Geoffrey N. Pendleton

Learn More
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)
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 νFν 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 have recently completed a search of 6 years of archival BATSE data for gammaray 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)
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). We have collected time-resolved spectral fit parameters for over 100 bright bursts observed by the Burst And(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)
We have analyzed the evolution of the spectral hardness parameter, Epk (the maximum of the νFν spectrum) as a function of fluence in gamma-ray bursts. We fit 41 pulses within 26 bursts with the trend reported by Liang & Kargatis (1996) which found that Epk decays exponentially with respect to photon fluence Φ(t). We also fit these pulses with a slight(More)
We have developed an automatic search procedure to identify lowenergy 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 report evidence that the asymptotic low-energy power-law slope a (below the spectral break) of BATSE gamma-ray burst (GRB) photon spectra evolves with time rather than remaining constant. We find that a high degree of positive correlation exists between the time-resolved spectral break energy Epk and a. In samples of 18 “hard-to-soft” and 12 “tracking”(More)
Angular sky exposure is presented for a number of published BATSE gamma-ray burst catalogs. A new algorithm was required due to telemetry gaps resulting from onboard tape recorder failures; the new algorithm improves the 1B Catalog exposure calculation. The most influential effects limiting BATSE’s exposure are (1) deadtime due to triggering, (2) sky(More)