The Palermo Swift-BAT hard X-ray catalogue III. Results after 54 months of sky survey

We present the Second Palermo Swift-BAT hard X-ray catalogue obtained by analysing data acquired in the first 54 months of the Swift mission. Using our software dedicated to the analysis of data from coded mask telescopes, we analysed the BAT survey data in three energy bands (15-30 keV, 15-70 keV, 15-150 keV), obtaining a list of 1256 detections above a significance threshold of 4.8 standard deviations. The identification of the source counterparts is pursued using two strategies: the analysis of field observations of soft X-ray instruments and cross-correlation of our catalogue with source databases.The survey covers 50% of the sky to a 15--150 keV flux limit of 1.0 x 10^-11 erg s^-1 cm^-2 and 9.2 x 10^-12 erg s^-1 cm^-2 for |b| 10 degrees, respectively. The Second Palermo Swift-BAT hard X-ray catalogue includes 1079 (86%) hard X-ray sources with an associated counterpart (26 with a double association and 2 with a triple association) and 177 BAT excesses (14%) that still lack a counterpart. The distribution of the BAT sources among the different object classes consists of 19% Galactic sources, 57% extragalactic sources, and 10% sources with a counterpart at softer energies whose nature has not yet been determined. About half of the BAT associated sources lack a counterpart in the ROSAT catalogues. This suggests that either moderate or strong absorption may be preventing their detection in the ROSAT energy band. The comparison of our BAT catalogue with the Fermi Large Area Telescope First Source Catalogue identifies 59 BAT/Fermi correspondences: 48 blazars, 3 Seyfert galaxies, 1 interacting galaxy, 3 high mass X-ray binaries, and 4 pulsars/supernova remnants. This small number of correspondences indicates that different populations make the sky shine in these two different energy bands

Modeling the flaring activity of the high z, hard X-ray selected blazar IGR J22517+2217

We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray data from INTEGRAL and Swift-BAT survey, to investigate the physical properties of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217, through the modelization of its broad band spectral energy distribution (SED) in two different activity states. Through the analysis of the new Suzaku data and the flux selected data from archival hard X-ray observations, we build the source SED in two different states, one for the newly discovered flare occurred in 2005 and one for the following quiescent period. Both SEDs are strongly dominated by the high energy hump peaked at 10^20 -10^22 Hz, that is at least two orders of magnitude higher than the low energy (synchrotron) one at 10^11 -10^14 Hz, and varies by a factor of 10 between the two states. In both states the high energy hump is modeled as inverse Compton emission between relativistic electrons and seed photons produced externally to the jet, while the synchrotron self-Compton component is found to be negligible. In our model the observed variability can be accounted for by a variation of the total number of emitting electrons, and by a dissipation region radius changing from within to outside the broad line region as the luminosity increases. In its flaring activity, IGR J22517+2217 shows one of the most powerful jet among the population of extreme, hard X-ray selected, high redshift blazar observed so far.Comment: Accepted for publication in MNRA

Galaxy Clusters in the Swift/BAT era II: 10 more Clusters detected above 15 keV

We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters' emission in the 0.3-200keV band can be explained by a multi-temperature thermal model confirming our previous results. For two clusters (Bullet and Abell 3667) we find evidence for the presence of a hard X-ray excess. In the case of the Bullet cluster, our analysis confirms the presence of a non-thermal, power-law like, component with a 20-100 keV flux of 3.4 \times 10-12 erg cm-2 s-1 as detected in previous studies. For Abell 3667 the excess emission can be successfully modeled as a hot component (kT=~13keV). We thus conclude that the hard X-ray emission from galaxy clusters (except the Bullet) has most likely thermal origin.Comment: Accepted for publication by Ap

BAT X-ray Survey - III: X-ray Spectra and Statistical Properties

In this concluding part of the series of three papers dedicated to the Swift/BAT hard X-ray survey (BXS), we focus on the X-ray spectral analysis and statistical properties of the source sample. Using a dedicated method to extract time-averaged spectra of BAT sources we show that Galactic sources have, generally, softer spectra than extragalactic objects and that Seyfert 2 galaxies are harder than Seyfert 1s. The averaged spectrum of all Seyfert galaxies is consistent with a power-law with photon index of 2.00 (+/-0.07). The cumulative flux-number relation for the extragalactic sources in the 14-170 keV band is best described by a power-law with a slope alpha=1.55 (+/-0.20) and a normalization of 9.6$\pm1.9 \times 10^{-3}$ AGN deg$^{-2}$ (or 396(+/-80) AGN all-sky) above a flux level of 2$\times 10^{-11}$erg cm$^{-2}$ s$^{-1}$ (~0.85 mCrab). The integration of the cumulative flux per unit area indicates that BAT resolves 1-2% of the X-ray background emission in the 14-170 keV band. A sub-sample of 24 extragalactic sources above the 4.5 sigma detection limit is used to study the statistical properties of AGN. This sample comprises local Seyfert galaxies (z=0.026, median value) and ~10% blazars. We find that 55% of the Seyfert galaxies are absorbed by column densities of Log(N_H)>22, but that none is a bona fide Compton-thick. This study shows the capabilities of BAT to probe the hard X-ray sky to the mCrab level.Comment: Accepted for publication in The Astrophysical Journal; 42 pages, 4 tables, 51 figure

Systematic search for gamma-ray periodicity in active galactic nuclei detected by the Fermi Large Area Telescope

We use nine years of gamma-ray data provided by the Fermi Large Area Telescope (LAT) to systematically study the light curves of more than two thousand active galactic nuclei (AGN) included in recent Fermi-LAT catalogs. Ten different techniques are used, which are organized in an automatic periodicity-search pipeline, in order to search for evidence of periodic emission in gamma rays. Understanding the processes behind this puzzling phenomenon will provide a better view about the astrophysical nature of these extragalactic sources. However, the observation of temporal patterns in gamma-ray light curves of AGN is still challenging. Despite the fact that there have been efforts on characterizing the temporal emission of some individual sources, a systematic search for periodicities by means of a full likelihood analysis applied to large samples of sources was missing. Our analysis finds 11 AGN, of which 9 are identified for the first time, showing periodicity at more than 4sigma in at least four algorithms. These findings will help in solving questions related to the astrophysical origin of this periodic behavior.Comment: 16 pages, 5 figures, 4 tables. Accepted by Ap

PKS 0537-286, carrying the information of the environment of SMBHs in the early Universe

We present the results of a multifrequency campaign on the high-redshift (z = 3.1) blazar PKS 0537-286. The source was observed at different epochs from 2006 to 2008 with INTEGRAL and Swift, and nearly simultaneously with ground-based near-IR/optical telescopes. The SEDs are compatible with a model based on synchrotron radiation and external inverse Compton scattering. The campaign gives an insight into the physical environment of the blazar.Comment: 8 pages, 5 figures, accepted for publication in A&

High-redshift blazars through nustar eyes

The most powerful sources among the blazar family are MeV blazars. Often detected at $z>2$, they usually display high X- and \gm-ray luminosities, larger-than-average jet powers and black hole masses $\gtrsim 10^9 M_{\odot}$. In the present work we perform a multiwavelength study of three high redshift blazars: 3FGL J0325.5+2223 ($z=2.06$), 3FGL J0449.0+1121 ($z= 2.15$), and 3FGL J0453.2$-$2808 ($z=2.56$), analysing quasi simultaneous data from GROND, \swift-UVOT and XRT, \nustar, and \fermi-LAT. Our main focus is on the hard X-ray band recently unveiled by \nustar~(3$-$79 keV) where these objects show a hard spectrum which enables us to constrain the inverse Compton peak and the jet power. We found that all three targets resemble the most powerful blazars, with the synchrotron peak located in the sub-millimeter range and the inverse Compton peak in the MeV range, and therefore belong to the MeV blazar class. Using a simple one zone leptonic emission model to reproduce the spectral energy distributions, we conclude that a simple combination of synchrotron and accretion disk emission reproduces the infrared-optical spectra while the X-ray to \gm-ray part is well reproduced by the inverse Compton scattering of low energy photons supplied by the broad line region. The black hole masses for each of the three sources are calculated to be $\gtrsim 4 \times 10^{8} M_{\odot}$. The three studied sources have jet power at the level of, or beyond, the accretion luminosity.Comment: 4 figures, 3 tables, accepted for publication in Ap

Extrinsic outflow graft flow obstruction in patients with HeartMate3 LVAD

Blood flow obstruction at the level of the outflow graft is a rare but severe complication of LVAD support. We present a series of five patients supported with HeartMate3 LVAD (Abbott Labs, Chicago, IL) that developed an outflow graft obstruction after 607–1250 days of support, during prolonged antithrombotic therapy. Three patients presented with severe symptoms of heart failure, were treated with endovascular stenting and experienced full recovery. Preoperative computed tomography angiography and intraoperative angiography together with intravascular ultrasound provided diagnosis and guided treatment. In two patients, outflow obstruction was an occasional finding at imaging without heart failure symptoms and a “watchful waiting” approach was adopted: delayed treatment in one of them was futile. This late adverse event is peculiar for its pathophysiology and not yet discussed among the mechanical circulatory support community

Imaging and monitoring in minimally invasive valve surgery using an intra-aortic occlusion device: A single center experience

Background: Minimally invasive approach through a right mini-thoracotomy is a world-wide used procedure for mitral valve surgery. We performed a retrospective analysis based on our center experience in order to propose an effective, safe and reproducible method using an intra-aortic occlusion device.Methods: This is a retrospective analysis on 48 consecutive patients undergoing mitral valve surgery through a right anterolateral mini-thoracotomy in our center. An intra-aortic occlusion device was used for aortic clamping and cardioplegia delivery. Simultaneous multi-plane three-dimensional echocardiography imaging was acquired to detect the venous cannulas position, the intra-aortic device location in the ascending aorta, the balloon inflation, the complete occlusion of the aorta, the cardioplegia delivery, the origin and the blood flow in the right coronary artery. Aortic root pressure was measured by the tip of the intra-aortic occlusion device. A bilateral upper extremity invasive arterial pressure monitoring was detected. Neuromonitoring was performed through bilateral cerebral oximetry.Results: The analysis has shown no aortic dissection, neurological damage type 1 and myocardial ischemia in the study population. In 3 cases a distal displacement of the intra-aortic occlusion device was promptly detected by the combined use of echocardiographic imaging and by a drop of the right cerebral oximetry saturation and of the right radial artery pressure.Conclusions: The combined use of transesophageal simultaneous multi- plane three- dimensional echocardiography imaging, bilateral upper extremity invasive arterial pressure monitoring, aortic root pressure and cerebral oximetry is an effective, safe and reproducible method in patients undergoing minimally invasive valve surgery using an intra-aortic occlusion device

Probing the central black hole in M87 with gamma-rays

Recent high-sensitivity observation of the nearby radio galaxy M87 have provided important insights into the central engine that drives the large-scale outflows seen in radio, optical and X-rays. This review summarizes the observational status achieved in the high energy (HE;<100 GeV) and very high energy (VHE; >100 GeV) gamma-ray domains, and discusses the theoretical progress in understanding the physical origin of this emission and its relation to the activity of the central black hole.Comment: Invited compact review to be published in Modern Physics Letters A; 19 pages, 4 figure