Abramowski, A.Büsching, I.Casanova, S.Davids, I.D.De Jager, O.C.Holleran, M.Sushch, I.Venter, C.H.E.S.S. Collaboration2012-09-042012-09-042011Abramowski, A. et al. 2011. Revisiting the Westerlund 2 field with the HESS telescope array. Astronomy & astrophysics, 525: Article no A46. [https://doi.org/10.1051/0004-6361/201015290]0004-63611432-0746 (Online)http://hdl.handle.net/10394/7228https://doi.org/10.1051/0004-6361/201015290https://www.aanda.org/articles/aa/abs/2011/01/aa15290-10/aa15290-10.htmlAims. Previous observations with the HESS telescope array revealed the existence of extended very-high-energy (VHE; E > 100 GeV) γ-ray emission, HESS J1023–575, coincident with the young stellar cluster Westerlund 2. At the time of discovery, the origin of the observed emission was not unambiguously identified, and follow-up observations have been performed to further investigate the nature of this γ-ray source. Methods. The Carina region towards the open cluster Westerlund 2 has been re-observed, increasing the total exposure to 45.9 h. The combined dataset includes 33 h of new data and now permits a search for energy-dependent morphology and detailed spectroscopy. Results. A new, hard spectrum VHE γ-ray source, HESS J1026–582, was discovered with a statistical significance of 7σ. It is positionally coincident with the Fermi LAT pulsar PSRJ1028–5819. The positional coincidence and radio/γ-ray characteristics of the LAT pulsar favors a scenario where the TeV emission originates from a pulsar wind nebula. The nature of HESS J1023–575 is discussed in light of the deep HESS observations and recent multi-wavelength discoveries, including the Fermi LAT pulsar PSRJ1022–5746 and giant molecular clouds in the region. Despite the improved VHE dataset, a clear identification of the object responsible for the VHE emission from HESS J1023–575 is not yet possible, and contribution from the nearby high-energy pulsar and/or the open cluster remains a possibility.Gamma rays: starsHII regionsArticle