  We present our discovery of pulsational radial-velocity variations in the
cool Ap star HD 75445, an object spectroscopically similar to the bright,
rapidly-oscillating Ap (roAp) star gamma Equ. Based on high-resolution
time-series spectroscopy obtained with the HARPS spectrometer at the European
Southern Observatory 3.6-m telescope, we detected oscillations in Nd II and Nd
III lines with a period close to 9 min and amplitudes of 20-30 m/s. Substantial
variation in the pulsational amplitude during our 3.8 h observing run reveals
the presence of at least three excited non-radial modes. The detection of
extremely low amplitude pulsations in HD 75445 indicates that the roAp
excitation mechanism produces variability in the radial velocity amplitude of
between a few tens m/s and several km/s. This supports the idea that many, if
not all, cool Ap stars occupying the roAp instability strip may harbour
non-radial pulsations, which currently remain undetected due to their small
photometric and radial-velocity amplitudes.
