A&A 490, 1151-1156 (2008)
DOI: 10.1051/0004-6361:200810562

Research Note

Gamma-ray burst detection with the AGILE mini-calorimeter

M. Marisaldi¹, C. Labanti¹, F. Fuschino¹, M. Galli², A. Argan³, G. Barbiellini^{4, 5}, M. Basset⁵, F. Boffelli^{6, 7}, A. Bulgarelli¹, P. Caraveo⁸, P. W. Cattaneo⁶, A. Chen^{8, 9}, V. Cocco³, E. Costa³, F. D'Ammando^{3, 10}, E. Del Monte³, G. De Paris³, G. Di Cocco¹, G. Di Persio³, I. Donnarumma³, Y. Evangelista³, M. Feroci³, A. Ferrari^{9, 11}, M. Fiorini⁸, L. Foggetta^{12, 13}, T. Froysland^{9, 10}, M. Frutti³, F. Gianotti¹, A. Giuliani⁸, I. Lapshov^{3, 14}, F. Lazzarotto³, F. Liello^{4, 5}, P. Lipari^{15, 16}, F. Longo^{4, 5}, M. Mastropietro¹⁷, E. Mattaini⁸, A. Mauri¹, F. Mauri⁶, S. Mereghetti⁸, E. Morelli¹, A. Morselli¹⁸, L. Pacciani³, A. Pellizzoni⁸, F. Perotti⁸, P. Picozza¹⁸, C. Pontoni⁵, G. Porrovecchio³, M. Prest^{12, 13}, G. Pucella³, M. Rapisarda¹⁹, A. Rappoldi⁶, E. Rossi¹, A. Rubini³, P. Soffitta³, M. Tavani^{3, 10}, A. Traci¹, M. Trifoglio¹, A. Trois³, E. Vallazza⁵, S. Vercellone⁸, V. Vittorini¹⁰, A. Zambra^{8, 9}, D. Zanello^{15, 16}, C. Pittori²⁰, F. Verrecchia²⁰, S. Cutini²⁰, D. Gasparrini²⁰, B. Preger²⁰, P. Santolamazza²⁰, P. Giommi²⁰, L. A. Antonelli²⁰, S. Colafrancesco²⁰, and L. Salotti<sup>21

1</sup>  INAF – IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
    e-mail: marisaldi@iasfbo.inaf.it
²  ENEA, via Martiri di Monte Sole 4, 40129 Bologna, Italy
³  INAF – IASF Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy
⁴  Dipartimento di Fisica Università di Trieste, via A. Valerio 2, 34127 Trieste, Italy
⁵  INFN Trieste, via A. Valerio 2, 34127 Trieste, Italy
⁶  INFN Pavia, via Bassi 6, 27100 Pavia, Italy
⁷  Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, via Bassi 6, 27100 Pavia, Italy
⁸  INAF – IASF Milano, via E. Bassini 15, 20133 Milano, Italy
⁹  CIFS Torino, via le Settimio Severo 63, 10133 Torino, Italy
¹⁰  Dipartimento di Fisica, Università Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
¹¹  Dipartimento di Fisica, Università di Torino, Torino, Italy
¹²  Dipartimento di Fisica, Università dell'Insubria, via Valleggio 11, 22100 Como, Italy
¹³  INFN Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
¹⁴  IKI, Moscow, Russia
¹⁵  INFN Roma “La Sapienza”, p.le Aldo Moro 2, 00185 Roma, Italy
¹⁶  Dipartimento di Fisica, Università La Sapienza, p.le Aldo Moro 2, 00185 Roma, Italy
¹⁷  CNR-IMIP, Area della Ricerca di Montelibretti, Roma, Italy
¹⁸  INFN Roma “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁹  ENEA Frascati, via Enrico Fermi 45, 00044 Frascati, Roma, Italy
²⁰  ASI Science Data Center, via E. Fermi 45, 00044 Frascati, Roma, Italy
²¹  Agenzia Spaziale Italiana, viale Liegi 26, 00198 Roma, Italy

Received 10 July 2008 / Accepted 13 August 2008

Abstract
Context. The mini-calorimeter (MCAL) instrument on-board the AGILE satellite is a non-imaging gamma-ray scintillation detector sensitive in the 300 keV–100 MeV energy range with a total on-axis geometrical area of 1400 cm². Gamma-ray bursts (GRBs) are one of the main scientific targets of the AGILE mission and the MCAL design as an independent self-triggering detector makes it a valuable all-sky monitor for GRBs. Furthermore MCAL is one of the very few operative instruments with microsecond timing capabilities in the MeV range.
Aims. In this paper the results of GRB detections with MCAL after one year of operation in space are presented and discussed.
Methods. A flexible trigger logic implemented in the AGILE payload data-handling unit allows the on-board detection of GRBs. For triggered events, energy and timing information are sent to telemetry on a photon-by-photon basis, so that energy and time binning are limited by counting statistics only. When the trigger logic is not active, GRBs can be detected offline in ratemeter data, although with worse energy and time resolution.
Results. Between the end of June 2007 and June 2008 MCAL detected 51 GRBs, with a detection rate of about 1 GRB/week, plus several other events at a few milliseconds timescales. Since February 2008 the on-board trigger logic has been fully active. Comparison of MCAL detected events and data provided by other space instruments confirms the sensitivity and effective area estimations. MCAL also joined the 3rd Inter-Planetary Network, to contribute to GRB localization by means of triangulation.

Key words: gamma rays: bursts -- instrumentation: detectors

© ESO 2008

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