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Structural and Electronic Properties of Isolated Nanodiamonds: A Theoretical Perspective

Description: Nanometer sized diamond has been found in meteorites, proto-planetary nebulae and interstellar dusts, as well as in residues of detonation and in diamond films. Remarkably, the size distribution of diamond nanoparticles appears to be peaked around 2-5 nm, and to be largely independent of preparation conditions. Using ab-initio calculations, we have shown that in this size range nanodiamond has a fullerene-like surface and, unlike silicon and germanium, exhibit very weak quantum confinement effe… more
Date: September 9, 2004
Creator: Raty, J & Galli, G
Partner: UNT Libraries Government Documents Department
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Status of Identification of VHE Gamma-Ray Sources

Description: With the recent advances made by Cherenkov telescopes such as H.E.S.S. the field of very high-energy (VHE) {gamma}-ray astronomy has recently entered a new era in which for the first time populations of Galactic sources such as e.g. Pulsar wind nebulae (PWNe) or Supernova remnants (SNRs) can be studied. However, while some of the new sources can be associated by positional coincidence as well as by consistent multi-wavelength data to a known counterpart at other wavelengths, most of the sources… more
Date: September 28, 2006
Creator: Funk, Stefan
Partner: UNT Libraries Government Documents Department
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Demystifying an Unidentified EGRET Source by VHE gamma-ray Observations

Description: In a novel approach in observational high-energy gamma-ray astronomy, observations carried out by imaging atmospheric Cherenkov telescopes provide necessary templates to pinpoint the nature of intriguing, yet unidentified EGRET gamma-ray sources. Using GeV-photons detected by CGRO EGRET and taking advantage of high spatial resolution images from H.E.S.S. observations, we were able to shed new light on the EGRET observed gamma-ray emission in the Kookaburra complex, whose previous coverage in th… more
Date: April 17, 2007
Creator: Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park; Funk, Stefan & /KIPAC, Menlo Park
Partner: UNT Libraries Government Documents Department
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VHE gamma-ray Emitting Pulsar Wind Nebulae Discovered by H.E.S.S.

Description: Recent advances in very-high-energy (VHE) gamma-ray astronomy have opened a new observational window on the physics of pulsars. The high sensitivity of current imaging atmospheric Cherenkov telescopes, and in particular of the H.E.S.S. array, has already led to the discovery of about a dozen VHE-emitting pulsar wind nebulae (PWNe) and PWN candidates. These include the plerions in the composite supernova remnants MSH 15-52, G21.5-0.9, Kes 75, and Vela, two sources in the Kookaburra, and the nebu… more
Date: June 5, 2008
Creator: Gallant, Y. A.; Carrigan, S.; Djannati-Atai, A.; Funk, S.; Hinton, J. A.; Hoppe, S. et al.
Partner: UNT Libraries Government Documents Department
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An Experimental and Theoretical Study on the Ionization Energies of Polyynes (H-(C = C)n-H; n = 1 - 9)

Description: We present a combined experimental and theoretical work on the ionization energies of polyacetylene -- organic molecules considered as important building blocks to form polycyclic aromatic hydrocarbons (PAHs) in the proto planetary nebulae such as of CRL 618. This set of astrophysical data can be utilized with significant confidence in future astrochemical models of photon-dominated regions and also of the proto planetary nebulae CRL 618. We recommend ionization energies of polyacetylenes from … more
Date: May 17, 2010
Creator: Kaiser, Ralf I.; Sun, Bian Jian; Lin, Hong Mao; Chang, Agnes H. H.; Mebel, Alexander M.; Kostko, Oleg et al.
Partner: UNT Libraries Government Documents Department
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Suzaku Observations of PSR B1259-63: A New Manifestation of Relativistic Pulsar Wind

Description: We observed PSR B1259-63, a young non-accreting pulsar orbiting around a Be star SS 2883, eight times with the Suzaku satellite from July to September 2007, to characterize the X-ray emission arising from the interaction between a pulsar relativistic wind and Be star outflows. The X-ray spectra showed a featureless continuum in 0.6-10 keV, modeled by a power law with a wide range of photon index 1.3-1.8. When combined with the Suzaku PIN detector which allowed spectral analysis in the hard 15-5… more
Date: April 27, 2009
Creator: Uchiyama, Yasunobu; Tanaka, Takaaki; Takahashi, Tadayuki; Mori, Koji & Nakazawa, Kazuhiro
Partner: UNT Libraries Government Documents Department
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Properties of LMC planetary nebulae and parent populations in the MACHO database

Description: The MACHO microlensing experiment's time-sampled photometry database contains blue and red lightcurves for nearly 9 million stars in the central bar region of the Large Magellanic Cloud (LMC). We have identified known LMC Planetary Nebulae (PN) in the database and find one, Jacoby 5, to be variable. We additionally present data on the ``parent populations`` of LMC PN, and discuss the star formation history of the LMC bar. 14 refs., 1 fig.
Date: October 1, 1996
Creator: Alves, D. R.; Alcock, C. & Cook, K. H.
Partner: UNT Libraries Government Documents Department
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On the origin of porphyritic chondrules

Description: A computer program for the complex equilibria in a cooling nebular gas was used to explore a possible origin of porphyritic chondrules, the major class of chondrules in chondritic meteorites. It uses a method of accurately calculating the thermodynamic properties of molten multicomponent aluminosilicates, which deduces the silicate condensates vs temperature and pressure of a nebular gas. This program is coupled with a chemical equilibrium algorithm for systems with at least 1000 chemical speci… more
Date: May 1, 1994
Creator: Blander, M.; Unger, L.; Pelton, A. & Ericksson, G.
Partner: UNT Libraries Government Documents Department
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BRIGHT Lights, BIG City: Massive Galaxies, Giant Ly-A Nebulae, and Proto-Clusters

Description: High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. They report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-{alpha} nebulae centered on the galaxies and to search for over-dense regions around them. They discuss the possible implications for our understandi… more
Date: August 1, 2002
Creator: van Breugel, W.; Reuland, M.; de Vries, W.; Stanford, A.; Dey, A.; Kurk, J. et al.
Partner: UNT Libraries Government Documents Department
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Photometry of SN 2002ic and implications for the progenitor mass-loss history

Description: We present new pre-maximum and late-time optical photometry of the Type Ia/IIn supernova 2002ic. These observations are combined with the published V-band magnitudes of Hamuy et al. (2003) and the VLT spectrophotometry of Wang et al. (2004) to construct the most extensive light curve to date of this unusual supernova. The observed flux at late time is significantly higher relative to the flux at maximum than that of any other observed Type Ia supernova and continues to fade very slowly a year a… more
Date: May 6, 2004
Creator: Wood-Vasey, W.M.; Wang, L. & Aldering, G.
Partner: UNT Libraries Government Documents Department
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Cosmic Ray e +/(e- + e+), p-bar/p Ratios Explained by an Injection Model Based on 2 Gamma-ray Observations

Description: We present a model of cosmic ray (CR) injection into the Galactic space based on recent {gamma}-ray observations of supernova remnants (SNRs) and pulsar wind nebulae (PWNe) by the Fermi Large Area Telescope (Fermi) and atmospheric Cherenkov telescopes (ACTs). Steady-state (SS) injection of nuclear particles and electrons (e{sup -}) from the Galactic ensemble of SNRs, and electrons and positrons (e{sup +}) from the Galactic ensemble of PWNe are assumed, with their spectra deduced from {gamma}-ra… more
Date: December 16, 2010
Creator: Kamae, T.; Lee, S. H.; Baldini, L.; Giordano, F.; Grondin, M.H.; Latronico, L. et al.
Partner: UNT Libraries Government Documents Department
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On the Nature of Ultraluminous X-Ray Sources, Or What a Black Hole Should Look Like

Description: We derive the luminosity-temperature relation for the accreting black holes (BHs). At the accretion rates below the critical Eddington, the BHs are described by the standard Shakura-Sunyaev model resulting in the L {infinity} T{sup 4} {infinity} M relation. At super-Eddington rates, {dot m} = {dot M}/{dot M}{sub Edd} >> 1, a strong outflow forms within the spherization radius R{sub sp} {infinity} {dot M}. If the angular momentum of the outflowing matter is conserved and typical outflow ve… more
Date: September 18, 2006
Creator: Poutanen, Juri; /Oulu U. /KIPAC, Menlo Park; Fabrika, Sergei; /Stavropol, Astrophys. Observ.; Butkevich, Alexey G.; /Oulu U. /Pulkovo Observ., St. Petersburg et al.
Partner: UNT Libraries Government Documents Department
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GLAST and Suzaku: Study on Cosmic-Ray Acceleration And Interaction in the Cosmos

Description: The Gamma-Ray Large Area Space Telescope (GLAST) is an international and multiagency mission scheduled for launch in the fall 2007. The Large Area Telescope (LAT), the primary instrument of the mission, will survey the high energy sky found to be very dynamic and surprisingly diverse by its predecessor the Energetic Gamma Ray Experiment Telescope (EGRET). GLAST-LAT will have a much improved sensitivity when compared with EGRET and extend the higher energy coverage to {approx} 300 GeV. The instr… more
Date: May 23, 2008
Creator: Kamae, T. & /KIPAC, Menlo Park /SLAC
Partner: UNT Libraries Government Documents Department
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Future GLAST Observations of Supernova Remnants And Pulsar Wind Nebulae

Description: Shell-type Supernova remnants (SNRs) have long been known to harbour a population of ultra-relativistic particles, accelerated in the Supernova shock wave by the mechanism of diffusive shock acceleration. Experimental evidence for the existence of electrons up to energies of 100 TeV was first provided by the detection of hard X-ray synchrotron emission as e.g. in the shell of the young SNR SN1006. Furthermore using theoretical arguments shell-type Supernova remnants have long been considered as… more
Date: September 26, 2007
Creator: Funk, S.
Partner: UNT Libraries Government Documents Department
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Refractory metal particles in refractory inclusions in the Allende meteorite

Description: An examination of refractory metal particles in five calcium-aluminum-rich inclusions in the Allende meteorite indicates a complex variety of compositions and large departures from equilibrium. These particles appear to have been primordial condensates which were isolated from the nebula and from each other at different times by cocondensing oxides. Selective diffusion and/or oxidation of the more oxidizable metals (Mo, W, Fe and Ni), phase segregations into different alloy phases (fcc, bcc, hc… more
Date: January 1, 1980
Creator: Fuchs, Louis H. & Blander, Milton
Partner: UNT Libraries Government Documents Department
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Relativistic shock waves and the excitation of plerions

Description: The shock termination of a relativistic magnetohydrodynamic wind from a pulsar is the most interesting and viable model for the excitation of the synchrotron sources observed in plerionic supernova remnants. We have studied the structure of relativistic magnetosonic shock waves in plasmas composed purely of electrons and positrons, as well as those whose composition includes heavy ions as a minority constituent by number. We find that relativistic shocks in symmetric pair plasmas create fully t… more
Date: January 7, 1991
Creator: Arons, J. (California Univ., Berkeley, CA (USA)); Gallant, Y.A. (California Univ., Berkeley, CA (USA). Dept. of Physics); Hoshino, Masahiro; Max, C.E. (California Univ., Livermore, CA (USA). Inst. of Geophysics and Planetary Physics) & Langdon, A.B. (Lawrence Livermore National Lab., CA (USA))
Partner: UNT Libraries Government Documents Department
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Very high energy gamma ray astrophysics

Description: The second reflector (project GRANITE) is on schedule. At present (January 1992) it and the 10 m reflector are obtaining stereoscopic views of gamma-ray air showers from the Crab Nebula which verify the expected performance of the twin reflector telescopes. With the additional improvements of the upgrade (a pending DOE proposal) the twin reflectors should reach a limiting intensity of 1% that of the Crab. The astonishing early results from the EGRET detector aboard the Compton Gamma Ray Observa… more
Date: February 1, 1992
Creator: Lamb, R.C. & Lewis, D.A.
Partner: UNT Libraries Government Documents Department
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Spectra of crab-like pulsars: A GRO perspective

Description: A single-parameter model has been constructed to calculate the continuum spectrum of energetic pulsed radiation resulted from the formation of a Crab-type charge depletion region (gap) in the outer magnetosphere of rapidly spinning pulsars (Ho 1989). We discuss the characteristics of the theoretical predictions for the Crab pulsar and the specific features expected in the energy bands of the Gamma-Ray Observatory (GRO). These features include a possible spectral dip in the 0.3 to 30 MeV range, … more
Date: January 1, 1989
Creator: Ho, Cheng
Partner: UNT Libraries Government Documents Department
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Chemical Engineering Division physical inorganic chemistry. Annual report, July 1975--June 1976

Description: The thermal conductivity of acetonitrile vapor has been measured at temperatures between 338 and 387/sup 0/K and pressures between 100 and 1050 torr. The pressure dependence of the thermal conductivities indicates the presence of dimeric vapor species with an association constant given by RT ln K/sub 2/ (atm/sup -1/) = 5002 - 21.15 T. Molecular orbital studies of hydrogen-bonded methyl alcohol vapor complexes indicate that, the cyclic tetramer is especially stable. Preliminary calculations on t… more
Date: January 1, 1976
Creator: Blander, M.; Curtiss, L. A.; Hsu, C. C.; Kucera, G. H.; Marr, J. J.; Papatheodorou, G. N. et al.
Partner: UNT Libraries Government Documents Department
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