Diffuse galactic gamma-ray emission is produced by the interaction of cosmicrays (CRs) with the interstellar environment. The study of gamma-ray emissionis therefore a powerful tool to investigate the origin of CRs and the processesthrough which they are accelerated. We aim to gain deeper insights of thenature of gamma-ray emission in the region of Orion, which is one of the beststudied sites of on-going star formation, by analysing data from the AGILEsatellite. The diffuse gamma-ray emission expected from the Orion region isrelatively high. Its separation from the galactic plane also ensures a very lowcontribution from foreground or background emission, which makes it an idealsite for studying the processes of particle acceleration in star formingenvironments. The AGILE data are modelled through a template that quantifiesthe gamma-ray diffuse emission expected from atomic and molecular hydrogen.Other sources of emission are modelled as an isotropic contribution. Gamma-rayemission exceeding the amount expected by the diffuse emission model isdetected with high level of significance. The main excess is in thehigh-longitude part of Orion A. A thorough analysis of this feature suggests aconnection between the observed gamma-ray emission and the B0.5 Ia star kOrionis. The location of the gamma-ray excess is compatible with the site wherestellar wind collides with the ISM. Both scattering on dark gas and cosmic-rayacceleration at the shock between the two environments are discussed aspossible explanations, with the latter hypothesis being supported by thehardness of the energy spectrum of the emission. If confirmed, this would bethe first direct detection of gamma-ray emission from the interaction betweenISM and a single star's stellar wind.

A new gamma-ray source unveiled by AGILE in the region of Orion

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