H.E.S.S. detects high VHE gamma-ray flux in PG 1553+113
ATel #12641; Mathieu de Naurois for the H. E.S. S. Collaboration
on 8 Apr 2019; 14:44 UT
Credential Certification: Michael Zacharias (mz@tp4.rub.de)
Subjects: TeV, VHE, AGN, Blazar
Following previous reports of high optical flux from the high-peaked BL
Lac object PG 1553+113 (#12631, #12635), the High Energy Stereoscopic
System (H.E.S.S.) performed very-high energy gamma-ray (VHE, E>100 GeV)
observations during the night of 8 April 2019 (00:20 until 03:30 UTC).
The preliminary results of the real-time analysis indicate a flux above
100 GeV of 2.7E-10 ph/cm^2/s corresponding to about 40% of the Crab
Nebula above the same energy threshold. This is brightest VHE flux
measured since 2012, when MAGIC observed a peak flux of 3.2E-10
ph/cm^2/s calculated for the same energy threshold (Aleksic 2015, MNRAS, 450, 4399).
While PG 1553+113 supposedly shows periodic brightening in a cycle of about 800 days (inferred from the GeV domain probed with Fermi-LAT), this maximum seems to be brighter than previous high states, and a broad multiwavelength coverage is strongly encouraged. H.E.S.S. will continue its observations over the next nights.
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, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, Sweden, UK, and the host country, Namibia.
