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GALI (Gamma-ray Burst Localizing Instrument) A New GRB Detector Concept

Presentation #111.12 in the session “Time Domain Astrophysics (Poster)”.

Published onApr 01, 2022
GALI (Gamma-ray Burst Localizing Instrument) A New GRB Detector Concept

The recent association of gamma-ray bursts (GRBs) with neutron star mergers highlighted the need for sensitive gamma-ray detectors with high localization accuracy. Identification of the host galaxy of the gravitational wave event GW170817 and the gamma-ray burst GRB170817A was only achieved 11 hours after initial detection due to difficulties surveying the uncertainty region of the gravitational wave event. A delay in the precise localization of GRBs causes loss of crucial data until observations at longer wavelengths can begin. Detectors with large viewing angles, preferably the entire sky, and considerably improved angular resolution of a few degrees can shorten the follow-up latency.

We present a novel gamma-ray detector aimed at improving the angular localization relative to the current state of the art. Our concept relies on a non-uniform pattern of small scintillators coupled to silicon photomultipliers. The detector utilizes mutual occultations between scintillators to reconstruct the GRB direction in the sky. Our simulations show that the achievable localization accuracy for such a configuration is considerably better than those obtained by larger scintillator assemblies while maintaining a field-of-view of the entire sky. We show that even for a reduced total effective area, our detector system still achieves better angular sensitivity relative to designs based on the current state of the art. Both simulations and experiments clearly show our novel concept can attain a considerable improvement in angular sensitivity without compromising sensitivity or field-of-view. The proposed detector concept is scalable and can fit small satellites and larger missions alike. We are currently building a GRB detector system with 362 small scintillators distributed among nine electronic boards to be installed on the ISS. Simulations predict that such an instrument will localize GRBs down to ±2.1 (4.7) degrees for a fluence of 10 (5) ph cm-2.

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