Compton-thick AGN in the NuSTAR era II: A deep NuSTAR and XMM-Newton view of the candidate Compton thick AGN in NGC 1358

We present the combined NuSTATR 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 physical motivated models, at >3 $\sigma$ confidence level. Our best-fit shows that the column density along the 'line-of-sight' of the obscuring material surrounding the accreting super-massive black hole is N$\rm _H$ = [1.96--2.80] $\times$ 10$^{24}$ cm$^{-2}$. The high-quality data from NuSTAR gives the best constraints on the spectral shape above $\sim$10 keV to date on NGC 1358. Moreover, by combining NuSTAR and XMM-Newton data, we find that the obscuring torus has a low covering factor ($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 $\lambda_{\rm Edd}$ $\sim$$4.7_{-0.3}^{+0.3}$ $\times$ 10$^{-2}$, which is in acceptable agreement with previous measurements. Finally, we find no evidence of short-term variability, over a $\sim$100 ks time-span, in terms of both 'line-of-sight' column density and flux.Comment: 12 pages, 6 figure

BASS XXXIII: Swift-BAT blazars and their jets through cosmic time

We derive the most up-to-date Swift-Burst Alert Telescope (BAT) blazar luminosity function in the 14-195 keV range, making use of a clean sample of 118 blazars detected in the BAT 105-month survey catalog, with newly obtained redshifts from the BAT AGN Spectroscopic Survey (BASS). We determine the best-fit X-ray luminosity function for the whole blazar population, as well as for Flat Spectrum Radio Quasars (FSRQs) alone. The main results are: (1) at any redshift, BAT detects the most luminous blazars, above any possible break in their luminosity distribution, which means we cannot differentiate between density and luminosity evolution; (2) the whole blazar population, dominated by FSRQs, evolves positively up to redshift z~4.3, confirming earlier results and implying lower number densities of blazars at higher redshifts than previously estimated. The contribution of this source class to the Cosmic X-ray Background at 14-195 keV can range from 5-18%, while possibly accounting for 100% of the MeV background. We also derived the average 14 keV-10 GeV SED for BAT blazars, which allows us to predict the number counts of sources in the MeV range, as well as the expected number of high-energy (>100 TeV) neutrinos. A mission like COSI, will detect 40 MeV blazars and 2 coincident neutrinos. Finally, taking into account beaming selection effects, the distribution and properties of the parent population of these extragalactic jets are derived. We find that the distribution of viewing angles is quite narrow, with most sources aligned within < 5{\deg} of the line of sight. Moreover, the average Lorentz factor, = 8-12, is lower than previously suggested for these powerful sources.Comment: Accepted for publication in the Astrophysical Journal; 33 pages; 8 Tables; 16 Figure

Detection of a gamma-ray flare from the high-redshift blazar DA 193

High-redshift ($z>2$) blazars are the most powerful members of the blazar family. Yet, only a handful of them have both X-ray and $\gamma$-ray detection, thereby making it difficult to characterize the energetics of the most luminous jets. Here, we report, for the first time, the Fermi-Large Area Telescope detection of the significant $\gamma$-ray emission from the high-redshift blazar DA 193 ($z=2.363$). Its time-averaged $\gamma$-ray spectrum is soft ($\gamma$-ray photon index = $2.9\pm0.1$) and together with a relatively flat hard X-ray spectrum (14$-$195 keV photon index = $1.5\pm0.4$), DA 193 presents a case to study a typical high-redshift blazar with inverse Compton peak being located at MeV energies. An intense GeV flare was observed from this object in the first week of 2018 January, a phenomenon rarely observed from high-redshift sources. What makes this event a rare one is the observation of an extremely hard $\gamma$-ray spectrum (photon index = $1.7\pm0.2$), which is somewhat unexpected since high-redshift blazars typically exhibit a steep falling spectrum at GeV energies. The results of our multi-frequency campaign, including both space- (Fermi, NuSTAR, and Swift) and ground-based (Steward and Nordic Optical Telescope) observatories, are presented and this peculiar $\gamma$-ray flare is studied within the framework of a single-zone leptonic emission scenario.Comment: 14 pages, 9 figures, 2 tables, to appear in the Astrophysical Journa

Compton-thick AGNs in the NuSTAR Era. III. A Systematic Study of the Torus Covering Factor

We present the analysis of a sample of 35 candidate Compton-thick active galactic nuclei (AGNs) selected in the nearby universe (average redshift 〈z〉 ~ 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 (N_(H,z)), the average torus column density (N H,tor), and the torus covering factor (f_c ). We compare the best-fit results obtained with the widely used MYTorus (Murphy & Yaqoob 2009) model with those of the recently published borus02 model (Baloković et al. 2018) used in the same geometrical configuration of MYTorus (i.e., with f_c = 0.5). We find a remarkable agreement between the two, although with increasing dispersion in N_(H,z) moving toward higher column densities. We then use borus02 to measure f_c . High-f c sources have, on average, smaller offset between N_(H,z) and N_(H,tor) than low-f_c ones. Therefore, low f c values can be linked to a "patchy torus" scenario, where the AGN is seen through an overdense region in the torus, while high-f c objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between f c and the AGN 2–10 keV luminosity, i.e., sources with higher f c values have on average lower luminosities

NuSTAR, Swift, and GROND observations of the flaring MeV blazar: PMN J0641−0320

MeV blazars are a sub-population of the blazar family, exhibiting larger-than-average jet powers, accretion luminosities, and black hole masses. Because of their extremely hard X-ray continua, these objects are best studied in the X-ray domain. Here, we report on the discovery by the Fermi Large Area Telescope and subsequent follow-up observations with NuSTAR, Swift, and GROND of a new member of the MeV blazar family: PMN J0641−0320. Our optical spectroscopy provides confirmation that this is a flat-spectrum radio quasar located at a redshift of z = 1.196. Its very hard NuSTAR spectrum (power-law photon index of ~1 up to ~80 keV) indicates that the emission is produced via inverse Compton scattering off of photons coming from outside the jet. The overall spectral energy distribution of PMN J0641−0320 is typical of powerful blazars and, using a simple one-zone leptonic emission model, we infer that the emission region is located either inside the broad line region or within the dusty torus

BAT AGN Spectroscopic Survey: XVI. General Physical Characteristics of BAT Blazars

The recently released 105-month Swift-Burst Alert Telescope (BAT) all-sky hard X-ray survey catalog presents an opportunity to study astrophysical objects detected in the deepest look at the entire hard X-ray (14–195 keV) sky. Here we report the results of a multifrequency study of 146 blazars from this catalog, quadrupling the number compared to past studies, by utilizing recent data from the Fermi-Large Area Telescope (LAT), Swift-BAT, and archival measurements. In our γ-ray analysis of ~10 yr of the LAT data, 101 are found as γ-ray emitters, whereas, 45 remains LAT undetected. We model the broadband spectral energy distributions with a synchrotron-inverse Compton radiative model. On average, BAT detected sources host massive black holes (M_(bh) ~ 10^9 M ⊙) and luminous accretion disks (L_d ~ 10^(46) erg s^(−1)). At high redshifts (z > 2), BAT blazars host more powerful jets with luminous accretion disks compared to those detected only with Fermi-LAT. We find good agreement in the black hole masses derived from the single-epoch optical spectroscopic measurements and standard accretion disk modeling approaches. Other physical properties of BAT blazars are similar to those known for Fermi-LAT detected objects

Next Generation Molecular Diagnosis of Hereditary Spastic Paraplegias: An Italian Cross-Sectional Study

Hereditary spastic paraplegia (HSP) refers to a group of genetically heterogeneous neurodegenerative motor neuron disorders characterized by progressive age-dependent loss of corticospinal motor tract function, lower limb spasticity, and weakness. Recent clinical use of next generation sequencing (NGS) methodologies suggests that they facilitate the diagnostic approach to HSP, but the power of NGS as a first-tier diagnostic procedure is unclear. The larger-than-expected genetic heterogeneity-there are over 80 potential disease-associated genes-and frequent overlap with other clinical conditions affecting the motor system make a molecular diagnosis in HSP cumbersome and time consuming. In a single-center, cross-sectional study, spanning 4 years, 239 subjects with a clinical diagnosis of HSP underwent molecular screening of a large set of genes, using two different customized NGS panels. The latest version of our targeted sequencing panel (SpastiSure3.0) comprises 118 genes known to be associated with HSP. Using an in-house validated bioinformatics pipeline and several in silico tools to predict mutation pathogenicity, we obtained a positive diagnostic yield of 29% (70/239), whereas variants of unknown significance (VUS) were found in 86 patients (36%), and 83 cases remained unsolved. This study is among the largest screenings of consecutive HSP index cases enrolled in real-life clinical-diagnostic settings. Its results corroborate NGS as a modern, first-step procedure for molecular diagnosis of HSP. It also disclosed a significant number of new mutations in ultra-rare genes, expanding the clinical spectrum, and genetic landscape of HSP, at least in Italy

Blazar spectral variability as explained by a twisted inhomogeneous jet

Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming1. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles2, with possible intervention of shock waves3,4 or turbulence5. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events6,7,8,9,10 and can also explain specific properties of blazar emission, such as intra-day variability11, quasi-periodicity12,13 and the delay of radio flux variations relative to optical changes14. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions—such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution—can explain snapshots of the spectral behaviour of blazars in many cases15,16. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities17 or rotation of the twisted jet6 cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016–2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle. The agreement between observations and theoretical predictions can be seen as further validation of the relativistic beaming theory