1,027 research outputs found
Gamma-ray burst observations with new generation imaging atmospheric Cerenkov Telescopes in the FERMI era
After the launch and successful beginning of operations of the FERMI
satellite, the topics related to high-energy observations of gamma-ray bursts
have obtained a considerable attention by the scientific community.
Undoubtedly, the diagnostic power of high-energy observations in constraining
the emission processes and the physical conditions of gamma-ray burst is
relevant. We briefly discuss how gamma-ray burst observations with ground-based
imaging array Cerenkov telescopes, in the GeV-TeV range, can compete and
cooperate with FERMI observations, in the MeV-GeV range, to allow researchers
to obtain a more detailed and complete picture of the prompt and afterglow
phases of gamma-ray bursts.Comment: 9 pages, two figures. Proceeding for the 6th "Science with the New
Generation of High Energy Gamma-Ray Experiments" worksho
Blazar Flaring Patterns (B-FlaP): Classifying Blazar Candidates of Uncertain type in the third Fermi-LAT catalog by Artificial Neural Networks
The Fermi Large Area Telescope (LAT) is currently the most important facility
for investigating the GeV -ray sky. With Fermi LAT more than three
thousand -ray sources have been discovered so far. 1144 () of
the sources are active galaxies of the blazar class, and 573 () are
listed as Blazar Candidate of Uncertain type (BCU), or sources without a
conclusive classification. We use the Empirical Cumulative Distribution
Functions (ECDF) and the Artificial Neural Networks (ANN) for a fast method of
screening and classification for BCUs based on data collected at -ray
energies only, when rigorous multiwavelength analysis is not available. Based
on our method, we classify 342 BCUs as BL Lacs and 154 as FSRQs, while 77
objects remain uncertain. Moreover, radio analysis and direct observations in
ground-based optical observatories are used as counterparts to the statistical
classifications to validate the method. This approach is of interest because of
the increasing number of unclassified sources in Fermi catalogs and because
blazars and in particular their subclass High Synchrotron Peak (HSP) objects
are the main targets of atmospheric Cherenkov telescopes.Comment: 18 pages, 17 figures, accepted for publication on MNRA
Exploring Quantum Gravity with Very-High-Energy Gamma-Ray Instruments - Prospects and Limitations
Some models for quantum gravity (QG) violate Lorentz invariance and predict
an energy dependence of the speed of light, leading to a dispersion of
high-energy gamma-ray signals that travel over cosmological distances. Limits
on the dispersion from short-duration substructures observed in gamma-rays
emitted by gamma-ray bursts (GRBs) at cosmological distances have provided
interesting bounds on Lorentz invariance violation (LIV). Recent observations
of unprecedentedly fast flares in the very-high energy gamma-ray emission of
the active galactic nuclei (AGNs) Mkn 501 in 2005 and PKS 2155-304 in 2006
resulted in the most constraining limits on LIV from light-travel observations,
approaching the Planck mass scale, at which QG effects are assumed to become
important. I review the current status of LIV searches using GRBs and AGN flare
events, and discuss limitations of light-travel time analyses and prospects for
future instruments in the gamma-ray domain.Comment: 11 pages, 4 figures, proceedings of "Science with the New Generation
of High Energy Gamma-Ray Experiments", Euganean Spa Area, Padova: October
8-10, 200
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