Abramowski, A.Büsching, I.Casanova, S.Pekeur, N.W.Sheidaei, F.Venter, C.Vorster, M.H.E.S.S. Collaboration2016-05-272016-05-272012Abramowski, A. et al. 2012. HESS observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae. Monthly notices of the Royal Astronomical Society, 424:128-135. [https://doi.org/10.1111/j.1365-2966.2012.21180.x]0035-87111365-2966 (Online)http://hdl.handle.net/10394/17532http://mnras.oxfordjournals.org/content/424/1/128.fullhttps://doi.org/10.1111/j.1365-2966.2012.21180.xThe massive binary system Eta Carinae and the surrounding HII complex, the Carina nebula, are potential particle acceleration sites from which very high energy (VHE; E ≥ 100 GeV) γ -ray emission could be expected. This paper presents data collected during VHE γ -ray observations with the HESS telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-h data set no hint of significant γ -ray emission from Eta Carinae has been found and an upper limit on the γ -ray flux of 7.7 × 10−13 ph cm−2 s−1 (99 per cent confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high energy (HE; 0.1 ≤ E ≤ 100 GeV) γ -ray emission by the Fermi Large Area Telescope up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the γ -ray spectrum between the HE and VHE γ -ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe γ –γ absorption losses in the wind collision region. Furthermore, the search for extended γ -ray emission from the Carina nebula resulted in an upper limit on the γ -ray flux of 4.2 × 10−12 ph cm−2 s−1 (99 per cent confidence level). The derived upper limit of ∼23 on the cosmic ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W28enISM: individual objects: Carina nebulaISM: individual objects: Eta Carinaopen clusters and associations: generalacceleration of particlesradiation mechanisms: non-thermalX-rays: binariesArticle