Context. Blazar flares provide a window onto the extreme physical processes occurring in relativistic outflows. Most numerical codes used for modelling blazar emission during flares use a simplified ...continuous-loss description of particle cooling due to the inverse Compton (IC) process, neglecting non-continuous (discrete) effects that arise in the Klein–Nishina (KN) regime. The significance of such effects has not yet been explored in detail. Aims. In this study, we investigate the importance of non-continuous Compton cooling losses and their impact on the electron spectrum and spectral energy distribution (SED) of blazars during high flux states (flares), as well as in the low state. Methods. We solve the full transport equation numerically, accounting for large relative jumps in energy by extending our existing blazar flare modelling code EMBLEM. We perform a detailed physical modelling of the brightest γ -ray flare of the archetypal flat-spectrum radio quasar (FSRQ) 3C 279 detected in June 2015. We then compare results obtained using the full cooling term and using the continuous-loss approximation. Results. We show that during flaring states of FSRQs characterised by high Compton dominance, the non-continuous cooling can lead to significant modification of the electron spectrum, introducing a range of distinct features, such as low-energy tails, hardening and/or softening, narrow and extended particle excesses, and shifts in the cooling break position. Such distortion translates to differences in the associated SED of up to ∼50%. This highlights the importance of non-continuous effects and the need to consider them in blazar emission models, particularly applied to extreme γ -ray flares.
ABSTRACT
Various attempts have been made in the literature at describing the origin and the physical mechanisms behind flaring events in blazars with radiative emission models, but detailed ...properties of multiwavelength (MWL) light curves still remain difficult to reproduce. We have developed a versatile radiative code, based on a time-dependent treatment of particle acceleration, escape, and radiative cooling, allowing us to test different scenarios to connect the continuous low-state emission self-consistently with that during flaring states. We consider flares as weak perturbations of the quiescent state and apply this description to the 2010 February MWL flare of Mrk 421, the brightest very high energy (VHE) flare ever detected from this archetypal blazar, focusing on interpretations with a minimum number of free parameters. A general criterion is obtained, which disfavours a one-zone model connecting low and high state under our assumptions. A two-zone model combining physically connected acceleration and emission regions yields a satisfactory interpretation of the available time-dependent MWL light curves and spectra of Mrk 421, although certain details remain difficult to reproduce. The two-zone scenario finally proposed for the complex quiescent and flaring VHE emitting region involves both Fermi-I and Fermi-II acceleration mechanisms, respectively, at the origin of the quiescent and flaring emission.
Abstract
Despite numerous studies, the origin of the
γ
-ray emission from blazars is still debated, in particular whether it is produced by leptonic or hadronic processes. In this study, we are ...testing the leptonic scenario for the flat-spectrum radio quasar 3C 279, assuming that the
γ
-ray emission is generated by inverse Compton scattering of external target photons from the broad-line region (IC-BLR scenario). For this purpose we use a 10 yr data set of the source consisting of the optical spectroscopy data from the Steward Observatory blazar monitoring program and Fermi Large Area Telescope
γ
-ray data. We search for a possible correlation between the Compton dominance and the emission-line luminosity using the discrete correlation function analysis. As a result, we find no significant correlation between these two quantities at any time lag value, while the emission-line luminosity displays a moderate correlation with the
γ
-ray flux at a zero time lag. We also reveal that the optical synchrotron continuum flux shows a pronounced correlation with the
γ
-ray flux, and therefore we interpret these results within the leptonic IC-BLR scenario where the variations in Compton dominance are primarily induced by changes in the magnetic field, rather than in the emission-line luminosity.
Context.
Sagittarius A*, the supermassive black hole at the center of our Galaxy, exhibits episodic near-infrared flares. The recent monitoring of three such events with the GRAVITY instrument has ...shown that some flares are associated with orbital motions in the close environment of the black hole. The GRAVITY data analysis indicates a super-Keplerian azimuthal velocity, while (sub-) Keplerian velocity is expected for the hot flow surrounding the black hole.
Aims.
We develop a semi-analytic model of the Sagittarius A* flares based on an ejected large plasmoid, inspired by recent particle-in-cell global simulations of black hole magnetospheres. We model the infrared astrometric and photometric signatures associated with this model.
Methods.
We considered a spherical macroscopic hot plasma region that we call a large plasmoid. This structure was ejected along a conical orbit in the vicinity of the black hole. This plasmoid was assumed to be formed by successive mergers of smaller plasmoids produced through magnetic reconnection that we did not model. Nonthermal electrons were injected into the plasmoid. We computed the evolution of the electron-distribution function under the influence of synchrotron cooling. We solved the radiative transfer problem associated with this scenario and transported the radiation along null geodesics of the Schwarzschild space time. We also took the quiescent radiation of the accretion flow into account, on top of which the flare evolves.
Results.
For the first time, we successfully account for the astrometric and flux variations of the GRAVITY data with a flare model that incorporates an explicit modeling of the emission mechanism. The prediction of our model and recent data agree well. In particular, the azimuthal velocity of the plasmoid is set by the magnetic field line to which it belongs, which is anchored in the inner parts of the accretion flow, hence the super-Keplerian motion. The astrometric track is also shifted with respect to the center of mass due to the quiescent radiation, in agreement with the difference measured with the GRAVITY data.
Conclusions.
These results support the hypothesis that magnetic reconnection in a black hole magnetosphere is a viable model for the infrared flares of Sagittarius A*.
The article summarises the advanced world experience in government regulation of the automotive industry using the example of the leading automotive manufacturing countries – China, Japan, India, ...South Korea, the USA, and the European Union. Leading approach to the study of this problem is the comparative method that has afforded revealing peculiarities of the primary measures applied by governments of the world to regulate the automotive industry have been identified. A unified model for government regulation of the automotive industry has been elaborated. The presented model contains a set of measures for government support for the automotive industry depending on the life cycle stage (inception, growth, stabilisation, top position, stagnation, decline, crisis) of the automotive industry and the level (high, medium, low) of competitiveness of automotive enterprises.
The First G-APD Cherenkov Telescope (FACT) demonstrates the usability of novel Geiger-mode operated Avalanche Photo Diodes (G-APD, often called SiPM) for Imaging Atmospheric Cherenkov Telescopes ...(IACT). The camera consists of 1440pixels with dedicated electronics operating at 2 Giga samples per second. It is installed on the refurbished HEGRA telescope with a mirror area of ≈9.5m2 on the Canary Island La Palma. FACT is taking data almost every night since the camera was installed in October 2011. It was possible to improve the data taking efficiency to very high values due to the very stable and reliable operation. This also allows to operate FACT remotely without any need for operators on site. Even remote human intervention became less and less frequent over the years, allowing operation to become mostly automatic. FACT is monitoring the long-term behavior of some very-high energy variable extra-galactic sources with unparalleled sampling density as well as testing the behavior of the sensors under severe weather conditions. Due to the long exposure of FACT's G-APDs under strong moonlight conditions it was possible to evaluate the aging effects of G-APDs due to collected charge. No indication of aging was found. No external calibration device is needed to operate FACT since the properties of the sensors themselves allow for a high precision self-calibration of the camera.
•SiPMs show no sign of ageing in 5years of operation.•High precision self calibration is possible without external calibration device.•Very high data taking efficiency has been reach due to excessive automation.
Neonates and infants are susceptible to hypoxaemia in the perioperative period. The aim of this study was to analyse interventions related to anaesthesia tracheal intubations in this European cohort ...and identify their clinical consequences.
We performed a secondary analysis of tracheal intubations of the European multicentre observational trial (NEonate and Children audiT of Anaesthesia pRactice IN Europe NECTARINE) in neonates and small infants with difficult tracheal intubation. The primary endpoint was the incidence of difficult intubation and the related complications. The secondary endpoints were the risk factors for severe hypoxaemia attributed to difficult airway management, and 30 and 90 day outcomes.
Tracheal intubation was planned in 4683 procedures. Difficult tracheal intubation, defined as two failed attempts of direct laryngoscopy, occurred in 266 children (271 procedures) with an incidence (95% confidence interval CI) of 5.8% (95% CI, 5.1–6.5). Bradycardia occurred in 8% of the cases with difficult intubation, whereas a significant decrease in oxygen saturation (SpO2<90% for 60 s) was reported in 40%. No associated risk factors could be identified among co-morbidities, surgical, or anaesthesia management. Using propensity scoring to adjust for confounders, difficult anaesthesia tracheal intubation did not lead to an increase in 30 and 90 day morbidity or mortality.
The results of the present study demonstrate a high incidence of difficult tracheal intubation in children less than 60 weeks post-conceptual age commonly resulting in severe hypoxaemia. Reassuringly, the morbidity and mortality at 30 and 90 days was not increased by the occurrence of a difficult intubation event.
NCT02350348.
Automotive industry is the strategically important part of the industry, which making the significant contribution in the formation of the gross domestic product, the attraction of investments and ...the creation of workplaces. The world experience of the automotive industry development shows the active participation of the states governments in the formation of the national automobile construction complexes, in particular, in the direction of the state stimulation of the internal demand for the domestic automobiles. At the same time, the growth of the internal demand for the domestic automobiles due to using the state measures creates not only new opportunities for the automotive enterprises, but also new threats. One of these threats is the risk of not receiving the desired economic effect (profit) by the automotive enterprises. The purpose of the article is the development of the methodical tools for the forecasting the economic risks of the automotive enterprises in the conditions of the state stimulation of the internal demand for the automobiles. In the article the methodical tools for the forecasting the economic risks of the automotive enterprises in the conditions of the state stimulation of the internal demand for the automobiles through the calculation of the amount of the expected profit and the level of the optimal economic risk are developed. At the same time, the forecasting the economic risks of the automotive enterprises in the conditions of the state stimulation of the internal demand for the automobiles is proposed to implement in the six variants of the ratio of the initial internal demand for the domestic automobiles, the planned (expected as the result of the state stimulation of the internal demand for the automobiles) demand for the domestic automobiles and the production capacity of the automotive enterprises. It was found out that the factors that cause the increase of the economic risks of the automotive enterprises in the conditions of the state stimulation of the internal demand for the automobiles are: the amount of the variable costs; the amount of the costs for the payment of the personnel labor of the enterprise; the cost of the automotive products; the size of the penalties for the failure to comply with the conditions of the concluded contracts for the production of automobiles; the amount of the capital investments. The factors that contribute to the reducing the economic risk of the automotive enterprises in the conditions of the state stimulation of the internal demand for the automobiles are: the volume of the orders for the automobiles, which was not accepted for the consideration when the planned production indicators were set; the value of the additional internal demand for the automobiles of the domestic production; the level of the income rate.
Hypertrophic pyloric stenosis in otherwise healthy neonates frequently requires urgent surgical procedure but anaesthesia care may result in respiratory complications, such as hypoxaemia, pulmonary ...aspiration of gastric contents, and postoperative apnoea. The primary aim was to study whether or not the incidence of difficult airway management and of hypoxaemia in neonates undergoing pyloric stenosis repair was higher than that in neonates undergoing other surgeries.
Data on neonates and infants undergoing anaesthesia and surgery for pyloric stenosis were extracted from the NEonate and Children audiT of Anesthesia pRactice In Europe (NECTARINE) database, for secondary analysis.
We identified 310 infants who had anaesthesia for surgery for pyloric stenosis. Difficult airway management (more than two attempts at laryngoscopy) was higher in children with pyloric stenosis when compared with the entire NECTARINE cohort (7.9% 95% confidence interval {CI}, 5.22–11.53 vs 4.4% 95% CI, 1.99–6.58; relative risk RR=1.81 95% CI, 1.21–2.69; P=0.004), whereas transient hypoxaemia with oxygen saturation <90% was comparable between the two cohorts. Postoperative complications occurred in 16 children (5.6%) within the 30-day follow-up. No mortality was reported at 30 and 90 days.
Children undergoing surgery for pyloric stenosis had a higher incidence of difficult intubation compared with the entire NECTARINE cohort.
NCT 02350348.
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