Median 1D power spectra for substructure GL-1 (black solid curves) and random samples (blue dashed curves). The 1σ and 3σ intervals of the random samples are shown as dark blue and light blue shaded regions, respectively. The x-axes represent 2π times the wavenumbers in the r (top panels) and ϕ (bottom panels) directions. The estimated accretion times are marked by black vertical dashed lines, with significances given in the legend. Left and right panels show the results using the A.-C. Eilers et al. (2019) and J. Bovy (2015) potentials, respectively. Subtitles indicate the substructure name, number of stars, bin width Δ, and applied uncertainty selection.