Intergalactic magnetic field studies by means of γ -ray emission from GRB 190114C

Abstract

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 $B=8\times10^{-21}$ G, $10^{-20}$ G, $3\times 10^{-20}$G and correlation length $\lambda>1$ 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.