The estimated spin state difference in OAO 1657−415's scaled orbital profile changes sign with 2–4 orbit blocks after 2021

We compare the orbital profile of OAO 1657−415 during spin loss and spin gain. We scale each interval by its own brightness. We use public Fermi GBM frequencies and Swift BAT daily 15–50 keV rates saved on 22 October 2026 UTC. Fixed three-orbit blocks define the spin state from a frequency slope. Each block gives a ratio between two rate means. The first covers orbital phases near 0.2 and 0.8. The second covers the central orbit. The principal sample starts after 2021. Its 16 accepted blocks span April 2022 to December 2025: nine show loss and seven show gain. The difference of mean ratios, loss minus gain, is −0.079. We resample runs of adjacent calendar blocks, including gaps. The 95% intervals are [−0.291, 0.152], [−0.288, 0.102], and [−0.256, 0.079] for runs of about 94, 188, and 376 days. All include zero. Two- and four-orbit blocks instead give differences of +0.091 and +0.022. A phase shift of −0.02 cycles gives intervals below zero. The main phase and a positive shift do not. The measured difference depends on the tested time blocks and phase assignment. This does not show that a physical profile change is absent. The result also depends on detected pulses, the public timing solution, daily phase averages, and sparse joint coverage. The package supplies frozen inputs, provenance, code, all attempted blocks, controls, and figures. A separate calculation checks all 86 accepted primary blocks in the earlier and later samples.

OAO 1657-415 · X-ray binaries · orbital profile · torque reversal · Fermi GBM · Swift BAT · reproducible astronomy