2008A&A...477L..29L

If relativistic particle acceleration takes place in colliding-wind binaries, hard X-rays and γ-rays are expected through inverse Compton emission, but to date these have never been unambiguously detected. To detect this emission, observations of {eta} Carinae were performed with INTEGRAL, leveraging its high spatial resolution. Deep hard X-ray images of the region of {eta} Car were constructed in several energy bands. The hard X-ray emission previously detected by BeppoSax around {eta} Car originates from at least 3 different point sources. The emission of {eta} Car itself can be isolated for the first time, and its spectrum unambiguously analyzed. The X-ray emission of {eta} Car in the 22-100keV energy range is very hard (Γ≃1±0.4) and its luminosity is 7x10³³erg/s. The observed emission is in agreement with the predictions of inverse Compton models, and corresponds to about 0.1% of the energy available in the wind collision. {eta} Car is expected to be detected in the GeV energy range.