Direct evidence for preburst stage of gamma-ray burst from GRB 221009A data

TL;DR

This paper provides direct observational evidence for a preburst phase in gamma-ray bursts, specifically in GRB 221009A, based on multi-instrument data analysis, suggesting a new stage in GRB emission not previously confirmed.

Contribution

It presents the first direct evidence of a preburst phase in GRBs, supported by data from Fermi and LHAASO, expanding understanding of GRB emission stages.

Findings

Evidence of multi-GeV photons emitted before lower-energy photons.

Identification of a new preburst phase in GRB evolution.

Support for Lorentz invariance violation scenarios.

Abstract

Previous research on Lorentz invariance violation in photons from gamma-ray bursts (GRBs) suggested a scenario where multi-GeV photons could be emitted before lower-energy photons at the GRB source frame. This implies the existence of a new preburst phase in addition to the traditionally identified prompt and afterglow stages observed in earlier studies. In this study, we present direct evidence for this novel preburst phase in gamma-ray bursts based on recent observations of GRB 221009A. Our analysis leverages data from the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) detectors of the Fermi Gamma-ray Space Telescope (FGST), as well as data from the KM2A detector of the Large High Altitude Air-shower Observatory (LHAASO).