scholarly journals Multiwavelength study of Fermi hard spectrum blazar B2 0806+35 using Swift, Fermi, and TACTIC observations

2018 ◽  
Vol 481 (4) ◽  
pp. 4505-4512 ◽  
Author(s):  
S Bhattacharyya ◽  
B Ghosal ◽  
P Chandra ◽  
K K Singh ◽  
K K Yadav ◽  
...  
Keyword(s):  
Hard Spectrum

scholarly journals EBL Inhomogeneity and Hard-Spectrum Gamma-Ray Sources

2017 ◽  
Vol 835 (2) ◽  
pp. 237 ◽  
Author(s):  
Hassan Abdalla ◽  
Markus Böttcher
Keyword(s):  
Gamma Ray ◽  
Hard Spectrum

scholarly journals Leptonic and Hadronic Modeling of Fermi-LAT Hard Spectrum Quasars and Predictions for High-energy Polarization

2018 ◽  
Vol 863 (1) ◽  
pp. 98 ◽  
Author(s):  
Vaidehi S. Paliya ◽  
Haocheng Zhang ◽  
Markus Böttcher ◽  
M. Ajello ◽  
A. Domínguez ◽  
...  
Keyword(s):  
High Energy ◽  
Hard Spectrum

Hard spectrum TeV blazars and intergalactic magnetic fields

2012 ◽  
Author(s):  
Timothy C. Arlen ◽  
Vladimir V. Vassiliev
Keyword(s):  
Magnetic Fields ◽  
Hard Spectrum

scholarly journals <i>Letter to the Editor</i>Forbush precursory increase and shock-associated particles on 20 October 1989

2002 ◽  
Vol 20 (8) ◽  
pp. 1247-1252 ◽  
Author(s):  
A. Struminsky
Keyword(s):  
Cosmic Rays ◽  
Rare Event ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Maximum Energy ◽  
Shock Acceleration ◽  
Interplanetary Magnetic Fields ◽  
Interplanetary Physics ◽  
Hard Spectrum ◽  
Flare Site

Abstract. Strong interplanetary disturbances may affect cosmic ray protons tremendously with energies less than 1 GeV, increasing their intensity by hundreds of percents, but they are not so effective for protons of higher energies. This energy limit is crucial to understand processes of cosmic ray propagation and acceleration in the heliosphere. The Forbush pre-increase and the effect of shock-associated particles observed on 20 October 1989 illustrate the problem. This is a rare event, when the energies of shock-associated particles measured by the GOES-7 satellite spread continuously to the neutron monitor energies. The Forbush pre-increase could be attributed to a single reflection of galactic cosmic rays from the magnetic wall observed at 12:00 UT. It had a very hard spectrum with maximum energy of modulation more than 10 GeV. The spectrum of shock-associated particles was soft and their maximum energy was less than 1 GeV. The problem of shock acceleration versus trapping is discussed for the 20 October 1989 event. It is argued that the shock-associated particles were accelerated near the flare site and then propagated to the Earth inside the trap between two magnetic walls at 12:00 UT and 17:00 UT.Key words. Interplanetary physics (cosmic rays; energetic particles; interplanetary magnetic fields)

scholarly journals Atmospheric ionization by high-fluence, hard-spectrum solar proton events and their probable appearance in the ice core archive

2016 ◽  
Vol 121 (6) ◽  
pp. 3017-3033 ◽  
Author(s):  
Adrian L. Melott ◽  
Brian C. Thomas ◽  
Claude M. Laird ◽  
Ben Neuenswander ◽  
Dimitra Atri
Keyword(s):  
Ice Core ◽  
Solar Proton ◽  
High Fluence ◽  
Hard Spectrum ◽  
Solar Proton Events ◽  
Atmospheric Ionization

scholarly journals Wind accretion in Cygnus X-1

2020 ◽  
Vol 637 ◽  
pp. A66 ◽  
Author(s):  
E. Meyer-Hofmeister ◽  
B. F. Liu ◽  
E. Qiao ◽  
R. E. Taam
Keyword(s):  
Black Hole ◽  
Stellar Wind ◽  
Binary Systems ◽  
Three Dimensional ◽  
Stable States ◽  
X Ray ◽  
Hard State ◽  
Hard Spectrum ◽  
Low Mass ◽  
Hydrodynamical Simulations

Context. Cygnus X-1 is a black hole X-ray binary system in which the black hole captures and accretes gas from the strong stellar wind emitted by its supergiant O9.7 companion star. The irradiation of the supergiant star essentially determines the flow properties of the stellar wind and the X-ray luminosity from the system. The results of three-dimensional hydrodynamical simulations of wind-fed X-ray binary systems reported in recent work reveal that the ionizing feedback of the X-ray irradiation leads to the existence of two stable states with either a soft or a hard spectrum. Aims. We discuss the observed radiation of Cygnus X-1 in the soft and hard state in the context of mass flow in the corona and disk, as predicted by the recent application of a condensation model. Methods. The rates of gas condensation from the corona to the disk for Cygnus X-1 are determined, and the spectra of the hard and soft radiation are computed. The theoretical results are compared with the MAXI observations of Cygnus X-1 from 2009 to 2018. In particular, we evaluate the hardness-intensity diagrams (HIDs) for its ten episodes of soft and hard states which show that Cygnus X-1 is distinct in its spectral changes as compared to those found in the HIDs of low-mass X-ray binaries. Results. The theoretically derived values of photon counts and hardness are in approximate agreement with the observed data in the HID. However, the scatter in the diagram is not reproduced. Improved agreement could result from variations in the viscosity associated with clumping in the stellar wind and corresponding changes of the magnetic fields in the disk. The observed dipping events in the hard state may also contribute to the scatter and to a harder spectrum than predicted by the model.

scholarly journals Kinetic parameters study based on burn-up for improving the performance of research reactor equilibrium core

2014 ◽  
Vol 29 (4) ◽  
pp. 253-258 ◽  
Author(s):  
Atta Muhammad ◽  
Masood Iqbal ◽  
Tayyab Mahmood
Keyword(s):  
Kinetic Parameters ◽  
Generation Time ◽  
Research Reactor ◽  
Prompt Neutron ◽  
Neutron Generation ◽  
Delayed Neutron ◽  
Fuel Burn ◽  
Hard Spectrum ◽  
Computer Codes ◽  
Enriched Uranium

In this study kinetic parameters, effective delayed neutron fraction and prompt neutron generation time have been investigated at different burn-up stages for research reactor's equilibrium core utilizing low enriched uranium high density fuel (U3Si2-Al fuel with 4.8 g/cm3 of uranium). Results have been compared with reference operating core of Pakistan research Reactor-1. It was observed that by increasing fuel burn-up, effective delayed neutron fraction is decreased while prompt neutron generation time is increased. However, over all ratio beff/L is decreased with increasing burn-up. Prompt neutron generation time L in the understudy core is lower than reference operating core of reactor at all burn-up steps due to hard spectrum. It is observed that beff is larger in the understudy core than reference operating core of due to smaller size. Calculations were performed with the help of computer codes WIMSD/4 and CITATION.

Hard Spectrum STFR (Spray Type Fast Reactor) Cooled by Water at 7.5 MPa

2004 ◽  
Author(s):  
Asashi Kitamoto ◽  
Yasunori Ohoka
Keyword(s):  
Fast Reactor ◽  
Void Ratio ◽  
Cross Flow ◽  
Hot Water ◽  
Future Performance ◽  
Mox Fuel ◽  
Fuel Burn ◽  
Hard Spectrum ◽  
Two Phases ◽  
Gen Iv

New concept of fast reactor (FR), i.e. the STFR (Spray Type FR), is proposed here to perform high burn-up of UO2 fuel or MOX fuel by the use of BWR technology, and to improve the backend process of discharged fuel. STFR can be realized by some important changes of BWR system, at 7.50MPa. In case of STFR, heat produced in the core is removed by the evaporation of sprayed hot water jetted to fuel with cross flow at 7.50MPa, and two phases (liquid and vapor) of coolant at high void ratio goes down to the bottom of PV (pressure vessel). This is an improved concept of BWR, which can be regarded as a breakthrough of FBR. This concept has not been listed in GEN IV. Future performance of STFR are as follows, (1) STFR can increase the fraction of direct fission of 238U with neutron reaction of higher energy than 1MeV, (2) STFR can burn the nuclear fuel to the higher burn-up (80 to 200GWd/Mg-HM) compared with BWR fuel burn-up. (3) Higher burn-up of fuel will reduce the frequency of reprocessing, so STFR can reduce the reprocessing cost per power production. (4) STFR can reduce the remains of Pu and MA (Minor Actinides: Np, Am, Cm etc.) in discharged fuel.

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