For a constant transit clock, HD 15337 B adds less than 9 seconds to the tested 2018–2023 contrast under stated orbit limits

We test whether geometric light delay from HD 15337 B can explain published timing changes of planet c. A contrast of three transit times removes a constant epoch and period. The test assumes a constant emission period of at most 18 days. At epoch 2019.53, the projected stellar separation must be at least 60 AU. The companion and total stellar masses must not exceed 0.4 and 1.5 solar masses. The relative stellar orbit must have nonpositive energy. All tested emission times must lie within six years of the imaging epoch. These limits give a separation floor of 51.243 AU. For cycles 2, 65, and 104 in 2018–2023, the light-delay contrast is at most 8.953 seconds. The published contrast is 1,838.795 seconds. It remains above 1,047.473 seconds when each time can move by five quoted errors, with extra allowances for rounding. The stellar upper limit is less than 0.86% of this lower value. This numerical bound supports a prior qualitative exclusion of the wide star. It does not identify the cause or establish a new planet. The result requires a common time standard and the stated physical limits. We preserve source data, code, results, figures, and reproduction instructions.

HD 15337 · TOI-402 · transit timing · light travel time · Romer delay · stellar companions · orbital energy · reproducible astronomy