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Artykuły w czasopismach na temat „Hard Electron Energy Spectra”

Autor: Grafiati

Data publikacji: 6 września 2023

Data aktualizacji: 7 września 2023

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1

Godleski, John J., Rebecca C. Stearns, and Emil J. Millet. "Electron spectroscopic imaging and analysis of electron energy loss spectra with an energy filtering Electron Microscope." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 404–5. http://dx.doi.org/10.1017/s0424820100153993.

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The Zeiss CEM902, energy filtering electron microscope, can be used to image the structure of unstained 30 nm sections of biologic materials, to image the distribution of selected elements in such sections, and to determine electron energy loss spectra (EELS) of elements in areas as small as 10 nm. Although the integrated computer in the latest version of the CEM902 can collect and display signals from the scintillation detector for recording EELS, our instrument did not have this capability. Therefore, we have added a Leading Edge Model D personal computer with a 20 Mbyte hard disk, Hercules

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2

Wadiasingh, Zorawar, Matthew G. Baring, Peter L. Gonthier, and Alice K. Harding. "Hard Spectral Tails in Magnetars." Proceedings of the International Astronomical Union 13, S337 (2017): 108–11. http://dx.doi.org/10.1017/s1743921317009073.

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AbstractPulsed non-thermal quiescent emission between 10 keV and around 150 keV has been observed in ~10 magnetars. For inner magnetospheric models of such hard X-ray signals, resonant Compton upscattering of soft thermal photons from the neutron star surface is the most efficient radiative process. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will em

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3

Khangulyan, Dmitry, Andrew M. Taylor, and Felix Aharonian. "The Formation of Hard Very High Energy Spectra from Gamma-ray Burst Afterglows via Two-zone Synchrotron Self-Compton Emission." Astrophysical Journal 947, no. 2 (2023): 87. http://dx.doi.org/10.3847/1538-4357/acc24e.

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Abstract Electron Compton scattering of target photons into the gamma-ray energy band (inverse Compton scattering; IC) is commonly expected to dominate the very high energy (VHE) spectra in gamma-ray bursts (GRBs) especially during the afterglow phase. For sufficiently large center-of-mass energies in these collisions, the effect of the electron recoil starts reducing the scattering cross-section (the Klein–Nishina regime). The IC spectra generated in the Klein–Nishina regime is softer and has a smaller flux level compared to the synchrotron spectra produced by the same electrons. The detectio

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4

Breuhaus, Mischa, Joachim Hahn, Carlo Romoli, et al. "Ultra-high energy inverse Compton emission from Galactic electron accelerators." EPJ Web of Conferences 280 (2023): 02001. http://dx.doi.org/10.1051/epjconf/202328002001.

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It is generally held that >100 TeV emission from astrophysical objects unambiguously demonstrates the presence of PeV protons or nuclei, due to the unavoidable Klein–Nishina suppression of inverse Compton emission from electrons. However, in the presence of inverse Compton dominated cooling, hard high-energy electron spectra are possible. We show that the environmental requirements for such spectra can naturally be met in spiral arms, and in particular in regions of enhanced star formation activity, the natural locations for the most promising electron accelerators: powerful young pulsars.

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5

Rudawy, P., M. Siarkowski, and R. Falewicz. "Plasma heating in the initial phase of solar flares." Proceedings of the International Astronomical Union 5, S264 (2009): 282–84. http://dx.doi.org/10.1017/s1743921309992791.

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AbstractIn this paper we analyze soft and hard X-ray emission of the 2002 September 20 M1.8 GOES class solar flare observed by RHESSI and GOES satellites, where soft X-ray emission precedes the onset of the main bulk hard X-ray emission by ~5 min. This suggests that an additional heating mechanism may be at work at the early beginning of the flare. However RHESSI spectra indicate presence of the non-thermal electrons also before impulsive phase. So, we assumed that a dominant energy transport mechanism during rise phase of solar flares is electron beam-driven evaporation. We used non-thermal e

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6

Kundu, M. R., S. M. White, N. Gopalswamy, and J. Lim. "Millimeter, Microwave, Hard X-Ray, and Soft X-Ray Observations of Energetic Electron Populations in Solar Flares." International Astronomical Union Colloquium 142 (1994): 599–610. http://dx.doi.org/10.1017/s0252921100077873.

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AbstractWe present comparisons of multiwavelength data for a number of solar flares observed during the major campaign of 1991 June. The different wavelengths are diagnostics of energetic electrons in different energy ranges: soft X-rays are produced by electrons with energies typically below 10 keV, hard X-rays by electrons with energies in the range 10-200 keV, microwaves by electrons in the range 100 keV-1 MeV, and millimeter-wavelength emission by electrons with energies of 0.5 MeV and above. The flares in the 1991 June active period were remarkable in two ways: all have very high turnover

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7

Bespalov, P. A., V. V. Zaitsev, and A. V. Stepanov. "Energetic Particles in a Flare Loop: Spectra and Radiation Signatures." Symposium - International Astronomical Union 142 (1990): 421–27. http://dx.doi.org/10.1017/s0074180900088343.

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It has been shown that high energy particle spectra, particle dynamics, and radiation in a flare loop are determined by wave-particle interactions. The electron-whistler interaction occurs under conditions of strong pitch angle diffusion that makes the particle distribution function isotropic. The flare loop electrons retain information about the particle source spectrum. The interaction of energetic ions with Alfven waves is characterized by strong, moderate, and weak diffusion. The time delays in hard X-ray and gamma-ray emission during one-step acceleration processes might be understood in

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8

Hu, Wen, Da-Hai Yan, and Qiang-Lin Hu. "Two-injection Scenario for the Hard X-Ray Excess Observed in Mrk 421." Astrophysical Journal 948, no. 2 (2023): 82. http://dx.doi.org/10.3847/1538-4357/accc2e.

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Abstract An interesting result that was recently reported for Mrk 421 is the detection of a significant excess at hard X-ray energies, which could provide useful information to investigate particle acceleration and emission mechanisms in the relativistic jet. Considering a two-injection scenario, we develop a self-consistent one-zone leptonic model to understand the origin of the hard X-ray excess in Mrk 421 during the period of extremely low X-ray and very high-energy flux in 2013 January. In the model, two populations of mono-energetic ultra-relativistic electrons are injected into the emiss

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9

Zhang, S. N. "High Energy Continuum Spectra from X-Ray Binaries." International Astronomical Union Colloquium 163 (1997): 41–52. http://dx.doi.org/10.1017/s0252921100042482.

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AbstractA variety of high energy (>1 keV) spectra have been observed in recent years from Black Hole (BH) and Neutron Star (NS) X-ray Binaries (XB). Some common physical components exist between BHXBs and NSXBs, resulting in some high energy spectral features. A common component between a BHXB and a weakly magnetized NSXB is the inner accretion disk region extending very close to the surface (for a NS) or the horizon (for a BH). The inner disk radiation can be described by a multi-color blackbody (MCB) spectral model. The surface radiation of the NS can be approximated by a Single Color Bla

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10

Ham, Seunggi, Jonghyeon Ryu, Hakmin Lee, et al. "Estimation of plasma parameters of X-pinch with time-resolved x-ray spectroscopy." Matter and Radiation at Extremes 8, no. 3 (2023): 036901. http://dx.doi.org/10.1063/5.0131369.

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We estimate the parameters of a Cu plasma generated by an X-pinch by comparing experimentally measured x-rays with synthetic data. A filtered absolute extreme ultraviolet diode array is used to measure time-resolved x-ray spectra with a spectral resolution of ∼1 keV in the energy range of 1–10 keV. The synthetic spectra of Cu plasmas with different electron temperatures, electron densities, and fast electron fractions are calculated using the FLYCHK code. For quantitative comparison with the measured spectrum, two x-ray power ratios with three different spectral ranges are calculated. We obser

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11

Sato, K., K. Hirata, S. Singh, et al. "Electronic structure of silver chalcogenides investigated by hard x-ray photoemission spectroscopy and density functional theory calculations." Journal of Applied Physics 132, no. 4 (2022): 045104. http://dx.doi.org/10.1063/5.0095987.

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We have investigated the electronic structure of silver chalcogenides Ag2 X ( X = S, Se, Te) and their solid solutions using hard x-ray photoemission spectroscopy in combination with density functional theory calculations using generalized gradient approximation (GGA). By including the corrections for on-site Coulomb interactions (GGA + U), we successfully reproduced the valence band photoemission spectra, which consist mainly of the Ag 4 d band, by calculation. The estimated values for U = 4–6 eV are slightly high for Ag 4 d electrons but are consistent with those used in previously reported

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12

Rodi, James, E. Jourdain, and J. P. Roques. "MAXI J1535–571 2017 Outburst Seen by INTEGRAL/SPI and Investigating the Origin of Its Hard Tail." Astrophysical Journal 935, no. 1 (2022): 25. http://dx.doi.org/10.3847/1538-4357/ac7fff.

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Abstract On 2017 September 2 MAXI J1535–571 went into outburst and peaked at ∼5 Crab in the 2–20 keV energy range. Early in the flare, the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) performed target of opportunity pointings and monitored the source as it transitioned from the hard state to the soft state. Using quasi-simultaneous observations from MAXI/GSC and INTEGRAL/SPI, we studied the temporal and spectral evolution of MAXI J1535–571 in the 2–500 keV range. Early spectra show a Comptonized spectrum and a high-energy component dominant above ∼150 keV. CompTT fits to the SPec

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13

Sahakyan, N. "Investigation of the γ-ray spectrum of CTA 102 during the exceptional flaring state in 2016–2017". Astronomy & Astrophysics 635 (березень 2020): A25. http://dx.doi.org/10.1051/0004-6361/201936715.

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The flat spectrum radio quasar CTA 102 entered an extended period of activity from 2016 to 2017 during which several strong γ-ray flares were observed. By using Fermi large area telescope data, a detailed investigation of γ-ray spectra of CTA 102 during the flaring period was performed. In several periods, the γ-ray spectrum is not consistent with a simple power-law, having a hard photon index with an index of ∼(1.8−2.0) that shows a spectral cut-off around an observed photon energy of ∼(9−16) GeV. The internal γ-ray absorption via photon-photon pair production on the broad-line-region-reflect

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14

Bassi, T., J. Malzac, M. Del Santo та ін. "On the nature of the soft γ-ray emission in the hard state of the black hole transient GRS 1716−249". Monthly Notices of the Royal Astronomical Society 494, № 1 (2020): 571–83. http://dx.doi.org/10.1093/mnras/staa739.

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ABSTRACT The black hole transient GRS 1716−249 was monitored from the radio to the γ-ray band during its 2016–2017 outburst. This paper focuses on the spectral energy distribution (SED) obtained in 2017 February–March, when GRS 1716−249 was in a bright hard spectral state. The soft γ-ray data collected with the INTEGRAL/SPI telescope show the presence of a spectral component that is in excess of the thermal Comptonization emission. This component is usually interpreted as inverse Compton emission from a tiny fraction of non-thermal electrons in the X-ray corona. We find that hybrid thermal/non

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15

Bhatta, Gopal, Maksym Mohorian, and Illya Bilinsky. "Hard X-ray properties of NuSTAR blazars." Astronomy & Astrophysics 619 (November 2018): A93. http://dx.doi.org/10.1051/0004-6361/201833628.

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Context. Investigation of the hard X-ray emission properties of blazars is key to the understanding of the central engine of the sources and associated jet process. In particular, simultaneous spectral and timing analyses of the intraday hard X-ray observations provide us a means to peer into the compact innermost blazar regions that are not accessible to our current instruments. Aims. The primary objective of the work is to associate the observed hard X-ray variability properties in blazars with their flux and spectral states, thereby, based on the correlation among these states, extract the

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16

AGUI, AKANE, YUJI SAITOH, AKITAKA YOSHIGOE, TAKESHI NAKATANI, TOMOHIRO MATSUSHITA, and MASAICHIRO MIZUMAKI. "HIGH ENERGY RESOLUTION MAGNETIC CIRCULAR DICHROISM MEASUREMENT OF THE FERRITE FAMILY." Surface Review and Letters 09, no. 02 (2002): 843–48. http://dx.doi.org/10.1142/s0218625x02003032.

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Magnetic circular dichroism (MCD) spectra of spinel ferrites MFe 2 O 4 (M = Co, Mn, Fe, Co and Ni) have been measured by using a photon-helicity-switching method. The method achieves high energy resolution and a low noise-to-signal ratio. The Fe L2,3 absorption spectra of MFe 2 O 4 show a similar spectral profile; on the other hand, the MCD spectra show the characteristic fine structures. These differences are attributed to the variety of 3d electron configuration of Fe ions ( Fe 2+ or Fe 3+) and the local symmetry (tetrahedral or octahedral). The origin of the positive peak of MFe 2 O 4 (M =

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17

Kalita, Nibedita, Alok C. Gupta, and Minfeng Gu. "Temporal and Spectral Variability of OJ 287 before the April–June 2020 Outburst." Galaxies 8, no. 3 (2020): 58. http://dx.doi.org/10.3390/galaxies8030058.

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We present the results of a temporal and spectral study of the BL Lacertae object OJ 287 in optical, UV, and X-ray bands with observations performed by Swift satellite during September 2019–March 2020. In this period, the source showed moderate variability characterized by variability amplitude of ∼22–31% in all the wavelengths on a short timescale, except the hard X-ray band which was variable by only ∼8%. We observed that the X-ray flux of the source was significantly dominated by the soft photons below 2 keV. Soft lags of ∼45 days were detected between the optical/UV and soft X-ray emission

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18

Salvat-Pujol, Francesc, Roser Valentí, and Wolfgang S. Werner. "Surface excitations in the modelling of electron transport for electron-beam-induced deposition experiments." Beilstein Journal of Nanotechnology 6 (June 3, 2015): 1260–67. http://dx.doi.org/10.3762/bjnano.6.129.

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The aim of the present overview article is to raise awareness of an essential aspect that is usually not accounted for in the modelling of electron transport for focused-electron-beam-induced deposition (FEBID) of nanostructures: Surface excitations are on the one hand responsible for a sizeable fraction of the intensity in reflection-electron-energy-loss spectra for primary electron energies of up to a few kiloelectronvolts and, on the other hand, they play a key role in the emission of secondary electrons from solids, regardless of the primary energy. In this overview work we present a gener

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Kajava, J. J. E., S. E. Motta, C. Sánchez-Fernández, and E. Kuulkers. "The December 2015 re-brightening of V404 Cygni." Astronomy & Astrophysics 616 (August 2018): A129. http://dx.doi.org/10.1051/0004-6361/201731768.

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In December 2015 the black hole binary V404 Cyg underwent a secondary outburst after the main June 2015 event. We monitored this re-brightening with the INTEGRAL and Swift satellites, and in this paper we report the results of the time-resolved spectral analysis of these data. The December outburst shared several characteristics with the June event. The well-sampled INTEGRAL light curve shows up to ten Crab flares, which are separated by relatively weak non-flaring emission phases when compared to the June outburst. The spectra are nicely described by absorbed Comptonization models, with hard

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Sapienza, Vincenzo, Marco Miceli, Aya Bamba, et al. "A Spatially Resolved Study of Hard X-Ray Emission in Kepler’s Supernova Remnant: Indications of Different Regimes of Particle Acceleration." Astrophysical Journal 935, no. 2 (2022): 152. http://dx.doi.org/10.3847/1538-4357/ac8160.

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Abstract Synchrotron X-ray emission in young supernova remnants (SNRs) is a powerful diagnostic tool to study the population of high-energy electrons accelerated at the shock front and the acceleration process. We performed a spatially resolved spectral analysis of NuSTAR and XMM-Newton observations of the young Kepler’s SNR, aiming to study in detail its nonthermal emission in hard X-rays. We selected a set of regions all around the rim of the shell and extracted the corresponding spectra. The spectra were analyzed by adopting a model of synchrotron radiation in the loss-limited regime, to co

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21

Liu, J., P. A. Crozier, G. G. Hembree, F. C. H. Luo, J. M. Cowley, and J. A. Venables. "Variations in Secondary Electron Emission from MgO Characterized by Secondary Electron Spectroscopy." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (1990): 336–37. http://dx.doi.org/10.1017/s0424820100180434.

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The recent developments of the in-lens field emission scanning electron microscopes make it possible to image specimen surfaces with subnanometer resolution by collecting high resolution type I secondary electron (SE) signals. SE images with a resolutiori better than 1 nm have also been obtained in scanning transmission electron microscope (STEM) instruments. A problem related to the correct interpretation of these high resolution images is the lack of knowledge on the energies of the collected electrons contributing to the images. On the other hand secondary electron spectroscopy (SES) on cle

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Melrose, D. B. "The Nature of Flat Spectrum Sources." Symposium - International Astronomical Union 175 (1996): 423–26. http://dx.doi.org/10.1017/s0074180900081328.

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Nonthermal radio sources near the Galactic Center with flat or weakly inverted spectra (S((ω) ∝ ωα with α ≳ 0) are attributed to optically thin synchrotron emission from a hard electron energy spectrum, N(ε) ∝ ε–α with a = 1 – 2α ≲ 1, produced by Fermi acceleration or diffusive shock acceleration at multiple shocks combined with a synchrotron pile up. This basic mechanism is also plausible for flat-spectrum AGN.

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23

Banerjee, Srimanta, Marat Gilfanov, Sudip Bhattacharyya, and Rashid Sunyaev. "Observing imprints of black hole event horizon on X-ray spectra." Monthly Notices of the Royal Astronomical Society 498, no. 4 (2020): 5353–60. http://dx.doi.org/10.1093/mnras/staa2788.

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ABSTRACT A fundamental difference between a neutron star (NS) and a black hole (BH) is the absence of a physical surface in the latter. For this reason, any remaining kinetic energy of the matter accreting on to a BH is advected inside its event horizon. In the case of an NS, on the contrary, accreting material is decelerated on the NS surface, and its kinetic energy is eventually radiated away. Copious soft photons produced by the NS surface will affect the properties of the Comptonized component dominating spectra of X-ray binaries in the hard state. Thus, parameters of the Comptonized spect

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24

Ding, G. Q., J. L. Qu, L. M. Song, et al. "Insight-HXMT Detections of Hard X-Ray Tails in Scorpius X-1." Astrophysical Journal 950, no. 1 (2023): 69. http://dx.doi.org/10.3847/1538-4357/accf91.

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Abstract Using the observations of the high-energy detector of the Hard X-ray Modulation Telescope (Insight-HXMT) for Scorpius X-1 from 2017 to 2020, we search for hard X-ray tails in the X-ray spectra in ∼30–200 keV. The hard X-ray tails are found throughout the Z-track on the hardness–intensity diagram, and the detected hard X-ray tails become hard and weak from the horizontal branch (HB), through the normal branch (NB), to the flaring branch (FB). Comparing the hard X-ray spectra of Insight-HXMT between Cyg X-1 and Sco X-1, it is concluded that the hard X-ray spectrum of Cyg X-1 shows a hig

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25

Kong, Xiangliang, Bin Chen, Fan Guo, et al. "Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources." Astrophysical Journal Letters 941, no. 2 (2022): L22. http://dx.doi.org/10.3847/2041-8213/aca65c.

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Abstract The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of nonthermal electrons and suggested that, in certain flare events, electrons are primarily accelerated in the loop top and likely experience trapping and/or scattering effects. By combining the focused particle transport equation with magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic particle model that naturally incorporates

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Done, C., and A. C. Fabian. "Pair Production in AGN." Symposium - International Astronomical Union 134 (1989): 194–96. http://dx.doi.org/10.1017/s007418090014080x.

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The X-ray luminosity and variability of many AGN are sufficiently extreme that any hard γ-rays produced in the source will collide with the X-rays and create electron-positron pairs, rather than escape. A small region where vast amounts of energy are produced, such as an AGN, is an ideal place to accelerate particles to relativistic energies and so produce γ-rays by Compton scattering. The observed X-ray spectra of AGN are hard and indicate that most of the luminosity is at the highest energies so that absorption of the γ-rays represents a large fraction of the energy flux, which can then be r

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Kong, Xiangliang, Jing Ye, Bin Chen, et al. "A Model of Double Coronal Hard X-Ray Sources in Solar Flares." Astrophysical Journal 933, no. 1 (2022): 93. http://dx.doi.org/10.3847/1538-4357/ac731b.

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Abstract A number of double coronal X-ray sources have been observed during solar flares by RHESSI, where the two sources reside at different sides of the inferred reconnection site. However, where and how these X-ray-emitting electrons are accelerated remains unclear. Here we present the first model of the double coronal hard X-ray (HXR) sources, where electrons are accelerated by a pair of termination shocks driven by bidirectional fast reconnection outflows. We model the acceleration and transport of electrons in the flare region by numerically solving the Parker transport equation using ve

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Lützenkirchen-Hecht, D., R. Wagner, S. Szillat, et al. "The multi-purpose hard X-ray beamline BL10 at the DELTA storage ring." Journal of Synchrotron Radiation 21, no. 4 (2014): 819–26. http://dx.doi.org/10.1107/s1600577514006705.

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The layout and the characteristics of the hard X-ray beamline BL10 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA are described. This beamline is equipped with a Si(111) channel-cut monochromator and is dedicated to X-ray studies in the spectral range from ∼4 keV to ∼16 keV photon energy. There are two different endstations available. While X-ray absorption studies in different detection modes (transmission, fluorescence, reflectivity) can be performed on a designated table, a six-axis kappa diffractometer is installed for X-ray scattering and refl

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Cheng, Shikui, Jie Zhang, Yipo Zhang, et al. "Development of hard X-ray spectrometer with full digital data acquisition for runaway electron studies at HL-2M." Journal of Instrumentation 18, no. 02 (2023): T02006. http://dx.doi.org/10.1088/1748-0221/18/02/t02006.

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Abstract The development of hard X-ray (HXR) spectrometers with full digital data acquisition for runaway electron studies on the HL-2M tokamak is presented. Consisting of large-sized NaI:Tl detectors and high-performance multichannel analyzers, this system can realize the measurement of HXR with energies ranging from 0.5 to 10 MeV, and spectrum temporal resolution of 1 ms. An average energy resolution of 56 keV at 662 keV has been achieved at counts rates of about 100 kcps. The spectra data is acquired by a digital-based data acquisition system with fast digitization and software signal proce

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Samoylova, Liubov, Ulrike Boesenberg, Aleksandr Chumakov, et al. "Diffraction properties of a strongly bent diamond crystal used as a dispersive spectrometer for XFEL pulses." Journal of Synchrotron Radiation 26, no. 4 (2019): 1069–72. http://dx.doi.org/10.1107/s1600577519004880.

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Self-amplified spontaneous emission (SASE) enables X-ray free-electron lasers (XFELs) to generate hard X-ray pulses of sub-100 fs duration. However, due to the stochastic nature of SASE, the energy spectrum fluctuates from pulse to pulse. Many experiments that employ XFEL radiation require the resolution of the spectrum of each pulse. The work presented here investigates the capacity of a thin strongly bent diamond crystal to resolve the energy spectra of hard X-ray SASE pulses by studying its diffraction properties. Rocking curves of the symmetric C*(440) reflection have been measured for dif

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Varga, L., and D. Venkatesan. "Detection of very soft X-ray spectra by balloon-borne detectors." Canadian Journal of Physics 69, no. 8-9 (1991): 999–1006. http://dx.doi.org/10.1139/p91-158.

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A balloon payload launched from Cold Lake, Alta., Canada, on October 14, 1982, measured the spectrum of X rays (E = 20–160 keV) with a hard and a very soft component. The latter contributes significantly only to the 20–40 keV channel; thus a "flapping motion" at the lower energy end of the composite spectrum is observed. We have simulated, using the Monte-Carlo technique, the propagation of X rays through the atmosphere and determined the e-folding energy of the very soft component, which we estimate to be 5 keV, at a particular time (10:45 UT). The electron spectrum producing this soft X-ray

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Ahnen, M. L., S. Ansoldi, L. A. Antonelli, et al. "Extreme HBL behavior of Markarian 501 during 2012." Astronomy & Astrophysics 620 (December 2018): A181. http://dx.doi.org/10.1051/0004-6361/201833704.

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Aims. We aim to characterize the multiwavelength emission from Markarian 501 (Mrk 501), quantify the energy-dependent variability, study the potential multiband correlations, and describe the temporal evolution of the broadband emission within leptonic theoretical scenarios. Methods. We organized a multiwavelength campaign to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-

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Ageeva, E. V., and B. N. Sabel’nikov. "X-RAY SPECTRAL MICROANALYSIS OF ELECTROEROSIVE POWDER MATERIAL OBTAINED IN AN ETHYL ALCOHOL MEDIUM FROM WASTE OF A NON-TUNGSTEN HARD ALLOY OF THE KNT16 BRAND." IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, no. 7(242) (July 29, 2020): 33–36. http://dx.doi.org/10.35211/1990-5297-2020-7-242-33-36.

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The first appearance of tungsten-free hard alloys (TFHA) was noted in the early 30s of the last century, but they did not receive due attention and, accordingly, spread due to insufficient strength and were replaced by tungsten-containing alloys of such groups as VK, TC and TTK. However, the rapidly developing shortage of expensive tungsten pushed in the late 50s to return to the search for hard alloys, the composition of which does not include tungsten. Due to the growing demand for tungsten-free hard alloys, the problem of recycling their waste with the possibility of reuse is acute in the i

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Rich, David, Diling Zhu, James Turner, Dehong Zhang, Bruce Hill, and Yiping Feng. "The LCLS variable-energy hard X-ray single-shot spectrometer." Journal of Synchrotron Radiation 23, no. 1 (2016): 3–9. http://dx.doi.org/10.1107/s1600577515022559.

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The engineering design, implementation, operation and performance of the new variable-energy hard X-ray single-shot spectrometer (HXSSS) for the LCLS free-electron laser (FEL) are reported. The HXSSS system is based on a cylindrically bent Si thin crystal for dispersing the incident polychromatic FEL beam. A spatially resolved detector system consisting of a Ce:YAG X-ray scintillator screen, an optical imaging system and a low-noise pixelated optical camera is used to record the spectrograph. The HXSSS provides single-shot spectrum measurements for users whose experiments depend critically on

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Zdziarski, A. A. "Radiative Processes and Geometry of Spectral States of Black-hole Binaries." Symposium - International Astronomical Union 195 (2000): 153–70. http://dx.doi.org/10.1017/s0074180900162898.

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I review radiative processes responsible for X-ray emission in the hard (low) and soft (high) spectral states of black-hole binaries. The main process in the hard state appears to be thermal Comptonization (in a hot plasma) of blackbody photons emitted by a cold disk. This is supported by correlations between the spectral index, the strength of Compton reflection, and the peak frequencies in the power-density spectrum, as well as by the frequency-dependence of Fourier-resolved spectra. Spectral variability may then be driven by the variable truncation radius of the disk. The soft state appears

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Laksman, Joakim, Florian Dietrich, Jia Liu, et al. "Development of a photoelectron spectrometer for hard x-ray photon diagnostics." Review of Scientific Instruments 93, no. 11 (2022): 115111. http://dx.doi.org/10.1063/5.0097525.

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The development and characterization of an angle-resolved photoelectron spectrometer, based on the electron time-of-flight concept, for hard x-ray photon diagnostics at the European Free-Electron Laser, are described. The instrument is meant to provide users and operators with pulse-resolved, non-invasive spectral distribution diagnostics, which in the hard x-ray regime is a challenge due to the poor cross-section and high kinetic energy of photoelectrons for the available target gases. We report on the performances of this instrument as obtained using hard x-rays at the PETRA III synchrotron

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David, Christian, Gediminas Seniutinas, Mikako Makita, et al. "Spectral monitoring at SwissFEL using a high-resolution on-line hard X-ray single-shot spectrometer." Journal of Synchrotron Radiation 28, no. 6 (2021): 1978–84. http://dx.doi.org/10.1107/s1600577521009619.

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The performance and parameters of the online photon single-shot spectrometer (PSSS) at the Aramis beamline of the SwissFEL free-electron laser are presented. The device operates between the photon energies 4 and 13 keV and uses diamond transmission gratings and bent Si crystals for spectral measurements on the first diffraction order of the beam. The device has an energy window of 0.7% of the median photon energy of the free-electron laser pulses and a spectral resolution (full width at half-maximum) ΔE/E on the order of 10−5. The device was characterized by comparing its performance with refe

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Rieger, E. "Gamma-Ray Precursors of Solar Flares." International Astronomical Union Colloquium 142 (1994): 645–48. http://dx.doi.org/10.1017/s0252921100077927.

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AbstractBursts have been observed by the gamma-ray spectrometer on SMM at medium- and high-energy gamma-rays that precede the flare maximum. The negligible contribution of nuclear lines in the spectra of these events and their impulsive appearance suggests that they are hard-electron-dominated events superposed on the flares. Spatial resolution at gamma-ray energies will be necessary to decide whether this kind of bursts is cospatial with the flares or whether they occur in the flares’ vicinity.Subject headings: Sun: flares — Sun: X-rays, gamma rays

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Sobacchi, Emanuele, Lorenzo Sironi, and Andrei M. Beloborodov. "Synchrotron self-Compton radiation from magnetically dominated turbulent plasmas in relativistic jets." Monthly Notices of the Royal Astronomical Society 506, no. 1 (2021): 38–51. http://dx.doi.org/10.1093/mnras/stab1702.

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ABSTRACT Relativistic jets launched by rotating black holes are powerful emitters of non-thermal radiation. Extraction of the rotational energy via electromagnetic stresses produces magnetically dominated jets, which may become turbulent. Studies of magnetically dominated plasma turbulence from first principles show that most of the accelerated particles have small pitch angles, i.e. the particle velocity is nearly aligned with the local magnetic field. We examine synchrotron self-Compton radiation from anisotropic particles in the fast cooling regime. The small pitch angles reduce the synchro

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Petrillo, Vittoria, Illya Drebot, Geoffrey Krafft, et al. "A Laser Frequency Transverse Modulation Might Compensate for the Spectral Broadening Due to Large Electron Energy Spread in Thomson Sources." Photonics 9, no. 2 (2022): 62. http://dx.doi.org/10.3390/photonics9020062.

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Compact laser plasma accelerators generate high-energy electron beams with increasing quality. When used in inverse Compton backscattering, however, the relatively large electron energy spread jeopardizes potential applications requiring small bandwidths. We present here a novel interaction scheme that allows us to compensate for the negative effects of the electron energy spread on the spectrum, by introducing a transverse spatial frequency modulation in the laser pulse. Such a laser chirp, together with a properly dispersed electron beam, can substantially reduce the broadening of the Compto

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Numazawa, Masaki, Yuichiro Ezoe, Takaya Ohashi, et al. "Suzaku observations of Jovian diffuse hard X-ray emission." Publications of the Astronomical Society of Japan 73, no. 4 (2021): 894–911. http://dx.doi.org/10.1093/pasj/psab053.

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Abstract We report on results of systematic analyses of the entire three X-ray data sets of Jupiter taken by Suzaku in 2006, 2012, and 2014. Jovian diffuse hard X-ray emission was discovered by Suzaku in 2006 when the solar activity went toward its minimum. The diffuse emission was spatially consistent with the Jovian inner magnetosphere and was spectrally fitted with a flat power-law function suggesting non-thermal emission. Thus, a scenario in which ultra-relativistic (tens of MeV) electrons in the Jovian inner magnetosphere inverse-Comptonize solar visible photons into X-ray bands has been

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Lei, Maichang, Yuan Zheng, Jianfu Zhang, and Jiancheng Wang. "Explaining the Multiwavelength Emission of Hard-TeV BL Lac Objects Using a Truncated Conical Jet Model." Research in Astronomy and Astrophysics 22, no. 4 (2022): 045005. http://dx.doi.org/10.1088/1674-4527/ac501e.

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Abstract Hard-TeV BL Lac objects are newly identified populations of active galactic nuclei with the emitted γ-ray photons well above TeV energies. In this paper, we explain the multiwavelength emission of six Hard-TeV BL Lac objects by using a truncated conical emission region of the jet, where the electron distribution is obtained by numerically solving the evolution equation along the jet self-consistently. For comparison, we also apply the model to Mrk 421 and Mrk 501, which are the potential candidates for the hard TeV emissions. We demonstrate that the model can satisfactorily reproduce

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Van Oss, R. F., G. H. J. Van Den Oord, and M. Kuperus. "Accretion Disk Flares in Energetic Radiation Fields." Symposium - International Astronomical Union 157 (1993): 217–18. http://dx.doi.org/10.1017/s0074180900174157.

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We consider the physics of magnetic flares in the energetic radiation field of an accretion disk corona (ADC). The X-ray emission from these flares is thought to be responsable for the observed hard powerlaw component in the X-ray spectra of galactic black hole candidates in their ‘high’ spectral state. During the flare event (inverse Compton) scattering of soft photons from the underlying disk into hard photons occurs on accelerated electrons in current sheets. The electrons are decelerated by the radiation drag force that results from the up-scattering. This friction-like effect of the inten

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Panontin, E., A. Dal Molin, M. Nocente та ін. "Comparison of unfolding methods for the inference of runaway electron energy distribution from γ-ray spectroscopic measurements". Journal of Instrumentation 16, № 12 (2021): C12005. http://dx.doi.org/10.1088/1748-0221/16/12/c12005.

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Abstract Unfolding techniques are employed to reconstruct the 1D energy distribution of runaway electrons from Bremsstrahlung hard X-ray spectrum emitted during plasma disruptions in tokamaks. Here we compare four inversion methods: truncated singular value decomposition, which is a linear algebra technique, maximum likelihood expectation maximization, which is an iterative method, and Tikhonov regularization applied to χ 2 and Poisson statistics, which are two minimization approaches. The reconstruction fidelity and the capability of estimating cumulative statistics, such as the mean and maxi

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Poutanen, Juri, Alexandra Veledina, and Andrzej A. Zdziarski. "Doughnut strikes sandwich: the geometry of hot medium in accreting black hole X-ray binaries." Astronomy & Astrophysics 614 (June 2018): A79. http://dx.doi.org/10.1051/0004-6361/201732345.

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We study the effects of the mutual interaction of hot plasma and cold medium in black hole binaries in their hard spectral state. We consider a number of different geometries. In contrast to previous theoretical studies, we use a modern energy-conserving code for reflection and reprocessing from cold media. We show that a static corona above an accretion disc extending to the innermost stable circular orbit produces spectra not compatible with those observed. They are either too soft or require a much higher disc ionization than that observed. This conclusion confirms a number of previous find

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Huotari, Simo. "X-ray Raman scattering spectroscopy." Acta Crystallographica Section A Foundations and Advances 70, a1 (2014): C219. http://dx.doi.org/10.1107/s2053273314097800.

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For elements with low atomic number, or shallow absorption edges falling in the energy range below ~1 keV, x-ray absorption studies are often limited by surface sensitivity and the necessity of a vacuum environment, making bulk-sensitive measurements and for example studies of liquids difficult. An exciting alternative is provided by X-ray Raman scattering (XRS) spectroscopy. It is used to measure a photon-in-photon-out process, where a hard x-ray photon loses only part of its energy creating an excitation of an inner core electron. As such, it is the x-ray analogue of electron energy loss spe

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Sarkar, Shilpa, Indranil Chattopadhyay, and Philippe Laurent. "Two-temperature solutions and emergent spectra from relativistic accretion discs around black holes." Astronomy & Astrophysics 642 (October 2020): A209. http://dx.doi.org/10.1051/0004-6361/202037520.

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Aims. We investigate a two-temperature advective transonic accretion disc around a black hole and analyse its spectrum in the presence of radiative processes such as bremsstrahlung, synchrotron, and inverse-Comptonisation. The aim is to link the emergent spectra with constants of motion of the accretion disc fluid, however, the number of unknowns in two-temperature theory exceeds the number of equations for a given set of constants of motion. We intend to remove the degeneracy using a general methodology and obtain a unique solution, along with its spectrum. Methods. We used hydrodynamic equat

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Min, Chang-Ki, Inhyuk Nam, Haeryong Yang, et al. "Hard X-ray self-seeding commissioning at PAL-XFEL." Journal of Synchrotron Radiation 26, no. 4 (2019): 1101–9. http://dx.doi.org/10.1107/s1600577519005460.

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A wake monochromator based on a large-area diamond single crystal for hard X-ray self-seeding has been successfully installed and commissioned in the hard X-ray free-electron laser (FEL) at the Pohang Accelerator Laboratory with international collaboration. For this commissioning, the self-seeding was demonstrated with a low bunch charge (40 pC) and the nominal bunch charge (180 pC) of self-amplified spontaneous emission (SASE) operation. The FEL pulse lengths were estimated as 7 fs and 29.5 fs, respectively. In both cases, the average spectral brightness increased by more than three times com

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Suleimanov, V. F., J. Poutanen, and K. Werner. "Accretion heated atmospheres of X-ray bursting neutron stars." Astronomy & Astrophysics 619 (November 2018): A114. http://dx.doi.org/10.1051/0004-6361/201833581.

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Some thermonuclear (type I) X-ray bursts at the neutron star surfaces in low-mass X-ray binaries take place during hard persistent states of the systems. Spectral evolution of these bursts is well described by the atmosphere model of a passively cooling neutron star when the burst luminosity is high enough. The observed spectral evolution deviates from the model predictions when the burst luminosity drops below a critical value of 20–70% of the maximum luminosity. The amplitude of the deviations and the critical luminosity correlate with the persistent luminosity, which leads us to suggest tha

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Sorokin, Andrey A., Yilmaz Bican, Susanne Bonfigt, et al. "An X-ray gas monitor for free-electron lasers." Journal of Synchrotron Radiation 26, no. 4 (2019): 1092–100. http://dx.doi.org/10.1107/s1600577519005174.

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A novel X-ray gas monitor (XGM) has been developed which allows the measurement of absolute photon pulse energy and photon beam position at all existing and upcoming free-electron lasers (FELs) over a broad spectral range covering vacuum ultraviolet (VUV), extreme ultraviolet (EUV) and soft and hard X-rays. The XGM covers a wide dynamic range from spontaneous undulator radiation to FEL radiation and provides a temporal resolution of better than 200 ns. The XGM consists of two X-ray gas-monitor detectors (XGMDs) and two huge-aperture open electron multipliers (HAMPs). The HAMP enhances the dete

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