Abstract: | Aims. Previous observations with the H.E.S.S. telescope array revealed the
existence of extended very-high-energy (VHE; E>100 GeV) {gamma}-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 {gamma}-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 {gamma}-ray source, HESSJ1026-582, was
discovered with a statistical significance of 7{sigma}. It is positionally
coincident with the Fermi LAT pulsar PSR J1028-5819. The positional coincidence
and radio/{gamma}-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 H.E.S.S. 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. |