1,384 research outputs found
Long-Term (9-Year) Response of Two Semiarid Grasslands to Prescribed Fire in the Southwestern USA
Historically, arid grasslands of SW USA experienced fire return intervals of 5-10 years. During the last 100 years, however, fire has been a rare event. Recent expansion of woody plants in arid grasslands has prompted managers to re-introduce fire as a tool to reduce abundance of woody plants and maintain perennial grass cover. The use of fire in desert grasslands poses unique challenges, however, due to extreme variability in rainfall patterns. Our research examines vegetation response to repeat fire in 2 desert grassland ecotones near Albuquerque, New Mexico (35.05o N 106.60o W)
Time Dependent Clustering Analysis of the Second BATSE Gamma-Ray Burst Catalog
A time dependent two-point correlation-function analysis of the BATSE 2B
catalog finds no evidence of burst repetition. As part of this analysis, we
discuss the effects of sky exposure on the observability of burst repetition
and present the equation describing the signature of burst repetition in the
data. For a model of all burst repetition from a source occurring in less than
five days we derive upper limits on the number of bursts in the catalog from
repeaters and model-dependent upper limits on the fraction of burst sources
that produce multiple outbursts.Comment: To appear in the Astrophysical Journal Letters, uuencoded compressed
PostScript, 11 pages with 4 embedded figure
AI Gamma-Ray Burst Classification: Methodology/Preliminary Results
Artificial intelligence (AI) classifiers can be used to classify unknowns,
refine existing classification parameters, and identify/screen out ineffectual
parameters. We present an AI methodology for classifying new gamma-ray bursts,
along with some preliminary results.Comment: 5 pages, 2 postscript figures. To appear in the Fourth Huntsville
Gamma-Ray Burst Symposiu
Average Emissivity Curve of BATSE Gamma-Ray Bursts with Different Intensities
Six intensity groups with ~150 BATSE gamma-ray bursts each are compared using
average emissivity curves. Time-stretch factors for each of the dimmer groups
are estimated with respect to the brightest group, which serves as the
reference, taking into account the systematics of counts-produced noise effects
and choice statistics. A stretching/intensity anti-correlation is found with
good statistical significance during the average back slopes of bursts. A
stretch factor ~2 is found between the 150 dimmest bursts, with peak flux
4.1 ph
cm^{-2} s^{-1}. On the other hand, while a trend of increasing stretching
factor may exist for rise fronts for burst with decreasing peak flux from >4.1
ph cm^{-2} s^{-1} down to 0.7 ph cm^{-2} s^{-1}, the magnitude of the
stretching factor is less than ~ 1.4 and is therefore inconsistent with
stretching factor of back slope.Comment: 21 pages, 3 figures. Accepted to Ap
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