H.E.S.S. and ATOM detection of renewed activity of the FSRQ 3C 279

ATel #11680; Mathieu de Naurois for the H. E.S. S. Collaboration
on 4 Jun 2018; 14:05 UT
Credential Certification: Michael Zacharias (m.zacharias@lsw.uni-heidelberg.de)

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H.E.S.S. observations at very-high energies (E>100 GeV) of the flat spectrum radio quasar 3C 279 (reshift z=0.536, R.A.: 12h56m11.1665s, Dec: -05d47m21.523s (J2000)) have been carried out over the last 3 nights on the basis of another strong flare in the high-energy gamma-ray band (E>100 MeV) detected with Fermi-LAT. A preliminary online analysis of the data acquired with CT5 (monoscopic analysis; telescope diameter 28m) indicate for the night June 2-3 a significance of 5.7sigma (in 2hrs of observations), which has risen to 7.2 sigma in 3hrs of observations in the night June 3-4. The rate of events appears constant in both nights. H.E.S.S. will continue observations of 3C 279 over the next nights, and multiwavelength follow-up observations are strongly encouraged. Optical observations with ATOM show an increase of apparent R-band magnitude from 14.4 for the night May 28-29 to 13.5 for the night June 1-2. In the following two nights, the optical flux has been detected at this elevated level with variability within 0.3 magnitudes. Observations of 3C 279 will be continued. This is the third time that 3C 279 has been detected at very-high energies this year, with a detection by H.E.S.S. in January (ATel #11239) and by MAGIC in April (ATel #11545). During this time, 3C 279 also showed strong optical variability (e.g. ATel #11624). H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes for the detection of VHE gamma-ray sources. H.E.S.S. is located in the Khomas Highland in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, the Czech Republic, France, Germany, Ireland, Poland, South Africa, Sweden, UK, and the host country, Namibia. ATOM (Automatic Telescope for Optical Monitoring) is a 75cm telescope located at the H.E.S.S. site. It regularly monitors galactic and extragalactic gamma-ray emitters.