An orbital phase test with three flux harmonics gives a minimum tail fraction near 0.02 in ten HD 118203 TESS intervals

We test a proposed link between light from HD 118203 and the orbital angular speed of its planet. We use five public 120-second TESS sectors from 2019 to 2024. We remove transits and divide each sector into two time intervals. We fit three flux harmonics to 100 phase-bin medians. For each interval, we compare the absolute flux derivative with orbital angular speed at 2,048 phase offsets. We define q as the fraction of offsets with a correlation at least as high as the measured alignment. The minimum q is 0.020508 in sector 22, interval 2, with correlation 0.746. The other nine intervals give q from 0.069824 to 0.978516. A nominal ten-test adjustment gives 0.205 for the minimum. The 2020 result depends on the curve method. A 701-cadence median filter gives q = 0.005859; removal of a linear trend gives 0.07666. Splitting that interval into two parts gives q = 0.03076 and 0.20654. Limited simulations show that q is an approximate phase reference, not an exactly calibrated p-value for real stellar noise. The data show a local alignment but do not establish a stable physical link. This exploratory study provides a new phase comparison on known planet data. The package includes source FITS files, hashes, code, all tested variants, simulation draws, figures, and reproduction instructions.

HD 118203 · TIC 286923464 · TESS · stellar variability · star-planet interaction · orbital phase · flux derivative · phase reference test · reproducible research