scholarly journals X-Ray Observations of Stellar Coronae and Winds

1980 ◽  
Vol 5 ◽  
pp. 853-856 ◽  
Author(s):  
Jean H. Swank
Keyword(s):  
Solid State ◽  
Line Emission ◽  
Low Energy ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
Flare Stars ◽  
High Space ◽  
To Come ◽  
Energy Detectors

Since the discovery in 1974 by Heise et al. (1975) with the ANS satellite of X-ray flares from YZ CMi and UV Cet, only a few attempts to observe X-rays from flare stars have succeeded. On the other hand, the discovery of X-ray emission from Capella by Catura, Acton and Johnson (1975) in a rocket flight has been followed by so many detections of RS CVn binaries by the low energy detectors (0.15 - 3 keV) of the HEAO A2 experiment that, while Catura et al. estimated that many variable soft X-ray sources probably exist, Walter, Charles and Bowyer (1978) could identify the RS CVn systems as a class of quiescent sources. They have higher temperatures than at first predicted, so they are ideal for detection in the energy range ¼ keV to a few keV, and the high space density provides many close candidates. Further information on these sources is now available from the GSFC Solid State Spectrometer Experiment on the Einstein Observatory, which with energy resolution of 140 eV can resolve the major complexes of line emission from Si, S, Fe and less abundant elements that are an important part of the emission of 10 million degree plasmas. The imaging experiments on the Einstein Observatory have detected X-ray emission from subsets of all types of stars, and results on the luminosities, variability and temperatures are just beginning to come out.

Exosat Observations of H2252−035: Pulse Phase and Orbital Phase Dependent Low Energy Absorption and Iron Line Emission

1987 ◽  
Vol 93 ◽  
pp. 281-292
Author(s):  
W. Pietsch ◽  
W. Voges ◽  
E. Kendziorra ◽  
M. Pakull
Keyword(s):  
Energy Absorption ◽  
Line Emission ◽  
Low Energy ◽  
Gas Absorption ◽  
X Rays ◽  
Medium Energy ◽  
Iron Line ◽  
X Ray ◽  
Low Energies ◽  
Optical Light Curve

AbstractThe 805 sec pulsing X-ray source H2252−035 has been observed for 7 h on September 14/15 and on September 17, 1983 in X-rays with the low energy telescope and the medium energy detectors of EXOSAT. While below 2 keV the semiamplitude of the 805 s pulses is ~ 100% in the 2.3–7.9 keV band it is only ~ 40%. X-ray dips that are more pronounced in low energies occur simultaneously with the orbital minimum of the optical light curve. The medium energy spectra during dips with respect to the non dip spectrum can be explained by just enhanced cold gas absorption of an additional absorbing column of 2 1022 cm−2. Model spectra for the 805 s minimum have to include a strong iron emission line at 6.55 keV with an equivalent width of 3 keV in addition to a reduced continuum intensity (radiating area) and enhanced low energy absorption.

scholarly journals X-Ray Emission Lines: Present and Future Experiments

1997 ◽  
Vol 159 ◽  
pp. 1-19
Author(s):  
H. Kunieda
Keyword(s):  
Line Profile ◽  
Line Emission ◽  
Low Noise ◽  
Low Energy ◽  
X Rays ◽  
Rapid Variability ◽  
Line Energy ◽  
X Ray ◽  
Proportional Counters ◽  
Ccd Detectors

AbstractAfter 34 years of X-ray astronomical observations, we approach the time when we will be able to explore AGN using line spectroscopy with newly developed technology and methods. In the beginning, X-rays from AGN were observed using proportional counters in a sort of photometric way, allowing us to determine that the continuum is a power law. This result suggested a predominance of non-thermal emission mechanisms in AGN. Rapid variability on time scales as short as 1000 seconds implied a small size for the X-ray emitting region, of order 1014cm, which is 3 orders of magnitude smaller than the optical emission-line regions.The first detection of line emission from AGN was the Fe-K line by the GINGA satellite. The line energy was 6.4 keV and its equivalent width was about 150 eV in Seyfert 1 galaxies. Detection became possible by use of large-area, low-noise proportional counters. The Fe-K line emission is important in X-ray astronomy because iron is rather abundant and this line is isolated in energy from neighboring lines.The Fe-K line profile has been examined with the CCD detectors on board ASCA. Many Seyfert 1 galaxies exhibit a broad-line profile of more than 1 keV width with an asymmetric tail on the low-energy side. This is explained as the fluorescence line from a relativistic accretion disk around a black hole, which is broadened by the Doppler motion and distorted by the strong gravitational field. The CCD detectors also revealed the absorption edges of warm material in the line of sight, which is ionized by the strong emission from AGN.In the next decade, new spectrometers will be launched which can perform spectroscopy with E/dE > 100: AXAF in 1998, XMM in 1999, and Astro-E in 2000. Dispersive spectrometers on board AXAF and XMM will be powerful tools for low-energy lines, while the calorimeter on board Astro-E will examine the Fe-K line profile. Spectral resolution E/dE of several hundred will reveal the intensity ratio of satellite and resonance lines. This will give us physical parameters, such as the density and absolute size of surrounding matter. We hope that the structure of the nucleus will be more deeply understood using X-ray spectroscopy with new instruments, and we will come close to the level of optical spectroscopy, which has worked well in the study of the outskirts of AGN.

scholarly journals Hard X-Ray Properties of Cataclysmic Variables

1979 ◽  
Vol 53 ◽  
pp. 135-138
Author(s):  
J.H. Swank
Keyword(s):  
Solid State ◽  
Proportional Counter ◽  
Cataclysmic Variables ◽  
High Energy ◽  
X Rays ◽  
Dwarf Novae ◽  
X Ray ◽  
Upper Limits ◽  
Energy Detectors ◽  
Einstein Observatory

The production of hard X-rays in accretion onto degenerate dwarfs appears manifested by such sources as the magnetic variables AM Herculis and 3U0311-227 and the dwarf novae SS Cygni, EX Hydrae and U Geminorum. Upper limits on flux above 2 keV from Ariel 5 (Watson, Sherrington and Jameson 1978) and from the high energy detectors of the HEAO A2 experiment show that only a few others usually exhibit more than ~10-11 ergs cm-2s-1 or ~ 1031 ergs s-1. However, while there are only a few sources that these experiments could study, their behavior is complex (Swank et al. 1977a; Ricketts, King and Raine 1979; Swank et al. 1978; Mason, Cordova and Swank 1979). This paper is a brief summary of results for AM Her, EX Hya, SS Cyg and U Gem obtained with the high energy detectors of the HEAO A2 experiment from 2-60 keV and the Solid State Spectrometer Experiment (SSS) with the Monitor Proportional Counter (MPC) on the Einstein Observatory.

scholarly journals IRIXS: a resonant inelastic X-ray scattering instrument dedicated to X-rays in the intermediate energy range

2020 ◽  
Vol 27 (2) ◽  
pp. 538-544
Author(s):  
Hlynur Gretarsson ◽  
Didem Ketenoglu ◽  
Manuel Harder ◽  
Simon Mayer ◽  
Frank-Uwe Dill ◽  
...  
Keyword(s):  
Energy Analysis ◽  
Intermediate Energy ◽  
Low Energy ◽  
The Other ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Crystal Analyzer ◽  
Lattice Planes ◽  
Ray Scattering

A new resonant inelastic X-ray scattering (RIXS) instrument has been constructed at beamline P01 of the PETRA III synchrotron. This instrument has been named IRIXS (intermediate X-ray energy RIXS) and is dedicated to X-rays in the tender-energy regime (2.5–3.5 keV). The range covers the L 2,3 absorption edges of many of the 4d elements (Mo, Tc, Ru, Rh, Pd and Ag), offering a unique opportunity to study their low-energy magnetic and charge excitations. The IRIXS instrument is currently operating at the Ru L 3-edge (2840 eV) but can be extended to the other 4d elements using the existing concept. The incoming photons are monochromated with a four-bounce Si(111) monochromator, while the energy analysis of the outgoing photons is performed by a diced spherical crystal analyzer featuring (102) lattice planes of quartz (SiO2). A total resolution of 100 meV (full width at half-maximum) has been achieved at the Ru L 3-edge, a number that is in excellent agreement with ray-tracing simulations.

scholarly journals The use of fricke dosimetry for low energy x-rays

2006 ◽  
Vol 49 (spe) ◽  
pp. 17-23 ◽  
Author(s):  
Carlos de Austerlitz ◽  
Viviane Souza ◽  
Heldio Pereira Villar ◽  
Aloisio Cordilha
Keyword(s):  
Ionization Chamber ◽  
Parallel Plate ◽  
Low Energy ◽  
Calibration Factor ◽  
X Rays ◽  
Measuring Systems ◽  
X Ray ◽  
Dose Measurements

The performance of four X-ray qualities generated in a Pantak X-ray machine operating at 30-100 kV was determined with a parallel-plate ionization chamber and a Fricke dosimeter. X-ray qualities used were those recommended by Deutsch Internationale Normung DIN 6809 and dose measurements were carried out with Plexiglas® simulators. Results have shown that the Fricke dosimeter can be used not only for soft X-ray dosimetry, but also for the maintenance of low-energy measuring systems' calibration factor.

Isoelastic Cementless Total Hip Replacement in Rheumatoid Arthritis. Long-Term Results

1992 ◽  
Vol 2 (2) ◽  
pp. 43-46
Author(s):  
U. Fusco ◽  
R. Capelli ◽  
A. Avai ◽  
M. Gerundini ◽  
L. Colombini ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Hip Replacement ◽  
The Other ◽  
Long Term Results ◽  
X Rays ◽  
X Ray ◽  
The Mean ◽  
Cementless Total Hip Replacement

Between 1980 and 1987 we have implanted 46 isoelastic cementless THR in 40 patients affected with rheumatoid arthritis. We have reviewed 38 hips clinically and by X-ray. The mean follow-up was 8,5 years. Harris hip scores ranged from 30.6 preoperatively to 73,4 post-operatively when reviewed. While on the other hand Merle D'Aubigné hip scores ranged from 7,06 pre-operatively to 15,59 post-operatively. All patients have been satisfied, and X-rays showed an improvement for both Charnely and Gruen X-ray score.

Synthèse et caractérisation des oxypentafluorouranates(VI) NH4UOF5, KUOF5, RbUOF5 et CsUOF5

1978 ◽  
Vol 56 (14) ◽  
pp. 1874-1880 ◽  
Author(s):  
Philippe Joubert ◽  
Roland Bougon ◽  
Bernard Gaudreau
Keyword(s):  
Infrared Spectroscopy ◽  
Solid State ◽  
Alkali Metal ◽  
Vibrational Spectroscopy ◽  
Uranium Atom ◽  
The Other ◽  
Metal Fluoride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman And Infrared Spectroscopy

The oxypentafluorouranates(VI) MUOF5, where M = NH4, K, Rb, Cs, have been synthetized from reaction of UOF4 with the ammonium or corresponding alkali metal fluoride in liquid SO2. According to X-ray diffraction, Raman and infrared spectroscopy, and from an isomorphism with the corresponding hexafluorouranates(V) MUF6, two different environments around the uranium atom are observed. In CsUOF5 the five fluorine atoms and the oxygen around the uranium result in a pseudo-octahedral surrounding whereas for the other complexes (M = NH4, K, Rb) each uranium is surrounded by eight light atoms forming a dodecahedron. In this structure the dodecahedra are linked together by fluorine atoms to form infinite chains. The UOF5− ion has been characterized by vibrational spectroscopy in the solid state. The proposed assignment, which was made with the assumption of a C4v symmetry of the UOF5− ion, was confirmed by a force constant calculation. From these data and contrary to the values reported for comparable oxypentafluoroanions, the axial fluorine is found to be less ionic than the equatorial ones.

SOFT X-RAY EMISSION IN THE (1.0–1.5 KEV) WINDOW WITH NITROGEN FILLING IN A LOW ENERGY PLASMA FOCUS

2002 ◽  
Vol 16 (09) ◽  
pp. 309-318 ◽  
Author(s):  
M. SHAFIQ ◽  
SARTAJ ◽  
S. HUSSAIN ◽  
M. SHARIF ◽  
S. AHMAD ◽  
...  
Keyword(s):  
Plasma Focus ◽  
Pressure Range ◽  
Filling Pressure ◽  
Pinhole Camera ◽  
Low Energy ◽  
X Rays ◽  
System Efficiency ◽  
Current Sheath ◽  
Pin Diodes ◽  
X Ray

A study of soft X-ray emission in the 1.0–1.5 keV energy range from a low energy (1.15 kJ) plasma focus has been conducted. X-rays are detected with the combination of Quantrad Si PIN-diodes masked with Al (50 μm), Mg (100 μm) and Ni (17.5 μm) filters and with a pinhole camera. The X-ray flux is found to be measurable within the pressure range of 0.1–1.0 mbar nitrogen. In the 1.0–1.3 keV and 1.0–1.5 keV windows, the X-ray yield in 4π-geometry is 1.03 J and 14.0-J, respectively, at a filling pressure of 0.25 mbar and the corresponding efficiencies are 0.04% and 1.22%. The total X-ray emission in 4π-geometry is 21.8 J, which corresponds to the system efficiency of about 1.9%. The X-ray emission is found dominantly as a result of the interaction of energetic electrons in the current sheath with the anode tip. Images recorded by the pinhole camera confirm the emission of X-rays from the tip of the anode.

scholarly journals THE SKIN REACTIONS PRODUCED BY ALTERNATIONS OF HEAT AND X-RAY AT VARIOUS TIME INTERVALS

1931 ◽  
Vol 53 (3) ◽  
pp. 405-411 ◽  
Author(s):  
James A. Hawkins
Keyword(s):  
Guinea Pig ◽  
The Other ◽  
X Rays ◽  
Time Intervals ◽  
Skin Reactions ◽  
X Ray ◽  
Critical Dose

Areas on the abdomen of the same guinea pig were exposed to suberythemal doses of soft X-rays, to heat of an intensity below the critical dose for the production of burns, and to both radiations in sequence with various time intervals between the exposures. The only effect of exposure to X-ray or heat alone was a slight scaling of the skin. The areas exposed to heat and X-radiation developed well-marked and persistent burns when the exposure to one agent was made within 3 hours of the other. Scaling of the skin developed when the exposure to one agent was made 1 day after the other. This scaling was more marked and lasted longer than the scaling produced by either agent alone. The results were the same no matter in which sequence the agents were applied.

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