A 0.75 m/s wave at 0.978386 days has at most 2.2 percent Gaussian detection power in 59 HD 40307 repeat nights

We test a known short-period alternative for HD 40307 f with 275 HARPS exposures on 59 repeat nights. Free night offsets and four longer-period waves remove slow changes. At a fixed period of 0.978386 days and amplitude 0.75 m/s, a two-coefficient Gaussian test has power of 1.76 to 2.12 percent over all phases at a 1 percent false alarm probability under reported errors. An added independent 1 m/s exposure error reduces power to 1.08 to 1.16 percent. The measured primary fit gives a conditional night-sign tail fraction of 0.403. A small period change gives 0.027 in one exploratory control, which does not pass a correction for 12 settings. Direct fits and Gaussian injections check the calculation. The result limits this within-night test, not full orbit models. Unknown covariance, fixed circular waves and shared spectra limit interpretation. No new planet or independent confirmation is found. Code, aggregate results, source hashes, a figure and external-data retrieval steps are included.

astronomy · HD 40307 · HARPS · daily alias · within-night velocity · sensitivity · null result