Doctor of Philosophy (PhD)


Physics and Astronomy

Document Type



Earth occultation provides a means of monitoring gamma-ray sources over the entire sky. This technique has been demonstrated with the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) active from 1991 to 2000, and is now being used with the Gamma-ray Burst Monitor (GBM) instrument on the Fermi mission. Although this approach provides a powerful wide field monitoring capability, the BATSE and GBM implementations of this technique have so far limited the analysis to a catalog of previously identified sources. In this dissertation, an indirect imaging method is described that permits searching for unknown sources by applying the Differential Filter Technique to archival BATSE data. Using this technique, occultation steps are transformed into gaussian-like features with amplitudes corresponding to the intensities measured from each pixel in the sky. With approximately 85% of the sky occulted every spacecraft orbit, the about 51 day precession period of the CGRO orbit makes it possible to perform an all-sky survey. By comparing both significance and the shape of the source of interest, we can finalize both known and unknown sources with spatial resolution to less than 0.5 degree. A reanalysis of the BATSE data has been performed, making it possible to complete the BATSE catalog of high energy sources, to address long-standing questions of systematic effects in the BATSE results, and to compare the new BATSE results to the current Fermi/GBM catalog in order to perform a study over 22 years of variations in the hard X-ray/low energy gamma-ray sky.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Cherry, Michael