A Streamer Driving Misalignment in the Circumtriple Disk of GW Ori

Abstract

GW Orionis is a triple stellar system with a disk featuring three misaligned dust rings. We present ALMA molecular line data of CO isotopologues, revealing a streamer feeding the disk in $^{12}$CO and $^{13}$CO. Through multi-pointing observations, we find the streamer extends to $\sim30''$ on-sky ($\sim12,000$~AU) and estimate a mass of 1.6 M$_{\rm Jup}$ using $^{13}$CO. Fitting the morphology and kinematics of the streamer, we estimate the mass infall timescale of 0.04 Myrs and a mass infall rate of $3.6\times10^{-8}$~M$_{\odot}$~yr$^{-1}$, approximately an order of magnitude lower than the stellar accretion rate. Our best-fit trajectory shows that the streamer meets the disk at the outermost dust ring and that the streamer's angular momentum vector is closely aligned with this outermost ring within $\approx3^\circ$, in contrast to the $\approx32^\circ$ misalignment with the innermost ring, suggesting the streamer is the likely cause of the misalignment. However, the total angular momentum of the streamer is smaller than that of GW Ori's disk; this, together with the low accretion rate, indicates that we are probably witnessing the end stages of infall. Total Power observations reveal bright emission connecting the streamer to the surrounding star-forming region, with a projected distance falling well within the Bondi-Hoyle radius, implying the streamer could have originated through Bondi-Hoyle accretion as GW Ori moves through its natal cloud. Together, these results suggest that GW Ori remains dynamically linked to its parental cloud through ongoing accretion, with the streamer serving as the likely driver of its misaligned disk structure.