H.E.S.S. detection of the CSO PMN J1603-4904 at very-high-energy gamma rays
ATel #17205; Stefan J. Wagner (U Heidelberg, Germany), for the H. E.S. S. collaboration
on 25 May 2025; 17:09 UT
Credential Certification: Stefan J. Wagner (swagner@lsw.uni-heidelberg.de)
Subjects: Radio, Gamma Ray, >GeV, TeV, VHE, Request for Observations, AGN, Blazar, Quasar
PMN J1603-4904 is an active galactic nucleus at R.A. (J2000) 16h03m51s, DEC (J2000) -49d04'05" and at a redshift of z=0.23 (Goldoni et al., 2016, A&A 586, L2). It is a known GeV gamma-ray emitter (e.g., 1FHL,
Ackermann et al., 2013, ApJS 209, 34), but was so far not detected as a very-high-energy (E>100 GeV) gamma-ray source. Its radio morphology suggests that it is not a blazar but rather a compact symmetric object (CSO), as proposed in Mueller et al. (2014, A&A 562, 1).
H.E.S.S. conducted observations of the source in the night 23-24 May 2025 (JD 2460819) that lasted for 4h45min. The source was detected in the on-site analysis with a significance of 9 sigma. Observations one night later (24-25 May 2025, JD 2460820), lasting for another 4.75 hours, confirmed the detection (on-site significance of 8 sigma). In both nights the source is significantly brighter than in earlier observations with H.E.S.S.
H.E.S.S. will continue observations of this source over the next nights, and observations at other wavelengths are strongly encouraged. ToO observations have been granted with Swift and SVOM.
H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes to study 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, Denmark, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, UK, and the host country, Namibia.
