Observation of Secondary O in the Interstellar Neutral Gas Flow with the Interstellar Boundary Explorer (IBEX)

Neutral atom imaging observations of the interstellar gas flow in the inner heliosphere provide the most detailed information about the physical conditions of the surrounding interstellar medium and the interaction of this flow with the outer heliosheath. Key to the latter diagnostics is a secondary component of the interstellar neutral gas flow that originates from charge exchange interstellar neutrals with outer heliosheath ions, which are diverted around the heliosphere. Thus their trajectories contain information about the deceleration, deflection, and heating of interstellar plasma in the outer heliosheath. The Interstellar Boundary Explorer (IBEX) intercepts the interstellar neutral atom flow trajectories at their perihelion at 1 AU and identifies the species with its low energy neutral atom camera IBEX-Lo. We have now observed the interstellar neutral flow with IBEX-Lo over three consecutive years and identified neutral interstellar H, He, O, and Ne in the flow observations. Already over the first two years, strong indications for a secondary flow component of O and He emerged. Based on three ISM flow passages thus far, we will characterize its strength relative to the primary interstellar O flow and its arrival direction relative to the interstellar flow as observed for primary interstellar He and O with IBEX. We will discuss potential implications of these findings.