Gamma Ray Bursts from the early Universe: predictions for present-day and future instruments

TL;DR

This paper analyzes the characteristics needed for instruments to detect high-redshift Gamma Ray Bursts, compares current and planned missions, and predicts their capabilities to observe GRBs beyond redshift 6.

Contribution

It identifies key instrument features for detecting early universe GRBs and evaluates the potential of upcoming missions to observe these distant phenomena.

Findings

Swift can detect GRBs at z>6 and possibly z>10 with lower thresholds.

INTEGRAL and GLAST are less effective for high-z GRB detection due to FOV and sensitivity.

Future missions like EXIST will significantly improve high-z GRB observations.

Abstract

Long Gamma Ray Bursts (GRBs) constitute an important tool to study the Universe near and beyond the epoch of reionization. We delineate here the characteristics of an 'ideal' instrument for the search of GRBs at z>6-10. We find that the detection of these objects requires soft band detectors with a high sensitivity and moderately large FOV. In the light of these results, we compare available and planned GRB missions, deriving conservative predictions on the number of high-z GRBs detectable by these instruments along with the maximum accessible redshift. We show that the Swift satellite will be able to detect various GRBs at z>6, and likely at z>10 if the trigger threshold is decreased by a factor of ~2. Furthermore, we find that INTEGRAL and GLAST are not the best tool to detect bursts at z>6: the former being limited by the small FOV, and the latter by its hard energy band and relatively low sensitivity. Finally, future missions (SVOM, EDGE, but in particular EXIST) will provide a good sample of GRBs at z>6 in a few years of operation.