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

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 12.2 σ . 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.