The Late-time X-ray Behavior of Short Gamma-ray Bursts: Implications for Energetics and Rates

Chandra TOO observations are uniquely suited to determine the SGRB opening angle distribution. Here, we propose to utilize the sensitivity of Chandra to measure a jet break in the afterglow of a SGRB. We request a pair of TOO observations of a SGRB with a bright X-ray afterglow, on timescales of �3-7 days and �15-25 days to probe a range of �j� > 5-20 degrees. The detection of a break will directly lead to an opening angle measurement, while a non-detection will place a meaningful lower limit.