118532651
AGILE Observations of Terrestrial Gamma-Ray Flashes
The AGILE satellite, operating since mid 2007 and primarily devoted to high-energy astrophysics,is one of the only three currently operating space instruments capable of detecting TerrestrialGamma-Ray Flashes (TGFs), together with RHESSI and Fermi-GBM. Thanks to the AGILEMini-Calorimeter instrument energy range extended up to 100MeV and its ﬂexible trigger logic onsub-millisecond time scales, AGILE is detecting more than 10 TGFs/month, adding a wealth ofobservations which pose severe constrains on production models. The main AGILE discoveries inTGF science during two and a half years of observations are the following: 1) the TGF spectrumextends well above 40 MeV, 2) the high energy tail of the TGF spectrum is harder than expectedand cannot be easily explained by previous theoretical models, 3) TGFs can be localized from spaceusing high-energy photons detected by the AGILE gamma-ray imaging detector. In this presenta-tion we will describe the characteristics of the 2.5-years AGILE TGF sample, focusing on the recentresults concerning the TGF high-energy spectral characteristics.I. INTRODUCTION
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The Mini-Calorimeter on-board AGILE: The first year in space
AGILE, the Italian space mission dedicated to gamma-ray and hard-X astrophysics, was successfully launched on 23rd April 2007 and is currently fully operative. The Mini-Calorimeter (MCAL) on-board the AGILE satellite is a scintillation detector made of 20 kg of segmented CsI(Tl) scintillator with photodiode readout with a total geometrical area of 1400 cm2. MCAL can work both as a slave of the AGILE Silicon tracker and as an independent detector for gamma-ray bursts (GRB) detection in the 300 keV - 100 MeV energy range. Despite its limited thickness, due to weight constraints, MCAL has proven to successfully self-trigger GRBs at MeV energies providing photon-by-photon data with less than 2 μs time resolution and almost all-sky detection capabilities. The instrument design and characteristics, as well as the in-flight performance after one year of operation in space and the scientific results obtained so far are reviewed and discussed.
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Test campaign of the mini-calorimeter for the AGILE satellite
The AGILE Mini-Calorimeter (MCAL, with total on-axis radiation length 1.5 X0) comprises 2 orthogonal planes each consisting of 16 CsI(Tl) bars. Its primary purpose is the energy determination of gamma-rays detected by the Gamma-Ray Imaging Detector (GRID) Tracker (energy range 30 MeV–50 GeV). In addition, the MCAL is capable of independently triggering and detecting gamma-ray bursts and other impulsive events in the energy range 0.25–250 MeV. A MCAL prototype, comprising 8 CsI(Tl) detector elements, was tested both with laboratory sources and with charged particles (p=1 GeV/c) during an AGILE Beam Test carried out in November 2000 at the CERN T11 beamline (East Hall, CERN PS). The test setup included a prototype of the electronic chain. A prototype of the digital data acquisition chain, which will be the baseline of the payload Electronic Ground Support Equipment, was also built and tested. We present the preliminary results of this test campaign dedicated to characterizing the detector unit and electronics.
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AGILE, a satellite for high energy γ-ray astrophysics: prospects for the Mini-Calorimeter
AGILE is an ASI (Italian Space Agency) small space mission for high energy astrophysics in the gamma ray energy range 30MeV–50GeV, and in the X-ray band 10keV–40keV. AGILE is composed of three scientific detectors: a TungstenSilicon Tracker, a CsI Mini-Calorimeter and a Silicon based X-ray detector (Super-Agile), moreover an anticoincidence system carries out background rejection. The satellite’s payload will have good imaging performances (with angular resolution of a few arc-minutes in the gamma ray band), good timing resolution and a large field of view (about 1/5 of the sky). AGILE detection principle is based on the pair production process that arises from the interaction between high energy photons and the Tungsten layers of the Silicon Tracker. The Silicon Tracker is designed to determine the direction of the incoming radiation, while the Mini-Calorimeter evaluates the energy of the interacting photons. The Mini-Calorimeter can also work as a stand-alone gamma ray detector in the energy range 250keV–250MeV, with no imaging capabilities, for the detection of transients and gamma ray burst events (in cooperation with Super-Agile) and for the evaluation of gamma ray background fluctuations. In this paper a description of the Mini-Calorimeter is done.
118592254
The agile alert system for gamma-ray transients
In recent years, a new generation of space missions has offered great opportunities for discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) on board the AGILE space mission. AGILE-GRID, sensitive in the energy range of 30?MeV-30?GeV, has detected many ?-ray transients of both galactic and extragalactic origin. This work presents the AGILE innovative approach to fast ?-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for ?-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, via e-mail, and via push notifications from an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in ?-ray astrophysics.
119226776
The AGILE Science Alert System
The AGILE Science Alert System has been developed to provide prompt processing of science data for detection and alerts on gamma-ray galactic and extra galactic transients, gamma-ray bursts, X-ray bursts and other transients in the hard X-rays. The system is distributed among the AGILE Data Center (ADC) of the Italian Space Agency (ASI), Frascati (Italy), and the AGILE Team Quick Look sites, located at INAF/IASF Bologna and INAF/IASF Roma. We present the Alert System architecture and performances in the first 2 years of operation of the AGILE payload.
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Comparison of the ATLAS and CMS discovery potential for the H -> gamma gamma channel at the LHC
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Collider physics: LHC
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Tagging of low-pt electrons from b decays with the ATLAS electromagnetic calorimeter
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Status of the ATLAS calorimetry simulation for the TP in DICE