Ground-based calibration and characterization of the Fermi Gamma-Ray Burst Monitor Detectors

TL;DR

This paper details the ground-based calibration and characterization of the Fermi GBM detectors, essential for accurate gamma-ray burst detection and localization, through simulations supported by calibration measurements.

Contribution

It provides a comprehensive calibration of the GBM detectors' response, including energy relation, resolution, and effective area, enhancing GRB measurement accuracy.

Findings

Detectors' energy response characterized across angles

Calibration improves accuracy of GRB localization

Effective area and resolution quantified for all detectors

Abstract

One of the scientific objectives of NASA's Fermi Gamma-ray Space Telescope is the study of Gamma-Ray Bursts (GRBs). The Fermi Gamma-Ray Burst Monitor (GBM) was designed to detect and localize bursts for the Fermi mission. By means of an array of 12 NaI(Tl) (8 keV to 1 MeV) and two BGO (0.2 to 40 MeV) scintillation detectors, GBM extends the energy range (20 MeV to > 300 GeV) of Fermi's main instrument, the Large Area Telescope, into the traditional range of current GRB databases. The physical detector response of the GBM instrument to GRBs is determined with the help of Monte Carlo simulations, which are supported and verified by on-ground individual detector calibration measurements. We present the principal instrument properties, which have been determined as a function of energy and angle, including the channel-energy relation, the energy resolution, the effective area and the spatial homogeneity.