Search of the pair echo signatures in the high-energy light curve of GRB190114C

Abstract: A model of the time delayed electromagnetic cascade "echo" is applied to the bright gamma-ray burst GRB190114C - the first gamma-ray burst to be contemporaneously detected in high and very high energy gamma-ray bands. It is shown that the internal spread of the cascade in the absence of the intervening magnetic fields dilutes the "echo" emission over $10^3-10^5$ seconds depending on the energy. Accounting for the measured source flux in the $0.3-1$ TeV gamma-ray band, the prediction of the "echo" model is shown to match the detected lower-energy gamma-ray emission $10^4$ seconds after the burst. However, the "echo" emission remains indistinguishable from the intrinsic GRB190114C flux within the measurement uncertainties. Implications of this in the context of the intergalactic magnetic field measurement are discussed.