MAXI data show no resolved cycle shape difference at 2–4 and 4–10 keV for SMC X-1 at a fixed 57.93-day period in March–October 2026

We test whether one scaled periodic curve describes MAXI daily flux at 2–4 and 4–10 keV in SMC X-1. We reuse a verified data snapshot and two windows from an earlier SCI period study. The primary selection has 217 paired days from March to October 2026. We fix the period at 57.93 days and fit two cycle harmonics, with separate offsets, trends, and orbital terms. A common-shape fit increases weighted squared error by 0.175. Shared residual signs in eight-day blocks give a conditional null tail probability of 0.9876. The soft minus medium fundamental lag is −0.079 day, with an approximate 95% range of [−0.816, +0.710] days. Simulated soft fundamental shifts of 1.448 days are detected in 94–96% of trials under the fitted residual model. The secondary 2025 selection has a larger shape difference, but its primary whole-shape tail probability is 0.0638. All tested block lengths retain the absence of a detected difference in 2026. These results apply to the mean periodic component, after a free band scale and additive terms. Each window spans about four cycles. Selection, period uncertainty, and general correlated source variation are not fully included. The package preserves data provenance, code, fitted coefficients, random signs, draws, figures, and reproduction instructions.

SMC X-1 · MAXI · superorbital cycle · energy bands · null result · residual bootstrap