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, Bernlöhr K, Bi B, Böttcher M, Boisson C, Bolmont J, Brun F, Bruno B, Burger-Scheidlin C, Cecchin Momesso D, Celic J, Cerruti M, Chen A, Chernyakova M, Chibueze JO, Chibueze O, Cornejo B, Cotter G, Damascene Mbarubucyeye J, Davids ID, De Assis Scarpin J, De Bony De Lavergne M, De Naurois M, De Oña Wilhelmi E, Delgado Giler AG, Devin J, Djannati-Ataï A, Dmytriiev A, Egberts K, Egg K, Ernenwein JP, Esca Nuela Nieves C, Feijen K, Filipovic MD, Fontaine G, Funk S, Gabici S, Genaro Dantas Xavier M, Glicenstein JF, Glombitza J, Goswami P, Heckmann L, Hess B, Hinton JA, Hofmann W, Holch TL, Holler M, Horns D, Jamrozy M, Jankowsky F, Jaroschewski I, Jung-Richardt I, Kasprzak K, Katarzyåà  Ski K, Kerszberg D, Khelifi B, Komin N, Kosack K, Kostunin D, Guedes Lang R, Lazareviä S, Lemière A, Lenain JP, Liniewicz P, Luashvili A, Mackey J, Malyshev D, Marandon V, Mayer M, Mehta A, Mitchell A, Moderski R, Mohrmann L, Montanari A, Moulin E, Niemiec J, Moghadam MO, Panny S, Parsons RD, 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 JN, Si Said W, Stawarz L, Steinmassl S, Takahashi T, Tanaka T, Taylor AM, Taylor GL, Terrier R, Unbehaun T, van Eldik C, Vecchi M, Venter C, Vink J, Wach T, Wagner SJ, Wierzcholska A, Zacharias M, Zech A, Zhong W (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Book Volume: 706

Article Number: A246

DOI: 10.1051/0004-6361/202557228

Abstract

Context. PKS 0346-27 is a low synchrotron peaked blazar at redshift 0.991. The very high energy (VHE; Ea >a 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 (za a ³a 1) blazars. Importantly, extending the redshift range of VHE-detected blazars to za a 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 0346a 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 6.3I 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 (Ea >a 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 sourceas 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 a ³80.

Authors with CRIS profile

Involved external institutions

University of Namibia (UNAM) Namibia (NA) Max-Planck-Institut für Kernphysik (MPIK) / Max Planck Institute for Nuclear Physics Germany (DE) Institute of Research into the Fundamental Laws of the Universe / Institut de recherche sur les lois fondamentales de l'univers (IRFU) France (FR) Sorbonne Université France (FR) Humboldt-Universität zu Berlin Germany (DE) Leopold-Franzens-Universität Innsbruck / University of Innsbruck Austria (AT) Deutsches Elektronen-Synchrotron DESY Germany (DE) University of Montpellier / Université Montpellier France (FR) Ruprecht-Karls-Universität Heidelberg Germany (DE) DIAS Dunsink Observatory Ireland (IE) Institute of Nuclear Physics Polish Academy of Sciences / Instytut Fizyki Jądrowej im. Henryka Niewodniczańskiego Polskiej Akademii Nauk Poland (PL) Universität Potsdam Germany (DE) Noordwes-Universiteit / North-West University South Africa (ZA) University of Amsterdam Netherlands (NL) Université Paris-Saclay France (FR) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) Eberhard Karls Universität Tübingen Germany (DE) Paris Observatory / Observatoire de Paris France (FR) University of the Witwatersrand (WITS) South Africa (ZA) Jagiellonian University / Uniwersytet Jagielloński (UJ) Poland (PL) Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences Poland (PL) Yerevan Physics Institute (YerPhI) / Երևանի Ֆիզիկայի Ինստիտուտ Armenia (AM) Laboratoire Leprince-Ringuet (LLR) France (FR) University of Oxford United Kingdom (GB) Aix-Marseille University / Aix-Marseille Université France (FR) University of Western Sydney Australia (AU) Universität Hamburg (UHH) Germany (DE) Nicolaus Copernicus University (NCU) / Uniwersytet Mikołaja Kopernika w Toruniu (UMK) Poland (PL) University of Tokyo Japan (JP) Konan University / 甲南大学 Japan (JP) University of Groningen / Rijksuniversiteit Groningen Netherlands (NL)

How to cite

APA:

Aharonian, F., Backes, M., Batzofin, R., Becherini, Y., Berge, D., Bernlöhr, K.,... Zhong, W. (2026). H.E.S.S. detection and multi-wavelength study of the z-1 blazar PKS 0346-27. Astronomy & Astrophysics, 706. https://doi.org/10.1051/0004-6361/202557228

MLA:

Aharonian, F., et al. "H.E.S.S. detection and multi-wavelength study of the z-1 blazar PKS 0346-27." Astronomy & Astrophysics 706 (2026).

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