Journal Article

PUBDB-2026-02096

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png H.E.S.S. detection and multi-wavelength study of the z ∼ 1 blazar PKS 0346−27

Aharonian, F. ; Backes, M. ; Batzofin, R. ; Becherini, Y. ; Berge, D.DESY* ; Bernlöhr, K. ; Bi, B. (Corresponding author) ; Böttcher, M. (Corresponding author) ; Boisson, C. ; Bolmont, J.DESY* ; Brun, F. ; Bruno, B. ; Burger-Scheidlin, C. ; Cecchin Momesso, D. ; Celic, J. ; Cerruti, M. ; Chen, A. ; Chernyakova, M. ; Chibueze, J. O. ; Chibueze, O. (Corresponding author) ; Cornejo, B. ; Cotter, G. ; Damascene Mbarubucyeye, J. ; Davids, I. D. ; de Assis Scarpin, J. ; de Bony de Lavergne, M. ; de Naurois, M. ; de Ona Wilhelmi, E. M.DESY* ; Delgado Giler, A. G. ; Devin, J. ; Djannati-Ataï, A. ; Dmytriiev, A. ; Egberts, K.Extern* ; Egg, K. ; Ernenwein, J.-P. ; Esca nuela Nieves, C. ; Feijen, K. ; Filipovic, M. D. ; Fontaine, G. ; Funk, S. ; Gabici, S. ; Genaro, M. ; Glicenstein, J. F. ; Glombitza, J. ; Goswami, P. ; Heckmann, L. ; Hess, B. ; Hinton, J. A. ; Hofmann, W. ; Holch, T. L.DESY* ; Holler, M. ; Horns, D. ; Jamrozy, M. ; Jankowsky, F. ; Jaroschewski, I. ; Jung-Richardt, I. ; Kasprzak, K. ; Katarzyński, K. ; Kerszberg, D. ; Khélifi, B. ; Komin, N. ; Kosack, K. ; Kostunin, D.DESY* ; Lang, R. G. ; Lazarević, S. ; Lemière, A. ; Lenain, J.-P. ; Liniewicz, P. ; Luashvili, A. ; Mackey, J. ; Malyshev, D. ; Marandon, V. ; Mayer, M. ; Mehta, A. ; Mitchell, A. M. W. ; Moderski, R. ; Mohrmann, L.XFEL.EU* ; Montanari, A. ; Moulin, E. ; Niemiec, J. ; Moghadam, M. O. ; Panny, S. ; Parsons, R. D.Extern* ; Pensec, U. ; Pichard, P. ; Preis, T. ; Pühlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Reimer, A. ; Reimer, O. ; Reis, I. ; Rudak, B. ; Sabri, K. ; Sahakian, V. ; Jimeno, D. ; Santangelo, A. ; Sasaki, M. ; Schüssler, F. ; Shapopi, J. N. S. ; Si Said, W. ; Stawarz, Ł. ; Steinmassl, S. ; Takahashi, T. ; Tanaka, T. ; Taylor, A. M. ; Taylor, G. L. ; Terrier, R. ; Unbehaun, T. ; van Eldik, C. ; Vecchi, M. ; Venter, C. ; Vink, J. ; Wach, T. ; Wagner, S. J. ; Wierzcholska, A. ; Zacharias, M. ; Zech, A. ; Zhong, W.DESY*

2026
EDP Sciences Les Ulis

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Please use a persistent id in citations: doi:10.1051/0004-6361/202557228  doi:10.3204/PUBDB-2026-02096

Report No.: arXiv:2512.24228

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 6.3σ 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.Key words: radiation mechanisms: non-thermal / relativistic processes / galaxies: active / galaxies: individual: PKS 0346–27 / galaxies: jets / quasars: generalPublisher note: The year of the acceptance date was corrected to '2025' in the PDF file on 17 February 2026.

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Contributing Institute(s):

1. Gammaastronomie (Z_GA)
2. High Energy Steroscopic System (Z_HESS)
3. Datenverarbeitung (Z_DV)

Research Program(s):

1. 613 - Matter and Radiation from the Universe (POF4-613) (POF4-613)

Experiment(s):

1. High Energy Stereoscopic System

Appears in the scientific report 2026

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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