2007MNRAS.381.1301K

Recently, we discovered an entirely new type of variability in the upper atmospheres of rapidly oscillating Ap (roAp) stars. This manifests itself in amplitude modulation of the radial velocities that has not been previously detected in photometric studies of the same stars. To study this new variability further we obtained a full night, 8.85h, of high time resolution (70s), high spectral resolution (R = 105000), high signal-to-noise ratio (on average S/N ∼ 130) data with Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) for the roAp star HD134214. We also obtained 4.2h of new photometric data in Johnson B with the South African Astronomical Observatory (SAAO) 0.5-m telescope 2d later. HD134214 has been known for years to be singly periodic with a relatively stable amplitude in photometry; it has the highest pulsation frequency of any roAp star of 2.949mHz (P = 5.65min). Our new UVES data show this principal frequency, plus five other frequencies in amplitude spectra of rare earth elements lines and the Hα line. The new frequencies are stable over the 8.85h of observation, and the highest of them ν₂= 2.782mHz is the same as found in data taken 2yr earlier with UVES presented in the discovery paper. The amplitudes of the new frequencies drop faster with atmospheric depth than does the amplitude of the principal frequency, hence explaining why they are generally not seen in broad-band photometric measurements that sample on average more deeply in the atmosphere. Our new photometric measurements also detect ν₂for the first time in photometric data. Our analysis suggests that the new frequencies are associated with pulsation modes, but the nature of those modes and why they increase in amplitude with atmospheric height more strongly than the principal frequencies is not yet known.