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2000

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Articles 61 - 90 of 108

Full-Text Articles in Astrophysics and Astronomy

Electronic Structure Of Cu1-Xnixrh2s4 And Curh2se4: Band-Structure Calculations, X-Ray Photoemission, And Fluorescence Measurements, Gus L. W. Hart, W. E. Pickett, E. Z. Kurmaev, M. Neumann, D. Hartmann, A. Moewes, D. L. Ederer, R. Endoh, K. Taniguchi, S. Nagata Feb 2000

Electronic Structure Of Cu1-Xnixrh2s4 And Curh2se4: Band-Structure Calculations, X-Ray Photoemission, And Fluorescence Measurements, Gus L. W. Hart, W. E. Pickett, E. Z. Kurmaev, M. Neumann, D. Hartmann, A. Moewes, D. L. Ederer, R. Endoh, K. Taniguchi, S. Nagata

Faculty Publications

The electronic structure of spinel-type Cu1-xNixRh2S4 (x=0.0, 0.1, 0.3, 0.5, 1.0) and CuRh2Se4 compounds has been studied by means of x-ray photoelectron (SPS) and fluorescent spectroscopy. Cu L3, Ni L3, S L2,3, and Se M2,3 x-ray emission spectra (XES) were measured near thresholds at Beamline 8.0 of the Lawrence Berkeley Laboratory's Advanced Light Source. XES measurements of the constituent atoms of these compounds, reduced to the same binding energy scale, are found to be in excellent agreement with XPS valence bands. The calculated XES spectra which include dipole matrix elements show that the partial density of states reproduce experimental spectra …

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P-Selectin Or Intercellular Adhesion Molecule (Icam)-1 Deficiency Substantially Protects Against Atherosclerosis In Apolipoprotein E-Deficient Mice, Robert G. Collins, Rizwan Velji, Natalia V. Guevara, M. John Hicks, Lawrence Chan, Arthur L. Beaudet Jan 2000

P-Selectin Or Intercellular Adhesion Molecule (Icam)-1 Deficiency Substantially Protects Against Atherosclerosis In Apolipoprotein E-Deficient Mice, Robert G. Collins, Rizwan Velji, Natalia V. Guevara, M. John Hicks, Lawrence Chan, Arthur L. Beaudet

Physics & Astronomy Faculty Publications

The expression of leukocyte and endothelial cell adhesion molecules (CAMs) is essential for the emigration of leukocytes during an inflammatory response. The importance of the inflammatory response in the development of atherosclerosis is indicated by the increased expression of adhesion molecules, proinflammatory cytokines, and growth factors in lesions and lesion-prone areas and by protection in mice deficient in various aspects of the inflammatory response. We have quantitated the effect of deficiency for intercellular adhesion molecule (ICAM)-1, P-selectin, or E-selectin on atherosclerotic lesion formation at 20 wk of age in apolipoprotein (apo) E(- /-) (deficient) mice fed a normal chow diet. …

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The Optical Depth To Reionization As A Probe Of Cosmological And Astrophysical Parameters, Aparna Venkatesan Jan 2000

The Optical Depth To Reionization As A Probe Of Cosmological And Astrophysical Parameters, Aparna Venkatesan

Physics and Astronomy

Current data of high-redshift absorption-line systems imply that hydrogen reionization occurred before redshifts of about 5. Previous works on reionization by the first stars or quasars have shown that such scenarios are described by a large number of cosmological and astrophysical parameters. Here we adopt a semianalytic model of stellar reionization in order to quantify how the optical depth to reionization depends on such parameters, and combine this with constraints from the cosmic microwave background (CMB). We find this approach to be particularly useful in alleviating the well-known degeneracy in CMB parameter extraction between the optical depth to reionization and …

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The Universe On A Desktop: Observational Astronomy Simulations In The Instructional Laboratory, Laurence A. Marschall Jan 2000

The Universe On A Desktop: Observational Astronomy Simulations In The Instructional Laboratory, Laurence A. Marschall

Physics and Astronomy Faculty Publications

Though the value of hands-on learning has long been recognised by educators, it is difficult to design laboratories in astronomy classes that present realistic astrophysical techniques to undergraduate students. Unlike most other sciences, astronomy is largely observational, not experimental, and making useful observations involves expensive equipment over time scales inconvenient for pedagogy. In recent years, however, astronomy has gone almost completely digital, and the advent of large on-line databases and fast personal computers has made it possible to realistically simulate the experience of research astrophysics in the laboratory. Since 1992, Project CLEA (Contemporary Laboratory Experiences in Astronomy) has been developing …

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Reconciliation Of The Substorm Onset Determined On The Ground And At The Polar Spacecraft, P K. Toivanen, D N. Baker, W K. Peterson, H J. Singer, Niescja E. Turner, X Li, K Kauristie, M Syrjasuo, A Keiling, C A. Kletzing Jan 2000

Reconciliation Of The Substorm Onset Determined On The Ground And At The Polar Spacecraft, P K. Toivanen, D N. Baker, W K. Peterson, H J. Singer, Niescja E. Turner, X Li, K Kauristie, M Syrjasuo, A Keiling, C A. Kletzing

Physics and Astronomy Faculty Research

An isolated substorm on Oct. 17, 1997 during a close conjunction of the Polar spacecraft and the ground-based MIRACLE network is studied in detail. We identify signatures of substorm onset in the plasma sheet midway between the ionosphere and the equatorial plasma sheet, determine their timing relative to the ground signatures, and discuss their counterparts on the ground and in the equatorial plasma sheet. The substorm onset is determined as the negative bay onset at 2040:42(≠ 5 sec) UT coinciding with the onset of auroral precipitation, energization of plasma sheet electrons at Polar, and strong magnetic field variations perpendicular to …

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Entry Of Plasma Sheet Particles Into The Inner Magnetosphere Observed By Polar/Cammice, N Yu Ganushkina, T I. Pulkkinen, V A. Sergeev, M V. Kubyshkina, D N. Baker, Niescja E. Turner, M Grande, B Kellett, J F. Fennell, J L. Roeder, J A. Sauvaud, T A. Fritz Jan 2000

Entry Of Plasma Sheet Particles Into The Inner Magnetosphere Observed By Polar/Cammice, N Yu Ganushkina, T I. Pulkkinen, V A. Sergeev, M V. Kubyshkina, D N. Baker, Niescja E. Turner, M Grande, B Kellett, J F. Fennell, J L. Roeder, J A. Sauvaud, T A. Fritz

Physics and Astronomy Faculty Research

Statistical results are presented from Polar/CAMMICE measurements of events during which the plasma sheet ions have penetrated deeply into the inner magnetosphere. Owing to their characteristic structure in energy-time spectrograms, these events are called "intense nose events." Almost 400 observations of such structures were made during 1997. Intense nose events are shown to be more frequent in the dusk than in the dawn sector. They typically penetrate well inside L = 4, the deepest penetration having occurred around midnight and noon. The intense nose events are associated with magnetic (substorm) activity. However, even moderate activity (AE = 150-250 nT) resulted …

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Planetary Companions To The Metal-Rich Stars Bd -10°3166 And Hd 52265, R. Paul Butler, Steve Vogt, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Kevin Apps Jan 2000

Planetary Companions To The Metal-Rich Stars Bd -10°3166 And Hd 52265, R. Paul Butler, Steve Vogt, Geoffrey W. Marcy, Debra A. Fischer, Gregory W. Henry, Kevin Apps

Information Systems and Engineering Management Research Publications

Precise Doppler measurements from the Keck/HIRES spectrometer reveal periodic Keplerian velocity variations in the stars BD -10°3166 and HD 52265. BD -10°3166 (K0 V) has a period of 3.487 days and a semiamplitude of 61 m s-1. An orbital fit yields a companion mass M sin i = 0.48 MJUP, a semimajor axis of a = 0.046 AU, and an eccentricity of e = 0.05 (consistent with zero). HD 52265 (G0 V) has a period of 119.0 days, a semiamplitude of 45 m s-1, an eccentricity of 0.29, a semimajor axis of a = …

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Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock Jan 2000

Using Binary Star Observations To Bound The Mass Of The Graviton, Shane L. Larson, William A. Hiscock

All Physics Faculty Publications

Interacting white dwarf binary star systems, including helium cataclysmic variable (HeCV) systems, are expected to be strong sources of gravitational radiation, and should be detectable by proposed space-based laser interferometer gravitational wave observatories such as LISA. Several HeCV star systems are presently known and can be studied optically, which will allow electromagnetic and gravitational wave observations to be correlated. Comparisons of the phases of a gravitational wave signal and the orbital light curve from an interacting binary white dwarf star system can be used to bound the mass of the graviton. Observations of typical HeCV systems by LISA could potentially …

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Mev Measurements Of Γ-Ray Bursts By Cgro-Comptel: Revised Catalog, A Connors, C A. Young, K Bennett, W Collmar, W Hermsen, R M. Kippen, L Kuiper, Mark L. Mcconnell, R S. Miller, James M. Ryan, V Schonfelder, O R. Williams, C Winkler Jan 2000

Mev Measurements Of Γ-Ray Bursts By Cgro-Comptel: Revised Catalog, A Connors, C A. Young, K Bennett, W Collmar, W Hermsen, R M. Kippen, L Kuiper, Mark L. Mcconnell, R S. Miller, James M. Ryan, V Schonfelder, O R. Williams, C Winkler

Space Science Center

The imaging COMPTEL telescope has accumulated 0.1–30 MeV spectra, time-histories, and positions of more than forty γ-ray bursts within its ∼3 sr field of view in the eight years since its launch. CGRO-COMPTEL measures in both imaging “telescope” and single detector “burst spectroscopy” mode. In an ongoing collaboration with BACODINE/GCN, bursts are imaged automatically, with localizations relayed to a global network of multiwavelength observers in near real time (∼10 minutes). We have updated our burst search procedure in two ways: 1) using more sensitive search algorithms; and 2) using data from more detectors. The first are double change-point algorithms. With …

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Comptel Upper Limits For The 56co Γ-Rays From Sn1998bu, R Georgii, S Pluschke, R Diehl, W Collmar, G G. Lichti, V Schonfelder, H Bloemen, J Knodlseder, Mark L. Mcconnell, James M. Ryan, K Bennett Jan 2000

Comptel Upper Limits For The 56co Γ-Rays From Sn1998bu, R Georgii, S Pluschke, R Diehl, W Collmar, G G. Lichti, V Schonfelder, H Bloemen, J Knodlseder, Mark L. Mcconnell, James M. Ryan, K Bennett

Space Science Center

The type Ia supernova SN 1998bu in M96 was observed by COMPTEL for a total of 88 days starting 17 days after the detection of the SN. A special mode improving the low-energy sensitivity was invoked. We obtained images in the 847 keV and 1238 keV lines of 56Co using an improved point-spread function for the low-energies. We do not detect SN1998bu. Sensitive upper limits at both energies constrain the standard supernova model for this event.

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The Tigre Gamma-Ray Telescope, Terence J. O'Neill, D Battacharya, D Dixon, M Polson, R S. White, Allen Zych, James M. Ryan, Mark L. Mcconnell, John R. Macri, J Samimi, A Akyuz, W M. Mahoney, L Varnell Jan 2000

The Tigre Gamma-Ray Telescope, Terence J. O'Neill, D Battacharya, D Dixon, M Polson, R S. White, Allen Zych, James M. Ryan, Mark L. Mcconnell, John R. Macri, J Samimi, A Akyuz, W M. Mahoney, L Varnell

Space Science Center

TIGRE is an advanced telescope for gamma-ray astronomy with a few arcmin resolution. From 0.3 to 10 MeV it is a Compton telescope. Above 1 MeV, its multi-layers of double sided silicon strip detectors allow for Compton recoil electron tracking and the unique determination for incident photon direction. From 10 to 100 MeV the tracking feature is utilized for gamma-ray pair event reconstruction. Here we present TIGRE energy resolutions, background simulations and the development of the electronics readout system.

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The Comptel Instrumental-Line Background, G Weidenspointer, M Varendorff, U Oberlack, S Pluschke, D Morris, R Diehl, S C. Kappadath, Mark L. Mcconnell, James M. Ryan, V Schonfelder Jan 2000

The Comptel Instrumental-Line Background, G Weidenspointer, M Varendorff, U Oberlack, S Pluschke, D Morris, R Diehl, S C. Kappadath, Mark L. Mcconnell, James M. Ryan, V Schonfelder

Space Science Center

The instrumental-line background of the Compton telescope COMPTEL onboard the Compton Gamma-Ray Observatory is due to the activation and/or decay of a number of different isotopes. The major components of the COMPTEL instrumental-line background can be attributed to eight individual isotopes, namely 2D, 22Na, 24Na, 28Al, 40K, 52Mn, 57Ni, and 208Tl. In addition, evidence for the presence of 27Mg has been obtained in the search for gamma-ray lines from supernovae. The identification of the instrumental lines with specific isotopes is based on the line energies as well as on the variation of the activity with time, cosmic-ray intensity and deposited …

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Summary Of The First Comptel Source Catalogue, V Schonfelder, K Bennett, J J. Blom, H Bloemen, W Collmar, A Connors, R Diehl, W Hermsen, A Iyudin, R M. Kippen, J Knodlseder, L Kuiper, G G. Lichti, Mark L. Mcconnell, D Morris, R Much, U Oberlack, James M. Ryan, G Stacy, H Steinle, A W. Strong, R Suleiman, R Vandijk, M Varendorff, C Winkler, O R. Williams Jan 2000

Summary Of The First Comptel Source Catalogue, V Schonfelder, K Bennett, J J. Blom, H Bloemen, W Collmar, A Connors, R Diehl, W Hermsen, A Iyudin, R M. Kippen, J Knodlseder, L Kuiper, G G. Lichti, Mark L. Mcconnell, D Morris, R Much, U Oberlack, James M. Ryan, G Stacy, H Steinle, A W. Strong, R Suleiman, R Vandijk, M Varendorff, C Winkler, O R. Williams

Space Science Center

No abstract provided.

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Estimation Of Grb Detection By Fiberglast, Surasak Phengchamnan, K Aisaka, Muzaffer Atac, W Robert Binns, J Buckley, M L. Cherry, David B. Cline, Paul F. Dowkontt, John W. Epstein, M H. Finger, Gerald J. Fishman, T G. Guzik, P L. Hink, Martin H. Israel, S C. Kappadath, Gerald Karr, R M. Kippen, John R. Macri, Robert S. Mallozzi, Mark L. Mcconnell, Yuriy Pischalnikov, W Paciesas, Thomas A. Parnell, Geoffrey N. Pendleton, R D. Preece, Georgia A. Richardson, Keith R. Rielage, James M. Ryan, J G. Stacy, O T. Tumer, Donald B. Wallace, Robert B. Wilson Jan 2000

Estimation Of Grb Detection By Fiberglast, Surasak Phengchamnan, K Aisaka, Muzaffer Atac, W Robert Binns, J Buckley, M L. Cherry, David B. Cline, Paul F. Dowkontt, John W. Epstein, M H. Finger, Gerald J. Fishman, T G. Guzik, P L. Hink, Martin H. Israel, S C. Kappadath, Gerald Karr, R M. Kippen, John R. Macri, Robert S. Mallozzi, Mark L. Mcconnell, Yuriy Pischalnikov, W Paciesas, Thomas A. Parnell, Geoffrey N. Pendleton, R D. Preece, Georgia A. Richardson, Keith R. Rielage, James M. Ryan, J G. Stacy, O T. Tumer, Donald B. Wallace, Robert B. Wilson

Space Science Center

FiberGLAST is one of several instrument concepts being developed for possible inclusion as the primary Gamma-ray Large Area Space Telescope (GLAST) instrument. The predicted FiberGLAST effective area is more than 12,000 cm2 for energies between 30 MeV and 300 GeV, with a field of view that is essentially flat from 0°–80°. The detector will achieve a sensitivity more than 10 times that of EGRET. We present results of simulations that illustrate the sensitivity of FiberGLAST for the detection of gamma-ray bursts.

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Minute-Of-Arc Resolution Gamma Ray Imaging Experiment—Margie, S C. Kappadath, P P. Altice, M L. Cherry, T G. Guzik, J G. Stacy, John R. Macri, Mark L. Mcconnell, James M. Ryan, D L. Band, J L. Matteson, Terence J. O'Neill, Allen Zych, J Buckley, P L. Hink Jan 2000

Minute-Of-Arc Resolution Gamma Ray Imaging Experiment—Margie, S C. Kappadath, P P. Altice, M L. Cherry, T G. Guzik, J G. Stacy, John R. Macri, Mark L. Mcconnell, James M. Ryan, D L. Band, J L. Matteson, Terence J. O'Neill, Allen Zych, J Buckley, P L. Hink

Space Science Center

MARGIE (Minute-of-Arc Resolution Gamma-ray Imaging Experiment) is a large area(∼104 cm2), wide field-of-view (∼1 sr), hard X-ray/gamma-ray (∼20–600 keV) coded-mask imaging telescope capable of performing a sensitive survey of both steady and transient cosmic sources. MARGIE has been selected for a NASA mission-concept study for an Ultra Long Duration (100 day) Balloon flight. We describe our program to develop the instrument based on new detector technology of either cadmium zinc telluride (CZT) semiconductors or pixellated cesium iodide (CsI) scintillators viewed by fast-timing bi-directional charge-coupled devices (CCDs). The primary scientific objectives are to image faint Gamma-Ray Bursts (GRBs) in near-real-time at …

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Comptel Time-Averaged All-Sky Point Source Analysis, W Collmar, V Schonfelder, A W. Strong, H Bloemen, W Hermsen, Mark L. Mcconnell, James M. Ryan, K Bennett Jan 2000

Comptel Time-Averaged All-Sky Point Source Analysis, W Collmar, V Schonfelder, A W. Strong, H Bloemen, W Hermsen, Mark L. Mcconnell, James M. Ryan, K Bennett

Space Science Center

We use all COMPTEL data from the beginning of the CGRO mission (April ’91) up to the end of CGRO Cycle 6 (November ’97) to carry out all-sky point source analyses in the four standard COMPTEL energy bands for different time periods. We apply our standard maximum-likelihood method to generate all-sky significance and flux maps for point sources by subtracting off the diffuse emission components via model fitting. In addition, fluxes of known sources have been determined for individual CGRO Phases/Cycles to generate lightcurves with a time resolution of the order of one year. The goal of the analysis is …

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The Development Of A Position-Sensitive Czt Detector With Orthogonal Co-Planar Anode Strips, K Larson, L A. Hamel, V T. Jordanov, John R. Macri, Mark L. Mcconnell, James M. Ryan, O Tousignant, A Vincent Jan 2000

The Development Of A Position-Sensitive Czt Detector With Orthogonal Co-Planar Anode Strips, K Larson, L A. Hamel, V T. Jordanov, John R. Macri, Mark L. Mcconnell, James M. Ryan, O Tousignant, A Vincent

Space Science Center

We report on the simulation, construction, and performance of prototype CdZnTe imaging detectors with orthogonal coplanar anode strips. These detectors employ a novel electrode geometry with non-collecting anode strips in one dimension and collecting anode pixels, interconnected in rows, in the orthogonal direction. These detectors retain the spectroscopic and detection efficiency advantages of single carrier (electron) sensing devices as well as the principal advantage of conventional strip detectors with orthogonal anode and cathode strips, i.e. an N×N array of imaging pixels are with only 2N electronic channels. Charge signals induced on the various electrodes of a prototype detector with 8×8 …

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Energetic Proton Spectra In The 11 June 1991 Solar Flare, C A. Young, M B. Arndt, A Connors, Mark L. Mcconnell, G Rank, James M. Ryan, R Suleiman, V Schonfelder Jan 2000

Energetic Proton Spectra In The 11 June 1991 Solar Flare, C A. Young, M B. Arndt, A Connors, Mark L. Mcconnell, G Rank, James M. Ryan, R Suleiman, V Schonfelder

Space Science Center

We have studied a subset of the 11 June 1991 solar flare γ-ray data that we believe arise from soft proton or ion spectra. Using data from the COMPTEL instrument on the Compton Observatory we discuss the gamma-ray intensities at 2.223 MeV, 4–7 MeV, and 8–30 MeV in terms of the parent proton spectrum responsible for the emission.

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Gamma Ray Measurements Of The 1991 November 15 Solar Flare, M B. Arndt, K Bennett, A Connors, Mark L. Mcconnell, G Rank, James M. Ryan, V Schonfelder, R Suleiman, C A. Young Jan 2000

Gamma Ray Measurements Of The 1991 November 15 Solar Flare, M B. Arndt, K Bennett, A Connors, Mark L. Mcconnell, G Rank, James M. Ryan, V Schonfelder, R Suleiman, C A. Young

Space Science Center

The 1991 November 15 X1.5 flare was a well observed solar event. Comprehensive data from ground-based observatories and spacecraft provide the basis for a contextual interpretation of gamma-ray spectra from the Compton Gamma Ray Observatory (CGRO). In particular, spectral, spatial, and temporal data at several energies are necessary to understand the particle dynamics and the acceleration mechanism(s) within this flare. X-ray images, radio, Ca XIX data and magnetograms provide morphological information on the acceleration region [4,5], while gamma-ray spectral data provide information on the parent ion spectrum. Furthermore, time profiles in hard X-rays and gamma-rays provide valuable information on temporal …

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First Results Of A Study Of Tev Emission From Grbs In Milagrito, J E. Mcenery, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh Jan 2000

First Results Of A Study Of Tev Emission From Grbs In Milagrito, J E. Mcenery, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh

Space Science Center

Milagrito, a detector sensitive to γ-rays at TeV energies, monitored the northern sky during the period February 1997 through May 1998. With a large field of view and high duty cycle, this instrument was used to perform a search for TeV counterparts to γ-ray bursts. Within the Milagrito field of view 54 γ-ray bursts at keV energies were observed by the Burst And Transient Satellite Experiment (BATSE) aboard the Compton Gamma-Ray Observatory. This paper describes the results of a preliminary analysis to search for TeV emission correlated with BATSE detected bursts. Milagrito detected an excess of events coincident both spatially …

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Spectra Of A Recent Bright Burst Measured By Cgro-Comptel: Grb 990123, C A. Young, A Connors, K Bennett, W Collmar, W Hermsen, R M. Kippen, E Kolaczyk, L Kuiper, Mark L. Mcconnell, R S. Miller, James M. Ryan, V Schonfelder, O R. Williams, C Winkler Jan 2000

Spectra Of A Recent Bright Burst Measured By Cgro-Comptel: Grb 990123, C A. Young, A Connors, K Bennett, W Collmar, W Hermsen, R M. Kippen, E Kolaczyk, L Kuiper, Mark L. Mcconnell, R S. Miller, James M. Ryan, V Schonfelder, O R. Williams, C Winkler

Space Science Center

CGRO-COMPTEL measures gamma-ray burst positions, time-histories and spectra in the 0.1–30 MeV energy range, in both imaging “telescope” and single detector “burst spectroscopy” mode. GRB 990123, one of the most recent bright bursts seen by COMPTEL, was caught in the optical while the gamma-ray emission was ongoing. The burst spectral shape can be characterized by a peak in ν−Fν just below 1 MeV and a power-law tail above(photon index∼−2.4,) and flattening below. There is also spectral evolution by downward movement of the peak and/or softening of the power laws. We present light-curves, time resolved spectra and an image map for …

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Improved Comptel Maps Of The Milky Way, H Bloemen, K Bennett, W Collmar, R Diehl, W Hermsen, A Iyudin, J Knodlseder, Mark L. Mcconnell, James M. Ryan, V Schonfelder, A W. Strong Jan 2000

Improved Comptel Maps Of The Milky Way, H Bloemen, K Bennett, W Collmar, R Diehl, W Hermsen, A Iyudin, J Knodlseder, Mark L. Mcconnell, James M. Ryan, V Schonfelder, A W. Strong

Space Science Center

In the course of the mission we have gradually developed an analysis method that separates in an iterative manner the celestial emission and the (a priori unknown) instrumental background. It has become our standard analysis tool for point sources. We illustrate here that this method is widely applicable now. It provides mutually consistent sets of model-fitting parameters (spectra) and sky maps, both for continuum and line studies. Because of the wide applicability, it has been possible to make various cross-checks while building up confidence in this procedure.

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Milagro: A Tev Gamma-Ray Monitor Of The Northern Hemisphere Sky, B L. Dingus, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh Jan 2000

Milagro: A Tev Gamma-Ray Monitor Of The Northern Hemisphere Sky, B L. Dingus, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh

Space Science Center

A new type of very high energy (> a few 100 GeV) gamma-ray observatory, Milagro, has been built with a large field of view of >1 steradian and nearly 24 hours/day operation. Milagrito, a prototype for Milagro, was operated from February 1997 to May 1998. During the summer of 1998, Milagrito was dismantled and Milagro was built. Both detectors use a 80 m×60 m×8 mpond of water in which a 3 m×3 m grid of photomultiplier tubes detects the Cherenkov light produced in the water by the relativistic particles in extensive air showers. Milagrito was smaller and had only one …

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Detection Of 6 November 1997 Ground Level Event By Milagrito, A Falcone, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, John R. Macri, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, G Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh Jan 2000

Detection Of 6 November 1997 Ground Level Event By Milagrito, A Falcone, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, John R. Macri, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, G Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh

Space Science Center

Solar Energetic Particles (SEPs) with energies exceeding 10 GeV associated with the 6 November 1997 solar flare/CME (coronal mass ejection) have been detected with Milagrito, a prototype of the Milagro Gamma Ray Observatory. While SEP acceleration beyond 1 GeV is well established, few data exist for protons or ions beyond 10 GeV. The Milagro observatory, a ground based water Cherenkov detector designed for observing very high energy gamma ray sources, can also be used to study the Sun. Milagrito, which operated for approximately one year in 1997/98, was sensitive to solar proton and neutron fluxes above ∼4 GeV. In its …

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Results From The Milagrito Experiment, A J. Smith, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, G Sinnis, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh Jan 2000

Results From The Milagrito Experiment, A J. Smith, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, B L. Dingus, D E. Dorfan, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, G Sinnis, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh

Space Science Center

The Milagro water Cherenkov detector near Los Alamos, New Mexico is the first air shower detector capable of continuously monitoring the sky at energies between 500 GeV and 20 TeV. Preliminary results of the Milagro experiment are presented. A predecessor of the Milagro detector, Milagrito, was operational from February 1997 to May 1998. Milagrito consisted of 228 8″ photomultiplier tubes (PMTs) arranged in a grid with a 2.8 meter spacing and submerged in 1–2 meters of water. During its operation, Milagrito collected in excess of 9 billion events with a median energy of about 3 TeV. The detector’s sensitivity …

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Milagro: A Tev Observatory For Gamma-Ray Bursts, B L. Dingus, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh Jan 2000

Milagro: A Tev Observatory For Gamma-Ray Bursts, B L. Dingus, R Atkins, W Benbow, D Berley, M L. Chen, D G. Coyne, R W. Ellsworth, D Evans, A Falcone, L Fleysher, R Fleysher, G Gisler, J A. Goodman, T J. Haines, C M. Hoffman, S Hugenberger, L A. Kelley, I Leonor, Mark L. Mcconnell, J F. Mccullough, J E. Mcenery, R S. Miller, A I. Mincer, M F. Morales, P Nemethy, James M. Ryan, B Shen, A Shoup, C Sinnis, A J. Smith, G W. Sullivan, O T. Tumer, K Wang, M O. Wascko, S Westerhoff, D A. Williams, T Yang, G B. Yodh

Space Science Center

Observation of prompt TeV γ-rays from GRBs requires a new type of detector to overcome the low duty factor and small field of view of current TeV observatories. Milagro is such a new type of very high energy (> a few 100 GeV) gamma-ray observatory, which has a large field of view of >1 steradian and 24 hours/day operation. Milagrito, a prototype for Milagro, was operated from February 1997 to May 1998. During the summer of 1998, Milagrito was dismantled and Milagro was built. Both detectors use a 80 m×60 m×8 m pond of water in which a 3 m×3 …

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The Spectral Variability Of Cygnus X-1 At Mev Energies, Mark L. Mcconnell, K Bennett, H Bloemen, W Collmar, W Hermsen, L Kuiper, B F. Phlips, James M. Ryan, V Schonfelder, H Steinle, A W. Strong Jan 2000

The Spectral Variability Of Cygnus X-1 At Mev Energies, Mark L. Mcconnell, K Bennett, H Bloemen, W Collmar, W Hermsen, L Kuiper, B F. Phlips, James M. Ryan, V Schonfelder, H Steinle, A W. Strong

Space Science Center

In previous work, we have used data from the first three years of the CGRO mission to assemble a broad-band γ-ray spectrum of the galactic black hole candidate Cygnus X-1. Contemporaneous data from the COMPTEL, OSSE and BATSE experiments on CGRO were selected on the basis of the hard X-ray flux (45–140 keV) as measured by BATSE. This provided a spectrum of Cygnus X-1 in its canonical low X-ray state (as measured at energies below 10 keV), covering the energy range from 50 keV to 5 MeV. Here we report on a comparison of this spectrum to a COMPTELOSSE spectrum …

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Comptel 1.8 Mev All Sky Survey: The Cygnus Region, S Pluschke, R Diehl, V Schonfelder, G Weidenspointer, H Bloemen, W Hermsen, Mark L. Mcconnell, James M. Ryan, K Bennett, U Oberlack, J Knodlseder Jan 2000

Comptel 1.8 Mev All Sky Survey: The Cygnus Region, S Pluschke, R Diehl, V Schonfelder, G Weidenspointer, H Bloemen, W Hermsen, Mark L. Mcconnell, James M. Ryan, K Bennett, U Oberlack, J Knodlseder

Space Science Center

We present an updated version of COMPTEL’s 1.809 MeV sky survey. Based on eight years of observations we compare results from different imaging techniques using background from adjacent energy bands. We confirm the previously reported characteristics of the galactic 1.809 MeV emission, specifically an extended galactic ridge emission, mainly concentrated towards the inner galaxy, a peculiar emission feature in the Cygnus region, and a low-intensity ridge extending towards Carina and Vela. Because this gamma ray line is due to the decay of radioactive 26Al, predominantly synthesized in massive stars, one anticipates flux enhancements aligned with regions of recent star formation. …

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Sensitivity Curves For Spaceborne Gravitational Wave Interferometers, Shane L. Larson, William A. Hiscock, Ronald W. Hellings Jan 2000

Sensitivity Curves For Spaceborne Gravitational Wave Interferometers, Shane L. Larson, William A. Hiscock, Ronald W. Hellings

All Physics Faculty Publications

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic …

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Erratum: "Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms", Alejandro Garcia, F. Alexander, B. Alder Jan 2000

Erratum: "Cell Size Dependence Of Transport Coefficients In Stochastic Particle Algorithms", Alejandro Garcia, F. Alexander, B. Alder

Faculty Publications

No abstract provided.

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