High Energy Radiation from Pulsars

2000 ◽  
Vol 177 ◽  
pp. 427-432 ◽  
Author(s):  
K.S. Cheng
Keyword(s):  
Pair Production ◽  
Production Condition ◽  
Three Dimensional ◽  
High Energy ◽  
Polar Cap ◽  
High Energy Radiation ◽  
Particle Flows ◽  
Consistent Model ◽  
Local Properties ◽  
Vertical Size

AbstractWe propose a three dimensional pulsar magnetosphere model in which the vertical size of the outer gap is first determined by a self-consistent model in which the outer gap is limited by the pair production from collisions of thermal photons produced by polar cap heating of backflow outer gap current and the curvature photons emitted by the gap accelerated charged particles. The transverse size of the outer gap is determined by local pair production condition. In principle, there are two topologically disconnected outer gaps existing in the magnetosphere of a pulsar and both incoming and outgoing particle flows are allowed. And yet double-peak light curves with strong bridges are most common. Using this model and its local properties, we compare the model results with phase-resolved spectra of the Crab pulsar and Geminga.

scholarly journals A Three-dimensional Outer-magnetospheric Gap Model for Gamma-ray Pulsars: I. The Crab Pulsar

2000 ◽  
Vol 195 ◽  
pp. 223-232
Author(s):  
K. S. Cheng ◽  
M. Ruderman ◽  
L. Zhang
Keyword(s):  
Pair Production ◽  
Gamma Ray ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Crab Pulsar ◽  
Particle Flows ◽  
Consistent Model ◽  
Local Properties ◽  
Local Pair ◽  
Magnetic Pair

We use a three-dimensional pulsar magnetosphere model to study the geometry of outer-magnetospheric gaps. The vertical size of the “outer gap” is first determined by a self-consistent model in which the outer gap size is limited by pair production from collisions between (1) thermal photons produced from polar cap heating by backflow “outer gap” current, and (2) the curvature photons emitted by gap-accelerated charged particles. The transverse size of the outer gap is also determined by local pair production limits. In principle, there are two topologically disconnected outer gaps in the magnetosphere of a pulsar. Both incoming and outgoing particle flows are allowed. However, the emission morphologies produced by incoming particle flow is severely restricted by local pair production in the gap and the absorption of magnetic pair production near the star. Double-peaked light curves with strong bridges are most common. From the three-dimensional structure of the outer gap and its local properties, we calculate the emission morphologies and phase-resolved spectra of gamma-ray pulsars. Applications to the Crab pulsar illustrate the model.

scholarly journals Gel Dosimetry with Radio-Fluorogenic Coumarin

2018 ◽  
Author(s):  
Peter A. Sandwall ◽  
Brandt P. Bastow ◽  
Henry B. Spitz ◽  
Howard R. Elson ◽  
Michael Lamba ◽  
...  
Keyword(s):  
Free Radicals ◽  
Carboxylic Acid ◽  
Three Dimensional ◽  
High Energy ◽  
Water Radiolysis ◽  
Gel Dosimetry ◽  
Rate Dependency ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Hydroxyl Free Radicals

In radiotherapy, accurate deposition of energy to the targeted volume is vital to ensure effective treatment. Gel dosimeters are attractive detection systems, as tissue substitutes with potential to yield three-dimensional dose distributions. Radio-fluorogenesis is creation fluorescent chemical products in response to energy deposition from high-energy radiation. This report shares studies of a radio-fluorogenic gel dosimetry system, gelatin with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission, following UV to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated for this system. The response of the system was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship with a dose-rate dependency and no energy or type dependencies. This report supports the utility of gelatin-C3CA for phantom studies of radio-fluorogenic processes.

scholarly journals Two-pole Caustic Model for High-energy Radiation from Pulsars — Polarization

2004 ◽  
Vol 218 ◽  
pp. 373-374
Author(s):  
Jarosław Dyks ◽  
Alice K. Harding ◽  
Bronisław Rudak
Keyword(s):  
High Energy ◽  
Light Curves ◽  
Optical Data ◽  
Crab Pulsar ◽  
Gap Model ◽  
Polar Cap ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Cap Model

We present high-energy light curves and polarization properties of pulsars calculated within the recently proposed two-pole caustic model. The results are compared with the optical data for the Crab pulsar and with predictions of other high-energy pulsar models: the polar cap model, and the outer gap model.

scholarly journals High-energy radiation and pair production by Coulomb processes in particle-in-cell simulations

2019 ◽  
Vol 26 (10) ◽  
pp. 103109 ◽  
Author(s):  
B. Martinez ◽  
M. Lobet ◽  
R. Duclous ◽  
E. d'Humières ◽  
L. Gremillet
Keyword(s):  
Pair Production ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Particle In Cell

scholarly journals The Posttransit Tail of WASP-107b Observed at 10830 Å

2021 ◽  
Vol 162 (6) ◽  
pp. 284
Author(s):  
J. J. Spake ◽  
A. Oklopčić ◽  
L. A. Hillenbrand
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Stellar Winds ◽  
High Energy Radiation ◽  
Absorption Signal ◽  
Metastable Helium ◽  
Atmospheric Escape ◽  
First Time ◽  
Excess Absorption ◽  
Three Dimensional Simulations

Abstract Understanding the effects of high-energy radiation and stellar winds on planetary atmospheres is vital for explaining the observed properties of close-in exoplanets. Observations of transiting exoplanets in the triplet of metastable helium lines at 10830 Å allow extended atmospheres and escape processes to be studied for individual planets. We observed one transit of WASP-107b with NIRSPEC on Keck at 10830 Å. Our observations, for the first time, had significant posttransit phase coverage, and we detected excess absorption for over an hour after fourth contact. The data can be explained by a comet-like tail extending out to ∼7 planet radii, which corresponds to roughly twice the Roche lobe radius of the planet. Planetary tails are expected based on three-dimensional simulations of escaping exoplanet atmospheres, particularly those including the interaction between the escaped material and strong stellar winds, and have been previously observed at 10830 Å in at least one other exoplanet. With both the largest midtransit absorption signal and the most extended tail observed at 10830 Å, WASP-107b remains a keystone exoplanet for atmospheric escape studies.

scholarly journals Modelling X-ray and Gamma-ray Emission from Pulsars

2003 ◽  
Vol 214 ◽  
pp. 177-180
Author(s):  
B. Rudak ◽  
J. Dyks
Keyword(s):  
Space Charge ◽  
Gamma Ray ◽  
High Energy ◽  
Energy Spectra ◽  
Polar Cap ◽  
Unique Case ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Γ Ray

Lightcurves and broadband energy spectra of the brightest X/γ-ray sources among the rotation powered pulsars exhibit unexpected richness of features, making each object almost a unique case. This contribution presents how our models of high-energy radiation within the framework of SCLF (space charge limited flow) polar-cap scenarios tackle with some of these challenges.

Photo-degradation of monoazo dye blue 13 using advanced oxidation process

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Aqueous Solution ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
High Energy ◽  
Uv Exposure ◽  
H2o2 Concentration ◽  
Oxidizing Agent ◽  
Photo Degradation ◽  
High Energy Radiation ◽  
Uv Lamp

The high energy radiation overcome the bonding of solute in a solution and H2O2 acts as an oxidizing agent and generates a free radical in the solution which results in photo-degradation by converting the solute in to simple form and resultantly, colored substance under the effect of photo-degradation becomes colorless. The photo-degradation of monoazo dye Blue 13 in an aqueous solution was investigated using a laboratory scale UV lamp in the presence of H2O2 and for maximum degradation of dye, the independent parameter UV power, UV exposure time, pH and H2O2 concentration were optimized. It was found that neither UV in the presence of H2O2 is able to degrade Blue 13 under optimum condition. The results revealed that the use of both UV and H2O2 have pronounced effect on the discoloration of dyes which could be used for management of textile effluents contain waste dyes.

scholarly journals POSSIBILITY OF FORMING A LARGE DCC IN ULTRA-RELATIVISTIC HEAVY-ION COLLISIONS

2000 ◽  
Vol 15 (15) ◽  
pp. 2269-2288
Author(s):  
SANATAN DIGAL ◽  
RAJARSHI RAY ◽  
SUPRATIM SENGUPTA ◽  
AJIT M. SRIVASTAVA
Keyword(s):  
Three Dimensional ◽  
Thermal Fluctuations ◽  
Heavy Ion ◽  
High Energy ◽  
Chiral Condensate ◽  
Relativistic Heavy Ion Collisions ◽  
Maximum Temperature ◽  
Chiral Field ◽  
Heavy Nuclei ◽  
True Vacuum

We demonstrate the possibility of forming a single, large domain of disoriented chiral condensate (DCC) in a heavy-ion collision. In our scenario, rapid initial heating of the parton system provides a driving force for the chiral field, moving it away from the true vacuum and forcing it to go to the opposite point on the vacuum manifold. This converts the entire hot region into a single DCC domain. Subsequent rolling down of the chiral field to its true vacuum will then lead to emission of a large number of (approximately) coherent pions. The requirement of suppression of thermal fluctuations to maintain the (approximate) coherence of such a large DCC domain, favors three-dimensional expansion of the plasma over the longitudinal expansion even at very early stages of evolution. This also constrains the maximum temperature of the system to lie within a window. We roughly estimate this window to be about 200–400 MeV. These results lead us to predict that extremely high energy collisions of very small nuclei (possibly hadrons) are better suited for observing signatures of a large DCC. Another possibility is to focus on peripheral collisions of heavy nuclei.

scholarly journals Challenges and Opportunities for CsPbBr3 Perovskites in Low- and High-Energy Radiation Detection

2021 ◽  
pp. 1290-1314
Author(s):  
Lotte Clinckemalie ◽  
Donato Valli ◽  
Maarten B. J. Roeffaers ◽  
Johan Hofkens ◽  
Bapi Pradhan ◽  
...  
Keyword(s):  
Radiation Detection ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Challenges And Opportunities
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