51 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "X-Ray Sources"  
Results: 1 - 24 next
open access

Neutron star formation in theoretical supernovae. Low mass stars and white dwarfs

Description: The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced coll… more
Date: January 1, 1986
Creator: Nomoto, K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Review of the ultraviolet studies of galactic novae

Description: The ultraviolet studies of galactic novae both in outburst and also in quiescence have provided new and fundamental data on these exploding stars. As a direct result of the IUE spectral studies, we have identified a new class of novae in which the outburst occurs on an ONeMg white dwarf. We have also been able to determine ejected masses, elemental abundances, and ultraviolet light curves for a wide variety of nova outbursts. 70 refs.
Date: January 1, 1986
Creator: Starrfield, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Fate of accreting white dwarfs: Type I supernovae vs collapse

Description: The final fate of accreting C + O white dwarfs is either thermonuclear explosion or collapse, if the white dwarf mass grows to the Chandrasekhar mass. We discuss how the fate depends on the initial mass, age, composition of the white dwarf and the mass accretion rate. Relatively fast accretion leads to a carbon deflagration at low central density that gives rise to a Type Ia supernova. Slower accretion induces a helium detonation that could be observed as a Type Ib supernova. If the initial mas… more
Date: January 1, 1986
Creator: Nomoto, Ken'ichi
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Review of the classical nova outburst

Description: Observational studies have not only identified a new class of novae but theoretical simulations of this class have been found to be in excellent agreement with the observations. This new class consists of outbursts occurring on ONeMg white dwarfs in close binar systems in contrast to the other outbursts which are occurring on CO white dwarfs. We also review the effects of the ..beta../sup +/-unstable nuclei and show how their presence has a major effect on the evolution. 77 refs.
Date: June 1, 1986
Creator: Starrfield, S. & Sparks, W. M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Critical study of type II supernovae: equations of state and general relativity

Description: The relevance of relativistic gravitation and of the properties of nuclear matter at high density to supernova explosions is examined in detail. The existing empirical knowledge on the nuclear equation of state at densities greater than saturation, extracted from analysis of heavy ion collisions and from the breathing mode in heavy nuclei, is also considered. Particulars of the prompt explosions recently obtained theoretically by Baron, Cooperstein, and Kahana are presented. 40 refs., 9 figs., … more
Date: January 1, 1986
Creator: Kahana, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Supernovae and high density nuclear matter

Description: The role of the nuclear equation of state (EOS) in producing prompt supernova explosions is examined. Results of calculations of Baron, Cooperstein, and Kahana incorporating general relativity and a new high density EOS are presented, and the relevance of these calculations to laboratory experiments with heavy ions considered. 31 refs., 6 figs., 2 tabs.
Date: January 1, 1986
Creator: Kahana, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Hyperons in neutron stars

Description: Generalized beta equilibrium involving nucleons, hyperons, and isobars is examined for neutron star matter. The hyperons produce a considerable softening of the equation of state. It is shown that the observed masses of neutron stars can be used to settle a recent controversy concerning the nuclear compressibility. Compressibilities less than 200 MeV are incompatible with observed masses. 7 refs., 9 figs.
Date: April 1, 1986
Creator: Glendenning, N.K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Collapse of accreting carbon-oxygen white dwarfs induced by carbon deflagration at high density

Description: A critical condition is obtained for which carbon deflagration induces collapse of an accreting C + O white dwarf, not explosion. If the carbon deflagration is initiated at central density as high as 10/sup 10/ g cm/sup -3/ and if the propagation of the deflagration wave is slower than approx. 0.15 upsilon/sub s/ (upsilon/sub s/ is the sound speed), electron capture behind the burning front induces collapse to form a neutron star. This is the case for both conductive and convective deflagration… more
Date: January 1, 1986
Creator: Nomoto, K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Neutrino emission by the pair, plasma, and photo processes in the Weinberg-Salam model

Description: The results of numerical integrations of the rates and emissivities of the photo, pair, and plasma neutrino emission mechanisms in the Weinberg-Salam theory of the weak interaction are presented. The range of densities 10 gm cm/sup -3/ less than or equal to rho < 10/sup 14/ gm cm/sup -3/ and the temperature range 10/sup 8/K less than or equal to T less than or equal to 10/sup 11/K are considered. Fitting formulae, similar to those provided by Beaudet, Petrosian, and Salpeter, which reproduce th… more
Date: June 1, 1986
Creator: Schinder, P. J.; Schramm, D. N.; Witta, P. J.; Margolis, S. H. & Tubbs, D. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Techniques of absolute low energy x-ray calibration

Description: Recent advances in pulsed plasma research, materials science, and astrophysics have required many new diagnostic instruments for use in the low energy x-ray regime. The characterization of these instruments has provided a challenge to instrument designers and provided the momentum to improve x-ray sources and dosimetry techniques. In this paper, the present state-of-the-art in low energy x-ray characterization techniques is reviewed. A summary is given of low energy x-ray generator technology a… more
Date: January 1, 1986
Creator: Day, R.H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Facilities and techniques for x-ray diagnostic calibration in the 100-eV to 100-keV energy range

Description: The Lawrence Livermore National Laboratory (LLNL) has been a pioneer in the field of x-ray diagnostic calibration for more than 20 years. We have built steady state x-ray sources capable of supplying fluorescent lines of high spectral purity in the 100-eV to 100-keV energy range, and these sources have been used in the calibration of x-ray detectors, mirrors, crystals, filters, and film. This paper discusses our calibration philosophy and techniques, and describes some of our x-ray sources. Exa… more
Date: June 1, 1986
Creator: Gaines, J. L. & Wittmayer, F. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Thermodynamics of higher dimensional black holes

Description: We discuss the thermodynamics of higher dimensional black holes with particular emphasis on a new class of spinning black holes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional bl… more
Date: May 1, 1986
Creator: Accetta, F.S. & Gleiser, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Shock waves in luminous early-type stars

Description: Shock waves that occur in stellar atmospheres have their origin in some hydrodynamic instability of the atmosphere itself or of the stellar interior. In luminous early-type stars these two possibilities are represented by shocks due to an unstable radiatively-accelerated wind, and to shocks generated by the non-radial pulsations known to be present in many or most OB stars. This review is concerned with the structure and development of the shocks in these two cases, and especially with the mass… more
Date: July 1, 1986
Creator: Castor, John I.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

New Evidence From Soudan 1 for Underground Muons Associated With Cygnus X-3

Description: The Soudan 1 experiment has obtained additional evidence for underground muons associated with the x-ray pulsar Cygnus X-3. We report the preliminary analysis of data recorded during the October 1985 radio outburst of Cygnus X-3, which show a significant excess of muons for a narrow range of Cygnus X-3 phases.
Date: June 5, 1986
Creator: Ayres, D. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High spatial resolution in x-ray fluorescence

Description: The design of diffracting crystals for use in x-ray fluorescence spectrometers is discussed. Characteristics of the Johan and Johansson geometries are discussed and intensity profiles are developed. If the diffraction line has a finite width, concentration gradients will not be faithfully reproduced by gradients in the signal as the sample is scanned. Boundary effects for four types of concentration gradient are presented; as step function, linear gradients, exponential gradient, and Gaussian g… more
Date: January 1, 1986
Creator: Zahrt, J. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

X-ray data booklet. Revision

Description: A compilation of data is presented. Included are properties of the elements, electron binding energies, characteristic x-ray energies, fluorescence yields for K and L shells, Auger energies, energy levels for hydrogen-, helium-, and neonlike ions, scattering factors and mass absorption coefficients, and transmission bands of selected filters. Also included are selected reprints on scattering processes, x-ray sources, optics, x-ray detectors, and synchrotron radiation facilities. (WRF)
Date: April 1, 1986
Creator: Vaughan, D. (ed.)
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Wolter x-ray microscope calibration

Description: A 22 x Wolter microscope was calibrated after several months of operation in the Lawrence Livermore National laboratory (LLNL) Inertial Confinement Fusion program. Placing a point x-ray source at the microscope focus, I recorded the image plane spectrum, as well as the direct spectrum, and from the ratio of these two spectra derived an accurate estimate of the microscope solid angle in the 1 to 4 keV range. The solid angle was also calculated using the microscope geometry and composition. Compa… more
Date: June 1, 1986
Creator: Gerassimenko, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

High intensity line source for x-ray spectrometer calibration

Description: A high intensity electron-impact x-ray source using a one-dimensional Pierce lens has been built for the purpose of calibrating a bent crystal x-ray spectrometer. This source focuses up to 100 mA of 20-keV electrons to a line on a liquid-cooled anode. The line (which can serve as a virtual slit for the spectrometer) measures approximately 800 ..mu.. x 2 cm. The source is portable and therefore adaptable to numerous types of spectrometer applications. One particular application, the calibration … more
Date: June 1, 1986
Creator: Thoe, R.S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Non-thermal AGN models

Description: The infrared, optical and x-ray continua from radio quiet active galactic nuclei (AGN) are explained by a compact non-thermal source surrounding a thermal ultraviolet emitter, presumably the accretion disk around a supermassive black hole. The ultraviolet source is observed as the ''big blue bump.'' The flat (..cap alpha.. approx. = .7) hard x-ray spectrum results from the scattering of thermal ultraviolet photons by the flat, low energy end of an electron distribution ''broken'' by Compton los… more
Date: December 1, 1986
Creator: Band, D.L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Measurements of sin/sup 2/ theta/sub w/ from studies of the elastic scattering of neutrinos by protons and electrons

Description: This talk is intended as a brief report on studies of the elastic scattering of neutrinos by protons and electrons. Measurements of the ratios of muon antineutrino and muon neutrino elastic scattering on protons, and the corresponding ratio for elastic scattering on electrons minimize systematic experimental errors, and lead directly to values of the fundamental parameter of the electroweak interaction, the Weinberg Angle, with minimal ambiguity. Accordingly, the principal motivation in carryin… more
Date: January 1, 1986
Creator: Mann, A.K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Simple, compact, high brightness source for x-ray lithography and x-ray radiography

Description: A simple, compact, high brightness x-ray source has recently been built. This source utilizes a commercially available, cylindrical geometry electron beam evaporator, which has been modified to enhance the thermal cooling to the anode. Cooling is accomplished by using standard, low-conductivity laboratory water, with an inlet pressure of less than 50 psi, and a flow rate of approx.0.3 gal/min. The anode is an inverted cone geometry for efficient cooling. The x-ray source has a measured sub-mill… more
Date: February 19, 1986
Creator: Hawryluk, A.M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Review of spent-fuel photon and neutron source spectra

Description: The calculations of spent-fuel photon and neutron spectra have been significantly improved over the past several years. Methods for performing these computations at ORNL have been implemented in the ORIGEN2 and ORIGEN-S codes and the SAS2 control module of the SCALE system. The codes use photon data for delayed gamma rays, x-rays, spontaneous fission gamma rays, (..cap alpha..,n) reaction gamma rays, bremsstrahlung and decay constants, taken mainly from the Evaluated Nuclear Data Structure File… more
Date: January 1, 1986
Creator: Hermann, O.W. & Alexander, C.W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Relativistic field theory of neutron stars and their hyperon populations

Description: The nuclear many-body problem is examined by means of the formulation of an effective relativistic field theory of interacting hadrons. A relativistic field theory of hadronic matter is especially appropriate for the description of hot or dense matter, because of the appearance of antiparticles and higher baryon resonances and because it automatically respects causality. 8 refs., 7 figs., 1 tab. (WRF)
Date: January 1, 1986
Creator: Glendenning, N.K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen