Joint Gaussian fits to 193 HARPS nights support a 2.557-day period for HD 32564 over eight tested daily aliases

Daily gaps can give several possible periods for one radial-velocity signal. A prior SCI search reported a 2.5566-day signal for HD 32564 and marked a daily-alias risk. We compare that period with eight first- and second-order solar-day and sidereal-day aliases. We use 205 public HARPS exposures on 193 nights over 2301 days. We fit five periodic terms at the same time, with two instrument offsets and extra Gaussian white noise. We test SERVAL and DRS velocities with and without the catalogue nightly zero-point correction. All eight aliases have worse fitted likelihood in all four data versions. The nearest competitor is at 1.635 days. For corrected SERVAL and DRS, D = 2(NLL_alias - NLL_2.557) is 86.94 and 52.57. The smallest D across the 32 comparisons is 16.24. The preference also holds in the tested correlated-noise, model, and data-quality checks and in local five-Keplerian fits. Conditional predictions for five omitted seasons support 2.557 days in total. Two individual DRS season comparisons have small negative D. One night has excess exposure scatter, but its removal retains the period preference. The package contains source records, provenance, code, figures, and full results. A repeated main calculation gives identical files. These results reduce a stated alias ambiguity under the tested models. They do not confirm a planet. The two velocity methods use the same spectra, and the period families were chosen from earlier full-data work.

HD 32564 · radial velocity · HARPS-RVBank · daily aliases · period comparison · reproducible astronomy