H.E.S.S. detection and multi-wavelength study of the z ∼ 1 blazar PKS 0346−27
Year: 2026
Type: article
Abstract: Context. PKS 0346-27 is a low synchrotron peaked blazar at redshift 0.991. The very high energy (VHE; E > 100 GeV) spectra of blazars are always affected by γγ absorption by the extragalactic background light (EBL), and subsequently no blazars have been detected in VHE γ -rays at redshifts exceeding 1. Aims. This is the goal of a target-of-opportunity (ToO) programme by H.E.S.S.: to observe flaring high-redshift ( z ≳ 1) blazars. Importantly, extending the redshift range of VHE-detected blazars to z ≳ 1 will yield insights into the cosmological evolution of both the VHE blazar population and the EBL. Methods. We report H.E.S.S. ToO and multi-wavelength observations of the blazar PKS 0346−27. We analysed and modelled the H.E.S.S. data together with simultaneous data from Fermi -LAT, Swift (XRT and UVOT), using single-zone leptonic and hadronic models. Results. PKS 0346-27 was detected by H.E.S.S. at a significance of 6.3 σ during one night on 3 November 2021, while for other nights before and after this day, upper limits on the VHE flux have been determined. No evidence for intra-night γ -ray variability has been found. A flare in high-energy ( E > 100 MeV) γ -rays detected by Fermi -LAT preceded the H.E.S.S. detection by 2 days. A fit with a single-zone emission model to the contemporaneous spectral energy distribution during the detection night was possible with a proton-synchrotron-dominated hadronic model, requiring a proton-kinetic-energy-dominated jet power temporarily exceeding the source’s Eddington limit, although alternative (e.g. multi-zone) models cannot be ruled out. A one-zone leptonic model is, in principle, also able to fit the flare-state spectral energy distribution. However, it requires implausible parameter choices, in particular, extreme Doppler and bulk Lorentz factors of ≳80.
Source: Astronomy and Astrophysics
Authors: F. Aharonian, M. Backes, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, B. Bi, M. Böttcher, C. Boisson, J. Bolmont, F. Brun, B. Bruno, C. Burger-Scheidlin, D. Cecchin Momesso, J. Celic, M. Cerruti, A. Chen, M. Chernyakova, J. O. Chibueze, O. Chibueze, B. Cornejo, G. Cotter, J. Damascene Mbarubucyeye, I. D. Davids, J. de Assis Scarpin, M. de Bony de Lavergne, M. de Naurois, E. de Oña Wilhelmi, A. G. Delgado Giler, J. Devin, A. Djannati-Ataï, A. Dmytriiev, K. Egberts, K. Egg, J.-P. Ernenwein, C. Esca nuela Nieves, K. Feijen, M. D. Filipovic, G. Fontaine, S. Funk, S. Gabici, M. Genaro, J. F. Glicenstein, J. Glombitza, P. Goswami, L. Heckmann, B. Hess, J. A. Hinton, W. Hofmann, T. L. Holch, M. Holler, D. Horns, M. Jamrozy, F. Jankowsky, I. Jaroschewski, I. Jung-Richardt, K. Kasprzak, K. Katarzyński, D. Kerszberg, B. Khélifi, N. Komin, K. Kosack, D. Kostunin, R. G. Lang, S. Lazarević, A. Lemière, J.-P. Lenain, P. Liniewicz, A. Luashvili, J. Mackey, D. Malyshev, V. Marandon, M. Mayer, A. Mehta, A. M. W. Mitchell, R. Moderski, L. Mohrmann, A. Montanari, E. Moulin, J. Niemiec, M. O. Moghadam, S. Panny, R. D. Parsons, U. Pensec, P. Pichard, T. Preis, G. Pühlhofer, M. Punch, A. Quirrenbach, A. Reimer, O. Reimer, I. Reis, B. Rudak, K. Sabri, V. Sahakian, D. Jimeno, A. Santangelo, M. Sasaki, F. Schüssler, J. N. S. Shapopi, W. Si Said, Ł. Stawarz, S. Steinmassl, T. Takahashi, T. Tanaka, A. M. Taylor, G. L. Taylor, R. Terrier, T. Unbehaun, C. van Eldik, M. Vecchi, C. Venter, J. Vink, T. Wach, S. J. Wagner, A. Wierzcholska, M. Zacharias, A. Zech, W. Zhong
Institutions: Dublin Institute For Advanced Studies, Max Planck Institute for Nuclear Physics, University of Namibia, North-West University, University of Potsdam, Centre National de la Recherche Scientifique, Université Paris Cité, Linnaeus University, Deutsches Elektronen-Synchrotron DESY, Humboldt-Universität zu Berlin, University of Tübingen, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Laboratoire de Physique Nucléaire et de Hautes Énergies, Institut National de Physique Nucléaire et de Physique des Particules, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, CEA Paris-Saclay - Etablissement de Saclay, Institut de Recherche sur les Lois Fondamentales de l'Univers, Friedrich-Alexander-Universität Erlangen-Nürnberg, University of the Witwatersrand, Dublin City University, University of Oxford, École Polytechnique, Institut Polytechnique de Paris, Laboratoire Leprince-Ringuet, Aix-Marseille Université, Centre de physique des particules de Marseille, Université de Montpellier, Laboratoire Univers et Particules de Montpellier, Western Sydney University, Heidelberg University, Universität Innsbruck, Universität Hamburg, Jagiellonian University, Nicolaus Copernicus University, Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Institute of Physics, Institute of Nuclear Physics, Polish Academy of Sciences, A. Alikhanyan National Laboratory, Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Konan University, University of Groningen, University of Amsterdam
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Funders: Alexander von Humboldt-Stiftung, National Research Foundation, Science Foundation Ireland, Deutsche Forschungsgemeinschaft, Universiteit van Amsterdam, Irish Research Council, Bundesministerium für Bildung und Forschung, Austrian Science Fund, Knut och Alice Wallenbergs Stiftelse, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, National Commission on Research, Science and Technology, University of Namibia, Bundesministerium für Bildung, Wissenschaft und Forschung, Science and Technology Facilities Council, Japan Society for the Promotion of Science, Institut National de Physique Nucléaire et de Physique des Particules
Awards: G196419191, G2591624031, G6649312515
OpenAlex ID: W7123510009