The First Fermi LAT Gamma-Ray Burst Catalog

TL;DR

This paper presents the first catalog of high-energy gamma-ray bursts detected by the Fermi LAT, analyzing 35 GRBs over three years and detailing their spectral and temporal properties.

Contribution

It provides the first systematic compilation and analysis of high-energy gamma-ray emission from GRBs detected by Fermi LAT, including methodology and detailed properties.

Findings

28 GRBs detected above 100 MeV

LAT emission often delayed and longer-lasting than GBM emission

LAT spectra dominated by a power-law component

Abstract

In three years of observations since the beginning of nominal science operations in August 2008, the Large Area Telescope (LAT) on board the Fermi Gamma Ray Space Telescope has observed high-energy (>20 MeV) \gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ~ 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared to emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.