93 research outputs found
Identifying the 3FHL Catalog. VI. Results of the 2019 Gemini Optical Spectroscopy
No full textActive galactic nuclei with their relativistic jets pointed toward the observer are a class of luminous gamma-ray sources commonly known as blazars. The study of this source class is essential to unveil the physical processes powering these extreme jets, to understand their cosmic evolution, as well as to indirectly probe the extragalactic background light. To do so, however, one needs to correctly classify and measure a redshift for a large sample of these sources. The Third Fermi–LAT Catalog of High-Energy Sources (3FHL) contains 1212 blazars detected at energies greater than 10 GeV. However, ∼25% of these sources are unclassified and ∼56% lack redshift information. To increase the optical completeness of blazars in the 3FHL catalog, we devised an optical spectroscopic follow-up campaign using 4 m and 8 m telescopes. In this paper, we present the results of the last part of this campaign, where we observed 5 blazars using the 8 m Gemini-S telescope in Chile. We report all the 5 sources to be classified as BL Lacs, a redshift lower limit for 2 sources, and featureless spectra for the remaining 3 sources. We also performed a one-zone leptonic fit to the two sources with the redshift lower limits
Compton-thick AGNs in the NuSTAR Era
No full textWe present the 2-100 keV spectral analysis of 30 candidate Compton-thick-(CT-)active galactic nuclei (AGNs) selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. The average redshift of these objects is , and they all lie within â1⁄4500 Mpc. We used the MyTorus model to perform X-ray spectral fittings both without and with the contribution of the Nuclear Spectroscopic Telescope Array (NuSTAR) data in the 3-50 keV energy range. When the NuSTAR data are added to the fit, 13 out of 30 of these objects (43% of the whole sample) have intrinsic absorption NH3Ï confidence level, i.e., they are reclassified from Compton thick to Compton thin. Consequently, we infer an overall observed fraction of the CT-AGN, with respect to the whole AGN population, lower than the one reported in previous works, as low as â1⁄44%. We find evidence that this overestimation of NHis likely due to the low quality of a subsample of spectra, either in the 2-10 keV band or in the Swift-BAT one
Identifying the 3FHL Catalog. IV. Swift Observations of Unassociated Fermi-LAT 3FHL Sources
No full textThe Fermi Large Area Telescope (Fermi-LAT) 3FHL catalog is the latest catalog of >10 GeV sources and will remain an important resource for the high-energy community for the foreseeable future. Therefore, it is crucial that this catalog is made complete by providing associations for most sources. In this paper, we present the results of the X-ray analysis of 38 3FHL sources. We found a single bright X-ray source in 20 fields, two sources each in two fields, and none for the remaining 16. The analysis of the properties of the 22 3FHL fields with X-ray sources led us to believe that most (∼19/22) are of extragalactic origin. A machine-learning algorithm was used to determine the source type and we find that 15 potential blazars are likely BL Lacertae objects (BL Lac objects). This is consistent with the fact that BL Lac objects are by far the most numerous population detected above >10 GeV in the 3FHL
Compton-thick AGNs in the NuSTAR Era. II. A Deep NuSTAR and XMM-Newton View of the Candidate Compton-thick AGN in NGC 1358
No full textWe present the combined NuSTAR and XMM-Newton 0.6-79 keV spectral analysis of a Seyfert 2 galaxy, NGC 1358, which we selected as a candidate Compton-thick (CT) active galactic nucleus (AGN) on the basis of previous Swift/BAT and Chandra studies. According to our analysis, NGC 1358 is confirmed to be a CT-AGN using physically motivated models, at >3σ confidence level. Our best fit shows that the column density along the line of sight of the obscuring material surrounding the accreting supermassive black hole is N H = (1.96-2.80) × 1024 cm-2. The high-quality data from NuSTAR give the best constraints on the spectral shape above ∼10 keV to date on NGC 1358. Moreover, by combining NuSTAR and XMM-Newton data, we find that the obscuring torus has a low covering factor (f c < 0.17), and the obscuring material is distributed in clumps, rather than uniformly. We also derive an estimate of NGC 1358's Eddington ratio, finding it to be λ Edd ∼ × 10-2, which is in acceptable agreement with previous measurements. Finally, we find no evidence of short-term variability, over a ∼100 ks time span, in terms of both line-of-sight column density and flux
Chandra and NuSTAR Follow-up Observations of Swift-BAT-selected AGNs
No full textBased on current models of the cosmic X-ray background (CXB), heavily obscured active galactic nuclei (AGNs) are expected to make up ~10% of the peak emission of the CXB and ~20% of the total population of AGNs, yet few of these sources have been recorded and characterized in current surveys. Here we present the Chandra follow-up observation of 14 AGNs detected by Swift-BAT. For five sources in the sample, NuSTAR observations in the 3-80 keV band are also available. The X-ray spectral fitting over the 0.3-150 keV energy range allows us to determine the main X-ray spectral parameters, such as the photon index and the intrinsic absorption, of these objects and to make hypotheses on the physical structures responsible for the observed spectra. We find that 13 of the 14 objects are absorbed AGNs, and one is a candidate Compton-thick AGN, having intrinsic absorption NH>1024cm-2. Finally, we verified that the use of NuSTAR observations is strategic to strongly constrain the properties of obscured AGNs, since the best-fit values we obtained for parameters such as the power-law photon index Gamma and the intrinsic absorption NH changed sometimes significantly fitting the spectra with and without the use of NuSTAR data
NuSTAR Perspective on High-redshift MeV Blazars
No full textWith bolometric luminosities exceeding 1048 erg s-1, powerful jets, and supermassive black holes at their center, MeV blazars are some of the most extreme sources in the universe. Recently, the Fermi-Large Area Telescope detected five new gamma-ray emitting MeV blazars beyond redshift z = 3.1. With the goal of precisely characterizing the jet properties of these extreme sources, we started a multiwavelength campaign to follow them up with joint Nuclear Spectroscopic Telescope Array, Swift, and the Southeastern Association for Research in Astronomy's optical telescopes. We observe six high-redshift quasars, four of them belonging to the new gamma-ray emitting MeV blazars. Thorough X-ray analysis reveals spectral flattening at soft X-ray for three of these objects. The source NVSS J151002+570243 also shows a peculiar rehardening of the X-ray spectrum at energies E > 6 keV. Adopting a one-zone leptonic emission model, this combination of hard X-rays and gamma-rays enables us to determine the location of the Inverse Compton peak and to accurately constrain the jet characteristics. In the context of the jet-accretion disk connection, we find that all six sources have jet powers exceeding accretion disk luminosity, seemingly validating this positive correlation even beyond z > 3. Our six sources are found to have black holes, further raising the space density of supermassive black holes in the redshift bin z = [3, 4]
GIFT-1, a phase IIa clinical trial to test the safety and efficacy of IFNγ administration in FRDA patients
No full textFriedreich's ataxia is an autosomal recessive progressive degenerative disorder caused by deficiency of the protein frataxin. The most common genetic cause is a homozygotic expansion of GAA triplets within intron 1 of the frataxin gene leading to impaired transcription. Preclinical in vivo and in vitro studies have shown that interferon gamma (IFNγ) is able to up-regulate the expression of frataxin gene in multiple cell types. We designed a phase IIa clinical trial, the first in Italy, aimed at assessing both safety and tolerability of IFNγ in Friedreich's patients and ability to increase frataxin levels in peripheral blood mononuclear cells. Nine patients (6 female and 3 males aged 21-38 years) with genetically confirmed disease were given 3 subcutaneous escalating doses (100, 150 and 200 μg) of IFNγ (human recombinant interferon 1 b gamma, trade name IMUKIN®), over 4 weeks. The primary end-point was the assessment of the safety and tolerability of IFNγ by means of standard clinical and hematological criteria. The secondary end-point was the detection of changes of frataxin levels in peripheral blood mononuclear cells after each single escalating dose of the drug. IFNγ was generally well tolerated, the main adverse event was hyperthermia/fever. Although, increases in frataxin levels could be detected in a minority of patients, these changes were not significant. A large phase III multicenter, randomized clinical trial with IFNγ in Friedreich's ataxia patients is currently ongoing. This study is expected to conclusively address the clinical efficacy of IFNγ therapy in patients with Friedreich's ataxia
Surveying the rural village of Al-Jāyyah (Ma’an Governorate, Jordan): archaeological methodologies and first results
No full textSurveying the rural village of Al-Jāyyah (Ma’an Governorate, Jordan): archaeological methodologies and first results. A contribution to the knowledge of the Shawbak territorial settlement in the longue durée
This paper presents some preliminary results about systematic Light Archaeology surveys (integrating Building and Landscape Archaeology) that the author is leading in the village of Al-Jāyyah, SE ofthe Shawbak castle, within the archaeological investigations on the landscape surrounding the fortress managed by the Italian archaeological Mission‘Medieval Petra,’ University of Florence. The aim of the surveys is to investigate the historical connection between the castle and the village, suggested by some Medieval written sources. The research’s preliminary outcomes are confirming that even if the present appearance of the village is modern, it preserves significant Medieval material evidences plausibly linked to the Crusader suburb and the Islamic madīnah of Shawbak
Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor
No full textWe present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift ázñ 0.03) with the Swift-BAT 100-month survey. All sources have available NuSTAR data, thus allowing us to constrain with unprecedented quality important spectral parameters such as the obscuring torus line-of-sight column density (NH,z), the average torus column density (NH,tor), and the torus covering factor ( fc). We compare the best-fit results obtained with the widely used MYTorus (Murphy & Yaqoob 2009) model with those of the recently published borus02 model (Balokovi? et al. 2018) used in the same geometrical configuration of MYTorus (i.e., with fc?=?0.5). We find a remarkable agreement between the two, although with increasing dispersion in NH,z moving toward higher column densities. We then use borus02 to measure fc. High-fc sources have, on average, smaller offset between NH,z and NH,tor than low-fc ones. Therefore, low fc values can be linked to a "patchy torus" scenario, where the AGN is seen through an overdense region in the torus, while high-fc objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between fc and the AGN 2-10 keV luminosity, i.e., sources with higher fc values have on average lower luminosities
XMM–NuSTAR Observation and Multiwavelength Spectral Energy Distribution Modeling of Blazar 4FGL J1520.8–0348
No full textActive galactic nuclei (AGNs) can power relativistic jets, which are called blazars when pointed close to our line of sight. Depending on the presence or absence of emission lines in their optical spectra, blazars are categorized into flat spectrum radio quasars (FSRQs) or BL Lacertae (BL Lac) objects. According to the “blazar sequence,” as synchrotron peak frequency ( ) shifts to higher energies, the synchrotron peak luminosity decreases. This means that BL Lac objects as luminous as FSRQs, and with synchrotron peak frequencies Hz, should not exist. Detected as a high-synchrotron peak (HSP; Hz) BL Lac object, 4FGL J1520.8-0348 shows high γ -ray luminosity ( L _γ > 10 ^46 erg s ^−1 ), being at a high redshift of z = 1.46. Since it is an outlier in the “blazar sequence,” the process of its jet acceleration and power may be different from bona fide BL Lac objects. In this work, we constrain its spectral energy distribution (SED) by modeling the multiwavelength data from infrared to γ -ray regime. Simultaneous X-ray data were obtained from X-ray Multi-Mirror Mission and Nuclear Spectroscopic Telescope Array to constrain the synchrotron emission and underlying electron distribution. On undertaking the SED modeling of the source, including the effect of extragalactic background light, we conclude that the source is more likely to be a “blue FSRQ” or “masquerading BL Lac” where the BL Lac object is actually an FSRQ in disguise
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