[en] The INTEGRAL satellite, with the hard X-ray/soft gamma ray telescope IBIS onboard, will be launched in 2002. The core program observations include the Galactic Plane Survey and the Galactic Central Radian Deep Exposure. They will respectively provide a weekly coverage of a significant part of the Galactic plane and a deep exposure of the central region of the Galaxy. Both will lead to the discovery of new transient sources, X-ray Novae being the best example. We discuss the possible strategies and results of IBIS/INTEGRAL detection and follow-up observations of X-ray Novae

[en] The central 600 parsecs of our Galaxy can be considered a kind of laboratory for modern astrophysics because in the few square degrees of sky covered by this region, several important non-thermal high energy processes take place and can be studied in detail with the new telescopes operating both in on-ground and in space. In addition to the closest supermassive Black Hole to the solar system the region hosts several other compact and diffuse sources of high-energy radiation whose characteristics need to be studied at different wavelengths from radio to TeV gamma-rays in order to understand the physical processes at work. This paper presents a review of the characteristics of the Galactic Center region from a multiwavelength phenomenological point of view, and giving special emphasis to the sources and processes that shed light on the high-energy phenomena taking place in the region. (author)

[en] An X-ray exploration of a region of the Galactic plane in Carina near l = 284 deg with the Einstein Observatory is presented, consisting of two IPC and one HRI fields. Three new X-ray sources are seen, of which one is clearly extended and can be associated with RCW 49, an H II region/emission nebula, containing a cluster of young stars. The X-ray data could be consistent with a central source of diffuse emission; however, the X-ray flux appears significantly greater than that expected for an object like RCW 49. 33 references

[en] The INTEGRAL satellite, with the hard X-ray/soft gamma ray telescope IBIS onboard, will be launched in 2001. The core program observations include the Galactic Plane Survey (GPS) and the Galactic Plane Deep Exposure (GCDE). They will respectively provide a weekly coverage of a significant part of the Galactic plane and a deep exposure of the central region of the Galaxy. Both will lead to the discovery of new transient sources, X-ray Novae being the best example. We discuss the possible strategies and results of IBIS/INTEGRAL detection and follow-up observations of X-ray Novae in the framework of the Galactic Plane Survey

[en] Results are presented of several Einstein and Exosat X-ray observations of 4U 1145 - 619, an X-ray pulsar orbiting the Be star HD 102567/Hen 715 with marked transient behavior. Pulse-timing analysis of data from imaging instruments on both missions was performed using a period-folding technique, which showed an interesting variation of the light curve shape. During observations at periastron, where the source was predictably brighter, a strong variability was observed on the time scale of several thousand seconds. The global X-ray picture presented can be interpreted in the context of an eccentric binary system with variable accretion, but especially the low-energy Exosat channel multiplier array pulsed light curve raises new questions on the detailed accretion geometry. 24 references

[en] The Imager on Board Integral Satellite (IBIS) is the imaging instrument of the INTEGRAL satellite, the hard-X/soft-gamma ray ESA mission to be launched in 2001. It provides diagnostic capabilities of fine imaging (12' FWHM), source identification and spectral sensitivity to both continuum and broad lines over a broad (15 keV-10 MeV) energy range. It has a continuum sensitivity of 2 10^-7 ph cm^-2 s^-1 at 1 MeV for a 10⁶ seconds observation and a spectral resolution better than 7% at 100 keV and of 6% at 1 MeV. The imaging capabilities of the IBIS are characterized by the coupling of the above quoted source discrimination capability with a very wide field of view (FOV), namely 9 deg. x 9 deg. fully coded, 29 deg. x 29 deg. partially coded FOV. We present simulations of IBIS observations of the Galactic Center based on the results of the SIGMA Galactic Center survey. They show the capabilities of this instrument in discriminating between different sources while at the same time monitoring a huge FOV. It will be possible to simultaneously take spectra of all of these sources over the FOV even if the sensitivity decreases out of the fully coded area. It is envisaged that a proper exploitation of both the FOV dimension and the source localization capability of the IBIS will be a key factor in maximizing its scientific output

[en] A new generation of large area semiconductor based γ-ray camera for astrophysics space application has been developed through the γ-ray IBIS (Imager on Board INTEGRAL Satellite) telescope program, on board the ESA INTEGRAL satellite. This instrument features a coded-mask aperture imaging system, active and passive shields and two detector arrays. The first one (ISGRI : INTEGRAL Soft Gamma-Ray Imager) is made of 16384 CdTe detectors (4x4 mm large, 2 mm thick) operating at room temperature and will operate between 15 keV and 1 MeV. The second detector array (PICsIT : Pixelated CsI Telescope) is made of 4096 CsI scintillators (9.2x9.2 mm large, 30 mm high) coupled to silicon PIN photodiodes working between 150 keV and 10 MeV. IBIS combine broad band energy, spectroscopic capabilities and high spatial resolution imaging (12 arcmin) over a wide field of view (∼20 deg. x 20 deg., 50% sensitivity). A 'flight-like' model of the detectors has been built, integrated and successfully tested. After a description of the IBIS imaging principle, we will report results obtained with the qualification model of the ISGRI camera

[en] We report preliminary results from a multiwavelength campaign aimed at the flaring activity of Sgr A*, which was carried out in early April 2009. Simultaneous data were collected in X-ray, near-infrared, and submillimeter wavebands with the XMM-Newton satellite, the VLT, and the APEX telescope, respectively. We present the detection of several flares and briefly discuss their properties in the context of the synchrotron self-Compton and plasmoid expansion models. (authors)

[en] An array of 30 position sensitive scintillator bars has been tested in a gamma-ray beam from I.N.S.T.N. Van de Graff facility at the Centre d'Etudes Nucleaires, Saclay, France. The gamma-ray energies ranged from 6 MeV to 17 MeV. The bars are similar to those proposed for use in the GRASP gamma-ray telescope satellite imaging plane. They are manufactured from CsI(T1) covered with a highly reflective diffusive wrapping, and are read out using large area PIN photodiodes. Each bar measures 15.0 cm by 1.3 cm by 1.3 cm. The beam test unit was comprised of 30 bars stacked in a 5 by 6 array. The photodiodes were optically coupled to the end face of each bar and were connected to a processing chain comprised of a low noise preamplifier, a high gain shaping amplifier, and a digitisation and data collection system. Several experiments were performed with the unit to assess the spectral response, position resolution, and background rejection capabilities of the complete detector. The test procedure is explained and some results are presented

[en] Aims. HETE J1900.1 - 2455 is the seventh known X-ray transient accreting millisecond pulsar and has been in outburst for more than one year. We compared the data on HETE J1900.1 - 2455 with other similar objects and made an attempt at deriving constraints on the physical processes responsible for a spectral formation. Methods. The broad-band spectrum of the persistent emission in the 2 - 300 keV energy band and the timing properties were studied using simultaneous INTEGRAL and publicly available RXTE data obtained in October 2005. The properties of the X-ray bursts observed from HETE J1900.1 - 2455 were also investigated. Results. The spectrum is well described by a two- component model consisting of a blackbody- like soft X- ray emission at 0.8 keV temperature and a thermal Comptonized spectrum with electron temperature of 30 keV and Thomson optical depth τ_T similar to 2 for the slab geometry. The source is detected by INTEGRAL up to 200 keV at a luminosity of 5 * 10³⁶ erg s^-1 (assuming a distance of 5 kpc) in the 0.1 - 200 keV energy band. We have also detected one type I X- ray burst which shows photospheric radius expansion. The burst occurred at an inferred persistent emission level of similar to 3 - 4% of the Eddington luminosity. Using data for all X- ray bursts observed to date from HETE J1900.1 - 2455, the burst recurrence time is estimated to be about 2 days. No pulsations have been detected either in the RXTE or in the INTEGRAL data which puts interesting constraints on theories of magnetic field evolution in neutron star low- mass X- ray binaries. (authors)