Results 1 - 10 of 12860
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[en] We report on the 2020 reactivation of the energetic high magnetic field pulsar PSR J1846–0258 and its pulsar wind nebula (PWN) after 14 yr of quiescence with new Chandra and Green Bank Telescope observations. The emission of short-duration bursts from J1846–0258 was accompanied by an enhancement of X-ray persistent flux and significant spectral softening, similar to those observed during its first bursting episode in 2006. The 2020 pulsar spectrum is described by a power-law model with a photon index Γ = 1.7 ± 0.3 in comparison to a Γ = 1.2 ± 0.1 before outburst, and shows evidence of an emerging thermal component with blackbody temperature kT = 0.7 ± 0.1 keV. The 0.5–10 keV unabsorbed flux increased from × 10−12 erg cm−2 s−1 in quiescence to × 10−11 erg cm−2 s−1 following the outburst. We did not detect any radio pulsations from the pulsar at 2 GHz, and we place an upper limit of 7.1 μJy and 55 mJy for the coherent pulsed emission and single pulses, respectively. The 2020 PWN spectrum, characterized by a photon index of 1.92 ± 0.04 and X-ray luminosity of (1.2 ± 0.1) × 1035 erg s−1 at a distance of 5.8 kpc, is consistent with those observed before the outburst. An analysis of regions closer to the pulsar shows small-scale time variabilities and brightness changes over the 20 yr period from 2000 to 2020, while the photon indices did not change. We conclude that the outburst in PSR J1846–0258 is a combination of crustal and magnetospheric effects, with no significant burst-induced variability in its PWN based on the current observations.
[en] The characteristic X-ray intensities of Ag-Lα, Lβ1, Lβ2 and Lγ1 are measured in electron-impact ionization at energy of 10 keV. The emission angle in this work ranges from 0° to 20° at interval of 5°. The angular dependence of L X-ray intensity ratios has been investigated for Lα / Lβ1, Lβ2 / Lβ1 and Lγ1 / Lβ1. It is found from the experimental results that the emissions of Lβ1, Lβ2 and Lγ1 X-rays are spatially isotropic, while the Lα X-rays exhibit anisotropic emission. Consequently, the alignment behavior of vacancy states is discussed with thorough analysis of vacancy transfer process. - Highlights: • Only the Lα X-rays are found to be spatially anisotropic in the measurement. • The alignment of L3-subshell is influenced by vacancy transfer process. • Different alignment behaviors in previous work have been clarified.
[en] The assignment of the value for spin to a large number of resonances makes it possible to study various quantities as a function of the two spin states, J = I ± 1/2. The authors observed, in particular, the strength function S0 for target nuclei of spin I = 1/2 (Y, Ag, Tm, Pt). S0 is the same for the spins J = 0 and J = 1. For target nuclei of spin I = 3/2 (Cl, Cu, Ga, As, Br, Ba, Au), S0 for spin state J=2 is twice as large as for J = 1. There is a discussion of the results obtained in the energy range of a few keV. (author)
[fr]L'attribution de la valeur du spin a un grand nombre de resonances permet l'etude de differentes quantites en fonction des deux etats de spin J= I ± 1/2. La fonction densite S0 a ete en particulier etudiee pour des noyaux cibles de spin I = 1/2 (Y, Ag, Tm, Pt); la valeur S0 est la meme pour les valeurs de spin J = 0 et J = 1. Pour les noyaux cibles I = 3/2 (Cl, Cu, Ga, As, Br, Ba, Au), la valeur S0 pour l'etat de spin J = 2 est deux fois plus grande que la valeur S0 pour J= 1. Les resultats obtenus dans le domaine d'energie de quelques keV sont presentes et discutes. (author)
[en] Classical dynamics simulations of sputtering have been carried out for 3 keV Ar projectiles incident on Cu(1 0 0) crystallite targets with a range of lateral and vertical dimensions. The purpose of the simulations was to document the effects of containment failure on the predicted sputter yields and to establish criteria for convergence of the predicted sputtering properties to asymptotic values. Failure of lateral containment produces sputter yield errors due to both lateral truncation of the target (which understates yields) and to sputtering from the edge faces of the target crystallite (which overstates yields). Failure of vertical containment understates sputter yields. For practical purposes, sputter yield containment can be achieved using a 12-layer Cu(1 0 0) target with 441 atoms per layer, provided that the contribution from atoms originating from the crystallite edge faces is excluded from the sputter yield estimates
[en] Highlights: • SDCT provides excellent image quality at low keV levels. • SDCT enables the assessment of arteries in venous phase. • MonoE imaging from SDCT showed distinct different luminal diameters than conventional imaging. - Abstract: ObjectivesTo investigate the utilization of virtual mono-energetic images (MonoE) at low kiloelectron volt (keV) levels derived from a dual-layer spectral detector CT (SDCT) for the assessment of abdominal arteries in venous contrast phase scans using arterial phase imaging as an internal reference standard.
[en] Observations of 3-12 keV X-ray emission from NGC 5128 (Cen A) were made by Vela spacecraft over the period 1969-1979. These data are in good agreement with previously reported data, but are much more complete. Numerous peaks of X-ray intensity occurred during the period 1973-1975, characterized by rapid increases and equally rapid decreases (in less than 10 days). Thus it seems probable that most of the X-ray flux from the nucleus of Cen A came from a single source of small size. (Auth.)
[en] The photon diagnostics available at the SwissFEL Aramis beamline are described. The working principles of various devices, their function and their expected or measured performance are discussed. The SwissFEL Aramis beamline, covering the photon energies between 1.77 keV and 12.7 keV, features a suite of online photon diagnostics tools to help both users and FEL operators in analysing data and optimizing experimental and beamline performance. Scientists will be able to obtain information about the flux, spectrum, position, pulse length, and arrival time jitter versus the experimental laser for every photon pulse, with further information about beam shape and size available through the use of destructive screens. This manuscript is an overview of the diagnostics tools available at SwissFEL and presents their design, working principles and capabilities. It also features new developments like the first implementation of a THz-streaking based temporal diagnostics for a hard X-ray FEL, capable of measuring pulse lengths to 5 fs r.m.s. or better.
[en] Electron and nuclear transitions in the nuclear excitation by electron transition (NEET) process have been investigated. The NEET transitions for nuclei are presented in a table in which the electron and nuclear transitions, their transition energies, transition multipoles, and nuclear spin angular momentum are given. The elements are listed for which the difference between the electron and nuclear transition energy is <5 keV, because the NEET probability will be appreciable if the electron transition energy is close to the nuclear transition one. As both the experimental and theoretical studies for NEET are at an early stage, only the elements and their parameters related to NEET are listed here. The present compilation, however, provides a useful direction for future studies of NEET and its applications to nuclear science