Study of GALIs ability to localize gamma-ray bursts on a low orbit satellite using monte-carlo simulation

For more than half a century, the question of origin for gamma-ray bursts (GRBs) has been studied by the scientific community. Since the first publication about the subject in 1973, many questions still remain regarding the source of these highly energetic explosions.  Lasting from less than a second to several dozen, arriving uniformly from all over the sky and with varying light curves, many of their characteristics are studied.

Helpfully, following the initial burst a longer lived ‘afterglow’ arrives, consisting of energies from X-ray to radio. Since this light can be detected and studied using telescopes, unlike gamma-rays, it is a key part of our study of GRBs. In order for these telescopes to record the ‘afterglow’ as it arrives, the setup needs the ability to detect the initial GRB, as well as to be able to localize it. Thus, the current scientific instruments that detect GRBs have localization abilities, as well as a wide field of view, with fast communication with the other instruments and observatories.

The Technion’s GALI (GAmma-ray burst Localization Instrument) detector is designed to have the detection and localization abilities of existing detectors, yet importantly with a much smaller volume. It uses mutual shielding to localize arriving GRBs, by using likelihood analysis on the relative number of counts in each of its scintillators compared to an initial calibration map. Thus it is able to recreate the angle by using a single relatively small device.

Understanding how well this design is able to recreate the angle of arrival for GRBs is the goal of this thesis. Understanding how we expect the estimation uncertainty to behave for different GRBs, how its placement on a satellite might change the results, and to test alternate versions to better understand how the flexible design of the instrument influences its capabilities. This is done using monte-carlo simulations based on MEGAlib, as well as using previously detected GRBs recorded by FERMIs GBM to learn how GALIs detection ability is by comparison