AGILE gamma-ray detection of the exceptional GRB 221009A

Abstract

Gamma-ray emission in the MeV-GeV range from explosive cosmic events is of invaluable relevance to understanding physical processes related to the formation of neutron stars and black holes. Here we report on the detection by the AGILE satellite in the MeV-GeV energy range of the remarkable long-duration gamma-ray burst GRB 221009A. The AGILE onboard detectors have good exposure to GRB 221009A during its initial crucial phases. Hard X-ray/MeV emission in the prompt phase lasted hundreds of seconds, with the brightest radiation being emitted between 200 and 300 seconds after the initial trigger. Very intense GeV gamma-ray emission is detected by AGILE in the prompt and early afterglow phase up to 10,000 seconds. Time-resolved spectral analysis shows time-variable MeV-peaked emission simultaneous with intense power-law GeV radiation that persists in the afterglow phase. The coexistence during the prompt phase of very intense MeV emission together with highly nonthermal and hardening GeV radiation is a remarkable feature of GRB 221009A. During the prompt phase, the event shows spectrally different MeV and GeV emissions that are most likely generated by physical mechanisms occurring in different locations. AGILE observations provide crucial flux and spectral gamma-ray information regarding the early phases of GRB 221009A during which emission in the TeV range was reported.

Accepted for publication in ApJL on September 19, 2023. Published online on October 17, 2023. Revised Figure 5 (June 13, 2024)

References in corpus (8)

• Teraelectronvolt emission from the $\gamma$-ray burst GRB 190114C
• A tera-electronvolt afterglow from a narrow jet in an extremely bright gamma-ray burst 221009A
• Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow
• Properties of the extremely energetic GRB~221009A from Konus-WIND and SRG/ART-XC observations
• GRB 221009A: Discovery of an Exceptionally Rare Nearby and Energetic Gamma-Ray Burst
• The Radio to GeV Afterglow of GRB 221009A
• The IXPE view of GRB 221009A
• The AGILE Data Center and its Legacy

Cited by in corpus (12)

• Carpet-3 detection of a photon-like air shower with estimated primary energy above 100 TeV in a spatial and temporal coincidence with GRB 221009A
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• The brightest GRB ever detected: GRB 221009A as a highly luminous event at z = 0.151
• Theoretical modeling of the exceptional GRB 221009A afterglow
• GRB 221009A and the Apparently Most Energetic Gamma-Ray Bursts
• Camelidae on BOAT: observation of a second spectral component in GRB 221009A
• TeV Afterglows of Gamma-Ray Bursts: Theoretical Analysis and Prospects for Future Observations
• GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts
• Two-component jet model for the afterglow emission of GRB 201216C and GRB 221009A and implications for jet structure of very-high-energy gamma-ray bursts
• Modelling multiwavelength afterglows of the VHE-GRB population
• Catching TeV emission from GRB 221009A and alike with LHAASO, LACT and SWGO
• Modeling the imprints of large-scale magnetized structures on $\gamma$-rays from extragalactic transients