Detection of very-high-energy gamma-ray emission from the FSRQ PKS 1725+123 with H.E.S.S.
ATel #17346; Stefan Wagner for the H. E.S. S. collaboration
on 20 Aug 2025; 15:06 UT
Credential Certification: Fabian Schüssler (fabian.schussler@cea.fr)
Subjects: >GeV, TeV, VHE, AGN
The flat-spectrum radio quasar PKS 1725+123 (J2000: R.A. 17h28m07s, DEC +12d15m39s; redshift 0.586) has been reported as active in the high-energy gamma-ray and infrared bands throughout the year (ATels #17094, #17127, #17316). Following an alert of the Fermi-LAT data monitoring pipeline FlaapLUC (Lenain, 2018, A&C, 22, 9), the High Energy Stereoscopic System (H.E.S.S.) observed this source in the night 19-20 August (JD 2460907) for almost 3h. The preliminary onsite analysis results in a significance of more than 6 sigma. This confirms the discovery at very-high energies by MAGIC and LST-1 (ATel #17344), and is the first time H.E.S.S. has detected the source.
As PKS 1725+123 also flares in the optical domain (ATel #17345), multiwavelength observations are strongly encouraged. H.E.S.S. plans to continue observation in the upcoming nights.
H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes to study very-high-energy gamma-ray sources above an energy of 50 GeV. H.E.S.S. is located in the Khomas Highlands in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, Denmark, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, UK, and the host country, Namibia.
