Hard x-ray emission from η carinae

Context. If relativistic particle acceleration takes place in colliding-wind binaries, hard X-rays and gamma-rays are expected through inverse Compton emission, but to date these have never been unambiguously detected. Aims. To detect this emission, observations of. Carinae were performed with INTEGRAL, leveraging its high spatial resolution. Methods. Deep hard X-ray images of the region of. Car were constructed in several energy bands. Results. The hard X-ray emission previously detected by BeppoSax around eta Car originates from at least 3 different point sources. The emission of. Car itself can be isolated for the first time, and its spectrum unambiguously analyzed. The X-ray emission of. Car in the 22-100 keV energy range is very hard (Gamma similar or equal to 1 +/- 0.4) and its luminosity is 7 x 10(33) erg s(-1). Conclusions. 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.