H.E.S.S. detection of the PSR J0855−4644 nebula

¹ Yerevan State University, 1 Alek Manukyan St, Yerevan 0025, Armenia
² Max-Planck-Institut für Kernphysik, P.O. Box 103980, D 69029 Heidelberg, Germany
³ Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, DIAS Dunsink Observatory, Dublin D15 XR2R, Ireland
⁴ Laboratoire Leprince-Ringuet, Ècole Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France
⁵ University of Namibia, Department of Physics, Private Bag 13301, Windhoek 10005, Namibia
⁶ Centre for Space Research, North-West University, Potchefstroom 2520, South Africa
⁷ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25 D 14476, Potsdam, Germany
⁸ Université Paris Cité, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France
⁹ Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany
¹⁰ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, D 12489 Berlin, Germany
¹¹ LUX, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, 5 Pl. Jules Janssen, 92190 Meudon, France
¹² Sorbonne Université, CNRS/IN2P3, Laboratoire de Physique Nucléaire, et de Hautes Energies, LPNHE, 4 place Jussieu, 75005 Paris, France
¹³ IRFU, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette, France
¹⁴ Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Nikolaus-Fiebiger-Str. 2, 91058 Erlangen, Germany
¹⁵ Instytut Fizyki Jacadrowej PAN, ul. Radzikowskiego 152, ul. Radzikowskiego 152, 31-342 Kraków, Poland
¹⁶ School of Physics, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, Johannesburg 2050, South Africa
¹⁷ School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University, Glasnevin, Dublin D09 W6Y4, Ireland
¹⁸ University of Oxford, Department of Physics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK, United Kingdom
¹⁹ Aix Marseille Université, CNRS/IN2P3, CPPM, Marseille, France
²⁰ Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS/IN2P3, CC 72, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France
²¹ Université Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, F-33170 Gradignan, France
²² School of Science, Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
²³ Landessternwarte, Universität Heidelberg, Königstuhl, D 69117 Heidelberg, Germany
²⁴ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, D 72076 Tübingen, Germany
²⁵ Universität Innsbruck, Institut für Astro- und Teilchenphysik, Technikerstraße 25, 6020 Innsbruck, Austria
²⁶ Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, D 22761 Hamburg, Germany
²⁷ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
²⁸ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland
²⁹ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
³⁰ University of Leicester, School of Physics and Astronomy, University Road, Leicester LE1 7RH, United Kingdom
³¹ GRAPPA, Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
³² School of Physical Sciences, University of Adelaide, Adelaide 5005, Australia
³³ Yerevan Physics Institute, 2 Alikhanian Brothers St., 0036 Yerevan, Armenia
³⁴ Department of Physics, Konan University, 8-9-1 Okamoto, Higashinada, Kobe, Hyogo 658-8501, Japan
³⁵ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
³⁶ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
³⁷ FSLAC IRL 2009, CNRS/IAC, La Laguna, Tenerife, Spain
³⁸ Now at: Euro-Mediterranean Center on Climate Change (CMCC), Lecce, Italy

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Received: 1 December 2025
Accepted: 7 February 2026

Abstract

Context. HESS J0852−463 is a TeV γ-ray source located in the Galactic plane. The region consists of a supernova remnant (SNR, RX J0852.0−4622) with a shell-like morphology, commonly referred to as Vela Junior, and a pulsar named PSR J0855−4644. Pulsars are among the most efficient leptonic accelerators in our Galaxy, making this region particularly interesting to study.

Aims. We utilise the most recent data taken by the High Energy Stereoscopic System (H.E.S.S.) to investigate any γ-ray emission associated with the pulsar in this region, PSR J0855−4644.

Methods. We applied a full forward-folding method on the H.E.S.S. data. Utilising 3D modelling techniques, we evaluated the TeV γ-ray emission towards the various components of this complex system.

Results. The distinct energy-dependent morphology observed in our data motivates further investigation of this source. We resolved the emission in the Vela Junior region into various components, several of which correspond to the SNR itself. In particular, we find a new extended component coincident with the position of PSR J0855−4644. The spectrum follows a power-law distribution with a best-fit index of Γ_E = 1.81 ± 0.07_stat, which differs from the properties of the surrounding γ-ray emission of the Vela Junior SNR. A one-zone leptonic joint fit between the X-rays (from XMM-Newton) and γ-rays (from H.E.S.S.) leads to a lower limit on the magnetic field of 1.6 μG and a spectral index of α = 1.88 ± 0.01, in line with expectations of pulsar wind nebulae (PWNe).

Conclusions. In this paper, we report the first detection of the PWN of PSR J0855−4644 at TeV energies with the H.E.S.S. experiment, at a significance of 12.2σ. This is attributed to the advanced techniques of the 3D analysis. Based on the pulsar’s characteristics, its PWN is consistent with the known TeV PWNe population in the Galaxy.