Chasing extreme blazars with INTEGRAL

Within the blazar population, hard X-ray selected objects are of particular interest as they tend to lie at each end of the blazar sequence. In particular, flat spectrum radio quasars located at high redshifts display the most powerful jets, the largest black hole masses and the most luminous accretion disks: their spectral energy distribution has a Compton peak in the sub-MeV region which favours their detection by instruments like INTEGRAL/IBIS and Swift/BAT. These sources are even more extreme than blazars selected in other wavebands, like, for example, the gamma-ray range explored by Fermi. Here we report on a sample of 12 high redshift blazars detected so far by INTEGRAL, including 3 newly identified objects. Some properties of the combined IBIS/BAT sample of high redshift blazars (z>2) are also compared to those of a similar similar sample obtained by Fermi.Comment: 4 pages, 2 figures. Proceedings of "An INTEGRAL view of the high-energy sky (the first 10 years)" the 9th INTEGRAL Workshop, October 15-19, 2012, Paris, France, in Proceedings of Science (INTEGRAL 2012), Eds. A. Goldwurm, F. Lebrun and C. Winkler, (http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176), id=05

BeppoSAX LECS background subtraction techniques

We present 3 methods for the subtraction of non-cosmic and unresolved cosmic backgrounds observed by the Low-Energy Concentrator Spectrometer (LECS) on-board BeppoSAX. Removal of these backgrounds allows a more accurate modeling of the spectral data from point and small-scale extended sources. At high (>|25| degree) galactic latitudes, subtraction using a standard background spectrum works well. At low galactic latitudes, or in complex regions of the X-ray sky, two alternative methods are presented. The first uses counts obtained from two semi-annuli near the outside of the LECS field of view to estimate the background at the source location. The second method uses ROSAT Position Sensitive Proportional Counter (PSPC) all-sky survey data to estimate the LECS background spectrum for a given pointing position. A comparison of the results from these methods provides an estimate of the systematic uncertainties. For high galactic latitude fields, all 3 methods give 3 sigma confidence uncertainties of <0.9 10^-3 count/s (0.1-10 keV), or <1.5 10^-3 count/s (0.1-2 keV). These correspond to 0.1-2.0 keV fluxes of 0.7-1.8 and 0.5-1.1 10^-13 erg/cm2/s for a power-law spectrum with a photon index of 2 and photoelectric absorption of 3 10^20 and 3 10^21 atom/cm2, respectively. At low galactic latitudes, or in complex regions of the X-ray sky, the uncertainties are a factor ~2.5 higher.Comment: 13 pages. Accepted for publication in A&A

Swift/XRT follow-up observations of unidentified INTEGRAL/IBIS sources

Many sources listed in the 4th IBIS/ISGRI survey are still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies (< 10 keV). The cross-correlation between the list of IBIS sources in the 4th catalogue and the Swift/XRT data archive is of key importance to search for the X-ray counterparts; in fact, the positional accuracy of few arcseconds obtained with XRT allows us to perform more efficient and reliable follow-up observations at other wavelengths (optical, UV, radio). In this work, we present the results of the XRT observations for four new gamma-ray sources: IGR J12123-5802, IGR J1248.2-5828, IGR J13107-5626 and IGR J14080-3023. For IGR J12123-5802 we find a likely counterpart, but further information are needed to classified this object, IGR J1248.2-5828 is found to be a Seyfert 1.9, for IGR J13107-5626 we suggest a possible AGN nature, while IGR J14080-3023 is classified as a Seyfert 1.5 galaxy.Comment: 6 pages, 4 figure and 2 tables. Accepted for publication on PoS (contribution PoS(extremesky2009)018), proceedings of "The Extreme sky: Sampling the Universe above 10 keV", held in Otranto (Italy), 13-17 October 200

The INTEGRAL high energy cut-off distribution of type 1 AGN

In this letter we present the primary continuum parameters, the photon index Gamma and the high energy cut-off Ec, of 41 type-1 Seyfert galaxies extracted from the INTEGRAL complete sample of AGN. We performed a broad band (0.3-100 keV) spectral analysis by fitting simultaneously the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT respectively in order to investigate the general properties of these parameters in particular their distribution and mean values. We find a mean photon index for the whole sample of 1.73 with a standard deviation of 0.17 and a mean high energy cut-off of 128 keV with a standard deviation of 46 keV. This is the first time that the cut-off energy is constrained in a such large number of AGN. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region i.e. the plasma temperature kT_e from 20 to 100 keV and the optical depth tau <4. Finally, with the high S/N spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGN, allowing the determination of more physical models and so to better understand the continuum emission and geometry of the region surrounding black holes.Comment: 21 pages, 4 figures, 1 table. Accepted for publication on ApJ Letter

Broadband X-ray spectrum of the newly discovered broad line radio galaxy IGR J21247+5058

In this paper we present radio and high energy observations of the INTEGRAL source IGR J21247+5058, a broad line emitting galaxy obscured by the Galactic plane. Archival VLA radio data indicate that IGR J21247+5058 can be classified as an FRII Broad Line Radio Galaxy. The spectrum between 610 MHz and 15 GHz is typical of synchrotron self-absorbed radiation with a peak at 8 GHz and a low energy turnover; the core fraction is 0.1 suggestive of a moderate Doppler boosting of the base of the jet. The high energy broad-band spectrum was obtained by combining XMM-Newton and Swift/XRT observation with INTEGRAL/IBIS data. The 0.4-100 keV spectrum is well described by a power law, with slope $\Gamma$=1.5, characterised by complex absorption due to two layers of material partially covering the source and a high energy cut-off around 70-80 keV. Features such as a narrow iron line and a Compton reflection component, if present, are weak, suggesting that reprocessing of the power law photons in the accretion disk plays a negligible role in the source.Comment: 7 pages, 7 figures, 3 tables, accepted for pubblication on MNRA

Adaptive quasi-unsupervised detection of smoke plume by lidar

The early detection of fire is one of the possible applications of LiDAR techniques. The smoke generated by a fire is mainly compounded of CO2, H2O, particulate, and other combustion products, which involve the local variation of the scattering of the electromagnetic wave at specific wavelengths. The increases of the backscattering coefficient are transduced in peaks on the signal of the backscattering power recorded by the LiDAR system, located exactly where the smoke plume is, allowing not only the detection of a fire but also its localization. The signal processing of the LiDAR signals is critical in the determination of the performances of the fire detection. It is important that the sensitivity of the apparatus is high enough but also that the number of false alarms is small, in order to avoid the trigger of useless and expensive countermeasures. In this work, a new analysis method, based on an adaptive quasi-unsupervised approach was used to ensure that the algorithm is continuously updated to the boundary conditions of the system, such as the weather and experimental apparatus issues. The method has been tested on an experimental campaign of 227 pulses and the performances have been analyzed in terms of sensitivity and specificity

Hard X-ray selected giant radio galaxies - I. The X-ray properties and radio connection

We present the first broad-band X-ray study of the nuclei of 14 hard X-ray selected giant radio galaxies, based both on the literature and on the analysis of archival X-ray data from NuSTAR, XMM-Newton, Swift and INTEGRAL. The X-ray properties of the sources are consistent with an accretion-related X-ray emission, likely originating from an X-ray corona coupled to a radiatively efficient accretion flow. We find a correlation between the X-ray luminosity and the radio core luminosity, consistent with that expected for AGNs powered by efficient accretion. In most sources, the luminosity of the radio lobes and the estimated jet power are relatively low compared with the nuclear X-ray emission. This indicates that either the nucleus is more powerful than in the past, consistent with a restarting of the central engine, or that the giant lobes are dimmer due to expansion losses.Comment: 11 pages, 3 figures. Accepted for publication in MNRA