M. Revnivtsev

INTEGRAL/IBIS all-sky survey in hard X-rays

We present results of an all-sky hard X-ray survey based on almost four years of observations with the IBIS telescope onboard the INTEGRAL observatory. The dead time-corrected exposure of the survey is ∼33 Ms. Approximately 12% and 80% of the sky has been covered to limiting fluxes lower than 1 and 5 mCrab, respectively. Our catalog of detected sources includes 403 objects, 316 of which exceed a 5σ detection threshold on the time-averaged map of the sky, and the rest were detected in various subsamples of exposures. Among the identified sources, 219 are Galactic (90 low-mass X-ray binaries, 76 high-mass X-ray binaries, 21 cataclysmic variables, 6 coronally active stars, and other types) and 137 are extragalactic, including 130 active galactic nuclei (AGNs) and 3 galaxy clusters. We derived number-flux functions of AGNs and Galactic sources. The logN–logS relation of non-blazar AGNs is based on 68 sources located at Galactic latitudes |b| > 5 ◦ , where the survey is characterized by high identification completeness, with fluxes higher than S lim = 1.1 × 10 −11 erg s −1 cm −2 (∼0.8 mCrab) in the 17−60 keV energy band. The cumulative AGN number-flux function can be described by a power law with a slope of 1.62 ± 0.15 and normalization of (5.7 ± 0.7) × 10 −3 sources per deg 2 at fluxes >1.43 × 10 −11 erg s −1 cm −2 (>1 mCrab). Those AGNs with fluxes higher than S lim make up ∼1% of the cosmic X-ray background at 17−60 keV. We present evidence of strong inhomogeneity in the spatial distribution of nearby (<70 Mpc) AGNs, which reflects the large-scale structure in the local Universe.

Hard X-ray view of the past activity of Sgr A in a natural Compton mirror

We report the association of the recently discovered hard X-ray source IGR J17475−2822 with the giant molecular cloud Sgr B2 in the Galactic Center region. The broad band (3-200 keV) spectrum of the source constructed from data of different observatories strongly supports the idea that the X-ray emission of Sgr B2 is Compton scattered and reprocessed radiation emitted in the past by the Sgr Asource. We conclude that 300-400 years ago Sgr Awas a low luminosity (L ≈ 1.5 × 10 39 erg s −1 at 2-200 keV) AGN with a characteristic hard X-ray spectrum (photon index Γ ≈ 1. 8). We estimate the mass and iron abundance of the Sgr B2 scattering gas at 2 × 10 6 M� (r/10 pc) 2 and 1.9 solar, respectively (where r is the radius of

INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth

Aims. We study the spectrum of the cosmic X-ray background (CXB) in energy range ∼5−100 keV. Methods. Early in 2006 the INTEGRAL observatory performed a series of four 30 ks observations with the Earth disk crossing the field of view of the instruments. The modulation of the aperture flux due to occultation of extragalactic objects by the Earth disk was used to obtain the spectrum of the Cosmic X-ray Background (CXB). Various sources of contamination were evaluated, including compact sources, Galactic Ridge emission, CXB reflection by the Earth atmosphere, cosmic ray induced emission by the Earth atmosphere and the Earth auroral emission. Results. The spectrum of the cosmic X-ray background in the energy band 5−100 keV is obtained. The shape of the spectrum is consistent with that obtained previously by the HEAO-1 observatory, while the normalization is ∼10% higher. This difference in normalization can (at least partly) be traced to the different assumptions on the absolute flux from the Crab Nebulae. The increase relative to the earlier adopted value of the absolute flux of the CXB near the energy of maximum luminosity (20−50 keV) has direct implications for the energy release of supermassive black holes in the Universe and their growth at the epoch of the CXB origin.

INTEGRAL insight into the inner parts of the galaxy: high mass X-ray binaries

Since its launch INTEGRAL has devoted a significant fraction of its observing time to the Galactic plane region. We present the results of INTEGRAL observations of the inner spiral arms of the Galaxy (Norma, Scutum and Sagittarius) with attention to high mass X-ray binaries. The increased sensitivity of the survey and possibility to detect absorbed sources significantly enlarged our sample of HMXBs in comparison with previous studies. For some absorbed sources we present for the first time high quality broadband (1-100 keV) energy spectra. We confirm pulsations of the X-ray flux of IGR J16358-4726, discovered by CHANDRA, and report discovery of pulsations with a period of 228 ± 6 sec from IGR J16465-4507. We confirm that the Galactic high mass X-ray binary distribution is significantly different from the distribution of low mass X-ray binaries concentrated in the Galactic Center. A large fraction of detected high mass X-ray binaries are absorbed sources.

Positron annihilation spectrum from the Galactic Centre region observed by SPI/ INTEGRAL

The electron-positron annihilation spectrum observed by SPI/INTEGRAL during deep Galactic Center region exposure is reported. The line energy (510.954

Statistical properties of local active galactic nuclei inferred from the RXTE 3-20 keV all-sky survey

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RXTE broadband X-ray spectra of intermediate polars and white dwarf mass estimates

0.075 keV) is consistent with the unshifted annihilation line. The width of the annihilation line is 2.37

The spectrum of the cosmic X-ray background observed by RTXE/PCA

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A hard X-ray survey of the Sagittarius Arm Tangent with the IBIS Telescope of the INTEGRAL Observatory : A Catalog of sources

0.25 keV (FWHM), while the strength of the ortho-positronium continuum suggests that the dominant fraction of positrons (94

Super-Eddington outburst of V4641 Sgr

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