Abramowski, A.Böttcher, M.Davids, I.D.Ivascenko, A.Krüger, P.P.Pekeur, N.W.Seyffert, A.S.Spanier, F.Sushch, I.Van der Walt, D.J.Venter, C.H.E.S.S. Collaboration2016-08-302016-08-302015Abramowski, A. et al. 2015. Discovery of variable VHE γ-ray emission from the binary system 1FGL J1018.6-5856. Astronomy & astrophysics, 577: Article no A131. [https://doi.org/10.1051/0004-6361/201525699]0004-63611432-0746 (Online)http://hdl.handle.net/10394/18448https://doi.org/10.1051/0004-6361/201525699http://www.aanda.org/articles/aa/full_html/2015/05/aa25699-15/aa25699-15.htmlRe-observations with the HESS telescope array of the very high-energy (VHE) source HESS J1018–589 A that is coincident with the Fermi-LAT γ-ray binary 1FGL J1018.6–5856 have resulted in a source detection significance of more than 9σ and the detection of variability (χ2/ν of 238.3/155) in the emitted γ-ray flux. This variability confirms the association of HESS J1018–589 A with the high-energy γ-ray binary detected by Fermi-LAT and also confirms the point-like source as a new VHE binary system. The spectrum of HESS J1018–589 A is best fit with a power-law function with photon index Γ = 2.20 ± 0.14stat ± 0.2sys. Emission is detected up to ~20 TeV. The mean differential flux level is (2.9 ± 0.4) × 10-13 TeV-1 cm-2 s-1 at 1 TeV, equivalent to ~1% of the flux from the Crab Nebula at the same energy. Variability is clearly detected in the night-by-night light curve. When folded on the orbital period of 16.58 days, the rebinned light curve peaks in phase with the observed X-ray and high-energy phaseograms. The fit of the HESS phaseogram to a constant flux provides evidence of periodicity at the level of Nσ> 3σ. The shape of the VHE phaseogram and measured spectrum suggest a low-inclination, low-eccentricity system with amodest impact from VHE γ-ray absorption due to pair production (τ ≲ 1 at 300 GeV)enX-rays: binariesgamma rays: starsstars: individual: 1FGL J1018.6-5856radiation mechanisms: non-thermalacceleration of particlesArticle