Initial Results of New Tomographic Imaging of the Gamma-Ray Sky with BATSE

TL;DR

This paper introduces a novel tomographic imaging method using the Linear Radon Transform on BATSE data, enabling high-resolution gamma-ray sky maps and source localization within a single orbit cycle.

Contribution

It presents an innovative application of medical imaging techniques to gamma-ray astronomy, improving source localization and background removal in sky surveys.

Findings

Achieved <1 degree localization accuracy for gamma-ray sources.

Imaged sources up to ~2 MeV energy with a single precession cycle.

Developed a method for daily light curves and spectra of gamma-ray sources.

Abstract

We describe an improved method of mapping the gamma-ray sky by applying the Linear Radon Transform to data from BATSE on NASA's CGRO. Based on a method similar to that used in medical imaging, we use the relatively sharp (~0.25 deg) limb of the Earth to collimate BATSE's eight Large Area Detectors (LADs). Coupling this to the ~51-day precession cycle of the CGRO orbit, we can complete a full survey of the sky, localizing point sources to < 1 deg accuracy. This technique also uses a physical model for removing many sources of gamma-ray background, which allows us to image strong gamma-ray sources such as the Crab up to ~2 MeV with only a single precession cycle. We present the concept of the Radon Transform technique as applied to the BATSE data for imaging the gamma-ray sky and show sample images in three broad energy bands (23-98 keV, 98-230 keV, and 230-595 keV) centered on the positions of selected sources from the catalog of 130 known sources used in our Enhanced BATSE Occultation Package (EBOP) analysis system. Any new sources discovered during the sky survey will be added to the input catalog for EBOP allowing daily light curves and spectra to be generated. We also discuss the adaptation of tomographic imaging to the Fermi GBM occultation project.