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A preliminary conceptual design is presented for a large ground array, LATTES, dedicated to the study of high energy gamma rays in the TeV region. LATTES, located in South America at high altitude, more than 5000 m a.s.l. is complementary to the Northern Hemisphere HAWC in terms of full sky coverage. It will perform a continuous high-sensitivity sky survey and therefore it is complementary to the Cherenkov telescopes HESS (and CTA in the future) in terms of experimental method. [ABSTRACT FROM AUTHOR]

The detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra. Often neither the emission nor the variability features of recently discovered VHE-FSRQs can be explained with the models developed so far for BL Lacs. Here we present the latest MAGIC results for all the three FSRQs known to be VHE emitters. We start with the 2010 discovery of PKS 1222+21 (z = 0.432), whose fast variability challenges simple one-zone emission models, requiring a more complicated scenario. Second, we present the latest results on 3C 279, the most distant AGN (z = 0.536) and first FSRQ detected in very high energies. It was observed in 2011, first during a monitoring campaign and later observations were triggered by a flare detected with Fermi-LAT. Finally, we report the 2012 detection of PKS 1510-089 (z = 0.36). This summary of VHE observations is the first step for a forthcoming study of multiwavelength spectral properties of these sources aimed at identifying the physical processes responsible for their emission and at explaining their observed variability. [ABSTRACT FROM AUTHOR]

The BL Lac objects Mrk 421 and Mrk 501 are objects of a large multi-year multiinstrument campaign including VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC and VERITAS, among other instruments and collaborations. This extensive radio to TeV gamma-ray dataset provides an unprecedented temporal and energy coverage, which allows for detailed studies of the evolution of their broad-band spectral energy distribution that cannot be achieved on any other BL Lac object. We report on the temporal variability and spectral correlations from the 4.5 months-long campaigns of 2009. We show that Mrk 421 and Mrk 501 have differences in their broad band variability, suggesting different mechanisms for the production of the high-energy emission. In addition, we also report on two events of high activity in very high energies (VHE) of Mrk 501 during May 2009, one of which was not accompanied by enhanced optical/X-ray activity but showed a clear correlation with an increase in the polarized optical flux and a rotation of the polarization vector. This is the first time that such type of flaring activity is observed in a high-synchrotron-peaked BL Lac object. [ABSTRACT FROM AUTHOR]

On March 28th 2011, the Burst Alert Telescope (BAT) on board the Swift satellite detected a new transient event at first hand classified as a Gamma Ray Burst (GRB). However, the unusual X-ray flaring activity observed from a few hours up to days after the onset of the event pointed to a different nature for it. The long lasting activity in the X-ray band and the complex light curve behaviour with significant source re-brightening observed both in the near-infrared (near-IR) and radio band suggested its interpretation as a tidal disruption event "switching on" a dormant black hole in the nucleus of the host galaxy and giving start to an outflowing jet of relativistic matter. MAGIC observations started nearly 2.5 days after the trigger time and were carried on for about 18 days, collecting a total of 28 hours of data during dark time at a mean zenith angle of 35° No clear evidence for emission above an energy threshold of ∼ 100 GeV was found. [ABSTRACT FROM AUTHOR]