scholarly journals AstroSat observation of the HBL 1ES 1959+650 during its October 2017 flaring

2021 ◽  
Author(s):  
Zahir Shah ◽  
Savithri H Ezhikode ◽  
Ranjeev Misra ◽  
T R Rajalakshmi
Keyword(s):  
Time Scale ◽  
Rest Frame ◽  
Particle Density ◽  
Density Variation ◽  
Emission Region ◽  
Acceleration Time ◽  
X Ray ◽  
Total Observation ◽  
Region Size ◽  
Observation Period

Abstract We present the results of the X-ray flaring activity of 1ES 1959+650 during October 25-26, 2017 using AstroSat observations. The source was variable in the X-ray. We investigated the evolution of the X-ray spectral properties of the source by dividing the total observation period (∼130 ksecs) into time segments of 5 ksecs, and fitting the SXT and LAXPC spectra for each segment. Synchrotron emission of a broken power-law particle density model provided a better fit than the log-parabola one. The X-ray flux and the normalised particle density at an energy less than the break one, were found to anti-correlate with the index before the break. However, a stronger correlation between the density and index was obtained when a delay of ∼60 ksec was introduced. The amplitude of the normalised particle density variation |Δnγ/nγ| ∼ 0.1 was found to be less than that of the index ΔΓ ∼ 0.5. We model the amplitudes and the time delay in a scenario where the particle acceleration time-scale varies on a time-scale comparable to itself. In this framework, the rest frame acceleration time-scale is estimated to be ∼1.97 × 105 secs and the emission region size to be ∼6.73 × 1015 cms.

scholarly journals FORMATION OF RELATIVISTIC MHD JETS: STATIONARY STATE SOLUTIONS AND NUMERICAL SIMULATIONS

2008 ◽  
Vol 17 (10) ◽  
pp. 1677-1686 ◽  
Author(s):  
CHRISTIAN FENDT ◽  
ELISABETTA MEMOLA
Keyword(s):  
Stationary State ◽  
Rest Frame ◽  
Particle Density ◽  
Acceleration Process ◽  
Jet Formation ◽  
Low Velocity ◽  
X Ray ◽  
Disk Wind ◽  
Mhd Simulations ◽  
Dynamical Parameters

We discuss numerical results of relativistic magnetohydrodynamic (MHD) jet formation models. We first review some examples of stationary state solutions treating the collimation and acceleration process of relativistic MHD jets. We provide an a posteriori check for the MHD condition in highly magnetized flows, namely the comparison of particle density to Goldreich–Julian density. Using the jet dynamical parameters calculated from the MHD model, we show the rest-frame thermal X-ray spectra of the jet, from which we derive the overall spectrum taking into account a variation of Doppler boosting and Doppler shift of emission lines along the outflow. Finally, we present preliminary results of relativistic MHD simulations of jet formation demonstrating the acceleration of a low velocity (0.01 c) disk wind to a collimated high velocity (0.8 c).

The E-ring: interactions with plasma and implications for its evolution

1984 ◽  
Vol 75 ◽  
pp. 599-602
Author(s):  
T.V. Johnson ◽  
G.E. Morfill ◽  
E. Grun
Keyword(s):  
Time Scale ◽  
Particle Density ◽  
High Energy ◽  
Particle Removal ◽  
Density Region ◽  
Drag Forces ◽  
Orbit Evolution ◽  
History Of ◽  
Ring Particle ◽  
Ring Material

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.

scholarly journals The frequency of Kozai–Lidov disc oscillation driven giant outbursts in Be/X-ray binaries

2019 ◽  
Vol 489 (2) ◽  
pp. 1797-1804 ◽  
Author(s):  
Rebecca G Martin ◽  
Alessia Franchini
Keyword(s):  
Orbital Period ◽  
Time Scale ◽  
Orbital Plane ◽  
Material Flows ◽  
X Ray ◽  
System Parameters ◽  
Be Star ◽  
Chaotic Nature ◽  
X Ray Binaries ◽  
Good Agreement

ABSTRACT Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai–Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that the disc aspect ratio is sufficiently small. The eccentric disc overflows its Roche lobe and material flows from the Be star disc over to the companion neutron star causing X-ray activity. With N-body simulations and steady state decretion disc models we explore system parameters for which a disc in the Be/X-ray binary 4U 0115+634 is KL unstable and the resulting time-scale for the oscillations. We find good agreement between predictions of the model and the observed giant outburst time-scale provided that the disc is not completely destroyed by the outburst. This allows the outer disc to be replenished between outbursts and a sufficiently short KL oscillation time-scale. An initially eccentric disc has a shorter KL oscillation time-scale compared to an initially circular orbit disc. We suggest that the chaotic nature of the outbursts is caused by the sensitivity of the mechanism to the distribution of material within the disc. The outbursts continue provided that the Be star supplies material that is sufficiently misaligned to the binary orbital plane. We generalize our results to Be/X-ray binaries with varying orbital period and find that if the Be star disc is flared, it is more likely to be unstable to KL oscillations in a smaller orbital period binary, in agreement with observations.

scholarly journals Energetic characterization and radiographic analysis of torrefied coated MDF residues

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paula Gabriella Surdi de Castro ◽  
Vinícius Resende de Castro ◽  
Antonio José Vinha Zanuncio ◽  
José Cola Zanuncio ◽  
Angélica de Cássia Oliveira Carneiro ◽  
...  
Keyword(s):  
Moisture Content ◽  
Energy Production ◽  
Medium Density Fiberboard ◽  
Volatile Matter ◽  
Density Variation ◽  
Low Oxygen ◽  
Wood Panel ◽  
X Ray ◽  
Energetic Characterization ◽  
Elementary Chemical

AbstractThe use of wood panel residues as biomass for energy production is feasible. Heat treatments can improve energy properties while minimizing the emission of toxic gases due to thermoset polymers used in Medium Density Fiberboard (MDF) panels. Torrefaction or pre-carbonization, a heat treatment between 200 and 300 °C with low oxygen availability accumulates carbon and lignin, decreases hygroscopicity, and increases energy efficiency. The objective of this work was to evaluate the energy parameters (immediate, structural, and elementary chemical composition, moisture content, and yield) and density in torrefied MDF panels. The torrefaction improved the energetic features of coated MDF, decreasing the moisture content, volatile matter, and consequently, concentrating the carbon with better results in the samples torrefied for 40 min. The densitometric profiles of the torrefied MDF, obtained by X-ray densitometry, showed a decrease in the apparent density as torrefaction time increased. The digital X-ray images in gray and rainbow scale enabled the most detailed study of the density variation of MDF residues.

scholarly journals GP management of community-acquired pneumonia in Italy: the ISOCAP study

2005 ◽  
Vol 63 (1) ◽  
Author(s):  
C.M. Sanguinetti ◽  
F. De Benedetto ◽  
C.F. Donner
Keyword(s):  
Outpatient Treatment ◽  
The Elderly ◽  
Community Acquired Pneumonia ◽  
Microbiological Analysis ◽  
X Ray ◽  
Systemic Arterial Hypertension ◽  
Chest X Ray ◽  
Socioeconomic Burden ◽  
Copd Diagnosis ◽  
Observation Period

Background. Community-Acquired Pneumonia (CAP) is still a significant problem in terms of incidence, mortality rate, particularly in infants and the elderly, and socioeconomic burden. General Practitioners (GPs) are the first reference for patients with this disease, but there are few published studies regarding the outpatient treatment of CAP. Methods. The ISOCAP study aimed to identify the type and outcome of the diagnostic-therapeutic management of CAP by GPs in Italy, within the framework of developing a closer interrelationship between GPs and pulmonary specialists. Thirty-six Pulmonary Divisions throughout Italy each contacted 5 local GPs who agreed to recruit the first 5 consecutive patients who consulted them for suspected CAP within the study’s 1-year observation period. Results. A total of 183 GPs took part in the study and enrolled, by the end of the observation period, 763 CAP patients; of these, complete data was available for 737 patients [males=373, females=364, mean age (±SD) 58.8±19.6 years]. 64.4% of patients had concomitant diseases, mainly systemic arterial hypertension and COPD. Diagnosis of CAP was based by GPs on physical examination only in 41.6% of cases; in the remaining chest X-ray was also performed. In only 4.6% of patients were samples sent for microbiological analysis. All patients were treated with antibiotics: 76.7% in mono-therapy, 23.3% with a combination of antibiotics. The antibiotic class most prevalently used in mono-therapy was cephalosporin, primarily ceftriaxone; the most frequently used combinations were cephalosporin+macrolide and cephalosporin+quinolone. Mono-therapy was effective in 70% of cases, the combination of two or more antibiotics in 91.2% of patients. Overall treatment efficacy was 94.7%; hospitalisation was required in 8.5% of cases. Conclusions. Outpatient management of CAP by GPs in Italy is effective, hospitalisation being necessary only in the most severe cases due to age, co-morbidities or extent of pneumonia. This signifies a very significant savings in national health costs.

scholarly journals Variability in Quasar Broad Absorption Line Outflows

2009 ◽  
Vol 5 (S267) ◽  
pp. 394-394
Author(s):  
Daniel M. Capellupo ◽  
Fred Hamann ◽  
Joseph C. Shields ◽  
Tom A. Barlow ◽  
Paola Rodriguez
Keyword(s):  
Physical Properties ◽  
Galaxy Evolution ◽  
High Velocity ◽  
Rest Frame ◽  
Structure Evolution ◽  
Cover Time ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Quasar Spectra ◽  
Observation Period

Broad absorption lines (BALs) in quasar spectra identify high-velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution (e.g., Di Matteo et al. 2005). Studying the variability in these BALs can help us understand the structure, evolution, and basic physical properties of these outflows. We are investigating BAL variability in a sample of 25 luminous quasars at 1.2 < z < 2.9 with multi-epoch observations that cover time scales from less than around a month to 7.7 years in the quasar rest-frame. We investigate changes in the C iv λ1549 BALs, and we see a variety of phenomena, including some BALs that either appeared or disappeared completely and other BALs that did not change at all over the whole observation period.

scholarly journals Characterization of MgO:Cd thin films grown by SILAR method

2018 ◽  
Vol 96 (7) ◽  
pp. 804-809 ◽  
Author(s):  
Harun Güney ◽  
Demet İskenderoğlu
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Soda Lime ◽  
Morphological Properties ◽  
Emission Region ◽  
Soda Lime Glass ◽  
Silar Method ◽  
Soda Lime Glass Substrate ◽  
X Ray ◽  
Cd Doping

The undoped and 1%, 2%, and 3% Cd-doped MgO nanostructures were grown by SILAR method on the soda lime glass substrate. X-ray diffractometer (XRD), ultraviolet–visible spectrometer, scanning electron microscope, photoluminescence (PL), and X-ray photoelectron spectroscopy measurements were taken to investigate Cd doping effects on the structural, optical, and morphological properties of MgO nanostructures. XRD measurements show that the samples have cubic structure and planes of (200), (220) of MgO and (111), (200), and (220) of CdO. It was observed that band gaps increase with rising Cd doping rate in MgO thin film. The surface morphology of samples demonstrates that MgO nanostructures have been affected by the Cd doping. PL measurements show that undoped and Cd-doped MgO thin films can radiate in the visible emission region.

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