Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 21674

LIGO/Virgo G298048: H.E.S.S. very-high energy gamma-ray follow-up
2017-08-24T10:35:02Z (7 years ago)
Fabian Schussler at HESS Observatory <>
M. de Naurois on behalf of the H.E.S.S. collaboration

The H.E.S.S. array of imaging atmospheric Cherenkov telescopes was used to carry out follow-up observations of the GW trigger G298048 (GCN #21509) and monitoring of the possible counterpart SSS17a/DLT17ck (Coulter et al. GCN #21529; Yang et al., GCN #21531).
H.E.S.S. observations started August 17 at 18:00 UTC with three pointings derived from the HLV-Bayestar map (GCN #21513) without assumptions on the orientation of the system and cross correlated in three dimensions with the GLADE catalog [1]. The first of these pointings covered the region of NGC 4993 and the potential EM counterpart SSS17a/DLT17ck. We continued to monitor the region around SSS17a/DLT17ck during the following nights until the location moved outside the H.E.S.S. visiblity window. The last pointing was taken August 22, 18:00 UTC.
Each of our observations has a sensitivity of about 20% of the flux from the Crab nebula at 5 sigma. A preliminary analysis with an energy threshold of about 500GeV did not reveal significant gamma-ray emission in any of the datasets. Further analyses of the data are on-going.

H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes for the detection of very-high-energy gamma-ray sources and is located in the Khomas Highlands in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, the Czech Republic, France, Germany, Ireland, Netherlands, Japan, Poland, South Africa, Sweden, UK, and the host country, Namibia. For more details see

[1] GLADE website:
Looking for U.S. government information and services? Visit