Spectra of SO 5₅–4₄ (blue) and SO₂ 11_1,11–10_0,10 (gray) at the two resolved peak positions, together with the spectra obtained from FERIA, normalized to the SO intensity at the peak velocity of the IRE. The vertical dash-dotted line marks the systemic velocity of the protostar (7.5 km s⁻¹), whereas the thick dashed line marks the velocity of the streamer at the same distance from the protostar (in radius) as peak 2 (6.45 km s⁻¹; Appendix B).