scholarly journals A model for gamma-ray binaries, based on the effect of pair production feedback in shocked pulsar winds

2012 ◽  
Author(s):  
E. V. Derishev ◽  
F. A. Aharonian
Keyword(s):  
Pair Production ◽  
Gamma Ray ◽  
Pulsar Winds

Pair production opacities for gamma-ray burst spectra in the 10 GeV–1 TeV range

1998 ◽  
Vol 22 (7) ◽  
pp. 1115-1119
Author(s):  
Matthew G. Baring ◽  
Alice K. Harding
Keyword(s):  
Pair Production ◽  
Gamma Ray ◽  
Gamma Ray Burst

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.

A new method for calculating bulk density in pulsed neutron-gamma density logging

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. D219-D232
Author(s):  
Hu Wang ◽  
Wensheng Wu ◽  
Tianzhi Tang ◽  
Ruigang Wang ◽  
Aizhong Yue ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Pair Production ◽  
Bulk Density ◽  
Density Estimation ◽  
Measurement Accuracy ◽  
Gamma Ray ◽  
Estimation Algorithm ◽  
Gamma Density ◽  
Pulsed Neutron

Formation density is one of the most important parameters in formation evaluation. Radioisotope chemical sources are used widely in conventional gamma-gamma density (GGD) logging. Considering security and environmental risks, there has been growing interest in pulsed neutron generators in place of the radioactive-chemical source in using bulk-density measurements. However, there still is the requirement of high accuracy of the neutron-gamma density (NGD) calculation. Pair production is one of the factors influencing the accuracy of the results, which should be considered. We have adopted a method, based on the difference between the inelastic gamma-ray response of high- and low-energy windows, to reduce the impact of pair production upon calculating the bulk density. A new density estimation algorithm is derived based on the coupled-field theory and gamma-ray attenuation law in NGD logging. We analyze the NGD measurement accuracy with different mineral types, porosity, and pore fluid and determine the influence of the borehole environment on NGD logging. The Monte Carlo simulation results indicate that the improved processing algorithm limits the influence of the mineral type, porosity, or pore fluid. The NGD measurement accuracy is ±0.025 g/cm3 in shale-free formations, which is close to the GGD measurement (±0.015 g/cm3). Our results also show that the borehole environment has a significant impact on NGD measurement. Therefore, it is necessary to take the influence of the borehole parameters into account in NGD measurements. Combined with Monte Carlo simulation cases, we evaluate the application results of the new density estimation algorithm in various model wells.

scholarly journals Particle-in-cell simulations of pair discharges in a starved magnetosphere of a Kerr black hole

2018 ◽  
Vol 616 ◽  
pp. A184 ◽  
Author(s):  
Amir Levinson ◽  
Benoît Cerutti
Keyword(s):  
Black Hole ◽  
Pair Production ◽  
Gamma Ray ◽  
Kerr Black Hole ◽  
Particle In Cell ◽  
Spark Gap ◽  
Total Luminosity ◽  
General Relativistic ◽  
Low Amplitude ◽  
Gap Width

We investigate the dynamics and emission of a starved magnetospheric region (gap) formed in the vicinity of a Kerr black hole horizon, using a new, fully general relativistic particle-in-cell code that implements Monte Carlo methods to compute gamma-ray emission and pair production through the interaction of pairs and gamma rays with soft photons emitted by the accretion flow. It is found that when the Thomson length for collision with disk photons exceeds the gap width, screening of the gap occurs through low-amplitude, rapid plasma oscillations that produce self-sustained pair cascades, with quasi-stationary pair and gamma-ray spectra, and with a pair multiplicity that increases in proportion to the pair production opacity. The gamma-ray spectrum emitted from the gap peaks in the TeV band, with a total luminosity that constitutes a fraction of about 10−5 of the corresponding Blandford−Znajek power. This stage is preceded by a prompt discharge phase of duration ∼rg/c, during which the potential energy initially stored in the gap is released as a flare of curvature TeV photons. We speculate that the TeV emission observed in M87 may be produced by pair discharges in a spark gap.

A curvature-radiation-pair-production model for gamma-ray pulsars

1978 ◽  
Vol 225 ◽  
pp. 226 ◽  
Author(s):  
A. K. Harding ◽  
E. Tademaru ◽  
L. W. Esposito
Keyword(s):  
Pair Production ◽  
Gamma Ray ◽  
Production Model ◽  
Curvature Radiation
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