Measurement of the collinearity between planets in circular orbits and the α_j (t) basis for HD128621. A maximum of absorption of 25 ± 5% is observed for the rotational period of the star at 39 days. It demonstrates than even if the rotational signal is strongly mitigated, a real circular planetary signal at 39-days would not have been more absorbed than this. For the injected planetary signal at 54 days, the absorption is 3 ± 2%. Absorption at one-year and a half-year are also noticeable.