TITLE: GCN CIRCULAR NUMBER: 41095 SUBJECT: GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations DATE: 25/07/15 09:19:06 GMT FROM: Mathieu de Naurois at Laboratoire Leprince Ringuet, CNRS, Deputy Director of the H.E.S.S. Collaboration denauroi@in2p3.fr
The H.E.S.S. array of imaging atmospheric Cherenkov telescopes conducted follow-up observations of the transient EP250702a, at the localization provided by the EP-WXT (Cheng et al., GCN 40906). H.E.S.S. observed this source position for a total of 6 hours over 4 consecutive nights, starting on 2025-07-04, under fairly good observing conditions. A preliminary off-site analysis shows no evidence for a significant signal in either the full dataset or the four nights individually, consistent with the non-detection reported by the LST-1 and MAGIC telescopes (Paneque et al., GCN 41067). Our upper limits are expected to be compatible with the H.E.S.S. sensitivity curves (e.g., Fig. 6 of https://doi.org/10.22323/1.236.0847), scaled to the observation duration.
The observations took place during the following times: 2025-07-04, 00:06 - 03:01 UTC 2025-07-05, 00:48 - 02:19 UTC 2025-07-06, 01:41 - 03:08 UTC 2025-07-07, 02:36 - 03:00 UTC
H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes that detects very-high-energy gamma rays (>100 GeV) and is located in the Khomas Highland in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, Sweden, UK, and the host country, Namibia. For more details see https://hess.in2p3.fr/.
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