.The presence of delayed GeV emission after a strong transient, such as a GRB (Gamma-Ray Burst), in the VHE (Very-High Energy, E > 100 GeV) band can be the signature of a non-zero magnetic field in the intergalactic medium. We used a synchrotron self-Compton multiwavelength model to infer an analytical description of the intrinsic VHE spectrum (corrected for absorption by the Extragalactic Background Light, EBL) of GRB 190114C to predict the lightcurves and SEDs of the delayed emission with Monte Carlo simulations for different IGMF (Intergalactic Magnetic Field) configurations (strengths B = 8×10−21 G, 10−20 G, 3×10−20G and correlation length λ > 1 Mpc), and compared them with the Fermi-LAT (Fermi Large Area Telescope) limits computed for several exposure times. We found that Fermi LAT is not sensitive enough to constrain any IGMF strengths using GRB 190114C.
