Scan-averaged and noise-debiased 870 μm fringe amplitude (open blue circles, left axes) and S/N (filled red squares, right axes). Amplitudes and S/N are computed by first dividing each observing scan into short coherently integrated segments, which are then combined incoherently following the procedure in Rogers et al. (1995). Segment length is shown on the horizontal axis. Each subplot shows a different polarization on the ALMA–SMA baseline for a single scan on J0423−0120 (October 21, 09:38 UTC). Other detections listed in Table 1 have a similar dependence on segment duration but generally lower S/N. The noise-debiased amplitude and coherence time were derived using HOPS and are indicated by the horizontal blue dashed line and the vertical solid black line, respectively.