Detection of Gamma-ray Emission from the Eta-carinae Region

We present the results of extensive observations by the gamma-ray AGILE satellite of the Galactic region hosting the Carina nebula and the remarkable colliding wind binary Eta Carinae (η Car) during the period 2007 July – 2009 January. We detect a gamma-ray source (1AGL J1043-5931) consistent with the position of η Car. If 1AGL J1043-5931 is associated with the Car system our data provide the long sought first detection above 100 MeV of a colliding wind binary. The average gamma-ray flux above 100 MeV and integrated over the pre-periastron period 2007 July – 2008 October is Fγ = (37 ± 5) × 10 −8 ph cm s corresponding to an average gamma-ray luminosity of Lγ = 3.4 × 10 34 erg s for a distance of 2.3 kpc. We also report a 2-day gamma-ray flaring episode of 1AGL J1043-5931 on 2008 Oct. 11-13 possibly related to a transient acceleration and radiation episode of the strongly variable shock in the system. Subject headings: gamma rays: observations — stars: individual (Eta Carinae) — stars: winds, outflows — X-rays: binaries