The Fermi Gamma-Ray Burst Monitor

TL;DR

The Fermi Gamma-Ray Burst Monitor (GBM) enhances gamma-ray burst detection by extending energy coverage, enabling rapid localization, and supporting the Fermi Observatory's broader gamma-ray studies.

Contribution

GBM introduces a new detector array and onboard trigger system to improve gamma-ray burst detection and localization capabilities for the Fermi Observatory.

Findings

Detects ~250 GRBs per year

Extends energy range down to ~8 keV

Provides rapid burst localization for spacecraft re-orientation

Abstract

The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from the Fermi Observatory in the study of Gamma-Ray Bursts (GRBs). The primary objective of GBM is to extend the energy range over which bursts are observed downward from the energy range of the Large Area Telescope (LAT) on Fermi into the hard X-ray range where extensive previous data exist. A secondary objective is to compute burst locations on-board to allow re-orientiong the spacecraft so that the LAT can observe delayed emission from bright bursts. GBM uses an array of twelve sodium iodide scintillators and two bismuth germanate scintillators to detect gamma rays from ~8 keV to ~40 MeV over the full unocculted sky. The on-board trigger threshold is ~0.7 photons/cm2/s (50-300 keV, 1 s peak). GBM generates on-board triggers for ~250 GRBs per year.