11,067 research outputs found
The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 218 gamma-ray
bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of
these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO)
spacecraft. For any given burst observed by these two spacecraft, arrival time
analysis (or "triangulation") results in an annulus of possible arrival
directions whose half-width varies between 7 arcseconds and 32 arcminutes,
depending on the intensity and time history of the burst, and the distance of
the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE
error circle, resulting in an average reduction of the error box area of a
factor of 30.Comment: Accepted for publication in the Astrophysical Journal Supplemen
A direct N-body model of core-collapse and core oscillations
We report on the results of a direct N-body simulation of a star cluster that
started with N = 200 000, comprising 195 000 single stars and 5 000 primordial
binaries. The code used for the simulation includes stellar evolution, binary
evolution, an external tidal field and the effects of two-body relaxation. The
model cluster is evolved to 12 Gyr, losing more than 80% of its stars in the
process. It reaches the end of the main core-collapse phase at 10.5 Gyr and
experiences core oscillations from that point onwards -- direct numerical
confirmation of this phenomenon. However, we find that after a further 1 Gyr
the core oscillations are halted by the ejection of a massive binary comprised
of two black holes from the core, producing a core that shows no signature of
the prior core-collapse. We also show that the results of previous studies with
N ranging from 500 to 100 000 scale well to this new model with larger N. In
particular, the timescale to core-collapse (in units of the relaxation
timescale), mass segregation, velocity dispersion, and the energies of the
binary population all show similar behaviour at different N.Comment: 9 pages, 8 figures, accepted for publication in MNRA
The Interplanetary Network Supplement to the BeppoSAX Gamma-Ray Burst Catalogs
Between 1996 July and 2002 April, one or more spacecraft of the
interplanetary network detected 787 cosmic gamma-ray bursts that were also
detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera
experiments aboard the BeppoSAX spacecraft. During this period, the network
consisted of up to six spacecraft, and using triangulation, the localizations
of 475 bursts were obtained. We present the localization data for these events.Comment: 89 pages, 3 figures. Submitted to the Astrophysical Journal
Supplement Serie
The Ulysses Supplement to the BATSE 4Br Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network localization information for 147 gamma-ray
bursts observed by the Burst and Transient Source Experiment between the end of
the 3rd BATSE catalog and the end of the 4th BATSE catalog, obtained by
analyzing the arrival times of these bursts at the Ulysses and Compton
Gamma-Ray Observatory (CGRO) spacecraft. For any given burst observed by these
two spacecraft, arrival time analysis (or "triangulation") results in an
annulus of possible arrival directions whose half-width varies between 7
arcseconds and 2.3 degrees, depending on the intensity and time history of the
burst, and the distance of the Ulysses spacecraft from Earth. This annulus
generally intersects the BATSE error circle, resulting in an average reduction
of the error box area of a factor of 25.Comment: Accepted for publication in the Astrophysical Journal Supplemen
Risk Preferences, Perceptions and Systematic Biases
Replaced with revised version of paper 07/21/06.Risk and Uncertainty,
ECONOMIC AND ENVIRONMENTAL EFFECTS ASSOCIATED WITH REDUCING THE USE OF ATRAZINE: AN EXAMPLE OF CROSS-DISCIPLINARY RESEARCH
Restricting or eliminating the use of atrazine in the Midwest would have important economic consequences for farmers, consumers, and the environment. These consequences can only be evaluated with cooperation between economists and weed scientists. The weed control choice set available to farmers cannot be observed through deductive research. Economists and weed scientists worked together to identify all possible weed control strategies for corn and sorghum in the Midwest and to incorporate them into an economic model. An atrazine ban was found to be the costliest strategy, and a targeted, water-quality based strategy the most cost effective.Atrazine, Deductive research, Environmental exposure, Herbicides, Inductive research, Welfare, Crop Production/Industries,
No Evidence for Gamma-Ray Burst/Abell Cluster or Gamma- Ray Burst/Radio-Quiet Quasar Correlations
We examine the recent claims that cosmic gamma-ray bursts are associated with
either radio-quiet quasars or Abell clusters. These associations were based on
positional coincidences between cataloged quasars or Abell clusters, and
selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger
sample of gamma-ray bursts with more accurate positions, obtained by the 3rd
Interplanetary Network, to re-evaluate these possible associations. We find no
evidence for either.Comment: Accepted for publication in the Astrophysical Journa
PRODUCTION DECISIONS WITH UNCERTAIN MARKETS: THE CASE OF BT CORN
The effect of marketing uncertainty due to consumer opposition over genetically modified (GM) grain is modeled in the context of a producer's decision to plant GM. The model shows that a tendency to plant less GM acreage and obtain premium prices for Non-GM grain is tempered by increased price risk.Crop Production/Industries,
Feasibility study of an Integrated Program for Aerospace-vehicle Design (IPAD) system. Volume 1: Summary
An overview is provided of the Ipad System, including its goals and objectives, organization, capabilities and future usefulness. The systems implementation is also presented with operational cost summaries
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