In this paper we report on the third soft gamma-ray source catalog obtained with the IBIS/ ISGRI gamma-ray imager on board the INTEGRAL satellite. The scientific data set is based on more than 40 Ms of high-quality observations performed during the first 3.5 yr of Core Program and public IBIS/ ISGRI observations. Compared to previous IBIS/ISGRI surveys, this catalog includes a substantially increased coverage of extragalactic fields, and comprises more than 400 high-energy sources detected in the energy range 17Y100 keV, including both transients and faint persistent objects that can only be revealed with longer exposure times.

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In this paper we report the second soft gamma-ray source catalog obtained with the IBIS/ ISGRI gamma-ray imager on board the INTEGRAL satellite. The scientific data set is based on more than 10 Ms of high-quality observations performed during the first 2 years of Core Program and public IBIS/ISGRI observations, and covers $50% of the whole sky. The main aim of the first survey was to scan systematically, for the first time at energies above 20 keV, the whole Galactic plane to achieve a limiting sensitivity of $1 mcrab in the central radian. The target of the second year of the INTEGRAL mission lifetime was to expand as much as possible our knowledge of the soft gamma-ray sky, with the same limiting sensitivity, to at least 50% of the whole sky, mainly by including a substantial coverage of extragalactic fields. This catalog comprises more than 200 high-energy sources detected in the energy range 20-100 keV, including new transients not active during the first year of operation, faint persistent objects revealed with longer exposure time, and several Galactic and extragalactic sources in sky regions not observed in the first survey. The mean position error for all the sources detected with significance above 10 is $40 00 , enough to identify most of them with a known X-ray counterpart and to unveil the nature of most of the strongly absorbed ones, even though they are very difficult to detect in X-rays.

Context. IGR J18483−0311 is a poorly known transient hard X-ray source discovered by INTEGRAL during observations of the Galactic Center region performed between 23-28 April 2003. Aims. To detect new outbursts from IGR J18483−0311 using INTEGRAL and archival Swift XRT observations and finally to characterize the nature of this source using the optical/near−infrared (NIR) information available through catalogue searches. Methods. We performed an analysis of light curves and spectra of INTEGRAL and archival Swift XRT data as well as of optical/NIR catalogues. Results. We report on 5 newly discovered outbursts from IGR J18483−0311 detected by INTEGRAL. For two of them it was possible to constrain a duration of the order of a few days. The strongest outburst reached a peak flux of ∼120 mCrab (20-100 keV); its broad band JEM-X/ISGRI spectrum (3-50 keV) is best fitted by an absorbed cutoff power law with Γ=1.4±0.3, cutoff energy of 22 +7.5 −4.5 keV and N H =9 +5 −4 ×10 22 cm −2 . Timing analysis of INTEGRAL data allowed us to identify periodicities of 18.52 days and 21.0526 seconds which are likely the orbital period of the system and the spin period of the X-ray pulsar respectively. Swift XRT observations of IGR J18483−0311 provided a very accurate source position which strongly indicates a highly reddened star in the USNO-B1.0 and 2MASS catalogues as its possible optical/NIR counterpart. Conclusions. The X-ray spectral shape, the periods of 18.52 days and 21.0526 seconds, the high intrinsic absorption, the location in the direction of the Scutum spiral arm and the highly reddened optical object as possible counterpart, all favour the hypothesis that IGR J18483−0311 is a HMXB with a neutron star as compact companion. The system is most likely a Be X-ray binary, but a Supergiant Fast X-ray Transient nature can not be entirely excluded.

Analysis of INTEGRAL/IBIS survey observations has revealed that the rare intermediate polar and asynchronous polar cataclysmic variables (CVs) are consistently found to emit in the 20–100 keV energy band, whereas synchronous polars and the common non‐magnetic CVs rarely do so. From the correlation of a candidate INTEGRAL/IBIS survey source list with a CV catalogue, 15 CV detections by IBIS have been established including a new INTEGRAL source IGR J06253+7334. The properties of these sources and four additional CV candidates are discussed in the context of their 20–100 keV emission characteristics, and we conclude that the INTEGRAL mission is an important tool in the detection of new magnetic CV systems. Furthermore, analysis of the time‐averaged spectra of CVs detected by INTEGRAL indicates that although there is little difference between the spectral slopes of the different subtypes, intermediate polars may be considerably more luminous than polars in the soft gamma‐ray regime. We also present the detection of an unusual high‐energy burst from V1223 Sgr discovered by the inspection of the IBIS light curve. Additionally, we have compared the IBIS and optical American Association of Variable Star Observers (AAVSO) light curves of SS Cyg and extracted IBIS spectra during single periods of optical outburst and quiescence. We find that the 20–100 keV flux is an order of magnitude greater during optical quiescence. This is in agreement with previous studies which show that the hard X‐ray component of SS Cyg is suppressed during high accretion states.