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in creator/contributor: "Marshall, S L"

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Electroformation of Uranium Hemispherical Shells

Date: November 1989

Creator: Marshall, S. L.; Redey, L.; Vandegrift, G. F. & Vissers, D. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Continuing investigations for technology assessment of /sup 99/Mo production from LEU (low enriched Uranium) targets

Currently much of the world's supply of /sup 99m/Tc for medical purposes is produced from /sup 99/Mo derived from the fissioning of high enriched uranium (HEU). The need for /sup 99m/Tc is continuing to grow, especially in developing countries, where needs and national priorities call for internal production of /sup 99/Mo. This paper presents the results of our continuing studies on the effects of substituting low enriched Uranium (LEU) for HEU in targets for the production of fission product /… more

Date: January 1, 1987

Creator: Vandergrift, G. F.; Kwok, J. D.; Marshall, S. L.; Vissers, D. R. & Matos, J. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electroformation of uranium hemispherical shells

This effort was directed at developing an electrochemical process for forming uniform and dendrite-free deposits of uranium from molten salts. This process is to be used for the electroformation of free-standing hemispherical shells of uranium for nuclear applications. Electrodeposition of uranium onto a substrate was accomplished with a fused chloride mixture containing 42 wt% UCl{sub 3} and a fused chloride-fluoride mixture containing 4 wt % UF{sub 4}. Under pulsed potential control at 504{de… more

Date: November 1, 1989

Creator: Marshall, S.L.; Redey, L.; Vandegrift, G.F. & Vissers, D.R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The MACHO project: Microlensing and variable stars

The MACHO Project monitors millions of stars in the Large Magellanic Cloud, the Small Magellanic Cloud and the bulge of the Milky Way searching for the gravitational microlensing signature of baryonic dark matter. This Project has yielded surprising results. An analysis of two years of data monitoring the Large Magellanic Cloud points to {approximately} 50% of the mass of the Milky Way`s halo in compact objects of {approximately} 0.5 solar mass. An analysis of one year of monitoring the bulge h… more

Date: October 1, 1996

Creator: Alcock, C.; Alves, D. R.; Axelrod, T. S.; Bennett, D. P.; Marshall, S. L. & Minniti, D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The Partitioning of Acetate, Formate and Phosphates Around the Water/Steam Cycle

No Description Available.

Date: June 27, 2000

Creator: Guszkiewicz, M. S.; Joyce, D. B.; Marshall, S. L.; Palmer, D. A. & Simonson, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

RR Lyrae stars in the MACHO database

The MACHO Project has catalogued {approximately} 8000 RR Lyrae stars in the Large Magellanic Cloud, {approximately} 180 in the Galactic bulge, and {approximately} 50 in the Sgr dwarf galaxy. These variables are excellent distance indicators, and are used as tools to study the structure of the Large Magellanic Cloud and the bulge. The large datasets also probe uncommon pulsation modes. A number of double-mode RR Lyrae stars (RRd) are found in the Large Magellanic Cloud sample. These stars provid… more

Date: October 1, 1996

Creator: Minniti, D.; Alcock, C.; Alves, D. R.; Axelrod, T. S.; Bennett, D. P.; Cook, K. H. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The Partitioning of Acetic, Formic, and Phosphoric Acids Between Liquid Water and Steam

The chemical carryover of impurities and treatment chemicals from the boiler to the steam phase, and ultimately to the low-pressure turbine and condenser, can be quantified based on laboratory experiments preformed over ranges of temperature, pH, and composition. The two major assumptions are that thermodynamic equilibrium is maintained and no deposition, adsorption or decomposition occurs. The most recent results on acetic, formic and phosphoric acids are presented with consideration of the ef… more

Date: June 22, 1999

Creator: Gruszkiewicz, M. S.; Marshall, S. L.; Palmer, D. A. & Simonson, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The Early Optical Brightening in the GRB 071010B

We report the detection of early (60-230 s) optical emission of the gamma-ray burst afterglow of GRB071010B. No significant correlation with the prompt {gamma}-ray emission was found. Our high time-resolution data combining with other measurements within 2 days after the burst indicate that GRB071010B is composed of a weak early brightening ({alpha} {approx} 0.6), probably caused by the peak frequency passing through the optical wavelengths, followed by a decay ({alpha} {approx} -0.51), attribu… more

Date: April 8, 2008

Creator: Wang, J. H.; Schwamb, M. E.; Huang, K. Y.; Wen, C. Y.; Zhang, Z. W.; Wang, S. Y. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The MACHO Project HST Follow-Up: The Large Magellanic Cloud Microlensing Source Stars

We present Hubble Space Telescope (HST) WFPC2 photometry of 13 microlensed source stars from the 5.7 year Large Magellanic Cloud (LMC) survey conducted by the MACHO Project. The microlensing source stars are identified by deriving accurate centroids in the ground-based MACHO images using difference image analysis (DIA) and then transforming the DIA coordinates to the HST frame. None of these sources is coincident with a background galaxy, which rules out the possibility that the MACHO LMC micro… more

Date: June 25, 2009

Creator: Nelson, C. A.; Drake, A. J.; Cook, K. H.; Bennett, D. P.; Popowski, P.; Dalal, N. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The MACHO Project Sample of Galactic Bulge High-Amplitude Scuti Stars: Pulsation Behavior and Stellar Properties

We have detected 90 objects with periods and lightcurve structure similar to those of field {delta} Scuti stars, using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude {delta} Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground {delta} Scuti stars… more

Date: November 16, 1999

Creator: Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

MACHO Project Analysis of the Galactic Bulge Microlensing Events with Clump Giants as Sources

We present preliminary results of the analysis of 5 years of MACHO data on the Galactic bulge microlensing events with clump giants as sources. This class of events allows one to obtain robust conclusions because relatively bright clump stars are not strongly affected by blending. We discuss: (1) the selection of ''giant'' events, (2) the distribution of event durations, (3) the anomalous character of event durations and optical depth in the MACHO field 104 centered on (l,b) = (3{sup o}.1,-3{su… more

Date: March 6, 2002

Creator: Popowski, P.; Vandehei, T.; Griest, K.; Alcock, C.; Alves, D. R.; Allsman, R. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Upper Limits on the Number of Small Bodies in Sedna-Like Orbits by the TAOS Project

We present the results of a search for occultation events by objects at distances between 100 and 1000 AU in lightcurves from the Taiwanese-American Occultation Survey (TAOS). We searched for consecutive, shallow flux reductions in the stellar lightcurves obtained by our survey between 7 February 2005 and 31 December 2006 with a total of {approx} 4.5 x 10{sup 9} three-telescope simultaneous photometric measurements. No events were detected, allowing us to set upper limits on the number density … more

Date: November 13, 2009

Creator: Wang, J.; Lehner, M. J.; Zhang, Z.; Bianco, F. B.; Alcock, C.; Chen, W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey

Using 7 years of MACHO survey data, we present a new determination of the optical depth to microlensing towards the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg{sup 2} with 739000 clump giant sta… more

Date: July 14, 2005

Creator: Popowski, P.; Griest, K.; Thomas, C. L.; Cook, K. H.; Bennett, D. P.; Becker, A. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The TAOS Project Stellar Variability II. Detection of 15 Variable Stars

The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data - covering timescales from a fraction of a second to a few hundred days - are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars fro… more

Date: January 28, 2010

Creator: Mondal, S.; Lin, C. C.; Zhang, Z. W.; Alcock, C.; Axelrod, T.; Bianco, F. B. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Astrometry with the MACHO Data Archive

We present the preliminary results of our astrometric study of stellar motions along the lines of sight of the Magellanic Clouds and the Galactic bulge. We find that we are able to select stars with proper motions as small as 0.03 inch/yr from five years of PSF photometry due to the characteristic nature of the shapes the light curves of HFM stars. This shape arises from the proper motion of the object relative to the initial fixed centroid location where all photometry of the object is perform… more

Date: October 15, 2000

Creator: Drake, A. J.; Alcock, C.; Allsman, R.; Alves, D. R.; Axelrod, T. S.; Becker, A. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Variable stars in the MACHO bulge database

The MACHO Project has been monitoring large fields in the direction of the Galactic bulge, the LMC and SMC for over 6 years. The nightly observations of this microlensing survey provide very large databases for astronomers. The MACHO database contains {approximately}5 Terabytes of data as of mid-1998. For comparison, the HST Archive contains about {approximately}2 Tb, and the Sloan. Digital Sky Survey will reach {approximately}1.0 Tb. Our database can be used to attack a variety of astrophysica… more

Date: October 1, 1998

Creator: Quinn, P. J.; Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

MACHO RR lyrae in the inner halo and bulge

The RR Lyrse in the bulge have been proposed to be the oldest populations in the Milky Way, tracers of how the galaxy formed. We study here the distribution of ?{approximately}1600 bulge RR Lyrae stars found by the MACHO Project. The RR Lyrae with 0.4 ? R ? 3 kpc show a density law that is well fit by the extension of the metal-poor stellar halo present in the outer regions of the Milky Way.

Date: October 1, 1998

Creator: Drake, A.; Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T.S.; Becker, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Galactic Bulge Microlensing Events from the MACHO Collaboration

The authors present a catalog of 450 relatively high signal-to-noise microlensing events observed by the MACHO collaboration between 1993 and 1999. The events are distributed throughout the fields and, as expected, they show clear concentration toward the Galactic center. No optical depth is given for this sample since no blending efficiency calculation has been performed, and they find evidence for substantial blending. In a companion paper they give optical depths for the sub-sample of events… more

Date: June 16, 2005

Creator: Thomas, C. L.; Griest, K.; Popowski, P.; Cook, K. H.; Drake, A. J.; Minniti, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Galactic Bulge Microlensing Events from the MACHO Collaboration

No Description Available.

Date: July 14, 2005

Creator: Thomas, C. L.; Griest, K.; Popowski, P.; Cook, K. H.; Drake, A. J.; Minniti, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

MACHO project 9 million star color-magnitude diagram of the large magellanic cloud

The authors present a 9 million star color-magnitude diagram (9M CMD) of the Large Magellanic Cloud (LMC) bar. The 9M CMD reveals a complex superposition of different age and metallicity stellar populations, with important stellar evolutionary phases occurring over three orders of magnitude in number density. First, they count the non-variable red and blue supergiants, the associated Cepheid variables, and measure the stellar effective temperatures defining the Cepheid instability strip. Lifeti… more

Date: January 31, 2000

Creator: Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Basu, A.; Becker, A. C. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Binary Microlensing Events from the MACHO Project

This article presents the light curves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey that are likely examples of lensing by binary systems.

Date: March 27, 2000

Creator: Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Baines, D.; Becker, A. C. et al.

Item Type: Article

Partner: UNT College of Arts and Sciences