1990s and they have been confirmed by the data of the Fermi satellite. These results have, however, shown that our understanding of GRB physics is still unsatisfactory. The new generation of Cherenkov observatories and in particular the MAGIC telescope, allow for the first time the possibility to extend the measurement of GRBs from several tens up to hundreds of GeV energy range. Both leptonic and hadronic processes have been suggested to explain the possible GeV/TeV counterpart of GRBs. Observations with ground-based telescopes of very high energy (VHE) photons (E > 30 GeV) from these sources are going to play a key role in discriminating among the different proposed emission mechanisms, which are barely distinguishable at lower energies. MAGIC telescope observations of the GRB 090102 (z = 1.547) field and Fermi Large Area Telescope data in the same time interval are analysed to derive upper limits of the GeV/TeV emission. We compare these results to the expected emissions evaluated for different processes in the framework of a relativistic blastwave model for the afterglow. Simultaneous upper limits with Fermi and a Cherenkov telescope have been derived for this GRB observation. The results we obtained are compatible with the expected emission although the difficulties in predicting the HE and VHE emission for the afterglow of this event makes it difficult to draw firmer conclusions. Nonetheless, MAGIC sensitivity in the energy range of overlap with space-based instruments (above about 40 GeV) is about one order of magnitude better with respect to Fermi. This makes evident the constraining power of ground-based observations and shows that the MAGIC telescope has reached the required performance to make possible GRB multiwavelength studies in the VHE range., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, DFG Cluster of Excellence 'Origin and Structure of the Universe', DFG Collaborative Research Centers, Polish MNiSzW, NASA through the Fermi Guest Investigator, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2011 Elsevier B.V. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged.This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0., 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., German BMBF, MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Collaborative Research Centers, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. Supported by INFN Padova.We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by the grant DO02-353 of the Bulgarian NSF, by the grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0.The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat a l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucleaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden.Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d' Etudes Spatiales in France., We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs; E > 100 GeV). Power-law fits of the individual years are compatible with a steady mean photon index Gamma = 4.27 +/- 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma-ray variability. We also performed a temporal analysis of (all available) simultaneous Fermi/Large Area Telescope data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at VHEs with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone synchrotron self-Compton model, which gives the main physical parameters governing the VHE emission in the blazar jet., INFN Padova, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Spanish Consolider-Ingenio 2010 programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excellence, DFG Collaborative Research Centers, Polish MNiSzW, Istituto Nazionale di Astrofisica in Italy, Centre National d' Etudes Spatiales in France, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2014 SPIE. Conference on Ground-Based and Airborne Telescopes V (2014. Montreal-Canada). Artículo firmado por 131 autores. We gratefully acknowledge financial support from the following agencies and organizations: Ministerio de Ciencia, Tecnología e Innovación Productiva (MinCyT), Comisión Nacional de Energía Atómica (CNEA), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina; State Committee of Science of Armenia, Armenia; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brasil; Croatian Science Foundation, Croatia; Ministry of Education, Youth and Sports, MEYS LE13012, 7AMB12AR013, Czech Republic; Ministry of Higher Education and Research, CNRSINSU and CNRS-IN2P3, CEA-Irfu, ANR, Regional Council Ile de France, Labex ENIGMASS, OSUG2020 and OCEVU, France; Max Planck Society, BMBF, DESY, Helmholtz Association, Germany; Department of Atomic Energy, Department of Science and Technology, India; Istituto Nazionale di Astrofisica (INAF), MIUR, Italy; Istituto Nazionale di Fisica Nucleare (INFN), Italy; ICRR, University of Tokyo, JSPS, Japan; Netherlands Research School for Astronomy (NOVA), Netherlands Organization for Scientific Research (NWO), Netherlands; The Bergen Research Foundation, Norway; Ministry of Science and Higher Education, the National Centre for Research and Development and the National Science Centre, Poland; MINECO support through the National R+D+I, CDTI funding plans and the CPAN and MultiDark Consolider-Ingenio 2010 programme, Spain; Swedish Research Council, Royal Swedish Academy of Sciences, Sweden; Swiss National Science Foundation (SNSF), Ernest Boninchi Foundation, Switzerland; Durham University, Leverhulme Trust, Liverpool University, University of Leicester, University of Oxford, Royal Society, Science and Technologies Facilities Council, UK; U.S. National Science, The Cherenkov Telescope Array (CTA) project aims to implement the world’s largest next generation of Very High Energy gamma-ray Imaging Atmospheric Cherenkov Telescopes devoted to the observation from a few tens of GeV to more than 100 TeV. To view the whole sky, two CTA sites are foreseen, one for each hemisphere. The sensitivity at the lowest energy range will be dominated by four Large Size Telescopes, LSTs, located at the center of each array and designed to achieve observations of high red-shift objects with the threshold energy of 20 GeV. The LST is optimized also for transient low energy sources, such as Gamma Ray Bursts (GRB), which require fast repositioning of the telescope. The overall design and the development status of the first LST telescope will be discussed., Unión Europea. FP7, Ministerio de Ciencia, Tecnología e Innovación Productiva (MinCyT), Argentina, Comisión Nacional de Energía Atómica (CNEA), Argentina, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina, State Committee of Science of Armenia, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brasil, Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Croatian Science Foundation, Ministry of Education, Czech Republic, Ministry of Higher Education and Research, Czech Republic, Ministry of Higher Education and Research, FRance, Regional Council Ile de France, Max Planck Society, Germany, BMBF, Germany, DESY, Germany, Helmholtz Association, Germany, Department of Atomic Energy, India, Department of Science and Technology, India, Istituto Nazionale di Astrofisica (INAF), Italy, MIUR, Italy, Istituto Nazionale di Fisica Nucleare (INFN), Italy, ICRR, Japan, University of Tokyo, JSPS, Japan, Netherlands Research School for Astronomy (NOVA), Netherlands Organization for Scientific Research (NWO), The Bergen Research Foundation, Norway, Ministry of Science and Higher Education, Poland, National Centre for Research and Development and the National Science Centre, Poland, MINECO support through the National R+D+I, CDTI, Spain, CPAN, Spain, Consolider-Ingenio 2010 programme, Spain, Swedish Research Council, Royal Swedish Academy of Sciences, Swiss National Science Foundation (SNSF), Ernest Boninchi Foundation, Switzerland, Durham University, UK, Leverhulme Trust, UK, Liverpool University, University of Leicester, University of Oxford, Royal Society, Science and Technologies Facilities Council, UK, U.S. National Science Foundation, U.S. Department of Energy, Argonne National Laboratory, USA, Barnard College, USA, University of California, University of Chicago, Columbia University, Georgia Institute of Technology, Institute for Nuclear and Particle Astrophysics (INPACMRPI program), USA, Iowa State University, Washington University McDonnell Center for the Space Sciences, USA, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MCI is gratefully acknowledged. This work was also supported by ETH research grant TH 34/043, by the Polish MNiSzW grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. We thank Dan Harris for providing preliminary results on Chandra observations., M87 is the only known nonblazar radio galaxy to emit very high energy (VHE) gamma rays. During a monitoring program of M87, a rapid flare in VHE gamma-rays was detected by the MAGIC telescope in early 2008. The flux was found to be variable above 350 GeV on a timescale as short as 1 day at a significance level of 5.6 sigma. The highest measured flux reached 15% of the Crab Nebula flux. We observed several substantial changes of the flux level during the 13 day observing period. The flux at lower energies (150-350 GeV), instead, is compatible with being constant. The energy spectrum can be described by a power law with a photon index of 2.30 +/- 0.11(stat) +/- 0.20(syst). The observed day-scale flux variability at VHE prefers the M87 core as source of the emission and implies that either the emission region is very compact (just a few Schwarzschild radii) or the Doppler factor of the emitting blob is rather large in the case of a nonexpanding emission region., German BMBF, German MPG, Italian INFN, Spanish MCI, ETH, Polish MNiSzW, YIP of the Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO, 2016. Artículo firmado por 155 autores. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2012-39502), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Centro de Excelencia Severo Ochoa SEV-2012- 0234, CPAN CSD2007-00042, and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 268740 of the Academy of Finland, by the Croatian Science Foundation (HrZZ) Project 09/176 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0., The Geminga pulsar, one of the brighest gamma-ray sources, is a promising candidate for emission of very-high-energy (VHE > 100 GeV) pulsed gamma rays. Also, detection of a large nebula have been claimed by water Cherenkov instruments. We performed deep observations of Geminga with the MAGIC telescopes, yielding 63 hours of good-quality data, and searched for emission from the pulsar and pulsar wind nebula. We did not find any significant detection, and derived 95% confidence level upper limits. The resulting upper limits of 5.3 × 10^(−13) TeV cm^(−2)s^(−1) for the Geminga pulsar and 3.5 × 10^(−12) TeV cm^(−2)s^(−1) for the surrounding nebula at 50 GeV are the most constraining ones obtained so far at VHE. To complement the VHE observations, we also analyzed 5 years of Fermi-LAT data from Geminga, finding that the sub-exponential cut-off is preferred over the exponential cut-off that has been typically used in the literature. We also find that, above 10 GeV, the gamma-ray spectra from Geminga can be described with a power law with index softer than 5. The extrapolation of the power-law Fermi-LAT pulsed spectra to VHE goes well below the MAGIC upper limits, indicating that the detection of pulsed emission from Geminga with the current generation of Cherenkov telescopes is very difficult., Ministerio de Economía y Competitividad (MINECO), German BMBF and MPG, Italian INFN and INAF, Swiss National Fund SNF, Japanese JSPS and MEXT, Centro de Excelencia Severo Ochoa, Spanish Consolider-Ingenio 2010 programme, Academy of Finland, Croatian Science Foundation (HrZZ), University of Rijeka, DFG Collaborative Research Centers, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© Elsevier Science. The MAGIC Collaboration thanks the IAC for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma and gratefully acknowledges the support of the German BMBF and MPG, the Italian INFN and the Spanish CICYT. This work was also supported by ETH Research Grant TH 34/04 3 and the Polish MNiI Grant 1P03D01028. The work of J.E. and N.E.M. was partially supported by the European Union through the Marie Curie Research and Training Network UniverseNet MRTN-CT-2006-035863, and that of D.V.N. by DOE grant DE-FG02-95ER40917., We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index similar or equal to 1 + (E/M-QGn)(n), n = 1, 2. Parametrizing the delay between gamma-rays of different energies as Delta t = +/-tau E-1 or Delta t = +/-tau E-q(2), we find tau(1) = (0.030 +/- 0.012) s/GeV at the 2.5-sigma level, and tau(q) = (3.71 +/- 2.57) x 10(-6) s/GeV2, respectively. We use these results to establish lower limits M-QG1 > 0.21 X 10(18) GeV and M-QG2 > 0.26 x 10(11) GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect. (C) 2008 Elsevier B.V. All rights reserved., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH Research Grant TH, Polish MNiI, European Union through the Marie Curie Research and Training Network UniverseNet, DOE, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO. We would like to thank the anonymous referee as well as the Associate Editor M. Walmsley for fruitful comments and suggestions. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma., 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, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excelle, DFG Collaborative Research Centers, Polish MNiSzW, National Science Foundation, MultiDark, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 program, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," and by the Polish MNiSzW Grant N N203 390834., We report on the observation of the region around supernova remnant G65.1+0.6 with the stand-alone MAGIC-I telescope. This region hosts the two bright GeV gamma-ray sources 1FGL J1954.3+2836 and 1FGL J1958.6+2845. They are identified as GeV pulsars and both have a possible counterpart detected at about 35 TeV by the Milagro observatory. MAGIC collected 25.5 hr of good quality data and found no significant emission in the range around 1 TeV. We therefore report differential flux upper limits, assuming the emission to be point-like (<= 0 degrees.1) or within a radius of 0 degrees.3. In the point-like scenario, the flux limits around 1 TeV are at the level of 3% and 2% of the Crab Nebula flux for the two sources, respectively. This implies that the Milagro emission is either extended over a much larger area than our point-spread function or it must be peaked at energies beyond 1 TeV, resulting in a photon index harder than 2.2 in the TeV band., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Spanish Consolider-Ingenio, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We are grateful for discussions with Kouichi Hirotani.We also would like to thank the IAC for the excellent working conditions at the ORM in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Spanish CICYT, ETH research grant TH 34/04 3, and the PolishMNiI grant 1P03D01028 is gratefully acknowledged., We report about very high energy (VHE) gamma-ray observations of the Crab Nebula with the MAGIC telescope. The gamma-ray flux from the nebula was measured between 60 GeV and 9 TeV. The energy spectrum can be described by a curved power law dF/dE = f(0)(E/300 GeV)([a+b log)((E/300 GeV)])(10) with a flux normalization f(0) of (6.0 +/- 0.2(stat)) x 10(-10) cm(-2) s(-1) TeV-1, a = 2.31 +/- 0.06(stat), and b = 0.26 +/- 0.07(stat). The peak in the spectral energy distribution is estimated at 77 +/- 35 GeV. Within the observation time and the experimental resolution of the telescope, the gamma-ray emission is steady and pointlike. The emission's center of gravity coincides with the position of the pulsar. Pulsed gamma-ray emission from the pulsar could not be detected. We constrain the cutoff energy of the pulsed spectrum to be less than 27 GeV, assuming that the differential energy spectrum has an exponential cutoff. For a superexponential shape, the cutoff energy can be as high as 60 GeV., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, PolishMNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie programme, the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, grant DO02-353 of the Bulgarian NSF, grant 127740 of the Academy of Finland, the YIP of the Helmholtz Gemeinschaft, the DFG Cluster of Excellence "Origin and Structure of the Universe", the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0 and the Formosa Program between the National Science Council in Taiwan and the Consejo Superior de Investigaciones Cientificas in Spain administered through the grant number NSC100-2923-M-007-001-MY3., 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., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG, DFG Collaborative Research Centers, Polish MNiSzW, National Science Council in Taiwan, Consejo Superior de Investigaciones Científicas in Spain, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO. We thank the anonymous referee for valuable comments. We would like to thank Andrey Kravtsov for the useful comments on the paper. We would like to thank the Instituto de Astrof´ısica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish ConsoliderIngenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0. C.P. gratefully acknowledges financial support of the Klaus Tschira Foundation. A.P. acknowledges NSF grant AST 0908480 for support., 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, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, CPAN project of Spanish Consolider-Ingenio programme, MultiDark project of Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG, DFG Collaborative Research Centers, Polish MNiSzW, Klaus Tschira Foundation, NSF, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© Elsevier. The authors wish to thank the financial support given by the CICYT (project FPA2003-9543-C02-01) which made this work possible, and the IAC for providing excellent working conditions in La Palma. The MAGIC telescope is mainly supported by BMBF (Germany), CICYT (Spain), INFN and MUR (Italy). We also acknowledge Razmik Mirzoyan, Manel Martinez, Eva Domingo and the IFAE engineering team, Alex Gonzalez and Isaac Martinez for their valuable help in the installation. Also, we thank Juan Cortina and Emma On˜ a-Wilhelmi of the IFAE group for their suggestions and help in modifying the PMT base., The MAGIC telescope has been designed for the observation of Cherenkov light generated in Extensive Air Showers initiated by cosmic particles. However, its 17m diameter mirror and optical design makes the telescope suitable for direct optical observations as well. In this paper, we report about the development of a system based on the use of a dedicated photo-multiplier (PMT) for optical observations. This PMT is installed in the centre of the MAGIC camera (the so-called central pixel). An electro-to-optical system has been developed in order to transmit the PMT output signal by an optical fibre to the counting room, where it is digitized and stored for off-line analysis. The performance of the system using the optical pulsation of the Crab nebula as calibration source is presented. The time required for a 5 sigma detection of the Crab pulsar in the optical band is less than 20s. The central pixel will be mainly used to perform simultaneous observations of the Crab pulsar both in the optical and gamma-ray regimes. It will also allow for periodic testing of the precision of the MAGIC timing system using the Crab rotational optical pulses as a very precise timing reference. (c) 2008 Elsevier B.V. All rights reserved., CICYT, German BMBF, INFN, MUR, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Supported by INFN Padova., Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well-described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be Gamma = 1.65 +/- 0.02 and S(1) (keV) = 215 +/- 5 nJy in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum (Gamma = 1.50 +/- 0.01) with a nearly doubled X-ray flux density of S(1 keV) = 404(-5)(+6) nJy Moreover, significant hard X-ray signals were detected up to similar to 27 keV. In cooperation with Suzaku, simultaneous radio, optical, and very-high-energy gamma-ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 +/- 0.46 Jy and 8.93 +/- 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2-3 than those in the quiescent state (1.73 +/- 0.26 Jy and 3.03 +/- 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable gamma-ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff at around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons., INFN Padova, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German Bundesministerium für Bildung und Forschung and Max-Planck-Gesellschaft, the Italian Istituto Nazionale de Fisica Nucleare, and the Spanish Comisión Interministerial de Ciencias y Tecnología is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/04 3 and grant 1P03D01028 from the Polish Ministerstwo Nauki i Informatyzacji., The MAGIC collaboration has studied the high-frequency-peaked BL Lac object 1ES 1218 + 30.4, at a redshift z = 0.182, using the MAGIC imaging air Cerenkov telescope located on the Canary Island of La Palma. A gamma-ray signal was observed with 6.4 sigma significance. The differential energy spectrum for an energy threshold of 120 GeV can be fitted by a simple power law, yielding F-E = (8.1 +/- 2.1) x 10(-7)[E/(250 GeV)](-3.0 +/- 0.4) TeV-1 F (E) m(-2) s(-1). During the 6 days of observation in 2005 January, no time variability on timescales of days was found within the statistical errors. The observed integral flux above 350 GeV is nearly a factor of 2 below the upper limit reported by the Whipple collaboration in 2003., German Bundesministerium für Bildung und Forschung, Max-Planck-Gesellschaft, Italian Istituto Nazionale de Fisica Nucleare, Spanish Comisión Interministerial de Ciencias y Tecnología, ETH, Polish Ministerstwo Nauki i Informatyzacji, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© Elsevier Science.We thank Jens Zimmermann for fruitful discussions about the RF method and for comparisons of the RF method with a Neural Net approach., The paper describes an application of the tree classification method Random Forest (RF), as used in the analysis of data from the ground-based gamma telescope MAGIC. In such telescopes, cosmic gamma-rays are observed and have to be discriminated against a dominating background of hadronic cosmic-ray particles. We describe the application of RF for this gamma/hadron separation. The RF method often shows superior performance in comparison with traditional semi-empirical techniques. Critical issues of the method and its implementation are discussed. An application of the RF method for estimation of a continuous parameter from related variables, rather than discrete classes, is also discussed. (C) 2008 Published by Elsevier B.V., Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO, 2012. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESSMAGIC /2010/0. We thank R. Bühler, L. Costamante and B. Giebels for providing H.E.S.S. and multi-wavelength data. We also thank the anonymous referee for useful comments which helped to improve the manuscript., Context. The high frequency peaked BL Lac PKS 2155-304 with a redshift of z = 0.116 was discovered in 1997 in the very high energy (VHE, E > 100 GeV) gamma-ray range by the University of Durham Mark VI gamma-ray Cherenkov telescope in Australia with a flux corresponding to 20% of the Crab Nebula flux. It was later observed and detected with high significance by the southern Cherenkov observatory H. E. S. S. establishing this source as the best studied southern TeV blazar. Detection from the northern hemisphere is difficult due to challenging observation conditions under large zenith angles. In July 2006, the H. E. S. S. collaboration reported an extraordinary outburst of VHE gamma-emission. During the outburst, the VHE gamma-ray emission was found to be variable on the time scales of minutes and with a mean flux of similar to 7 times the flux observed from the Crab Nebula. Follow-up observations with the MAGIC-I standalone Cherenkov telescope were triggered by this extraordinary outburst and PKS 2155-304 was observed between 28 July to 2 August 2006 for 15 h at large zenith angles. Aims. We studied the behavior of the source after its extraordinary flare. Furthermore, we developed an analysis method in order to analyze these data taken under large zenith angles. Methods. Here we present an enhanced analysis method for data taken at high zenith angles. We developed improved methods for event selection that led to a better background suppression. Results. The quality of the results presented here is superior to the results presented previously for this data set: detection of the source on a higher significance level and a lower analysis threshold. The averaged energy spectrum we derived has a spectral index of (-3.5 +/- 0.2) above 400 GeV, which is in good agreement with the spectral shape measured by H. E. S. S. during the major flare on MJD 53 944. Furthermore, we present the spectral energy distribution modeling of PKS 2155-304. With our observations we increased t, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Spanish Consolider-Ingenio 2010 programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excellence “Origin and Structure of the Universe”, DFG Collaborative Research Centers, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the anonymous referee for valuable comments. We thank Volker Springel for the important work on CR implementation into the GADGET code and comments on the paper. We also thank Yoel Rephaeli for the useful comments on the paper and Eugene Churazov for providing us XMM-Newton X-ray contours. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MICINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant N N203 390834, by the YIP of the Helmholtz Gemeinschaft, and by grant DO02-353 of the Bulgarian National Science Fund., The Perseus galaxy cluster was observed by the MAGIC Cherenkov telescope for a total effective time of 24.4 hr during 2008 November and December. The resulting upper limits on the gamma-ray emission above 100 GeV are in the range of 4.6-7.5 x 10(-12) cm(-2) s(-1) for spectral indices from -1.5 to -2.5, thereby constraining the emission produced by cosmic rays, dark matter annihilations, and the central radio galaxy NGC 1275. Results are compatible with cosmological cluster simulations for the cosmic-ray-induced gamma-ray emission, constraining the average cosmic ray-to-thermal pressure to < 4% for the cluster core region (< 8% for the entire cluster)., German BMBF, German MPG, Italian INFN, Spanish MICINN, Polish MNiSzW, Helmholtz Gemeinschaft, Bulgarian National Science Fund, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2015. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the ERDF funds under the Spanish MINECO is gratefully acknowledged. This work was also supported by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 127740 of the Academy of Finland, by the Croatian Science Foundation (HrZZ) Project 09/176, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzWgrant 745/N-HESS-MAGIC/2010/0. J.C. acknowledges support by the Spanish Ministerio de Economía y Competividad (MINECO) under grant AYA2010-18080. The authors thank the anonymous referee for a thorough review and a very constructive list of remarks that helped improving the quality and clarity of this manuscript., Context. MWC 656 has recently been established as the first observationally detected high-mass X-ray binary system containing a Be star and a black hole (BH). The system has been associated with a gamma-ray flaring event detected by the AGILE satellite in July 2010. Aims. Our aim is to evaluate if the MWC 656 gamma-ray emission extends to very high energy (VHE > 100 GeV) gamma rays. Methods. We have observed MWC 656 with the MAGIC telescopes for ∼23 hours during two observation periods: between May and June 2012 and June 2013. During the last period, observations were performed contemporaneously with X-ray (XMM-Newton) and optical (STELLA) instruments. Results. We have not detected the MWC 656 binary system at TeV energies with the MAGIC Telescopes in either of the two campaigns carried out. Upper limits (ULs) to the integral flux above 300 GeV have been set, as well as differential ULs at a level of ∼ 5% of the Crab Nebula flux. The results obtained from the MAGIC observations do not support persistent emission of very high energy gamma rays from this system at a level of 2.4% the Crab flux., German BMBF, German MPG, Italian INFN, Spanish MINECO, Academy of Finland, by the Croatian Science Foundation (HrZZ), DFG Collaborative Research Centers, Polish MNiSzWgrant, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2009. We thank the anonymous referee for comments. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN and Spanish MCINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration., Aims. We report upper limits to the very high energy flux (E > 100 GeV) of the flat spectrum radio quasar 3C454.3 (z = 0.859) derived by the Cherenkov telescope MAGIC during the high states of July/August and November/December 2007. We compare the upper limits derived in both time slots with the available quasi-simultaneous MeV-GeV data from the AGILE gamma-ray satellite and interpret the observational results in the context of leptonic emission models. Methods. The source was observed with the MAGIC telescope during the active phases of July-August 2007 and November-December 2007 and the data were analyzed with the MAGIC standard analysis tools. For the periods around the ends of July and November, characterized by the most complete multifrequency coverage, we constructed the spectral energy distributions using our data together with nearly simultaneous multifrequency (optical, UV, X-ray and GeV) data. Results. Only upper limits can be derived from the MAGIC data. The upper limits, once corrected for the expected absorption by the extragalactic background light, together with nearly simultaneous multifrequency data, allow us to constrain the spectral energy distribution of 3C 454.3. The data are consistent with the model expectations based on inverse Compton scattering of the ambient photons from the broad line region by relativistic electrons, which robustly predicts a sharp cut-off above 20-30 GeV., German BMBF, MPG, Italian INFN, Spanish MCINN, Polish MNiSzW, ETH, Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MCINN is gratefully acknowledged. This work was also supported by ETH Research grant TH 34/043, by the Polish MNiSzW grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. Finally, we thank the anonymous referees for useful comments., We present the result of the observation of the ultrafaint dwarf galaxy Willman 1 performed with the 17 m MAGIC telescope during 15.5 hr between March and May 2008. No significant gamma-ray emission was found. We derived upper limits of the order of 10(-12) ph cm(-2) s(-1) on the integral flux above 100 GeV, which we compare with predictions from several of the established neutralino benchmark models in the mSUGRA parameter space. The neutralino annihilation spectra are defined after including the recently quantified contribution of internal bremsstrahlung from the virtual sparticles that mediate the annihilation. Flux boost factors of three orders of magnitude are required even in the most optimistic scenario to match our upper limits. However, uncertainties in the dark matter intrinsic and extrinsic properties (e.g., presence of substructures, Sommerfeld effect) may significantly reduce this gap., ETH Research, Polish MNiSzW, German BMBF, MPG, Italian INFN, Spanish MCINN, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 Elsevier B.V. Artículo firmado por 167 autores. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO, and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Centro de Excelencia Severo Ochoa SEV-2012-0234, CPAN CSD2007-00042, and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 268740 of the Academy of Finland, by the Croatian Science Foundation (HrZZ) Project 09/176 and the University of Rijeka Project 13.12.1.3.02, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0. We thank the two anonymous referees for thorough reading and helpful comments on the manuscript., The MAGIC telescopes are two Imaging Atmospheric Cherenkov Telescopes (IACTs) located on the Canary island of La Palma. The telescopes are designed to measure Cherenkov light from air showers initiated by gamma rays in the energy regime from around 50 GeV to more than 50 TeV. The two telescopes were built in 2004 and 2009, respectively, with different cameras, triggers and readout systems. In the years 2011-2012 the MAGIC collaboration undertook a major upgrade to make the stereoscopic system uniform, improving its overall performance and easing its maintenance. In particular, the camera, the receivers and the trigger of the first telescope were replaced and the readout of the two telescopes was upgraded. This paper (Part I) describes the details of the upgrade as well as the basic performance parameters of MAGIC such as raw data treatment, linearity in the electronic chain and sources of noise. In Part II, we describe the physics performance of the upgraded system., German BMBF and MPG, Italian INFN and INAF, Swiss National Fund SNF, ERDF under the Spanish MINECO, Japanese JSPS, MEXT, Centro de Excelencia Severo Ochoa, Spanish Consolider-Ingenio 2010 programme, Academy of Finland, Croatian Science Foundation (HrZZ), University of Rijeka, the DFG Collaborative Research Centers, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the IAC for the excellent working conditions at the ORM.We also thank the support given by the Chandra telescope and the MERLIN interferometer through their Discretionary Director Time programs, as well as the observing time provided by the e-EVN, and the NRAO VLA and VLBA interferometers via Target of Opportunity proposals.We are grateful to the anonymous referee for the useful comments and suggestions which have improved this paper greatly. The support of the German BMBF and MPG, the Italian INFN, the Spanish MEC, the ETH esearch Grant TH34/04 3 and the PolishMNiIGrant 1P03D01028 is gratefully acknowledged. This research is partially supported by the Ramón y Cajal programme of the Spanish MEC. The European VLBI Network (EVN) is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils. e-VLBI developments in Europe are supported by EC DG-INFSO funded Communication Network Development project, EXPReS, contract 02662. MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC. This work has benefited from research funding from the European Community’s sixth Framework Programme under RadioNet R113CT 2003 5058187. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc., We present the results of the first multiwavelength observing campaign on the high-mass X-ray binary LS I + 61 303, comprising observations at the TeV regime with the MAGIC telescope, along with X-ray observations with Chandra, and radio interferometric observations with the MERLIN, EVN, and VLBA arrays, in 2006 October and November. From our MERLIN observations, we can exclude the existence of large-scale (similar to 100 mas) persistent radio jets. Our 5.0 GHz VLBA observations display morphological similarities to previous 8.4 GHz VLBA observations carried out at the same orbital phase, suggesting a high level of periodicity and stability in the processes behind the radio emission. This makes it unlikely that variability of the radio emission is due to the interaction of an outflow with variable wind clumps. If the radio emission is produced by a milliarcsecond scale jet, it should also show a stable, periodic behavior. It is then difficult to reconcile the absence of a large-scale jet (similar to 100 mas) in our observations with the evidence of a persistent relativistic jet reported previously. We find a possible hint of temporal correlation between the X-ray and TeV emissions and evidence for radio/TeV noncorrelation, which points to the existence of one population of particles producing the radio emission and a different one producing the X-ray and TeV emissions. Finally, we present a quasi-simultaneous energy spectrum including radio, X-ray, and TeV bands., German BMBF, German MPG, Italian INFN, Spanish MEC, ETH Research Grant, PolishMNiIGrant, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. Supported by INFN Padova, Italy.We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence "Origin and Structure of the Universe," and by the Polish MNiSzW Grant N N203 390834. The Fermi data were obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), provided by NASA's Goddard Space Flight Center., We report new observations of the intermediate-frequency peaked BL Lacertae object 3C 66A with the MAGIC telescopes. The data sample we use were taken in 2009 December and 2010 January, and comprises 2.3 hr of good quality data in stereoscopic mode. In this period, we find a significant signal from the direction of the blazar 3C 66A. The new MAGIC stereoscopic system is shown to play an essential role for the separation between 3C 66A and the nearby radio galaxy 3C 66B, which is at a distance of only 6'. The derived integral flux above 100 GeV is 8.3% of the Crab Nebula flux and the energy spectrum is reproduced by a power law of photon index 3.64 +/- 0.39(stat) +/- 0.25(sys). Within errors, this is compatible with the one derived by VERITAS in 2009. From the spectra corrected for absorption by the extragalactic background light, we only find small differences between the four models that we applied, and constrain the redshift of the blazar to z < 0.68., INFN Padova, Italy, German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, Spanish Consolider-Ingenio 2010 programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excellence "Origin and Structure of the Universe", Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We acknowledge A. Reimer for providing us the theoretical curves depicted in Figure 1. We also would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, Italian INFN, and Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH 34/043, by the Polish MNiSzW grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft., High-energy gamma-ray emission is theoretically expected to arise in tight binary star systems (with high mass loss and high-velocity winds), although the evidence of this relationship has proven to be elusive so far. Here we present the first bounds on this putative emission from isolated Wolf-Rayet (WR) star binaries, WR 147 and WR 146, obtained from observations with the MAGIC telescope., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish MNiSzW, YIP of the Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Origin and Structure of the Universe,” and by the Polish MNiSzW Grant N N203 390834, We present very high energy (E > 100 GeV) gamma-ray observations of the gamma-ray binary system LS I +61 degrees 303 obtained with the MAGIC stereo system between 2009 October and 2010 January. We detect a 6.3 sigma gamma-ray signal above 400 GeV in the combined data set. The integral flux above an energy of 300 GeV is F(E > 300 GeV) = (1.4 +/- 0.3(stat) +/- 0.4(syst)) x 10(-12) cm(-2) s(-1), which corresponds to about 1.3% of the Crab Nebula flux in the same energy range. The orbit-averaged flux of LS I +61 degrees 303 in the orbital phase interval 0.6-0.7, where a maximum of the TeV flux is expected, is lower by almost an order of magnitude compared to our previous measurements between 2005 September and 2008 January. This provides evidence for a new low-flux state in LS I +61 degrees 303. We find that the change to the low-flux state cannot be solely explained by an increase of photon-photon absorption around the compact star., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excellence "Origin and Structure of the Universe", CPAN, Bulgarian NSF, Academy of Finland, Polish MNiSzW, MultiDark, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2009. We would like to thank the IAC for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN and the Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH-34/04-3 and by Polish grant MNiI 1P03D01028., The active galactic nucleus PG1553+113 was observed by the MAGIC telescope in July 2006 during a multiwavelength campaign, in which telescopes in the optical, X-ray, and very high energies participated. Although the MAGIC data were affected by strong atmospheric absorption (calima), they were analyzed after applying a correction. In 8.5 h, a signal was detected with a significance of 5.0 sigma. The integral flux above 150 GeV was (2.6 +/- 0.9) x 10(-7) ph s(-1) m(-2). By fitting the differential energy spectrum with a power law, a spectral index of -4.1 +/- 0.3 was obtained., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish grant, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2010. We would like to thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN and Spanish MICINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft. We also thank Yizhong Fan for continuous theoretical support. Lorenzo Amati, Cristiano Guidorzi, Alessandra Galli, Daniele Malesani and Ruben Salvaterra for useful discussions. We finally remark the very constructive report from the referee which helped to substantially improve the paper., Context. Gamma-ray bursts are cosmological sources emitting radiation from the gamma-rays to the radio band. Substantial observational efforts have been devoted to the study of gamma-ray bursts during the prompt phase, i.e. the initial burst of high-energy radiation, and during the long-lasting afterglows. In spite of many successes in interpreting these phenomena, there are still several open key questions about the fundamental emission processes, their energetics and the environment. Aims. Independently of specific gamma-ray burst theoretical recipes, spectra in the GeV/TeV range are predicted to be remarkably simple, being satisfactorily modeled with power-laws, and therefore offer a very valuable tool to probe the extragalactic background light distribution. Furthermore, the simple detection of a component at very-high energies, i.e. at similar to 100GeV, would solve the ambiguity about the importance of various possible emission processes, which provide barely distinguishable scenarios at lower energies. Methods. We used the results of the MAGIC telescope observation of the moderate resdhift (z similar to 0.76) GRB 080430 at energies above about 80 GeV, to evaluate the perspective for late-afterglow observations with ground based GeV/TeV telescopes. Results. We obtained an upper limit of F(95% CL) = 5.5 x 10(-11) erg cm(-2) s(-1) for the very-high energy emission of GRB 080430, which cannot set further constraints on the theoretical scenarios proposed for this object also due to the difficulties in modeling the low-energy afterglow. Nonetheless, our observations show that Cherenkov telescopes have already reached the required sensitivity to detect the GeV/TeV emission of GRBs at moderate redshift (z less than or similar to 0.8), provided the observations are carried out at early times, close to the onset of their afterglow phase., German BMBF, German MPG, Italian INFN, Spanish MICINN, ETH, Polish MNiSzW, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We acknowledge the use of public data from the Swift and RXTE data archives. The Metsahovi team acknowledges the support from the Academy of Finland for the observing projects (numbers 212656, 210338, among others). This research has made use of data obtained from the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA), projects BK150, BP143, and BL149 (MOJAVE). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The St. Petersburg University team acknowledges support from the Russian RFBR foundation via grant 09-02-00092. AZT-24 observations are made within an agreement between Pulkovo, Rome and Teramo observatories. This research is partly based on observations with the 100 m telescope of the MPIfR (Max-Planck-Institut fur Radioastronomie) at Effelsberg, as well as with the Medicina and Noto telescopes operated by INAF-Istituto di Radioastronomia. RATAN-600 observations were supported in part by the RFBR grant 08-02-00545 and the OVRO 40 m program was funded in part by NASA (NNX08AW31G) and the NSF (AST-0808050). The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. M. Villata organized the optical-to-radio observations by GASP-WEBT as the president of the collaboration. The Abastumani Observatory team acknowledges financial support by the Georgian National Science Foundation through grant GNSF/ST07/4-180., We report on the gamma-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) gamma-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index Gamma = 1.78 +/- 0.02 and average photon flux F(>0.3 GeV) = (7.23 +/- 0.16) x 10(-8) ph cm(-2) s(-1). Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor similar to 3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in gamma-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site., Academy of Finland, Russian RFBR foundation, RFBR, NASA, NSF, Smithsonian Institution, Academia Sinica, Georgian National Science Foundation, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the IAC for the excellent working conditions at the Observatory de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and the Spanish CICYT is gratefully acknowledged. This work was also supported by ETH research grant TH 34/04 3 and the Polish MNiI grant 1P03D01028., We report the detection of a new source of very high energy (VHE; E-gamma >= 100 GeV) gamma- ray emission located close to the Galactic plane, MAGIC J0616 + 225, which is spatially coincident with supernova remnant IC 443. The observations were carried out with the MAGIC telescope in the periods 2005 December-2006 January and 2006 December-2007 January. Here we present results from this source, leading to a VHE gamma-ray signal with a statistical significance of 5.7 sigma in the 2006/2007 data and a measured differential gamma-ray flux consistent with a power law, described as dN(gamma)/(dA dt dE) = (1.0 +/- 0.2) x 10(-11) (E/0.4 TeV)(-3.1 +/- 0.3) cm(-2) s(-1) TeV-1. We briefly discuss the observational technique used and the procedure implemented for the data analysis. The results are placed in the context of the multiwavelength emission and the molecular environment found in the region of IC 443., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish MNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We would like to thank the IAC for the excellent working conditions at the ORM in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Spanish CICYT, ETH research grant TH 34/04 3, and the Polish MNiI grant 1P03D01028 is gratefully acknowledged. We also thank H. D. and M. F. Aller, at the University of Michigan Radio Observatory, for providing us with the UMRAO data., The high-frequency-peaked BL Lacertae object Markarian 180 (Mrk 180) was observed to have an optical outburst in 2006 March, triggering a Target of Opportunity observation with the MAGIC telescope. The source was observed for 12.4 hr, and very high energy gamma-ray emission was detected with a significance of 5.5 sigma. An integral flux above 200 GeV of (2.3 +/- 0.7) x 10(-11) cm(-2) s(-1) was measured, corresponding to 11% of the Crab Nebula flux. A rather soft spectrum with a photon index of has been determined. No significant flux -3.3 x 0.7 variation was found., German BMBF, German MPG, Italian INFN, Spanish CICYT, ETH, Polish MNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and the Spanish MICINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant NN203 390834, and by theYIP of the Helmholtz Gemeinschaft. We thank D.A. Smith and the Nancay Radio Observatory operated by the Paris Observatory (associated with the French CNRS) for the ephemerides of PSR J0218+4232, and also S. M. Ransom (NRAO) for the ephemerides of PSR J0205+6449., The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions., German BMBF, German MPG, Italian INFN, Spanish MICINN, ETH Research Grant, Polish MNiSzW, YIP of the Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, and Spanish MCINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft., The MAGIC telescope observed the region around the distant blazar 3C 66A for 54.2 hr in 2007 August-December. The observations resulted in the discovery of a gamma-ray source centered at celestial coordinates R.A. = 2(h)23(m)12(s) and decl.=43 degrees 0'.7 (MAGIC J0223+430), coinciding with the nearby radio galaxy 3C 66B. A possible association of the excess with the blazar 3C 66A is discussed. The energy spectrum of MAGIC J0223+430 follows a power law with a normalization of (1.7 +/- 0.3(stat) +/- 0.6(syst)) x 10(-11) TeV(-1) cm(-2) s(-1) at 300 GeV and a photon index Gamma = -3.10 +/- 0.31(stat) +/- 0.2(syst)., German BMBF, German MPG, Italian INFN, Spanish MCINN, ETH, Polish MNiSzW, YIP of the Helmholtz Gemeinschaft, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© The American Astronomical Society. We thank Neil Gehrels and the whole Swift team for the ToO observations and the Suzaku team for their assistance in the analysis of our Suzaku data.We thank the IAC for the excellent working conditions at the ORM. We acknowledge financial support from the ASI-INAF contract I /088/06/0. TheMAGIC project is supported by the German BMBF and MPG, the Italian INFN, the Spanish CICYT, the Swiss ETH Research Grant TH34/04, and the Polish MNiI Grant 1P03D01028., We present the results from a multiwavelength campaign on the TeV blazar 1ES 1959+650, performed in 2006 May. Data from the optical, UV, soft- and hard-X-ray, and very high energy (VHE) gamma-ray ( E > 100 GeV) bands were obtained with the Suzaku and Swift satellites, the MAGIC telescope, and other ground-based facilities. The source spectral energy distribution (SED), derived from Suzaku and MAGIC observations at the end of 2006 May, shows the usual double hump shape, with the synchrotron peak at a higher flux level than the Compton peak. With respect to historical values, during our campaign the source exhibited a relatively high state in X-rays and optical, while in the VHE band it was at one of the lowest level so far recorded. We also monitored the source for flux spectral variability on a time window of 10 days in the optical-UVand X-ray bands and 7 days in the VHE band. The source varies more in the X-ray than in the optical band, with the 2-10 keV X-ray flux varying by a factor of similar to 2. The synchrotron peak is located in the X-ray band and moves to higher energies as the source gets brighter, with the X-ray fluxes above it varying more rapidly than the X-ray fluxes at lower energies. The variability behavior observed in the X-ray band cannot be produced by emitting regions varying independently and suggests instead some sort of "standing shock'' scenario. The overall SED is well represented by a homogeneous one-zone synchrotron inverse Compton emission model, from which we derive physical parameters that are typical of high-energy peaked blazars., ASI-INAF, German BMBF, German MPG, Italian INFN, Spanish CICYT, Swiss ETH, Polish MNiI, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2012. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant DO02-353 of the Bulgarian NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Excellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0. The Metsähovi team acknowledges the support from the Academy of Finland to our observing projects (numbers 212656, 210338, 121148, and others). The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Instituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Instituto Nazionale di Astrofisica in Italy and the Centre Nati, Context. We present the discovery of very high energy (VHE, E > 100 GeV) gamma-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to gamma-rays. Aims. We study the VHE gamma-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths. Methods. Triggered by an optical outburst, MAGIC observed the source in 2011 January-February for 20.3 h. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Metsahovi radio telescope. We also present the analysis of older MAGIC data taken in 2010. Results. The MAGIC observations of 1ES 1215+303 carried out in 2011 January-February resulted in the first detection of the source at VHE with a statistical significance of 9.4 sigma. Simultaneously, the source was observed in a high optical and X-ray state. In 2010 the source was observed in a lower state in optical, X-ray, and VHE, while the GeV gamma-ray flux and the radio flux were comparable in 2010 and 2011. The spectral energy distribution obtained with the 2011 data can be modeled with a simple one zone SSC model, but it requires extreme values for the Doppler factor or the electron energy distribution., German BMBF, German MPG, Italian INFN, Swiss National Fund SNF, Spanish MICINN, Marie Curie program, CPAN project of the Spanish Consolider-Ingenio programme, MultiDark project of the Spanish Consolider-Ingenio programme, Bulgarian NSF, Academy of Finland, YIP of the Helmholtz Gemeinschaft, DFG Cluster of Excellence "Origin and Structure of the Universe", DFG Collaborative Research Centers, Polish MNiSzW grant, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub