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Sezione
HEP Colloquia 2025
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Europe/Rome
Sala Consiliare (Department of Physics)
Sala Consiliare
Department of Physics
Description
Systematic Study of Gamma-ray Bursts Prompt Emission Spectra from keV to GeV Energies: Implications for Prompt and Early TeV Detections
The prompt emission of gamma-ray bursts (GRBs) is widely believed to originate from electrons accelerated to non-thermal energies in internal shocks, producing spectra that typically peak in the keV–MeV range. Over the past 15 years of Fermi-LAT operations, numerous GRBs have exhibited high-energy (HE; GeV) gamma-ray emission temporally coincident with the prompt phase but displaying diverse spectral properties. While this GeV emission has often been attributed to early afterglow radiation, our systematic analysis provides new insights.
I present results from a comprehensive study of GRBs jointly detected by Fermi/GBM and Fermi/LAT during the prompt emission phase, employing a physical synchrotron model to interpret the broadband (keV–GeV) spectra. The temporal and spectral analyses reveal that, in many cases, the GeV emission forms part of the main prompt spectral component. However, in other bursts, the GeV photons are associated with a distinct high-energy spectral component, potentially extending into the very-high-energy (VHE; TeV) domain.
I will discuss the physical origin of these GeV photons and the implications of such a secondary spectral component in the context of upcoming Cherenkov Telescope Array Observatory (CTAO) observations. Particular emphasis will be placed on the case of GRB 221009A, where the identification of a secondary component -- through extensive broadband modeling using data from Fermi/GBM, KONUS, Fermi/LAT, AGILE, and LHAASO -- offers valuable insights into the nature of prompt and early VHE emission.
I present results from a comprehensive study of GRBs jointly detected by Fermi/GBM and Fermi/LAT during the prompt emission phase, employing a physical synchrotron model to interpret the broadband (keV–GeV) spectra. The temporal and spectral analyses reveal that, in many cases, the GeV emission forms part of the main prompt spectral component. However, in other bursts, the GeV photons are associated with a distinct high-energy spectral component, potentially extending into the very-high-energy (VHE; TeV) domain.
I will discuss the physical origin of these GeV photons and the implications of such a secondary spectral component in the context of upcoming Cherenkov Telescope Array Observatory (CTAO) observations. Particular emphasis will be placed on the case of GRB 221009A, where the identification of a secondary component -- through extensive broadband modeling using data from Fermi/GBM, KONUS, Fermi/LAT, AGILE, and LHAASO -- offers valuable insights into the nature of prompt and early VHE emission.
Organised by
Prof. Umberto D'Alesio - umberto.dalesio@ca.infn.it
Dr. Nanako Kato - nanako.kato@dsf.unica.it
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