Spectroastrometry of two [Fe ii] lines and two Brackett lines. Top: stellar spectrum. The [Fe ii] lines at 1.644 μm and 1.677 μm (extent of each line profile indicated by a horizontal bracket) are overwhelmed by the stellar flux. Bottom: spatial position of the flux centroid relative to that of the star. Both Fe lines show clear signatures of bipolar outflow, while the Brackett lines are centered on the stellar position at all velocities. The [Fe ii] 1.677 μm line is located at the edge of an order and has an uncertain velocity zero point.