Speaker
Description
A cosmological origin of magnetic fields in large-scale structures implies the existence of a weak intergalactic magnetic field (IGMF) in cosmic voids, which remains undetected. High-energy gamma rays from distant transients, provide an indirect probe: during propagation, TeV γ-rays initiate electromagnetic cascades whose charged components are deflected by the IGMF, producing a characteristic time-delayed emission at GeV energies.
The most stringent lower limits to date, derived from gamma-ray bursts (GRBs) observed with the Fermi-LAT, reach B ≳ 10⁻¹⁷ G, but depend on assumptions about the intrinsic temporal behaviour of the source emission.
In this work, we introduce a novel binned likelihood framework to analyse time delays in gamma-ray light curves, removing the need for assumptions on the intrinsic variability of the source. This approach enables a more robust and conservative determination of IGMF constraints.
We apply this method to simulated and observed light curves of transient sources, including GRBs and active galactic nuclei (AGN) flares, across a range of redshifts, in the context of observations with the Cherenkov Telescope Array Observatory, in particular its Large-Sized Telescopes (LSTs). Leveraging its unprecedented sensitivity at very high energies, our approach allows us to constrain the IGMF strength within the range B ~ 10⁻²⁰ - 10⁻¹⁶ G under minimal assumptions, significantly improving upon current limits.
