scholarly journals The Radiation Transfer of Soft X-rays

1997 ◽  
Vol 166 ◽  
pp. 337-340 ◽  
Author(s):  
Jürgen Kerp ◽  
Jochen Pietz
Keyword(s):  
Power Law ◽  
Intensity Distribution ◽  
Galactic Halo ◽  
Background Radiation ◽  
Plasma Temperature ◽  
Intensity Variation ◽  
Background Intensity ◽  
X Rays ◽  
Energy Bands ◽  
X Ray

AbstractWe discuss the link between the halo plasma temperature and the power-law spectral index of the extragalactic background radiation. This link is of strong influence for the derivation of the Galactic halo intensity distribution. In principal, we can distinguish between two combinations of Galactic halo plasma temperature and power-law slope. The first combination consists of a halo plasma of Thalo = 106 K and an E−2 approximation of the extragalactic background radiation. The second combination is Thalo = 106.2 K and an E−1.5. Both combinations are in agreement with recent observational results, thus it is not feasible to discriminate between both models on the basis of X-ray data available. But, the soft X-ray background intensity distribution in the ¼ keV and ¾ keV ROSAT energy bands differs significantly. The Thalo = 106 K and an E−2 allows a patchy ¼ keV intensity distribution while the Thalo = 106.2 K and an E−1.5 predicts a much smoother intensity variation since the hotter halo plasma accounts for a significant fraction of the ¾ keV background radiation.

scholarly journals Temporal and Spectral Variability of OJ 287 before the April–June 2020 Outburst

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 58
Author(s):  
Nibedita Kalita ◽  
Alok C. Gupta ◽  
Minfeng Gu
Keyword(s):  
Power Law ◽  
Lower Energy ◽  
X Rays ◽  
Power Law Model ◽  
Energy Bands ◽  
Spectral Variability ◽  
X Ray ◽  
Bl Lacertae ◽  
Inverse Compton ◽  
Absorbed Power

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 emissions, while there is no correlation between the hard X-rays and the lower energy bands indicating the presence of two emission components or electron populations. Although two components contribute to the X-ray emission, most of the 0.3–10 keV spectra were well fitted with an absorbed power-law model which outlines the dominance of synchrotron over inverse Compton (IC) mechanism. The X-ray spectra follow a weak “softer when brighter” trend.

A computer-based method of measuring the integrated intensities of the reflections on the X-ray diffraction photograph of an oriented crystalline polymer

1987 ◽  
Vol 20 (3) ◽  
pp. 246-255 ◽  
Author(s):  
I. H. Hall ◽  
J. Z. Neisser ◽  
M. Elder
Keyword(s):  
Intensity Distribution ◽  
Statistical Tests ◽  
Structure Refinement ◽  
Intensity Variation ◽  
Crystalline Polymer ◽  
Background Intensity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Photograph ◽  
Integrated Intensities

The method is designed to be used with a batch-processing computer system and will determine the integrated intensities of the spots on an X-ray diffraction photograph of an oriented fibre of a partially crystalline synthetic polymer. It is necessary to assume that the spot boundary is elliptical, that the intensity distribution along any line through the centre of this ellipse is Gaussian, and that the background intensity variation is linear over the region of a spot; these are justified experimentally, although, in the radial direction, the choice of a Gaussian intensity distribution is probably theoretically unsound. The computational procedures correct for minor differences between users in the choice of input parameters and reject bad choices. The method was applied to determine the intensities of the 30 visible spots in the diffraction photograph of oriented poly(trimethyleneterephthalate) which were used in a subsequent structure refinement. successful integrations were obtained for 22 spots, the failures being (1) pairs of similar intensity just resolved by eye, (2) better resolved pairs of which one member is stronger than the other, or (3) very weak. Statistical tests indicated very much better internal consistency of data than is usually obtained with these materials, and enabled a rational weighting scheme to be used in the structure refinement. The R factor of 7.9% obtained is unusually low, indicating much improved accuracy over earlier methods.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

Contribution of x-ray total reflection to the background intensity in EPMA

1990 ◽  
Vol 48 (2) ◽  
pp. 202-203
Author(s):  
Werner P. Rehbach ◽  
Peter Karduck
Keyword(s):  
Atomic Number ◽  
Target Material ◽  
Total Reflection ◽  
Background Intensity ◽  
X Rays ◽  
Characteristic Radiation ◽  
X Ray

In the EPMA of soft x rays anomalies in the background are found for several elements. In the literature extremely high backgrounds in the region of the OKα line are reported for C, Al, Si, Mo, and Zr. We found the same effect also for Boron (Fig. 1). For small glancing angles θ, the background measured using a LdSte crystal is significantly higher for B compared with BN and C, although the latter are of higher atomic number. It would be expected, that , characteristic radiation missing, the background IB (bremsstrahlung) is proportional Zn by variation of the atomic number of the target material. According to Kramers n has the value of unity, whereas Rao-Sahib and Wittry proposed values between 1.12 and 1.38 , depending on Z, E and Eo. In all cases IB should increase with increasing atomic number Z. The measured values are in discrepancy with the expected ones.

Diffuse scattering and phason modes in the i-AlPdMn quasicrystalline phase

2005 ◽  
Vol 220 (12) ◽  
Author(s):  
Marc de Boissieu ◽  
Sonia Francoual
Keyword(s):  
Elastic Constant ◽  
Elastic Constants ◽  
Intensity Distribution ◽  
Diffuse Scattering ◽  
Hydrodynamic Theory ◽  
Quasicrystalline Phase ◽  
X Rays ◽  
X Ray ◽  
Long Wavelength ◽  
Diffusive Modes

AbstractWe review results obtained in the study of the diffuse scattering in the i-AlPdMn quasicrystal. Most of the diffuse scattering is the result of long wavelength phason modes. The shape and intensity distribution of the diffuse scattering is well reproduced using the generalised elasticity theory and two phason elastic constants. The temperature dependence of the diffuse scattering indicates a softening of the phason elastic constant as the temperature is lowered. Using coherent X-rays and photo-correlation X-ray spectroscopy, it is shown that phason modes are collective diffusive modes, in agreement with the hydrodynamic theory of long wavelength fluctuations in quasicrystals.

scholarly journals XMM-Newton and Fermi/LAT view on the supernova remnant 3C434.1

2019 ◽  
Vol 631 ◽  
pp. A179
Author(s):  
V. Doroshenko ◽  
D. Malyshev ◽  
G. Pühlhofer ◽  
B. Dincel ◽  
M. Sasaki ◽  
...  
Keyword(s):  
Power Law ◽  
Supernova Remnant ◽  
X Rays ◽  
Significant Excess ◽  
X Ray ◽  
Thermal Origin

We report on XMM-Newton observations of the supernova remnant (SNR) 3C434.1 (G94.0+1.0), the first in X-rays since the ROSAT era. Our analysis confirms the thermal origin of the observed extended X-ray emission, whose morphology appears more complex than previously reported. In particular, part of the shell shows a significantly harder spectrum which is consistent with a power law, and it is, therefore, likely of non-thermal origin. Motivated by these finding, we revisited the GeV observations of the field taken with the Fermi observatory. A significant excess associated with the remnant was detected, which is likely associated with non-thermal X-ray emission from part of the shell. The analysis of the Fermi data resulted in the serendipity discovery of GeV emission from the nearby SNR G093.7-00.2. Finally, we searched for a possible compact remnants within the shell, however, no obvious candidates could be identified due to the fairly large positional uncertainties.

scholarly journals Electrons and X-Ray Emission of Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 409-413
Author(s):  
V. G. Kurt
Keyword(s):  
Solar Activity ◽  
Statistical Analysis ◽  
Solar Flare ◽  
Frequency Dependence ◽  
Power Law ◽  
Solar Flares ◽  
X Rays ◽  
Fast Electrons ◽  
X Ray ◽  
Flare Frequency

A statistical analysis of solar flare X-rays and interplanetary particle fluxes, measured onboard VENERA-13, 14 Spacecraft, was performed. The correlation of fluences for different manifestations of solar flares is strong, especially for fast electrons and hard and soft X-ray emissions. Frequency dependence on fluence value ϵi for practically all Kinds of solar flare emission can be described by power law ν (ϵ > ϵO) ∼ ϵ−0.45±0.15 which does not change significantly with solar activity. For different Hα flare importances the values of ϵi were obtained. It is proposed that appearance of certain energy flare frequency is strongly dependent on some scale factor.

scholarly journals Iron Line Emission from NGC1068

1989 ◽  
Vol 134 ◽  
pp. 167-172
Author(s):  
Katsuji Koyama
Keyword(s):  
Energy Range ◽  
Power Law ◽  
Equivalent Width ◽  
Line Emission ◽  
X Rays ◽  
Iron Line ◽  
X Ray ◽  
Central Engine ◽  
Photon Index ◽  
The Continuum

X-ray emission in the 2–10 keV energy range was observed with the Ginga satellite from the Seyfert 2 galaxy NGC1068. The continuum spectrum can be described by a power-law of photon index about 1.5. An intense iron line at 6.5 keV with an equivalent width of 1.3 keV was clearly noticed. The X-ray flux was about 6 × 10 −12 erg/sec/cm2 or 3 × 1041 erg/sec, assuming a distance of 22 Mpc. The observed spectrum is consistent with the scattering and reprocessing of X-rays by the gas surrounding the central engine. With this picture we estimate that the X-ray flux of the central engine is about 1043 - 1044 erg/sec, a typical value for a Seyfert 1 galaxy.

scholarly journals Theoretical analysis of the background intensity distribution in X-ray Birefringence Imaging using synchrotron bending-magnet radiation

2015 ◽  
Vol 117 (16) ◽  
pp. 164902 ◽  
Author(s):  
John P. Sutter ◽  
Igor P. Dolbnya ◽  
Stephen P. Collins ◽  
Kenneth D. M. Harris ◽  
Gregory R. Edwards-Gau ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Intensity Distribution ◽  
Background Intensity ◽  
X Ray

scholarly journals Middle aged γ-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula

2020 ◽  
Author(s):  
D A Zyuzin ◽  
A V Karpova ◽  
Y A Shibanov ◽  
A Y Potekhin ◽  
V F Suleimanov
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Power Law ◽  
Thermal Emission ◽  
Single Pulse ◽  
X Rays ◽  
Middle Aged ◽  
X Ray ◽  
Photon Index ◽  
Γ Ray

Abstract We analyze new XMM-Newton and archival Chandra observations of the middle-aged γ-ray radio-quiet pulsar J1957+5033. We detect, for the first time, X-ray pulsations with the pulsar spin period of the point-like source coinciding by position with the pulsar. This confirms the pulsar nature of the source. In the 0.15–0.5 keV band, there is a single pulse per period and the pulsed fraction is ≈18 ± 6 per cent. In this band, the pulsar spectrum is dominated by a thermal emission component that likely comes from the entire surface of the neutron star, while at higher energies (≳ 0.7 keV) it is described by a power law with the photon index Γ ≈ 1.6. We construct new hydrogen atmosphere models for neutron stars with dipole magnetic fields and non-uniform surface temperature distributions with relatively low effective temperatures. We use them in the spectral analysis and derive the pulsar average effective temperature of ≈(2 − 3) × 105 K. This makes J1957+5033 the coldest among all known thermally emitting neutron stars with ages below 1 Myr. Using the interstellar extinction–distance relation, we constrain the distance to the pulsar in the range of 0.1–1 kpc. We compare the obtained X-ray thermal luminosity with those for other neutron stars and various neutron star cooling models and set some constraints on latter. We observe a faint trail-like feature, elongated ∼8 arcmin from J1957+5033. Its spectrum can be described by a power law with a photon index Γ = 1.9 ± 0.5 suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

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