Polarimetric observations at the epochs of ESO-VLTI AMBER and PIONIER data of Achernar analyzed in this work (vertical hatched bars). All the measurements are compatible with null/negligible polarization. The horizontal gray bars indicate the weighted average of the polarization: 0.019 ± 0.012%. Vertical lines correspond to epochs of Hα (dotted) and Hβ (dot-dashed) data observations with colors corresponding to the spectra shown in Fig. 3. The spectroscopic and polarimetric data are thus contemporaneous and embrace the interferometric observations in time.