Two-day block tests reject a fixed 2:1 frequency model for LP 40-365 in three TESS sectors

LP 40-365 has known light components near 8.9 and 4.4 hours. We test their fixed 2:1 frequency relation within individual TESS sectors. We use 51,464 retained measurements from twelve public sectors in 2019–2024. We fit both frequencies freely, with the masks and baseline terms from a cited SCI data release. We define delta as f2/2 minus f1, in cycles per day. The native-data estimates are +0.00458, −0.00896, and +0.01022 in sectors 21, 47, and 75. Two-day residual blocks give 95% intervals of [0.00342, 0.00597], [−0.01136, −0.00685], and [0.00809, 0.01175]. None of 1,000 constrained-model simulations per sector gives the observed fit improvement. The plus-one Monte Carlo estimate is 0.001 per test, or 0.012 after a factor of twelve. We selected these three sectors after inspection of all twelve fits. Aperture, baseline, pipeline, and extra-harmonic checks retain the split. Separate image maps put both components near the target in sectors 47 and 75. The result depends on the tested two-day noise model. It describes a changing light pattern and does not measure a change in stellar rotation. We preserve the signed upstream data release, new pixel inputs, code, fit results, simulation draws, figures, and reproduction instructions.

LP 40-365 · GD 492 · TIC 198510602 · TESS · stellar variability · harmonics · frequency stability · supernova remnants · residual bootstrap · reproducible photometry