Related papers: Swift observations of IBL and LBL objects
Based on RXTE scans and observations with the SWIFT/XRT telescope and INTEGRAL observatory, we report the identification of four X-ray sources discovered during the RXTE Slew Survey of the |b|>10deg sky with nearby (z ~ 0.017-0.098)…
Current surveys of Active Galactic Nuclei (AGN) find only a very small fraction of AGN contributing to the Cosmic X-ray Background (CXB) at energies above 15 keV. Roughly 99% of the CXB is so far unresolved. In this work we address the…
Context. Serendipitous X-ray surveys have proven to be an efficient way to find rare objects, for example tidal disruption events, changing-look active galactic nuclei (AGN), binary quasars, ultraluminous X-ray sources (ULXs), and…
Analyzing light curves of a complete sample of bright Swift long gamma-ray bursts (LGRBs) of which the peak photon fluxes constructed with the bin width of 1 second in the Swift 15-350 keV energy band exceed 2.6 photons cm$^{-2}$s$^{-1}$,…
This talk focuses on the statistical properties of X-ray selected BL Lacertae objects (XBLs) whose catalogue has been compiled. It consists of 312 sources from different X-ray surveys, unambiguously identified to mid-2010. Results of the…
Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, plus archival data from two on-line sky surveys, we have obtained optical spectroscopy for 29 counterparts of unclassified or poorly…
Many of the new high energy sources discovered both by INTEGRAL/IBIS and Swift/BAT have been characterised thanks to extensive, multi-band follow-up campaigns, but there are still objects whose nature remains to be asserted. In this paper…
We present new BeppoSAX LECS and MECS observations, covering the energy range 0.1 - 10 keV (observer's frame), of four BL Lacertae objects selected from the 1 Jy sample. All sources display a flat (alpha_x ~ 0.7) X-ray spectrum, which we…
Hard X-ray ($\geq 10$ keV) observations of Active Galactic Nuclei (AGN) can shed light on some of the most obscured episodes of accretion onto supermassive black holes. The 70-month Swift/BAT all-sky survey, which probes the 14-195 keV…
Nearly 50% of all sources detected by the Fermi Large Area Telescope are classified as blazars or blazar candidates, one of the most elusive classes of active galaxies. Additional blazars can also be hidden within the sample of unidentified…
Hard X-ray surveys are an important tool for the study of active galactic nuclei (AGN): they provide almost an unbiased view of absorption in the extragalactic population, allow the study of spectral features such as reflection and high…
We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGN). The Swift/Burst Alert Telescope all-sky survey provides an unbiased,…
Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, we have obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected…
It is well accepted that unabsorbed as well as absorbed AGN are needed to explain the nature and the shape of the Cosmic X-ray background, even if the fraction of highly absorbed objects (dubbed Compton-thick sources) substantially still…
The broadband emission observed from radio galaxies, BL Lac objects and quasars is thought to be produced by energetic electrons confined in plasma blobs which are ejected from supermassive black holes at relativistic speeds. The lower…
Abridged : The various IBIS/ISGRI catalogues contain a large population of hard X-ray sources whose nature is still unknown. Even if the $>20$ keV positional uncertainty provided by ISGRI is unprecedented, it is still too large to pinpoint…
The determination of the broad (0.1-100 keV) spectra of active galaxies is crucial for understanding and discriminating among emission models, for estimating the properties of the Comptonising/reflecting region around the central black hole…
Aims. We aim to determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects. Methods. We secured medium resolution optical and near-infrared spectra of 4 bright BL Lac objects of unknown redshift using the…
We present a detailed analysis of the most luminous and obscured Active Galactic Nuclei (AGNs) detected in the ultra-hard X-ray band (14-195 keV) by Swift/BAT. Our sample comprises 21 X-ray luminous (log $L_X/{\rm erg\,s^{-1}}>44.6$, 2-10…
Blazars, the peculiar class of active galactic nuclei (AGN), are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across…