Jet Lorentz Factor Constraint for GRB 221009A Based on the Optical Depth of the TeV Photons

The recent detection of teraelectronvolt (TeV) photons from the record-breaking gamma-ray burst GRB 221009A during its prompt phase poses challenges for constraining its Lorentz factor. We reevaluate the constraints on the jet Lorentz factor considering a two-zone model, wherein the TeV photons orig...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2023-10, Vol.956 (2), p.L38
Main Authors: Gao, Duan-Yuan, Zou, Yuan-Chuan
Format: Article
Language:English
Subjects:
Afterglows
Emission
Gamma ray bursts
Gamma rays
High energy astrophysics
Light curve
Lorentz factor
Optical analysis
Optical thickness
Photons
Relativistic jets
Ultra-high-energy cosmic radiation
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Summary:The recent detection of teraelectronvolt (TeV) photons from the record-breaking gamma-ray burst GRB 221009A during its prompt phase poses challenges for constraining its Lorentz factor. We reevaluate the constraints on the jet Lorentz factor considering a two-zone model, wherein the TeV photons originate from the external shock region while the lower-energy MeV photons come from the internal prompt emission region. By properly accounting for the evolution of the MeV photon spectrum and light curve, we calculate the optical depth for TeV photons and derive a minimum Lorentz factor of about 300. It is consistent with the afterglow modeling for the TeV emission.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/acfed1