Prospective Annual Detection Rate of High-energy Gamma-Ray Bursts with LHAASO-WCDA

Abstract

Abstract Gamma-ray bursts (GRBs) are considered one of the most violent, explosive events in the universe and serve as high-redshift probes for cosmological study due to their high-energy observations. Such observations, particularly in the GeV regime, have already proven fruitful for deriving useful scientific results, such as the determination of extragalactic background light (EBL) and the stringent constraint on the Lorentz invariance violation effect. Owing to the advantages of a very large effective area, a low threshold energy, a wide field of view, and high duty cycle, the upcoming Large High Altitude Air Shower Observatory–Water Cerenkov Detector Array (LHAASO-WCDA) will have potential sensitivity for discovering GRBs in the 100 GeV energy region. In this work, a sample of GRBs has been generated and examined based on existing observations reported by the Large Area Telescope on board the Fermi satellite. The Fermi spectra are extrapolated to high energy by taking into account the absorption due to the pair production processes occurring between γ rays and EBL. With an assumption that an ultrahigh-energy component accounts for 10% of the total luminosity, it is found that LHAASO-WCDA has a GRB detection rate of ∼one GRB per year.