Symmetric and triangle-shaped variability of blazars

AbstractSymmetric and triangle-shaped flux variability in X-ray and gamma-ray light curves is observed from many blazars. We derived the X-ray spectrum changing in time by using a kinetic equation of high energy electrons. Giving linearly changing the injection of low energy electrons into accelerating and emitting region, we obtained the preliminary results that represent the characteristic X-ray variability of the linear flux increase with hardening in the rise phase and the linear decrease with softening in the decay phase.

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On Lensless Imaging of Organics with Neutrons, X-Rays, Helium Atoms and Low Energy Electrons: Damage and Iterative Phase Retrieval

Microscopy and Microanalysis ◽

10.1017/s1431927600027410 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 268-269

Author(s):

J.C.H. Spence ◽

U. Weierstall ◽

J. Fries

Keyword(s):

Phase Retrieval ◽

Iterative Algorithms ◽

High Energy ◽

Low Energy ◽

X Rays ◽

Noise Sources ◽

Helium Atoms ◽

High Energy Electrons ◽

Elastic Event ◽

Low Energy Electrons

Recent experiments with X-rays and high energy electrons have shown that image recovery from diffracted intensities is possible for non-periodic objects using iterative algorithms. Application of these methods to biological molecules raises the crucial problem of radiation damage, which may be quantified by Q = ΔE σi/σe, the amount of energy deposited by inelastic events per elastic event. Neutrons, helium atoms and low energy electrons below most ionization thresholds produce the smallest values of Q (see for TMV imaged at 60 eV). For neutrons (λ = 10-2Å, and deuterated, 15N-abelled molecules) Q is ∼3000 times smaller (∼50 times for λ = 1.8Å) than for electrons (80- 500keV) and about 4x 106 times smaller than for soft X-rays (1.5Å). Since σe for neutrons is about 105 times smaller than for electrons (and about 10 times smaller than for soft X-rays), a 105 times higher neutron dose is required to obtain the same S/N in a phase contrast image compared with electrons, if other noise sources are absent.

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EGRET Limits on High-Energy Gamma-Ray Emission from X-Ray-- and Low-Energy Gamma-Ray--selected Seyfert Galaxies

The Astrophysical Journal ◽

10.1086/187069 ◽

1993 ◽

Vol 416 ◽

pp. L53 ◽

Cited By ~ 23

Author(s):

Y. C. Lin ◽

D. L. Bertsch ◽

B. L. Dingus ◽

C. E. Fichtel ◽

R. C. Hartman ◽

...

Keyword(s):

Gamma Ray ◽

Seyfert Galaxies ◽

High Energy ◽

Low Energy ◽

X Ray ◽

High Energy Gamma ◽

Energy Gamma ◽

Gamma Ray Emission

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H.E.S.S. and Fermi-LAT observations of PSR B1259–63/LS 2883 during its 2014 and 2017 periastron passages

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936621 ◽

2020 ◽

Vol 633 ◽

pp. A102

Author(s):

◽

H. Abdalla ◽

R. Adam ◽

F. Aharonian ◽

F. Ait Benkhali ◽

...

Keyword(s):

Neutron Star ◽

Energy Range ◽

Gamma Rays ◽

Gamma Ray ◽

Broad Band ◽

High Energy ◽

Light Curves ◽

Companion Star ◽

Flux Variability ◽

The Times

Context. PSR B1259–63/LS 2883 is a gamma-ray binary system consisting of a pulsar in an eccentric orbit around a bright Oe stellar-type companion star that features a dense circumstellar disc. The bright broad-band emission observed at phases close to periastron offers a unique opportunity to study particle acceleration and radiation processes in binary systems. Observations at gamma-ray energies constrain these processes through variability and spectral characterisation studies. Aims. The high- and very-high-energy (HE, VHE) gamma-ray emission from PSR B1259–63/LS 2883 around the times of its periastron passage are characterised, in particular, at the time of the HE gamma-ray flares reported to have occurred in 2011, 2014, and 2017. Short-term and average emission characteristics of PSR B1259–63/LS 2883 are determined. Super-orbital variability is searched for in order to investigate possible cycle-to-cycle VHE flux changes due to different properties of the companion star’s circumstellar disc and/or the conditions under which the HE gamma-ray flares develop. Methods. Spectra and light curves were derived from observations conducted with the H.E.S.S-II array in 2014 and 2017. Phase-folded light curves are compared with the results obtained in 2004, 2007, and 2011. Fermi-LAT observations from 2010/11, 2014, and 2017 are analysed. Results. A local double-peak profile with asymmetric peaks in the VHE light curve is measured, with a flux minimum at the time of periastron tp and two peaks coinciding with the times at which the neutron star crosses the companion’s circumstellar disc (~tp ± 16 d). A high VHE gamma-ray flux is also observed at the times of the HE gamma-ray flares (~tp + 30 d) and at phases before the first disc crossing (~tp − 35 d). The spectral energy range now extends to below 200 GeV and up to ~45 TeV. Conclusions. PSR B1259–63/LS 2883 displays periodic flux variability at VHE gamma-rays without clear signatures of super-orbital modulation in the time span covered by the monitoring of the source with the H.E.S.S. telescopes. This flux variability is most probably caused by the changing environmental conditions, particularly at times close to periastron passage at which the neutron star is thought to cross the circumstellar disc of the companion star twice. In contrast, the photon index remains unchanged within uncertainties for about 200 d around periastron. At HE gamma-rays, PSR B1259–63/LS 2883 has now been detected also before and after periastron, close to the disc crossing times. Repetitive flares with distinct variability patterns are detected in this energy range. Such outbursts are not observed at VHEs, although a relatively high emission level is measured. The spectra obtained in both energy regimes displays a similar slope, although a common physical origin either in terms of a related particle population, emission mechanism, or emitter location is ruled out.

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The Role of Low Energy Electrons in Radiobiology and Cancer Treatment

Frontiers in Biomedical Technologies ◽

10.18502/fbt.v7i4.5317 ◽

2021 ◽

Author(s):

Sasan Esmaili ◽

Farzaneh Allaveisi

Keyword(s):

Cancer Treatment ◽

Anticancer Agents ◽

High Energy ◽

Low Energy ◽

New Drugs ◽

Particle Radiation ◽

Energy Radiation ◽

Regulatory Pathways ◽

High Energy Electrons ◽

Low Energy Electrons

Low energy radiation can be produced by all types of high energy radiation. Studies of low energy particle radiation help us to understand the chemistry induced by high energy radiations. Low energy electrons are capable of chemical selectivity in contrast to high energy electrons due to the large number of open dissociative channels in the former case and their resonant nature. Among different types of radiation, low energy electrons have a higher cross-section to DNA damage and they have an important role in the synergistic effect between radiation and chemotherapy anticancer agents in cancer treatment. Analysis of these combined records helps assign function of cells, identify metabolic and regulatory pathways and suggest targets for diagnostics and therapeutics identify animal models to develop new drugs, among other goals of biomedical interest.

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Constraining the shear acceleration model for the X-ray emission of large-scale extragalactic jets

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa4009 ◽

2021 ◽

Author(s):

F Tavecchio

Keyword(s):

Shear Layer ◽

Large Scale ◽

Gamma Ray ◽

Planck Equation ◽

High Energy ◽

Ultra High Energy ◽

Low Frequencies ◽

X Ray ◽

High Energy Electrons ◽

Extragalactic Jets

Abstract The nature of the intense X-ray emission from powerful extragalactic jets at large (>1 kpc) scale is still debated. The scenario that invokes the inverse Compton scattering of the CMB by electrons is challenged by the lack of gamma-ray emission in the GeV band. An alternative assumes synchrotron emission by a distinct population of ultra-high energy electrons. Here we present a concrete attempt to apply this scenario, exploring the specific model in which the ultra-high energy electrons are accelerated in a shear layer surrounding the jet. We limit the study to non-relativistic flows and particle acceleration is treated by a Fokker-Planck equation. The observed relation between low energy (radio, optical) and X-ray emission prompts us to assume that the required population of pre-accelerated particles is provided by a shock responsible for the acceleration of the electrons emitting at low frequencies. We apply the model to the emission of the principal knots of the jets of PKS 0637-752 and PKS 1136-135, two of the best studied objects. For the set of fiducial parameters adopted, the condition that the jet power does not exceeds a limiting value of 1048 erg s−1 constrains the magnetic field above 10 μG and indicates moderate beaming (δ ≃ 2) for PKS 0637-752. For both sources, the requirement that acceleration of the electrons proceeds faster than radiative cooling can be met if the magnetic turbulence in the shear layer follows a Kolmogorov spectrum, I(k)∝k−q with q = 5/3, but cannot satisfied in the Bohm-like case (q = 1).

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Analysis of Lateritic Material from Cerro Impacto by Instrumental Neutron Activation Employing a Low-Energy Photon Semiconductor and a High-Energy Ge(Li) Detector

Applied Spectroscopy ◽

10.1366/0003702864509600 ◽

1986 ◽

Vol 40 (2) ◽

pp. 140-144 ◽

Cited By ~ 5

Author(s):

J. J. Labrecque ◽

J. M. Beusen ◽

R. E. Van Grieken

Keyword(s):

Gamma Ray ◽

Slow Neutron ◽

High Energy ◽

Fluorescence Method ◽

Low Energy ◽

Standard Reference Materials ◽

Photon Detector ◽

Energy Photon ◽

X Ray ◽

Different Grain Size

Nineteen elements were determined in four different grain size fractions of a bulk geological material from Cerro Impacto for a study of the physical (mechanical) concentration process of different elements based upon the hardness of the different minerals. The analysis was performed by excitation of the sample with a high, slow neutron flux followed by gamma-ray spectroscopy with both a conventional Ge(Li) high-energy detector and a low-energy photon detector (LEPD). The accuracy of this method was studied with the use of two standard reference materials, SY-2 and SY-3, which are similar to the real samples. The values determined were also compared with a secondary target x-ray fluorescence method for all the elements that were suitable to both methods. Actually, the x-ray fluorescence method was found to be more complementary than competitive.

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Aperiodic Flux Variability in A 0535+262

Symposium - International Astronomical Union ◽

10.1017/s0074180900055777 ◽

1996 ◽

Vol 165 ◽

pp. 313-319

Author(s):

Mark H. Finger ◽

Robert B. Wilson ◽

B. Alan Harmon ◽

William S. Paciesas

Keyword(s):

Neutron Star ◽

Gamma Ray ◽

Beat Frequency ◽

Power Spectra ◽

Center Frequency ◽

X Ray ◽

Binary Pulsar ◽

Transient Source ◽

Flux Variability ◽

Burst And Transient Source

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.

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Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽

10.3390/galaxies9020036 ◽

2021 ◽

Vol 9 (2) ◽

pp. 36

Author(s):

Yoshiyuki Inoue ◽

Dmitry Khangulyan ◽

Akihiro Doi

Keyword(s):

Active Galactic Nuclei ◽

Gamma Ray ◽

Galactic Nuclei ◽

High Energy ◽

Thermal Activity ◽

X Ray ◽

Cascade Models ◽

Coronal Activity ◽

Ngc 1068 ◽

High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

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Combination of Dual-Energy X-ray Transmission and Variable Gas-Ejection for the In-Line Automatic Sorting of Many Types of Scrap in One Measurement

Applied Sciences ◽

10.3390/app11104349 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4349

Author(s):

Tianzhong Xiong ◽

Wenhua Ye ◽

Xiang Xu

Keyword(s):

High Efficiency ◽

Nearest Neighbor ◽

High Energy ◽

Dual Energy ◽

Center Of Gravity ◽

Low Energy ◽

Identification Accuracy ◽

Flow Process ◽

X Ray ◽

Automatic Sorting

As an important part of pretreatment before recycling, sorting has a great impact on the quality, efficiency, cost and difficulty of recycling. In this paper, dual-energy X-ray transmission (DE-XRT) combined with variable gas-ejection is used to improve the quality and efficiency of in-line automatic sorting of waste non-ferrous metals. A method was proposed to judge the sorting ability, identify the types, and calculate the mass and center-of-gravity coordinates according to the shading of low-energy, the line scan direction coordinate and transparency natural logarithm ratio of low energy to high energy (R_value). The material identification was satisfied by the nearest neighbor algorithm of effective points in the material range to the R_value calibration surface. The flow-process of identification was also presented. Based on the thickness of the calibration surface, the material mass and center-of-gravity coordinates were calculated. The feasibility of controlling material falling points by variable gas-ejection was analyzed. The experimental verification of self-made materials showed that identification accuracy by count basis was 85%, mass and center-of-gravity coordinates calculation errors were both below 5%. The method proposed features high accuracy, high efficiency, and low operation cost and is of great application value even to other solid waste sorting, such as plastics, glass and ceramics.

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