GALI: a Gamma-ray Burst Localizing Instrument

TL;DR

The paper introduces GALI, a novel gamma-ray detector using scintillator cubes for accurate, wide-field localization of GRBs, suitable for small satellite deployment.

Contribution

It presents a new detector concept leveraging mutual occultation of scintillators for precise GRB localization, scalable for various satellite sizes.

Findings

Prototype achieves a few degrees accuracy with laboratory tests.

Simulations indicate <2° localization accuracy for realistic GRBs.

Design is scalable for small and large satellite missions.

Abstract

The detection of astrophysical Gamma-Ray Bursts (GRBs) has always been intertwined with the challenge of identifying the direction of the source. Accurate angular localization of better than a degree has been achieved to date only with heavy instruments on large satellites, and a limited field of view. The recent discovery of the association of GRBs with neutron star mergers gives new motivation for observing the entire $\gamma$-ray sky at once with high sensitivity and accurate directional capability. We present a novel $\gamma$-ray detector concept, which utilizes the mutual occultation between many small scintillators to reconstruct the GRB direction. We built an instrument with 90 (9\,mm)$^3$ \csi~scintillator cubes attached to silicon photomultipliers. Our laboratory prototype tested with a 60\,keV source demonstrates an angular accuracy of a few degrees for $\sim$25 ph\,cm$^{-2}$ bursts. Simulations of realistic GRBs and background show that the achievable angular localization accuracy with a similar instrument occupying $1$l volume is $<2^\circ$. The proposed concept can be easily scaled to fit into small satellites, as well as large missions.