Geoffrey N. Pendleton

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Detectors aboard the Compton Gamma Ray Observatory have observed an unexplained terrestrial phenomenon: brief, intense flashes of gamma rays. These flashes must originate in the atmosphere at altitudes above at least 30 kilometers in order to escape atmospheric absorption and reach the orbiting detectors. At least a dozen such events have been detected over(More)
Using CGRO/BATSE hard X-ray (HXR) data and GHz radio monitoring data from the Green Bank Interferometer (GBI), we have performed a long term study (∼ 1800 days) of the unusual X-ray binary Cyg X-3 resulting in the discovery of a remarkable relationship between these two wavelength bands. We find that, during quiescent radio states, the radio flux is(More)
We investigate spectral evolution in 37 bright, long gamma-ray bursts observed with the BATSE Spectroscopy Detectors. High resolution spectra are characterized by the energy of the peak of νF ν and the evolution of this quantity is examined relative to the emission intensity. In most cases it is found that this peak energy either rises with or slightly(More)
We use dipole and quadrupole statistics to test the large-scale isotropy of the first 1005 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE). In addition to the entire sample of 1005 gamma-ray bursts, many subsets are examined. We use a variety of dipole and quadrupole statistics to search for Galactic and other predicted(More)
The synchrotron shock model (SSM) for gamma-ray burst emission makes a testable prediction: that the observed low-energy power-law photon number spectral index cannot exceed −2/3 (where the photon model is defined with a positive index: dN/dE ∝ E α). We have collected time-resolved spectral fit parameters for over 100 bright bursts observed by the Burst And(More)
We characterize the error distribution of BATSE GRB locations by mod-eling the distribution of separations between BATSE locations and IPN annuli. We determine error model parameters by maximizing likelihood and rank the models by their Bayesian odds ratios. The best models have several systematic error terms. The simplest good model has a 1.9 degree(More)
We have recently completed a search of 6 years of archival BATSE data for gamma-ray bursts (GRBs) that were too faint to activate the real-time burst detection system running onboard the spacecraft. These " non-triggered " bursts can be combined with the " triggered " bursts detected onboard to produce a GRB intensity distribution that reaches peak fluxes a(More)
We have developed an automatic search procedure to identify low-energy spectral features in GRBs. We have searched 133,000 spectra from 117 bright bursts and have identified 12 candidate features with significances ranging from our threshold of P = 5E−5 to P = 1E−7. Several of the candidates have been examined in detail, including some with data from more(More)
We describe a Bayesian methodology to evaluate the consistency between the reported Ginga and BATSE detections of absorption features in gamma ray burst spectra. Currently no features have been detected by BATSE, but this methodology will still be applicable if and when such features are discovered. The Bayesian methodology permits the comparison of(More)