X-ray Flares in Gamma-Ray Bursts at High and Very-High-Energies

@misc{tiwari2026xray,
  title = {{X-ray Flares in Gamma-Ray Bursts at High and Very-High-Energies}},
  author = {Pawan Tiwari and Biswajit Banerjee and Gor Oganesyan and Ansh Chopra and Annarita Ierardi and Marica Branchesi and Stefano Ascenzi and Maria Edvige Ravasio},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.00684},
  eprint = {2609.00684},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.00684},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - X-ray Flares in Gamma-Ray Bursts at High and Very-High-Energies
AU  - Pawan Tiwari
AU  - Biswajit Banerjee
AU  - Gor Oganesyan
AU  - Ansh Chopra
AU  - Annarita Ierardi
AU  - Marica Branchesi
AU  - Stefano Ascenzi
AU  - Maria Edvige Ravasio
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.00684
UR  - https://arxiv.org/abs/2609.00684
AB  - A significant fraction of GRB early afterglows exhibit fast and bright X-ray flares, discovered by Swift X-ray Telescope. Their rapid temporal variability and spectral evolution have suggested an internal shock origin, analogous to prompt MeV emission. However, their physical origin and radiation mechanism remain debated. High-energy (> 100 MeV) and very-high-energy (> 30 GeV) gamma-ray observations provide a powerful probe of flare dissipation region, constraining its size, magnetic field strength, and particle acceleration under the synchrotron self-Compton scenario in optically thin relativistic jets. We present a systematic multi-wavelength study of 66 X-ray flares from 47 GRBs observed by X-ray Telescope over 17 years, all within field of view of Fermi Large Area Telescope. We investigate their GeV counterparts and find that only five flares exhibit significant high-energy emission (> 3 sigma). Broadband spectral modeling indicates that this GeV emission is consistent with standard forward shock afterglow. We further investigate correlations between flare spectral properties and energy fluxes at 1 keV, 10 keV, and 1 GeV. Using a synchrotron self-Compton model, we constrain the physical conditions of the emitting region, including magnetic field strength, bulk Lorentz factor, and emission radius. For the most stringent GeV upper limits, we find a magnetic-to-electron luminosity ratio greater than or equal to 1, implying a highly magnetized emitting region. We predict very-high-energy gamma-ray emission from X-ray flares at early (~500s) and late (~5000s) times and assess their detectability with Cherenkov Telescopes. We find that later X-ray flares provide the most promising targets for follow-up observations owing to improved observational accessibility, sensitivity, and reduced response-time constraints of facilities such as Cherenkov Telescope Array Observatory.
ER  -