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We investigate temporally changing variability amplitudes and themulti-periodicity of the type-I Cepheid Polaris using 161 high-precision radialvelocity (RV) and bisector inverse span (BIS) measurements based on opticalspectra recorded using Hermes at the 1.2 m Flemish Mercator telescope on LaPalma, Canary Islands, Spain. Using an empirical template fitting method, weshow that Polaris' RV amplitude has been stable to within $\sim 30 \rm{ms}^{-1}$ between September 2011 and November 2018. We apply the templatefitting method to publicly accessible, homogeneous RV data sets from theliterature and provide an updated solution of Polaris' eccentric 29.3 yr orbit.While the inferred pulsation-induced RV amplitudes differ among individual datasets, we find no evidence for time-variable RV amplitudes in any of theseparately considered, homogeneous data sets. Additionally, we find thatincreasing photometric amplitudes determined using SMEI photometry are likelyspurious detections due to as yet ill-understood systematic effects ofinstrumental origin. Given this confusing situation, further analysis ofhigh-quality homogeneous data sets with well-understood systematics is requiredto confidently establish whether Polaris' variability amplitude is subject tochange over time. We confirm periodic bisector variability periods of 3.97 dand 40.22 d using Hermes BIS measurements and identify a third signal at aperiod of 60.17 d. Although the 60.17 d signal dominates the BIS periodogram,we caution that this signal may not be independent of the 40.22 d signal.Finally, we show that the 40.22 d signal cannot be explained by stellarrotation. Further long-term, high-quality spectroscopic monitoring is requiredto unravel the complete set of Polaris' periodic signals, which has thepotential to provide unprecedented insights into the evolution of Cepheidvariables.

Probing Polaris' Puzzling Radial Velocity Signals - Pulsational (In-)Stability, Orbital Motion, and Bisector Variations