Radial-velocity variations in pulsating Ap stars: PrIII and NdIII lines inthe spectrum of gamma Equ

Based on high-resolution CCD spectrograms obtained at the Coude focus of th e 2.6-m Crimean Astrophysical Observatory telescope on 13 nights from Augus t through November 1998, we study radial-velocity variations in the roAp st ar gamma Equ. The largest amplitude of the periodic radial-velocity variati ons (up to 0.8 km s(-1)) has been found using the spectral lines identified with Nd III 6145.07 Angstrom and Pr III 6160.24 Angstrom. The power spectr a for the data on each night exhibit a peak at a frequency of 1.35 +/- 0.05 mHz, which corresponds to a pulsation period of similar to 12.35 min. The other identified lines in the spectral range under study show no variabilit y that exceeds appreciably the accuracy of our measurements. The total powe r spectrum for Pr III 6160.24 Angstrom during the observations from August through November 1998 reveals the three most significant oscillation freque ncies of 1349, 1355, and 1365 mu Hz. Only one of the four frequencies found by Martinez et al. (1986) when analyzing photometric data roughly coincide s with our peak at 1365 mu Hz.