Monitoring the hard X-ray sky with SuperAGILE

¹ INAF – IASF Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy e-mail: marco.feroci@iasf-roma.inaf.it
² IKI, Moscow, Russia
³ ENEA Frascati, via Enrico Fermi 45, 00044 Frascati(RM), Italy
⁴ CNR, Istituto Metodologie Inorganiche e dei Plasmi, Area Ricerca Montelibretti, Italy
⁵ INAF – IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
⁶ Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
⁷ Dip. Fisica, Università di Trieste, via A. Valerio 2, 34127 Trieste, Italy
⁸ INFN Trieste, Padriciano 99, 34012 Trieste, Italy
⁹ Consorzio Interuniversitario Fisica Spaziale (CIFS), villa Gualino - v.le Settimio Severo 63, 10133 Torino, Italy
¹⁰ INFN Pavia, via Bassi 6, 27100 Pavia, Italy
¹¹ INAF – IASF Milano, via E. Bassini 15, 20133 Milano, Italy
¹² Dipartimento di Fisica, Universitá Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
¹³ ASI Science Data Center, ESRIN, 00044 Frascati(RM), Italy
¹⁴ Agenzia Spaziale Italiana, viale Liegi 26, 00198 Roma, Italy
¹⁵ Dipartimento di Fisica, Universitá di Torino, Torino, Italy
¹⁶ INFN Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁷ ENEA Bologna, via don Fiammelli 2, 40128 Bologna, Italy
¹⁸ INFN Roma 1, p.le Aldo Moro 2, 00185 Roma, Italy
¹⁹ Dip. Fisica, Università La Sapienza, p.le Aldo Moro 2, 00185 Roma, Italy
²⁰ Osservatorio Astronomico di Cagliari, loc. Poggio dei Pini, strada 54, 09012, Capoterra (CA), Italy
²¹ INAF – IASF Palermo, via Ugo La Malfa 153, 90146 Palermo, Italy

Received: 23 July 2009
Accepted: 19 October 2009

Abstract

Context. SuperAGILE is the hard X-ray monitor of the AGILE gamma ray mission, in orbit since 23 April 2007. It is an imaging experiment based on a set of four independent silicon strip detectors, equipped with one-dimensional coded masks, operating in the nominal energy range 18–60 keV.

Aims. The main goal of SuperAGILE is the observation of cosmic sources simultaneously with the main gamma-ray AGILE experiment, the Gamma Ray Imaging Detector (GRID). Given its ~steradian-wide field of view and its ~15 mCrab day-sensitivity, SuperAGILE is also well suited to the long-term monitoring of Galactic compact objects and the detection of bright transients.

Methods. The SuperAGILE detector properties and design allow for a 6 arcmin angular resolution in each of the two independent orthogonal projections of the celestial coordinates. Photon by photon data are continuously available by means of experiment telemetry, and are used to derive images and fluxes of individual sources, with integration times depending on the source intensity and position in the field of view.

Results. We report on the main scientific results achieved by SuperAGILE over its first two years in orbit, until April 2009. The scientific observations started in mid-July 2007, with the science verification phase, continuing during the complete AGILE Cycle 1 and the first ~half of Cycle 2. Despite the largely non-uniform sky coverage, due to the pointing strategy of the AGILE mission, a few tens of Galactic sources were monitored, sometimes for unprecedently long continuous periods, leading to the detection also of several bursts and outbursts. Approximately one gamma ray burst per month was detected and localized, allowing for prompt multiwavelength observations. A few extragalactic sources in bright states were occasionally detected as well. The light curves of sources measured by SuperAGILE are made publicly available on the web in almost real-time. To enable a proper scientific use of these, we provide the reader with the relevant scientific and technical background.