Optimizing Searches for Rare Transients

Author: David Burrows

Abstract: We discuss the optimization of gamma-ray burst (GRB) detectors with a goal of maximizing the detected number of bright high-redshift GRBs, in the context of design studies conducted for an X-ray transient detector on a future mission. We conclude that the optimal energy band for detection of high-z GRBs is below about 30 keV. We considered both lobster-eye and coded aperture designs operating in this energy band. Within the available mass and power constraints, we found that the coded aperture mask was preferred for the detection of high-z bursts with bright enough afterglows to probe galaxies in the era of the Cosmic Dawn. This initial conclusion was confirmed through detailed mission simulations that found that the selected design (an X-ray Coded Aperture Telescope) would detect four times as many bright, high-z GRBs as the lobster-eye design we considered. Such an instrument could detect ∼48 GRBs with z > 5 and fluence Sx > 3×10-7 erg cm-2 in a two year mission.