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

scholarly journals Detection of the Geminga pulsar with MAGIC hints at a power-law tail emission beyond 15 GeV

2020 ◽  
Vol 643 ◽  
pp. L14
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Gamma Ray ◽  
Low Energy ◽  
Significance Level ◽  
Inverse Compton Scattering ◽  
Curvature Radiation ◽  
Sensitivity Range ◽  
Inverse Compton ◽  
First Time

We report the detection of pulsed gamma-ray emission from the Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is the first time a middle-aged pulsar has been detected up to these energies. Observations were carried out with the MAGIC telescopes between 2017 and 2019 using the low-energy threshold Sum-Trigger-II system. After quality selection cuts, ∼80 h of observational data were used for this analysis. To compare with the emission at lower energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT data above 100 MeV were also analysed. From the two pulses per rotation seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC energy range, with a significance of 6.3σ. The spectrum measured by MAGIC is well-represented by a simple power law of spectral index Γ = 5.62 ± 0.54, which smoothly extends the Fermi-LAT spectrum. A joint fit to MAGIC and Fermi-LAT data rules out the existence of a sub-exponential cut-off in the combined energy range at the 3.6σ significance level. The power-law tail emission detected by MAGIC is interpreted as the transition from curvature radiation to Inverse Compton Scattering of particles accelerated in the northern outer gap.

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.

scholarly journals Pulsar Magnetospheres: Classical, Quasi-Classical and Quantum Descriptions

2000 ◽  
Vol 177 ◽  
pp. 457-460
Author(s):  
A. A. da Costa
Keyword(s):  
Kinetic Theory ◽  
Quantum Electrodynamics ◽  
Gamma Ray ◽  
Radiation Mechanisms ◽  
Radiative Processes ◽  
High Energies ◽  
Curvature Radiation ◽  
Pulsar Radiation ◽  
Relativistic Kinetic Theory ◽  
Random Curvature

AbstractThe plasma motion in pulsar magnetospheres is no longer classical, but quasi-classical, following stochastic trajectories, when random curvature radiation of high energetic gamma-ray photons takes place. This implies an extension to the relativistic kinetic theory of plasmas. But with high energies involved other quantum radiative processes become important, in the context of vacuum (quantum) electrodynamics. The consequences for pulsar radiation mechanisms will be outlined.

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.

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