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AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We compare the simulations with recent observations on these sources by INTEGRAL, Swift and Suzaku. Constraining reflection models for AGN with Simbol-X will help us to get a clear view of the processes and geometry near to the central engine in AGN, and will give insight to which sources are responsible for the Cosmic X-ray background at energies >20 keV. [ABSTRACT FROM AUTHOR]

We discuss the fueling of the central black hole in active galactic nuclei (AGN) in the framework of a clumpy accretion flow. Shocks between elements (clumps) forming the accretion flow are at the origin of the observed radiation. We expect a cascade of shocks, with optically thick shocks giving rise to optical/UV emission and optically thin shocks accounting for the X-ray emission. We associate the characteristic X-ray variability time scale derived within our model with the break time scale observed in the X-ray power spectral density (PSD). The predicted dependence of the variability time scale on black hole mass and accretion rate is in agreement with the observational relation obtained by McHardy et al. (2006). We further discuss X-ray spectral properties, in particular we compare the predicted hard X-ray power law slope with observations. Model results are able to reproduce the range of photon index typically measured in Seyfert galaxies and may account for the observed correlation between photon index and normalized accretion rate. [ABSTRACT FROM AUTHOR]

Some galaxy clusters are known to contain a large population of relativistic electrons, which produce radio emission through synchrotron radiation. Therefore, it is expected that inverse-Compton scattering of the relativistic electrons with the CMB produce non-thermal emission which should be observable in the hard X-ray domain. Here we focus on the recent results by INTEGRAL, which shed a new light on the non-thermal emission thanks to its angular resolution and sensitivity in the hard X-ray range. We also present the exciting prospects in this field for Simbol-X, which will allow us to detect the non-thermal emission in a number of clusters and map the magnetic field throughout the intra-cluster medium. [ABSTRACT FROM AUTHOR]

The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows to test the unified scheme for AGN. We present results based on the analysis of 199 AGN. A difference between the Seyfert types is detected in slightly flatter spectra with higher cut-off energies and lower luminosities for the type 2 AGN. When applying a Compton reflection model, the underlying continua (Γ≃1.95) appear the same in Seyfert 1 and 2, and the reflection strength is R≃1 in both cases, with differences in the inclination angle only. More luminous objects appear to be more massive and there is also a general trend for the absorbed sources and type 2 AGN to have lower Eddington ratios. The number counts are consistent with no evolution of the observed AGN. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2 galaxies, seen under different inclination angle and absorption. [ABSTRACT FROM AUTHOR]

We present some results of the deepest extragalactic survey performed by the INTEGRAL satellite. The fraction of very absorbed AGN is quite large. The sharp decrease in the absorption fraction with X-ray luminosity observed at lower-energy X-rays is not observed. The current lack of truly Compton-thick objects, with an upper limit of 14% to the size of this population, is just compatible with recent modeling of the cosmic X-ray background. We also study the prospects for a future hard X-ray serendipitous survey with Simbol-X. We show that Simbol-X will easily detect a large number of serendipitous AGN, allowing us to study the evolution of AGN up to redshifts about 2, opening the door to the cosmological study of hard X-ray selected AGN, which is barely possible with existing satellites like Swift and INTEGRAL. [ABSTRACT FROM AUTHOR]

We studied and compared the long term average hard X-ray (>20 keV) spectra of a sample of twelve bright low-mass X-ray binaries hosting a neutron star (NS). Our sample comprises the six well studied Galactic Z sources and six Atoll sources, four of which are bright (“GX”) bulge sources while two are weaker ones in the 2–10 keV range (H 1750-440 and H 1608-55). For all the sources of our sample, we analysed available public data and extracted average spectra from the IBIS/ISGRI detector on board INTEGRAL. We extend the detection of H 1750-440 up to 150 keV and discover a hard tail in the spectrum of the Atoll source GX 13+1. We can describe all the spectral states as well as the long known variability of the hard X-ray tails detected in some of these objects in terms of the bulk motion Comptonisation scenario. We find evidence that bulk motion, at the origin of the hard X-ray tail, is always present, its strength is related to the accretion rate and it is suppressed only in the presence of high local luminosity. Using radio data from the literature we find, in all Z sources and bright “GX” Atolls, a systematic positive correlation between the X-ray hard tail (40–100 keV) and the radio luminosity. This suggests that hard tails and energetic electrons causing the radio emission may have the same origin, most likely the Compton cloud located inside the NS magnetosphere. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Galactic Bulge region is a rich host of variable high-energy point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, X-ray pulsars, etc.. We have a program to monitor the Galactic Bulge region regularly and frequently with the γ-ray observatory INTEGRAL. As a service to the scientific community the high-energy light curves of all the active sources as well as images of the region are made available through the WWW. We show the first results of this exciting new program. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present results from simultaneous observations of Cyg X-1 with INTEGRAL and RXTE in 2002 November and December, employing the new RXTE calibration from HEASOFT 5.3. The broad-band X-ray/γ-ray spectrum is well described by Comptonization spectra with an additional reflection component. The temperature of the Comptonizing plasma is kTe ∼ 60–80 keV and its optical depth is τ ∼ 0.8–1.2. The covering factor of the reflector is Ω/2π ∼ 0.1. There is a possible soft excess below 10 keV, interpreted as emission from the accretion disk. The spectral parameters are slightly different from those obtained by us earlier due to the different RXTE-PCA calibration. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

XEUS is under study by ESA as part of the Horizon 2000+ program to utilize the International Space Station (ISS) for astronomical applications. XEUS will be a long-term X-ray observatory with an initial mirror area of 6 m² at 1 keV that will be grown to 30 m² following a visit to the ISS. The 1 keV spatial resolution is expected to be 2-5... HEW. XEUS will consist of separate detector and mirror spacecraft aligned by active control to provide a focal length of 50 m. A new detector spacecraft, complete with the next generation of instruments, will also be added after visiting the ISS. The limiting sensitivity will then be ∼4 x 10[sup -18] erg cm[sup -2] s[sup -1] around 250 times better than XMM. The properties of a 350 eV (rest-frame) equivalent width Fe line from a 10[sup 44] erg s[sup -1] AGN will be measurable out to z= 10, paving the way for detailed spectroscopic X-ray studies of some of the earliest known objects. [ABSTRACT FROM AUTHOR]

The INTEGRAL Science Data Center (ISDC) is designed as an interface between the INTEGRAL data and the user community. Its main task is to receive and process all the INTEGRAL data in order to (1) detect GRBs and other bright transient sources, for alerting the astronomical community and for initiating possible INTEGRAL Target Of Opportunity (TOO) observation, and (2) produce and archive a set of standard data products, and to distribute them to the observers. It is also foreseen to provide help and support to the observers in analyzing INTEGRAL data. The ISDC is funded by a consortium of European and US institutes. It is located in Versoix near Geneva. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

3C 273 is the brightest quasar in the sky and among the most extensively observed and studied AGN, therefore one of the most suitable targets for a long-term, multi-frequency study. The superposition of a thermal Comptonisation component, similar to that observed in Seyfert galaxies, and of a non-thermal component, related to the jet emission, seems to explain some of the spectral and timing properties of the X-ray emission of 3C 273. Yet, during some observations this dichotomy has not been observed and the variability properties could also be consistent with a single-component scenario, characterised by two parameters varying independently. In order to understand the nature of the X-ray emission in 3C 273, a series of observations up to 80–100 keV, possibly catching the source in different flux states, are essential. Simbol-X will be able to study the emission of 3C 273 in the broad 0.5–80 keV band with high sensitivity, allowing us to disentangle the emission from different spectral components, with 20–30 ks long observations. In addition, the shape and the origin of the high-energy emission of this quasar will be further constrained thanks to the AGILE and Fermi satellites, monitoring the γ-ray sky in the MeV-GeV energy domain. [ABSTRACT FROM AUTHOR]