GRB ID	Triggering instrument	Alert time (T0)	GRB RA (J2000)	GRB Dec (J2000)	H.E.S.S. window start	H.E.S.S. window end	Obs mode	Reaction	Contact

Summary

The above table summarizes H.E.S.S. GRB observations since the most recent camera upgrade in late 2019. It includes completed observations as well as planned ones. Please note that planned observations are subject to external effects such as weather conditions and technical difficulties, as well as burst advocate decisions, and are not guaranteed. In general, the H.E.S.S. burst advocate who is on call for a particular GRB will modify the table the morning after observations have been taken; after this point, the table elements will reflect the actual observations and not the planned ones.

The current H.E.S.S. GRB observation policy is to observe all well-localized GRBs that can be observed within 24 hours of the GRB trigger time, for the entirety of the observable window on the first night. H.E.S.S. also observes a subset of GRBs with larger localization uncertainties using a tiled observing pattern. We observe around 20-25 GRBs per year, of which roughly three quarters are observed with pointed observations and a quarter with tiled observations. In general, a small fraction of GRBs that pass our observing criteria are never observed due to burst advocate decision. Possible reasons are: The delay time is long and the observable window is short; the GRB notice was later retracted; the GRB was determined to be at a large redshift.

For questions or comments, including requests for more information on a particular GRB, please email contact.hess@hess-experiment.eu.

For general information about H.E.S.S. see https://www.mpi-hd.mpg.de/hfm/HESS/.

Explanations of columns

• GRB ID: GRB identifier from the triggering instrument (derived from automated notices) and/or the full alphanumeric name where applicable (manually entered)
• Triggering instrument: The GRB detector whose notification triggered H.E.S.S.; this is usually the detector with the best available localization at the time of the H.E.S.S. observations
• Alert time (T0): Trigger time of the GRB, for the triggering instrument, in UTC
• GRB RA (J2000), GRB Dec (J2000): Localization of the GRB by the triggering instrument, right ascension and declination, in both degrees and hms/dms. For tiled observations, this is the position of the first tile that H.E.S.S. observed or plans on observing.
• H.E.S.S. window start, H.E.S.S. window end: Either: The start and end of the time period when the GRB is visible to H.E.S.S. (usually below 60° zenith angle, sometimes below 45°) OR the start and end of the time period during which H.E.S.S. observed the GRB
• Obs mode: H.E.S.S. observation mode, either Pointed (for all well-localized GRBs) or Tiled (for GRBs with larger localization regions)
• Reaction: H.E.S.S. array reaction mode, either Automatic (for GRBs with very short observation delays) or Manual
• Contact: The name of the H.E.S.S. burst advocate for this GRB