Seven TESS sectors support a constant 0.33085540-day period for the known binary near GJ 251

Seven public TESS sectors support one period for the known binary signal in the GJ 251 aperture. The source is ASASSN-V J065445.43+331533.1, identified in earlier pixel work. We connect the phase of its dominant brightness component across 2,220 days. We add the 200-second Sector 1751 light curve from the January 2026 comet pointing to six earlier 120-second light curves. Joint spline and harmonic fits give an orbital period of 0.33085540 plus or minus 0.00000015 day. The error is one estimated standard error under the stated constant-clock and residual-group assumptions. The phase statistic is 3.66 for five degrees of freedom. A fit to the first six sectors predicts the 2026 phase with an offset of 126 seconds and a combined standard error of 226 seconds. This is a retrospective test; the 2026 data were seen during exploration. With all seven sectors, the tested changes in baseline, harmonics, flux product, quality mask, and error groups shift the period by at most 0.014 second. Removing the earliest sector changes the period by 0.040 second and increases the error to 0.026 second. A quadratic phase fit does not establish a period change. The result supplies a measured clock for known contaminating light in a planet-search field. It times a brightness component and assumes the prior source match. It does not identify physical eclipse contact times. The package includes all seven original light curves, hashes, archive and catalog provenance, code, phase covariance, a prediction tool, figures, and reproduction instructions.

TESS · eclipsing binary · GJ 251 · ASASSN-V J065445.43+331533.1 · Gaia DR3 939072235377460352 · phase connection · orbital period · photometric contamination · Sector 1751 · public data