| Effects of Model Chemistry and Data Biases on Stratospheric Ozone Assimilation |
22 JAN 2007 |
27 pages |
| Authors:
L. Coy; D. R. Allen; S. D. Eckermann; J. P. McCormack; I. Stajner; T. F. Hogan; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
 | The innovations or observation minus forecast (O-F) residuals produced by a data assimilation system provide a convenient metric of evaluating global analyses. In this study, O-F statistics from the Global Ozone Assimilation Testing System (GOATS) are used to examine how ozone assimilation products and their associated O-F statistics depend on input data biases and ozone photochemistry parameterizations (OPP). All the GOATS results shown are based on a 6-h forecast and ... |
|
| The NRL Mountain Wave Forecast Model (MWFM) [Preprint] |
17 JUN 2004 |
21 pages |
| Authors:
Stephen D. Eckermann; Jun Ma; Dave Broutman; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Department of Defense has a large and increasing investment in high-altitude long-endurance (HALE) reconnaissance aircraft. HALE aircraft have lightweight broad-winged designs, enabling them to reach stratospheric altitudes. These properties make them both aerodynamically and structurally vulnerable to any severe turbulence they intercept at altitude. Since the stratosphere is very dry and thus has no in situ cloud-related sources of turbulence from severe weather, only clear-air turbulence (CAT) can occur. ... |
|
| Timing Studies of X-Ray Binary Orbits |
2003 |
11 pages |
| Authors:
P. S. Ray; M. T. Wolff; K. S. Wood; P. Hertz; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| X-ray astronomy, by necessity, involves the study of highly variable stars, nearly all of them in binary systems where one member is a compact object such as a neutron star or black hole. These systems allow us to probe physical effects in regions of extreme gravity, high temperatures, and intense magnetic fields that are characteristic of compact objects and are unattainable in laboratory experiments. By studying the brightness variations and ... |
|
| X-ray Bursts in Neutron Star and Black Hole Binaries from USA and RXTE Data: Detections and Upper Limits |
2003 |
25 pages |
| Authors:
D. Tournear; E. Raffauf; E. D. Bloom; W. Focke; B. Giebels; G. Godfrey; P. M. Saz Parkinson; K. T. Reilly; K. S. Wood; P. S. Ray; M. T. Wolff; R. M. Bandyopadhyay; M. N. Lovellette; Jeffrey D> Scargle; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| Narayan and Heyl (2002) have developed a theoretical framework to convert suitable upper limits on type I X-ray bursts from accreting black hole candidates (BHCs) into evidence for an event horizon. However, no appropriate observational limit exists in the literature. In this paper we survey 2101.2 ks of data from the Unconventional Stellar Aspect (USA) X-ray timing experiment and 5142 ks of data from the Rossi X-ray Timing Explorer (RXTE) ... |
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| Climatology of Mountain Wave-Induced Turbulence in the Stratosphere over Central Asia: October-December 1994-2001 |
24 MAY 2002 |
52 pages |
| Authors:
Stephen D. Eckermann; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| This report summarizes experiments using the Naval Research Laboratory Mountain Wave Forecast Model to construct climatologies of stratospheric turbulence due to mountain wave breaking over central Asia during the months of Oct-Dec. Results are presented as standard monthly turbulence maps at three pressure (altitude)intervals in the 30-100 hPa range (heights 16-24 km) for the years 1994-2001. Both average and maximum turbulence levels are provided. Major findings are as follows (1) ... |
|
| X-ray Observations of Mkn 421 with USA |
2000 |
5 pages |
| Authors:
B. Giebels; K. S. Wood; R. M. Bandyopadhyay; E. Bloom; W. Focke; G. Fritz; G. Godfrey; P. Hertz; M. P. Kowalski; M. N. Lovellette; P. S. Ray; K. Reilly; P. Saz Parkinson; J. Scargle; G. Shabad; M. T. Wolff; D. Yentis; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| This paper presents the first AGN detections with the USA X-ray detector on board of ARGOS. We started observing the BL Lac object Mkn421 at the end of January 2000, when it was also observed by the CAT Cerenkov telescope (see Pierre Espigat, these proceedings), and optical telescopes (but the latter are not presented here). Mkn421 was at the beginning of a long period of high activity that lasted for ... |
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| A Model for Solar Coronal Mass Ejections |
01-Jan-1999 |
|
| Authors:
C R DeVore; S K Antiochos; J A Klimchuk; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
 | We propose a new model for the initiation of a solar coronal mass ejection (CME). The model agrees with two properties of CMEs and eruptive flares that have proved to be very difficult to explain with previous models: (a) Very low-lying magnetic field lines, down to the photospheric neutral line, can open toward infinity during an eruption. (b) The eruption is driven solely by magnetic free energy stored in a ... |
|
| RXTE Observations of BL Hyi and V2301 Oph |
1999 |
14 pages |
| Authors:
Michael T. Wolff; Kent S. Wood; James N. Imamura; Thomas Steiman-Cameron; John Middleditch; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We acquired x-ray data for the AM Herculis systems BL Hyi and V2301 Oph using the PCA detector on the Rossi X-Ray Timing Explorer during September-November 1997. We also obtained broad-band optical photometry for BL Hyi using the 1.5m telescope at the Cerro Tololo Inter-American Observatory during September 1997, that was simultaneous with one short stretch of RXTE x-ray observations. In both systems the x-ray emission is consistent with a ... |
|
| Histograms of Arecibo World Days Measurements and Linear-H Fits Between 1985 and 1995 |
30 NOV 1998 |
67 pages |
| Authors:
D. J. Melendez-Alvira; J. M. Picone; O. A. Kelley; Q. Zhou; M. P. Sulzer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| This document presents histograms of linear-H model fits to electron density profiles measured with the incoherent scatter radar of the Arecibo Observatory in Puerto Rico during the World Days between 1985 and 1995. The linear-H model is a four-parameter analytical function, which is shown to fit the measured electron density profiles with better than 10% accuracy. The histograms show the distribution of the four model parameters as well as statistical ... |
|
| Surprisingly Intense Neutron Emission from a Flare Behind the Limb of the Sun |
1998 |
21 pages |
| Authors:
R. J. Murphy; G. H. Share; K. W. DelSignore; X. -M. Hua; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment on board the Compton Gamma Ray Observatory observed a strong ux of neutrons from the behind- the-limb are that occurred on 1991 June 1. This is surprising if the neutrons were produced by thin target interactions in the Sun's corona as suggested by gamma-ray observations made by Granat/PHEBUS of this are. We compare neutron and gamma-ray observations of the June 1 are with thick target ... |
|
| Gamma-Ray Spectral States of Galactic Black Hole Candidates |
1998 |
28 pages |
| Authors:
J. E. Grove; W. N. Johnson; R. A. Kroeger; K. McNaron-Brown; J. G. Skibo; B. F. Phlips; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| OSSE has observed seven transient black hole candidates: GRO J0422+32, GX339-4, GRS 1716-249, GRS 1009-45, 4U 1543-47, GRO J1655-40, and GRS 1915+105. Two gamma-ray spectral states are evident and, based on a limited number of contemporaneous X-ray and gamma-ray observations, these states appear to be correlated with X-ray states. The former three objects show hard spectra below 100 keV (photon number indices, |
|
| Galactic Black Hole Binaries: High-Energy Radiation |
1997 |
20 pages |
| Authors:
J. E. Grove; J. E. Grindlay; B. A. Harmon; X. -M. Hua; D. Kazanas; M. McConnell; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| Observations of galactic black hole candidates made by the instruments aboard the Compton GRO in the hard X-ray and gamma-ray bands have significantly enhanced our knowledge of the emission properties of these objects. Understanding these observations presents a formidable challenge to theoretical models of the accretion flow onto the compact object and of the physical mechanisms that generate high-energy radiation. Here we summarize the current state of observations and theoretical ... |
|
| Gamma-Ray Emission from the Inner Galactic Ridge |
1997 |
30 pages |
| Authors:
R. L. Kinzer; W. R. Purcell; J. D. Kurfess; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| An improved measurement of the composite 0.05 to 10 MeV gamma-ray spectra as a function of longitude from the inner galactic ridge has been made using the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory. The continuum appears to be a composite of 3 independent components. A strong positron annihilation contribution is observed toward the center with an intensity which decreases rapidly with distance from the center ... |
|
| Accelerated Particle Composition and Energetics and Ambient Abundances from Gamma-Ray Spectroscopy of the 1991 June 4 Solar Flare |
1997 |
59 pages |
| Authors:
R. J. Murphy; G. H. Share; J. E. Grove; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment (OSSE) on board the COMPTON Gamma Ray Observatory observed the 1991 June 4 X12+ solar flare, one of the most intense nuclear gamma-ray line flares observed to date. Using these OSSE observations, we have derived time profiles of the various components of gamma-ray emission and obtained information about the accelerated particle spectra and composition and about the ambient plasma at the flare site. The main ... |
|
| Implications of the Diffuse Galactic Continuum |
1996 |
5 pages |
| Authors:
J. G. Skibo; R. Ramaty; W. R. Purcell; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| Observations made with Ginga, OSSE and COMPTEL provide evidence that the diffuse Galactic continuum emission extends down to -10 keV, and that the spectrum steepens below about several hundred keV. If this emission is electron bremsstrahlung, then a very large power (- 10(exp 43) erg s(exp -1) is required to maintain the electrons against energy losses to the interstellar medium. This exceeds by an order of magnitude the total power ... |
|
| Limits on Nuclear Gamma-Ray Emission from Orion |
1996 |
15 pages |
| Authors:
Ronald J. Murphy; Gerald H. Share; J. E. Grove; W. N. Johnson; James D. Kurfess; William R. Purcell; K. McNaron-Brown; Reuven Ramaty; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The discovery of gamma-ray line emission in the 3-7 MeV range from the Orion complex was recently reported (Bloemen et al. 1994). The observed Compton Telescope (COMPTEL) spectrum suggested that the emission results from the de-excitation of excited states of 12C and 16O. We report on a search for these lines using the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (CGRO) during a 5-week observation from ... |
|
| A Search for Fast Gamma Ray Pulsars with OSSE |
1995 |
28 pages |
| Authors:
P. Hertz; J. E. Grove; D. A. Grabelsky; S. M. Matz; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| Pulsar mode data from the Oriented Scintillation Spectrometer Experiment (OSSE) onboard the Compton Gamma Ray Observatory, with time resolution between 125 microsecond and 8 ms, have been analyzed for the presence of short period gamma-ray pulsations. Observations of known point sources (including SN 1987A, SN 1993J, GRO J0422+32, and several pulsars) and of regions where high densities of pulsars are expected (including the Galactic Center, the Galactic plane and arms, ... |
|
| OSSE Observations of Blazars |
1995 |
25 pages |
| Authors:
K. McNaron-Brown; W. N. Johnson; G. V. Jung; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; C. D. Dermer; D. A. Grabelsky; W. R. Pucell; M. P. Ulmer; M. Kafatos; P. A. Becker; R. Staubert; M. Maisack; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| Results are reported on observations obtained with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory (CGRO) of 17 active galactic nuclei known to exhibit blazar properties at other wavelengths. These observations span the period from 1991 June through 1994 May. Of the 33 high-confidence EGRET detections of blazars during CGRO observing phases 1 and 2 (1991 May 16 - 1993 Sept. 7), OSSE has observed ... |
|
| Observations of Discrete Galactic Sources with OSSE |
1995 |
10 pages |
| Authors:
J. D. Kurfess; M. S. Strickman; J. E. Grove; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment (OSSE) on the COMPTON Gamma Ray Observatory has undertaken comprehensive observations of many galactic sources since launch in April 1991. These include investigations of binary X-ray sources, pulsars, several transient X-ray sources observed as Targets-of- Opportunity, and Nova Cygni 1992. Multiple observations of the galactic center region were undertaken to map the diffuse galactic emission and study the several discrete sources in that region. An ... |
|
| The Soft Gamma-Ray Spectrum of A0535+26: Detection of an Absorption Feature at 110 keV by OSSE |
1995 |
16 pages |
| Authors:
J. E. Grove; M. S. Strickman; W. N. Johnson; J. D. Kurfess; R. L. Kinzer; C. H. Starr; G. V. Jung; E. Kendziorra; P. Kretschmar; M. Maisack; R. Staubert; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We present soft gamma-ray observations by the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (GRO) of the transient X-ray binary pulsar A0535+26. The observations were made 1994 February 8{17, immediately prior to the peak of a giant outburst. The phase- averaged spectrum is complex and cannot be described by a single-component model. We find that structure in the spectrum above 100 keV can best be modeled ... |
|
| Recent Results from OSSE on the Compton Observatory |
1995 |
14 pages |
| Authors:
J. D. Kurfess; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment on the COMPTON Observatory was designed to undertake a broad range of high energy astronomical observations. Many of these have been realized during the first three years of the mission. In this paper we present several of the recent results from OSSE. We highlight recent OSSE results on the galactic center region and on transient galactic X-ray sources. In addition, we present OSSE results on ... |
|
| OSSE Observations of 3C 273 |
1995 |
19 pages |
| Authors:
W. N. Johnson; C. D. Dermer; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; K. McNaron-Brown; E. Jourdain; G. V. Jung; D. A. Grabelsky; W. R. Purcell; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We report results of multiple observations of the quasar 3C 273 with the Oriented Scintillation Spectrometer Experiment (OSSE) instrument on the Compton Gamma Ray Observatory. These observations span the period from 1991 June through 1993 January and represent the most sensitive observations to date in low-energy gamma rays. The source was detected at historically weak 100 keV fluxes compared with previous measurements. Variability by factors of ~ 3 on time ... |
|
| The Average X-Ray/Gamma-Ray Spectra of Seyfert Galaxies From Ginga and OSSE and the Origin of the Cosmic X-Ray Background |
1995 |
12 pages |
| Authors:
Andrzej A. Zdziarski; W. N. Johnson; Chris Done; David Smith; Kellie McNaron-Brown; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We have obtained the first average 2-500 keV spectra of Seyfert galaxies, using the data from Ginga and GRO OSSE. Our sample contains 3 classes of objects with markedly different spectra: radio-quiet Seyfert 1s and 2s, and radio-loud Seyfert 1s. The average radio-quiet Seyfert 1 spectrum is well- fitted by a power law continuum with the energy spectral index approximately equal 0.9, a Compton reflection component corresponding to a ~ ... |
|
| Compton Observatory OSSE Observations of Supernova 1991T |
1995 |
13 pages |
| Authors:
M. D. Leising; W. N. Johnson; J. D. Kurfess; D. D. Clayton; D. A. Grabelsky; G. V. Jung; R. L. Kinzer; W. R. Purcell; M. S. Strickman; L. S. The; M. P. Ulmer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment on the Compton Observatory observed SN 1991T on three occasions in 1991. We find no evidence for 56Co gamma-ray line emission from SN 1991T in any of the three observations. Combining these measurements yields a 99% confidence upper limit of 4.1-6.6 x 10(exp -5) photons cu cm s(exp -1), depending on how the multiple observations are combined, for the 847 keV line flux in the ... |
|
| OSSE Observations of Centaurus A Over 18 Months |
1994 |
6 pages |
| Authors:
R. L. Kinzer; W. N. Johnson; J. D. Kurfess; M. S. Strickman; J. E. Grove; R. A. Kroeger; D. A. Grabelsky; W. R. Purcell; M. P. Ulmer; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| OSSE observed Centaurus A at energies between 0.05 and 10 MeV in 1991, 1992, and in 1993. During each observation, this AGN was found to be at relatively low intensities compared to previous observations. It exhibited roughly constant average intensity intervals of a few (5 to 8) days with abrupt (12 to 24-hour) intensity changes about the mean of as much as 60%. The spectral shape at low intensities can ... |
|
| Is the High-Energy Emission from Centaurus A Compton-Scattered Jet Radiation? |
1994 |
14 pages |
| Authors:
J. G. Skibo; C. D. Dermer; R. L. Kinzer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We consider whether the hard X-ray and soft gamma-ray emission from Centaurus A is beamed radiation from the active nucleus which is Compton-scattered into our line-of-sight. We derive the spectrum and degree of polarization of scattered radiation when incident beamed radiation is scattered from a cold (kappa Tau |
|
| Timing Noise Properties of GRO J0422+32 |
1994 |
15 pages |
| Authors:
J. E. Grove; M. S. Strickman; S. M. Matz; X.-M. Hua; D. Kazanas; L. Titarchuk; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| OSSE observed the transient black hole candidate GRO J0422+32 (XN Per 92) between 1992 August 11 and 1992 September 17. High time resolution data were obtained in several energy bands over the ~or- 35-600 keV range with a timing resolution of 8 ms. Power spectra at energies below 175 keV show substantial low-frequency red noise with a shoulder at a few -100 Hz, peaked noise with characteristic frequency near 0.2 ... |
|
| OSSE Observations of the Crab Pulsar |
1994 |
47 pages |
| Authors:
M. P. Ulmer; S. Lomatch; S. M. Matz; D. A. Grabelsky; W. R. Purcell; J. E. Grove; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; R. A. Cameron; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We present results of the Compton Gamma Ray Observatory OSSE observations of the Crab pulsar, made during MJD 48373-48406 (27 April 1991-30 May 1991) and MJD 48798-48804 (25 June 1992-1 July 1992). Pulsar light curves and spectra over the ~0.05 to 10 MeV range are presented. The arrival time of the gamma-ray peak and the radio peak agree to within 30 microsecs, which is better than the ~300 microsecs accuracy ... |
|
| Hard X Rays from Supernova 1993J |
1994 |
12 pages |
| Authors:
M. D. Leising; J. D. Kurfess; D. D. Clayton; D. A. Grabelsky; J. E. Grove; W. N. Johnson; G. V. Jung; R. L. Kinzer; R. A. Kroeger; W. R. Purcell; M. S. Strickman; L.-S The; M. P. Ulmer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Observatory observed SN 1993J during three intervals centered approximately 12, 30, and 108 days after its outburst. Hard X-ray emission was detected in the first two of these intervals. No emission was seen in the third observation or in two earlier observations in 1991 and 1992. The coincidence of the observed excess with the outburst of SN 1993J and the consistency ... |
|
| The Canonical Seyfert Spectrum: The Implications of OSSE Observations |
1994 |
11 pages |
| Authors:
W. N. Johnson; J. E. Grove; R. L. Kinzer; R. A. Kroeger; J. D. Kurfess; M. S. Strickman; K. McNaron-Brown; D. A. Grabelsky; W. R. Purcell; M. P. Ulmer; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| In its first two years of operation, the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (CGRO) observed 26 active galaxies classified as Seyferts. These objects were selected for their historical X-ray characteristics as identified by HEAO-1, EXOSAT and Ginga and include three of the gamma-ray emitting AGN detected prior to the launch of CGRO. OSSE detects approximately half of these objects at a significance of 5 ... |
|
| The Pulsed Hard X-Ray Spectrum of PSR B1509-58 |
1994 |
11 pages |
| Authors:
S. M. Matz; M. P. Ulmer; D. A. Grabelsky; W. R. Purcell; J. E. Grove; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| OSSE observed the 150 ms X-ray pulsar PSR B1509-58 in the supernova remnant MSH 15-52 for four weeks in 1992. The pulsed spectrum from 50 keV to 5 MeV is well-fit by a single power law photon spectrum of the form (3.14 plus or minus 0.16) x 10(exp 6) x(E/118.5 keV)(exp-1.68 plus or minus 0.09) photons cm(exp-2) s(exp-1) keV(exp -1). this is significantly harder than the Crab pulsar spectrum in ... |
|
| OSSE Observations of Galactic 511 keV Positron Annihilation Radiation: Initial Phase 1 Results |
10 MAY 1993 |
18 pages |
| Authors:
W. R. Purcell; D. A> Grabelsky; M. P. Ulmer; W. N. Johnson; R. L. Kinzer; J. D. Kurfess; M. S. Strickman; G. V. Jung; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory (GRO) has performed numerous observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron annihilation radiation and to search for time variability of the emission; the initial 511 keV line fluxes for the observations performed during the first 18 months of the GRO mission are presented. The 511 keV line flux ... |
|
| OSSE Observations of NGC 4151 |
1993 |
6 pages |
| Authors:
Michael Maisack; W. N. Johnson; R. L. Kinzer; M. S> Strickman; J. D. Kurfess; G. V. Jung; D. A. Drabelsky; W. R. Purcell; M. P. Ulmer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We report results of a two-week observation of NGC 4151 with the OSSE instrument. The source had a very soft spectrum which falls off exponentially with an e-folding energy of 39.2 plus or minus 1:5 keV in the energy range 65-800 keV, and had an intensity at 100 keV of 2.33 plus or minus 0:05 x 10(exp -2) photons sq cm sec (exp -1) MeV(exp -1). Simple pair cascade models ... |
|
| The Oriented Scintillation Spectrometer Experiment Instrument Description |
1993 |
68 pages |
| Authors:
NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment (OSSE) on the Arthur Holly Compton Gamma Ray Observatory satellite uses four actively- shielded NaI(Tl)- CsI (Na) phoswich detectors to provide gamma-ray line and continuum detection capability in the 0.05 - 10 MeV energy range. The instrument includes secondary capabilities for gamma-ray and neutron detection between 10 and 250 MeV. The detectors have 3.8 degrees x 11.4 degrees (FWHM) fields-of-view defined by tungsten collimators. Each ... |
|
| OSSE Observations of Cosmic Gamma-Ray Bursts |
1992 |
7 pages |
| Authors:
G. H. Share; W. N. Johnson; R. L. Kinzer; R. A. Kroeger; J. D. Kurfess; R. J. Murphy; M. S. Strickman; S. M. Matz; D. A. Grabelsky; W. R. Purcell; M. P. Ulmer; R. A. Cameron; G. V. Jung; J. E. Grove; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The Oriented Scintillation Spectrometer Experiment detected over 80 cosmic gamma-ray bursts from mid-April to late November 1991. Data at 16 ms resolution were accumulated from its large-area NaI shields in response to BATSE triggers. Rates in excess of 5000 cts/16 ms were observed from the 1991 May 3 burst. Bursts on June 1 and August 7 were observed in the spectrometer's aperture. Preliminary information on both the spectrum and location ... |
|
| Low-Frequency Observations of Galactic Supernova Remnants and the Distribution of Low-Density Ionized Gas in the Interstellar Medium |
15 DEC 1989 |
11 pages |
| Authors:
Namir E. Kassim; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| New long-wavelength observations of Galactic supernova remnants (SNRs) at 30.9 and 57.5 MHz are used to derive detailed low-frequency radio spectra for 32 SNRs. Of these, approximately two-thirds show turnovers at low frequencies, implying the presence of a widespread, but inhomogeneous, ionized absorbing medium along the lines of sight. These observations are combined with other low-frequency data to derive free-free optical depths toward 47 SNRs and to constrain the physical ... |
|
| Improved Estimates of Galactic H II Region Emission Measures and Filling Factors: Low-Frequency VLA Observations Near Sharpless 53 |
01 MAR 1989 |
11 pages |
| Authors:
Namir E. Kassim; Kurt W. Weiler; William C. Erickson; T. L. Wilson; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| VLA observations at 20 and 90 cm of five distant Galactic H II regions in an area including the Sharpless S53 complex have been used to measure their effective sizes and optically thick continuum flux densities. These data have been combined with shorter wavelength, optically thin flux density measurements and electron temperature estimates to determine accurate emission measures where previous results gave only lower limits. Our analysis indicates that existing ... |
|
| Heating-Related Flows in Cool Solar Loops |
01 MAY 88 |
|
| Authors:
J. A. Klimchuk; J. T. Mariska; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| The effects of spatial and temporal variations are investigated in the heating of cool-type solar loop models. In contrast to hot loops, these cool loops have temperature gradients that are everywhere shallow and maximum temperatures that are well below 10 K. The results of our numerical simulations show that spatial asymmetries in the energy input to cool loops will produce steady state, end-to-end flows. Velocities exceeding 20 km/s are possible. ... |
|
| Molecular Hydrogen Line Emission in Seyfert Galactic Nuclei |
15 SEP 1987 |
10 pages |
| Authors:
J. Fisher; T. R. Geballe; Howard A. Smith; M. Simon; J. W. Storey; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| We report on 2 micrometers spectroscopy of three Seyfert and two star burst galactic nuclei. We have detected line emission from vibrationally excited H2 in the Seyfert galactic nuclei NGC 1275, NGC 3227, and NGC 4151. For NGC 1275 and NGC 4151, these detections are the first reported detections of molecular line emission. We have also measured the Br(gamma) line flux in NGC 4151 and obtained an upper limit on ... |
|
| Luminous Molecular Hydrogen Emission in the Galaxy System NGC 3690-IC 694 |
01 OCT 1983 |
5 pages |
| Authors:
J. Fischer; M. Simon; J. Benson; P. M. Solomon; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
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| We report the detection of fine emission of vibrationally excited H2 from the galaxy system NGC 3690-IC 694. The line emission is distributed within the system. The total observed luminosity in the H2 upsilon = 1-0 S(l) line alone is approximately 1.5 x l0(exp 7) solar luminosity. We also detected Br(gamma) line emission of the system; its observed luminosity indicates that at least 4 X 10(exp 54) ionizing photons per ... |
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| A Quantitative Study of Magnetic Flux Transport on the Sun |
15 FEB 1983 |
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| Authors:
N. R. Sheeley Jr.; J. P. Boris; T. R. Young Jr.; C. R. DeVore; K. L. Harvey; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
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| A computational model, based on diffusion, differential rotation, and meridional flow, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, as have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. This paper presents the initial results of a project to simulate the transport of solar magnetic flux using diffusion, differential rotation, and meridional ... |
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| The Solar Radiation Field at Twilight Below 100 KM: A Spherical Model |
MAY 1982 |
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| Authors:
Donald E. Anderson Jr; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
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| Time dependent calculations of minor species distributions require as input the solar radiation field as a function of altitude and solar zenith angle. An isotropic spherical model of the radiation field has been developed to determine the solar radiation field in twilight. Comparison of the spherical model with a plane parallel model of the multiple scattering of radiation at twilight shows that: (1) for solar zenith angles less than 95 ... |
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| Comparison of VLBI, TV, and Traveling Clock Techniques for Time Transfer |
Dec-1981 |
12 pages |
| Authors:
K J Johnston; J H Spencer; E B Waltman; N J Santini; W J Klepezynski; D N Matsakis; P E Angerhofer; G H Kaplan; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
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| A three part experiment was conducted to develop and compare time transfer techniques. The experiment consisted of: I. a Very Long Baseline Interferometer (VLBI) between Maryland Point Observatory at Riverside, Maryland and NRAO at Green Bank, West Virginia; II. a high precision portable clock time transfer system between the two sites coordinated by the U. S. Naval Observatory in Washington, D. C.; and III. a television time transfer between the ... |
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| Detection in the Vacuum Ultraviolet. |
JUL 1976 |
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| Authors:
w. r. hunter; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
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Reports by Corporate Author
