991 research outputs found
The spectrum of cosmic electron with energies between 6 and 100 GeV
This experiment was carried out during three balloon flights which provided a total exposure of 3500 + or - 60 sq m sec sterad at an average depth of 4.8 g/sq cm The detector, in which the development of cascade showers in a 33.7 rl absorber was sampled by 10 scintillation counters and 216 Geiger-Muller tubes, was calibrated at the Cornell Electron Synchrotron, the separation of cosmic electrons from the nuclear background was confirmed by extensive analysis of data from the flights, from the calibration and from ground level exposure. The spectral intensity of primary cosmic ray electrons were found in particles/sq m sec sterad GeV. Similarly, the ground level spectrum of secondary cosmic ray electrons was also found. The steepness of the spectrum of cosmic electrons relative to that of nuclei implies one of the following conclusions: either the injection spectrum of electrons is steeper than that of nuclei, or the electron spectrum has been steepened by Compton/synchrotron losses in the energy range covered by the experiment
Capabilities of the GRO/BATSE for monitoring of discrete sources
Although the Burst and Transient Source Experiment (BATSE) to be flown on the Gamma Ray Observatory has as its primary objective the detection of gamma ray bursts, its uncollimated design will enable it to serve a unique function as an all-sky monitor for bright hard X-ray and low-energy gamma ray sources. Pulsating sources may be detected by conventional techniques such as summed-epoch and Fourier analyses. The BATSE will, in addition, be able to use Earth occultation in an unprecedented way to monitor sufficiently bright sources as often as several times per day over approx. 85% of the sky. Estimates of the expected BATSE sensitivity using both of these techniques are presented
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
From blast wave to observation
Gamma-ray burst (GRB) afterglows are well described by synchrotron emission
originating from the interaction between a relativistic blast wave and the
external medium surrounding the GRB progenitor. We introduce a code to
reconstruct spectra and light curves from arbitrary fluid configurations,
making it especially suited to study the effects of fluid flows beyond those
that can be described using analytical approximations. As a check and first
application of our code we use it to fit the scaling coefficients of
theoretical models of afterglow spectra. We extend earlier results of other
authors to general circumburst density profiles. We rederive the physical
parameters of GRB 970508 and compare with other authors.
We also show the light curves resulting from a relativistic blast wave
encountering a wind termination shock. From high resolution calculations we
find that the observed transition from a stellar wind type light curve to an
interstellar medium type light curve is smooth and without short-time
transitory features.Comment: conference proceedings 6th Huntsville symposium, 20-23 October 2008.
Editors: C.A. Meegan, N. Gehrels, and C. Kouvelioto
Properties of Gamma-Ray Burst Classes
The three gamma-ray burst (GRB) classes identified by statistical clustering
analysis (Mukherjee et al. 1998) are examined using the pattern recognition
algorithm C4.5 (Quinlan 1986). Although the statistical existence of Class 3
(intermediate duration, intermediate fluence, soft) is supported, the
properties of this class do not need to arise from a distinct source
population. Class 3 properties can easily be produced from Class 1 (long, high
fluence, intermediate hardness) by a combination of measurement error,
hardness/intensity correlation, and a newly-identified BATSE bias (the fluence
duration bias). Class 2 (short, low fluence, hard) does not appear to be
related to Class 1.Comment: 5 pages, 4 imbedded figures, presented at the 5th Huntsville
Gamma-Ray Burst Symposiu
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
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