The known GJ 3341 period gives lower later error than 60 tested rotation harmonics in HARPS data

We test whether third harmonics of rotation periods selected from early activity measurements predict the known GJ 3341 velocity wave. The fixed 14.207-day wave gives lower later error than all 60 tested alternatives from five indicators, two activity fits, three time splits, and two HARPS reductions. The main split gives planet gains of 23.2% in SERVAL and 18.5% in DRS. Some conditional comparison ranges include equal performance. A full rotation fit and three noise choices retain the point result. Early H-alpha bin resampling also favors the planet wave, but has broad period variation. At exactly 42.621 days, the third rotation harmonic is identical to the planet wave, so activity is not excluded. This test supports the known wave against the stated fixed alternatives. No new planet is claimed. Both reductions share spectra; no independent instrument confirms the test. The package includes code, aggregate evidence, hashes and an external retrieval recipe. Source records remain outside the bundle.

astronomy · GJ 3341 · HARPS · stellar activity · rotation harmonics · prediction · signal loss