scholarly journals X-rays and γ-rays from Supernova 1987a

1988 ◽  
Vol 108 ◽  
pp. 394-398
Author(s):  
P. Sutherland ◽  
Y. Xu ◽  
R. McCray ◽  
R. Ross
Keyword(s):  
Circumstellar Matter ◽  
Radioactive Material ◽  
Strong Line ◽  
X Rays ◽  
X Ray ◽  
Monte Carlo Calculations ◽  
Sn 1987A ◽  
Unique Event ◽  
Supernova 1987A ◽  
Γ Rays

SummaryThe observation of X-rays and γ-rays from SN 1987a can provide important constraints on parameters for models of this unique event. We present the results of detailed Monte Carlo calculations of the fluxes to be expected in several X-ray bands and for the strong line at 847 keV associated with the decay of 56Co. Our calculations use Model 10H of Woosley, Pinto, and Ensman(1988), with 0.075M⊙ of radioactive material. If it is assumed that there is no mixing of this material with the layers above, then the X-ray fluxes do not become detectable as early as the observations made by the Ginga team in August, 1987. If these observations correspond to X-rays arising from γ-rays Compton scattered down in energy in the supernova ejecta, rather than the interaction of the ejecta with circumstellar matter, then they can only be explained by mixing outward of radioactive material or an envelope with some combination of less mass or greater kinetic energy per unit mass.

scholarly journals Thermal X-Rays due to Ejecta/CSM Interaction in SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 450-451
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
H. Itoh ◽  
K. Nomoto ◽  
T. Shigeyama
Keyword(s):  
Light Curve ◽  
Photon Energy ◽  
Thermal Emission ◽  
Circumstellar Matter ◽  
Expansion Velocity ◽  
X Rays ◽  
X Ray ◽  
Sn 1987A ◽  
Inner Radius

The X-ray spectrum observed by Ginga is characterized by a component below 10keV which decreases with increasing photon energy, and a component above 10keV which is nearly flat. This unusual X-ray spectrum may be understood as follows; X-rays below 10keV is likely to be due to thermal emission coming from the shock-heated ejecta, and X-rays above 10keV to be due to γ-ray degradation inside the ejecta. If thermal emission due to the collision of the ejecta with circumstellar matter (CSM) is responsible for X-rays below 10keV, the epoch of the collision can be estimated to be ∼ 0.2yr after the explosion if ∼ 0.5yr is the time when the X-ray flux at ∼ 10keV reaches its maximum. The X-ray light curve then requires the inner radius of CSM to be ∼ 1×1016cm for an expansion velocity, Vex ≃2×109cm s−1.

Interaction of supernova ejecta with circumstellar matter and X-ray emission: SN 1987A & SN 1993J

1996 ◽  
Vol 145 ◽  
pp. 317-322
Author(s):  
T. Suzuki ◽  
K. Nomoto ◽  
T. Shigeyama ◽  
S. Kumagai
Keyword(s):  
Circumstellar Matter ◽  
Light Curves ◽  
X Rays ◽  
X Ray ◽  
Sn 1987A

We perform hydrodynamical calculations of the collision between the supernova ejecta and circumstellar matter for SN 1987A and SN 1993J. For SN 1987A we predict light curves of X-ray emissions from the shocked ring. For SN 1993J, thermal X-rays from the shocked circumstellar matter can consistently account for the observations with ROSAT, ASCA, and OSSE.

scholarly journals Evaluation the Safety and Security Procedures used In X-ray Clinics in Al-Harthiya-Baghdad

2021 ◽  
Vol 2114 (1) ◽  
pp. 012009
Author(s):  
Thuraya A. Abdul Hussian ◽  
Anwar kh. Farman
Keyword(s):  
Ionizing Radiation ◽  
X Rays ◽  
X Ray ◽  
Beta Particles ◽  
Medical Clinics ◽  
Γ Rays ◽  
Health Laws ◽  
Different Sources ◽  
Α Particles ◽  
Security Procedures

Abstract Radiation is a form of energy, its emitted either in the form of particles such as α-particles and β-particles (beta particles including the electron and the positron) or waves such as sunlight, X-rays and γ-rays. Radiation found everywhere around us and it comes from many different sources naturally or man-made sources. In this study a questionnaire was distributed to people working in the field of X-rays that used for a medical imaging (X-ray and CT-scan) to evaluate the extent of awareness and knowledge in estimate the damage of ionizing radiation as a result of wrong use. The questionnaire was distributed to medical clinics in Al-Harithiya in Baghdad, which it’s considered as one of the important areas in Iraq to attract and treat patients. It’s found that most of the commitment of radiography clinics by safety and security procedures. Most of the radiology clinics abide by most of the Iraqi Ministry of Health laws. However, some clinics did not implement some of the security and safety conditions

scholarly journals Pair Production in AGN

1989 ◽  
Vol 134 ◽  
pp. 194-196
Author(s):  
C. Done ◽  
A. C. Fabian
Keyword(s):  
Pair Production ◽  
Compton Scattering ◽  
Energy Flux ◽  
Large Fraction ◽  
Small Region ◽  
X Rays ◽  
X Ray ◽  
Electron Positron ◽  
Γ Rays ◽  
Radiant Power

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 re-radiated at lower energies. Pairs can thus effectively reprocess much of the radiant power in an AGN.

scholarly journals Thermal Radiation from a Neutron Star in SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 448-449
Author(s):  
Ken’ichi Nomoto ◽  
Sachiko Tsuruta
Keyword(s):  
Neutron Star ◽  
Surface Temperature ◽  
Large Magellanic Cloud ◽  
Initial Surface ◽  
X Rays ◽  
Surface Layers ◽  
Sn 1987A ◽  
Supernova 1987A ◽  
Hot Surface ◽  
Proto Neutron Star

The supernova 1987A in the Large Magellanic Cloud has provided a new opportunity to study the evolution of a young neutron star right after its birth. A proto-neutron star first cools down by emitting neutrinos that diffuse out of the interior within a minutes. After the neutron star becomes transparent to neutrinos, the neutron star core with > 1014 g cm−3 cools predominantly by Urca neutrino emission. However, the surface layers remain hot because it takes at least 100 years before the cooling waves from the central core reach the surface layers (Nomoto and Tsuruta 1981, 1986, 1987).From the hot surface, thermal X-rays are emitted. The detection limit for X- rays from SN 1987A by the Ginga satellite is 3 ×1036 erg s−1 (Makino 1987; Tanaka 1987). If the thermal X-rays are to be observed by Ginga, the surface temperature should continue to be as high as Ts > 8 ×106 (R/10km)−1/2 K until the ejecta becomes transparent. The exact value of the initial surface temperature depends on various factors during the violent stages of explosion, cooling stages of the proto-neutron star through diffusive neutrinos, and possible re-infalling of the ejected material. Therefore, until the surface layers become thermally relaxed Ts may satisfy the above condition.

scholarly journals Experiments to test whether the secondary γ-rays are polarised

1909 ◽  
Vol 83 (559) ◽  
pp. 40-49
Keyword(s):  
Magnetic Force ◽  
Maximum Force ◽  
X Rays ◽  
X Ray ◽  
Accelerated Motion ◽  
Straight Line ◽  
Γ Rays ◽  
Considerable Body

When an electron is given an accelerated motion along a straight line, a spherical pulse of electric and magnetic force is sent out, and the maximum force lies in a plane at right angles to the direction of acceleration. The want of symmetry in the distribution of the force with respect to the direction of acceleration of the electron gave rise to the term polarisation. Barkla has shown that the primary X-rays from an X-ray tube are partially polarised, that is to say, that the maximum radiation proceeds in a plane at right angles to the direction of propagation of the cathode rays. If the secondary X-rays are produced by electrons set in motion by the primary pulses we should expect that, under certain conditions, the secondary rays would also be polarised. This has also been shown to be the case by Barkla. Since there is a considerable body of evidence to show that X-rays and γ -rays are similar in kind, it was thought by the writer that it would be of importance to make some experiments in order to discover whether secondary γ -rays are polarised.

scholarly journals Hard X-Rays and Gamma-Rays from SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 446-447 ◽  
Author(s):  
M. Itoh ◽  
S. Kumagai ◽  
T. Shigeyama ◽  
K. Nomoto ◽  
J. Nishimura
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Gamma Rays ◽  
Mass Fraction ◽  
Heavy Elements ◽  
X Rays ◽  
X Ray ◽  
Sn 1987A ◽  
Mass Fractions ◽  
Theoretical Predictions

Gamma-rays originating from radioactive decays of 56Ni and 56Co and hard X-rays due to Compton degradation of γ-rays have been predicted to emerge when the supernova becomes sufficiently thin. The X-ray detections by Ginga (Dotani et al. 1988) and Kvant (Sunyaev et al. 1988) and more recent report of γ-ray detections by SMM (Matz et al. 1988) were much earlier than the theoretical predictions. (See Itoh et al. 1987 and references therein.)These observations would give important constraints on the distribution of the heavy elements and 56Co in the ejecta. We adopted the hydrodynamical model 11E1Y6 (Nomoto et al. 1988) and carried out Monte Carlo simulation for photon transfer. A step-like distribution of 56Co was assumed where the mass fraction of 56Co in the layers at Mr ≤ 4.6 M⊙, 4.6 − 6 M⊙, 6 − 8 M⊙, and 8 − 10 M⊙ are XCo = 0.0128, 0.0035, 0.0021, and 0.0011, respectively. Other heavy elements were distributed with mass fractions in proportion to 56Co.

Experimental determination of the total enhancement factor in x-ray microanalysis of thin overlayers

1990 ◽  
Vol 48 (2) ◽  
pp. 218-219
Author(s):  
A. G. Nassiopoulos ◽  
E. Valamontes ◽  
T. Travlos ◽  
C. Tsamis
Keyword(s):  
Enhancement Factor ◽  
Bulk Material ◽  
Primary Beam ◽  
X Rays ◽  
Correction Factors ◽  
X Ray ◽  
Backscattered Electrons ◽  
Monte Carlo Calculations ◽  
Cu Film

The total enhancement factor in X-ray Microanalysis of thin overlayers has been measured at different primary beam energies by comparing the signal from a thin film deposited on a bulk material to that from a thin unsupported film of the same composition. This enhancement factor contains the contribution of both backscattered electrons and characteristic and bremsstrahlung X-rays created in the bulk by the primary beam , which ionize the film in their way out of the sample.The experimental results from a Cu film on different substrates ( Si, Ni and Au ) are compared to Monte-Carlo calculations, performed by the authors. In these calculations [1,2] all three correction factors cited above (backscattering, characteristic and continuous X-rays from the bulk) are taken into account. It is thus demonstated that the contribution of continuous X-rays from the bulk take important values (as high as 12-14%) in cases where the substrate is of a high Z material at high primary beam energies (40 keV).

In Vivo X-Ray Fluorescence of Lead and Other Toxic Trace Elements

1994 ◽  
Vol 38 ◽  
pp. 563-572 ◽  
Author(s):  
David R. Chettle
Keyword(s):  
Blood Lead ◽  
Data Sets ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Fluorescence Measurements ◽  
Bone Lead ◽  
Γ Rays ◽  
Source Excitation

Abstract The first in vivo x-ray fluorescence measurements of lead in bone used y-rays from a 57Co source to excite Pb K x-rays. Later systems used γ-rays from 109Cd to excite Pb K x-rays or polarized x-rays to excite Pb L x-rays. All three approaches involve an extremely low effective dose to the subject. Of the two K x-ray techniques, 109Cd is more precise and more flexible in choice of measurement site. Pb L x-ray fluorescence (L-XRF) effectively samples lead at bone surfaces, whereas Pb K x-ray fluorescence (K-XRF) samples through the bulk of a bone. Both the polarized L-XRF and 109Cd K-XRF achieve similar precision. Renal mercury has recently been determined using a polarized x-ray source. Both renal and hepatic cadmium can be measured using polarized x-rays in conjunction with a Si(Li) detector. Platinum and gold have been measured both by radioisotopic source excitation and by using polarized x-rays, but the latter is to be preferred. Applications of Pb K-XRF have shown that measured bone lead relates strongly to cumulative lead exposure. Secondly, biological half lives of lead in different bone types have been estimated from limited longitudinal data sets and from some cross sectional surveys. Thirdly, the effect of hone lead as an endogenous source of lead has been demonstrated and it has been shown that a majority of circulating blood lead can be mobilized from bone, rather than deriving from new exposure, in some retired lead workers.

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