[en] The EIDOS gamma-ray Imager has been proposed in response to the INTEGRAL Announcement of Opportunity issued on the 1. July 1994. Through a combination of different detector technologies, it provides high-quality imaging of celestial gamma-ray sources in the energy range between 20 keV and 10 MeV combined with high continuum sensitivity, high sensitivity to both narrow and broadened gamma-ray lines and good spectral resolution. The instrument also offers sensitive polarimetry of gamma-ray sources. The scientific objects of this instrument are vast and range from studies of the most compact Galactic objects through to the structure of the Galaxy and on to active galactic nuclei. Careful attention has been taken to ensure that the design of the EIDOS Imager is compatible with the mission requirement for a Galactic Plane Survey

[en] The SAX (Satellite per Astronomia X) mission is a major joint program of the Italian Space Agency (ASI) and the Netherlands Agency for Space Programs (NIVR). In the framework of past and future X-ray missions the SAX satellite, launched in April 1996, stand out for its very wide spectral coverage from 0.1 to 200 keV with well-balanced performances of the low-energy and high-energy instrumentation. The sensitivity of the scientific payload will allow the exploitation of the full band of SAX also for weak sources (1/20 of 3C273) opening new perspectives in the study of spectral shape and variability of several classes of objects. In this paper the authors describe the main aspects of the mission, the instruments, the scientific objectives and operations

[en] The high-energy astrophysics community in Italy is involved in several major international projects, which concern the study, design, development, and operation of telescopes in the field of high-energy astronomy and cosmic ray physics. A number of balloon- or space-borne missions, with important Italian participation, are presently either operative or recently ended (BeppoSAX, XMM-Newton, HETE-2), just launched (INTErnational Gamma-Ray Astrophysics Laboratory, in October 2002), under development (Claire, Swift, AGILE, Gamma-Ray Large Area Telescope), or under study (XEUS, Constellation-X, Lobster, Medium Energy Gamma-ray Astronomy, MAX, Gamma Air Watch, Extreme Universe Space Observatory, Interstellar/Intergalactic Medium and gamma ray Burst Observatory Spectroscopy Survey, Hard X-ray Modulation Telescope). The techniques, detection systems, and design concepts chosen for these telescopes are different and depend upon their operative energy range and scientific objectives. This work will focus on the current status of these instruments and on the possible future developments

[en] The relative contribution to the gamma-ray background of different types of sources, namely Seyfert galaxies, quasars, BL Lac objects, radio galaxies, and field galaxies is estimated under the hypothesis that the cosmic diffuse flux is the result of a superposition of many unresolved galaxies. The gamma-ray data indicate that the Seyfert volume emissivity matches that of the diffuse background at few hundred keV and exceeds it at higher energies by as much as a factor of about four. While normal galaxies contribute less than 0.1 percent, BL Lac objects, quasars and radio galaxies may contribute as much as 5-10 percent each, even without significant evolution. In this paper, different ways of reconciling the observational data on active galaxies with the measured diffuse background level are explored. 17 references

No abstract available

[en] The Seyfert 1 galaxy MCG-6-30-15 (z≅0.008, L_B∼4x10⁴⁴ erg/s) was observed by XMM-Newton on 2000 June 11-12, for a total of 95 ks. The source shows high flux and spectral variability down to timescales of t ∼300 s. This work presents the results of the time-resolved spectral analysis of the brightest flare (a factor of 2 variation in ∼1000 s) which occurred during the observation. The analysis of such flare indicates: 1) a softening of the X-ray spectrum in phase with the flux, and 2) a soft-to-hard time lag of about ∼ 600 s. A strong and complex Fe-Kαemission feature is detected ∼ 3000 s after the flare. The same feature was not present before and during the flare. This may indicate that the Fe line was produced as a consequence of the flare. The present analysis allows the formulation of a different hypothesis for the physical mechanisms responsible for the X-ray emission

[en] In order to make a significant step forward in the low energy γ-ray astronomy, a telescope with high sensitivity and fine angular resolution with imaging capability down to a few tenths of a degree is required. The coded aperture mask used together with a position sensitive detector make possible the achievement of these capabilities. Laboratory tests of the position sensitive sodium iodide detection system and the expected performance of the coded imaging mask derived from simulations are presented

[en] IBIS (Imager on Board the Integral Satellite) is dedicated to fine imaging in the gamma-ray energy range. The imaging performances are achieved using a coded mask aperture system in conjunction with a position sensitive detector made of two layers. This multilayer structure of position sensitive detectors allows the application of Compton kinematics for background rejection. In order to determine the efficacy of this method, a reduced scale prototype of the instrument has been developed. The detection apparatus is composed by two scintillation matrices of 5x5 elements in the same configuration of IBIS. The upper layer pixel size is 13 x 13 x 3 mm whereas the lower layer pixel size is 13 x 13 x 30 mm. An hybrid technology electronics has been setup for signals shaping and discrimination, moreover a custom software package has been developed for system calibration and data analysis. The equipment has been tested at different energies by employing radioactive sources. The results are presented and compared, when possible, with Montecarlo simulations

[en] In this paper, the authors review the gamma-ray data on the active galactic nuclei observed to date and we draw some conclusions as to their general characteristics. A number of possible gamma-ray production mechanisms are discussed in light of these measurements. In particular, the relevance to gamma-ray emission of jet structures is presented. The active galaxies contribution to the cosmic diffuse background at gamma-ray energies is estimated. Future prospects for extragalactic gamma-ray astronomy are outlined in view of the coming generation of gamma-ray telescopes

[en] Position sensitive detectors coupled to coded masks are used for imaging in high energy astronomy. PICsIT is the γ-ray position sensitive detector of the IBIS telescope to be flown onboard the INTEGRAL satellite in 2001. PICsIT detector functionalities and scientific performances as a whole are described in details elsewhere in this Conference (Labanti et al. (Nucl. Instr. and Meth. A, this conference)). In this work, we present the aim, methodology, and results of the tests and calibrations performed on the first qualification lot of 136 PICsIT pixels carried out at SCIONIX laboratories in The Netherlands, in April 1999. Before being accepted for PICsIT, each detection unit has in fact to be fully characterized in terms of energy resolution and lower energy threshold. The principal aim of PICsIT pixel qualification campaign described in this work has been to measure the key parameters of each CsI(Tl)+photodiode detection unit: CsI(Tl) crystals light output, gain variation with temperature, energy resolution degradation due to scintillation light production and collection, inhomogeneity in the crystal, and the variation of these quantities after a thermo-vacuum stress treatment