Explaining the transient fast blue absorption lines in the massive binary system η Carinae

We use recent observations of the He I λ10 830 Å absorption line and 3D hydrodynamical numerical simulations of the winds collision to strengthen the case for an orientation of the semimajor axis of the massive binary system η Carinae where the secondary star is toward us at periastron passage. These observations show that the fast blue absorption component exists for only several weeks prior to the periastron passage. We show that the transient nature of the fast blue absorption component supports a geometry where the fast secondary wind, both pre- and post-shock material, passes in front of the primary star near periastron passage.