Aims. Our goal is to probe the GW Orionis multiplicity at angular scales at which we can spatially resolve the orbit.
Methods. We used the IOTA/IONIC3 interferometer to probe the environment of GW Orionis with an astronomical unit resolution in 2003, 2004, and 2005. By measuring squared visibilities and closure phases with a good UV coverage we carry out the first image reconstruction of GW Ori from infrared long-baseline interferometry.
Results.We obtained the first infrared image of a T Tauri multiple system with astronomical unit resolution. We show that GW Orionis is a triple system, resolve for the first time the previously known inner pair (separation ρ ~ 1.4 AU) and reveal a new more distant component (GW Ori C) with a projected separation of ~ 8 AU with direct evidence of motion. Furthermore, the nearly equal (2:1) H-band flux ratio of the inner components suggests that either GW Ori B is undergoing a preferential accretion event that increases its disk luminosity or that the estimate of the masses has to be revisited in favour of a more equal mass-ratio system that is seen at lower inclination.
Conclusions. Accretion disk models of GW Ori will need to be completely reconsidered because of this outer companion C and the unexpected brightness of companion B.
- binaries: general, stars: variables: T Tauri, Herbig Ae/Be, accretion, accretion disks, techniques: interferometric