TeV flaring activity of the AGN PKS 0625–354 in November 2018
Authors:   H.E.S.S. Collaboration, Aharonian F. , Ait Benkhali F. , Aschersleben J. , Ashkar H. , Backes M. , Baktash A. , Barbosa Martins V. , Barnard J. , Batzofin R. , Becherini Y. , Berge D. , Bernlöhr K. , Bi B. , Böttcher M. , Boisson C. , Bolmont J. , de Bony de Lavergne M. , Borowska J. , Bradascio F. , Breuhaus M. , Brose R. , Brown A. , Brun F. , Bruno B. , Bulik T. , Burger-Scheidlin C. , Bylund T. , Caroff S. , Casanova S. , Cecil R. , Celic J. , Cerruti M. , Chand T. , Chandra S. , Chen A. , Chibueze J. , Chibueze O. , Cotter G. , Damascene Mbarubucyeye J. , Davids I. D. , Djuvsland J. , Dmytriiev A. , Doroshenko V. , Egberts K. , Einecke S. , Ernenwein J.-P. , Fontaine G. , Füßling M. , Funk S. , Gabici S. , Ghafourizadeh S. , Giavitto G. , Glawion D. , Glicenstein J. F. , Glombitza J. , Goswami P. , Grolleron G. , Haerer L. , Hinton J. A. , Holch T. L. , Holler M. , Horns D. , Jamrozy M. , Jankowsky F. , Joshi V. , Jung-Richardt I. , Kasai E. , Katarzyński K. , Khatoon R. , Khélifi B. , Kluźniak W. , Komin Nu. , Kosack K. , Kostunin D. , Lang R. G. , Le Stum S. , Leitl F. , Lemière A. , Lenain J.-P. , Leuschner F. , Luashvili A. , Mackey J. , Marx R. , Mehta A. , Meyer M. , Mitchell A. , Moderski R. , Montanari A. , Moulin E. , de Naurois M. , Niemiec J. , O’Brien P. , Ohm S. , Olivera-Nieto L. , de Ona Wilhelmi E. , Ostrowski M. , Panny S. , Parsons R. D. , Pita S. , Prokhorov D. A. , Pühlhofer G. , Punch M. , Quirrenbach A. , Reichherzer P. , Reimer A. , Reimer O. , Ren H. , Rieger F. , Rudak B. , Sahakian V. , Salzmann H. , Sanchez D. A. , Sasaki M. , Schüssler F. , Schutte H. M. , Shapopi J. N. S. , Sol H. , Specovius A. , Spencer S. , Stawarz Ł. , Steenkamp R. , Steinmassl S. , Streil K. , Sushch I. , Suzuki H. , Takahashi T. , Tanaka T. , van Eldik C. , Vecchi M. , Veh J. , Venter C. , Wagner S. J. , Wierzcholska A. , Zacharias M. , Zargaryan D. , Zdziarski A. A. , Zech A. , Zouari S. , Żywucka N. 
Published: March 2024

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.