Detectivity of Fe Kα Lines in Gamma-RayBursts by Cerenkov Line Mechanism

Abstract

The Fe Kα lines in gamma-ray bursts (GRBs) produced withthe Cerenkov line mechanism are studied. We theoretically predictthe Fe Kα line luminosities in both the early (before 1hour) and late (~1 day) afterglows. Assuming about 200 GRBscould be detected by Swift per year, we sampled the redshiftof these GRBs using the Monte Carlo method according to the GRBformation rate derived from the statistical correlation betweenthe spectral peak energy and the peak luminosity of GRBs. Then weobtain the Fe Kα line flux distributions of the simulatedGRB sample in the early and late phases. The simulated resultsshow that the iron line flux is relatively low, so theline detection would be still a rare event at present. Inaddition, our results suggest that the iron lines from GRBs couldbe detected in the high redshift: z~3 for the early phaseand z~6 for the late phase. Therefore, it is possible thatthe identification of Fe Kα lines in GRBs provides a toolto directly measure redshift and to study the high-redshift GRBs in theSwift era.