TeV flaring activity of the AGN PKS 0625–354 in November 2018

Journal article

Most γ-ray detected active galactic nuclei are blazars with one of their relativistic jets pointing towards the Earth. Only a few objects belong to the class of radio galaxies or misaligned blazars. Here, we investigate the nature of the object PKS 0625−354, its γ-ray flux and spectral variability and its broad-band spectral emission with observations from H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S. light curve above 200 GeV shows an outburst in the first night of observations followed by a declining flux with a halving time scale of 5.9 h. The γγ-opacity constrains the upper limit of the angle between the jet and the line of sight to ∼10◦. The broad-band spectral energy distribution shows two humps and can be well fitted with a single-zone synchrotron self Compton emission model. We conclude that PKS 0625−354, as an object showing clear features of both blazars and radio galaxies, can be classified as an intermediate active galactic nuclei. Multi-wavelength studies of such intermediate objects exhibiting features of both blazars and radio galaxies are sparse but crucial for the understanding of the broad-band emission of γ-ray detected active galactic nuclei in general.

Authors: Aharonian, F; Benkhali, FA; Aschersleben, J; Ashkar, H; Backes, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: EDP Sciences
• Journal: Astronomy & Astrophysics
• Volume: 683
• Pages: A70-A70
• Publication date: 2024-03-06
• Acceptance date: 2023-12-26
• DOI: 10.1051/0004-6361/202348063
• EISSN: 1432-0746
• ISSN: 0004-6361
• Language: English
• Keywords: Physics; Radio galaxy; Active galactic nucleus; Flux (metallurgy); Astronomy; Light curve; Opacity; Line-of-sight; BL Lac object; Gamma ray; Astrophysics; Spectral energy distribution; Blazar; Galaxy; Fermi Gamma-ray Space Telescope