Astronomy and astrophysics vol:322 issue:2 pages:493-506
We investigate the optical line-profile variability of the prototype of the beta Cephei stars. From more than 600 spectra, with a typical signal to noise ratio of over 200 and high spectral resolution, we deduce that the variations show periodicity with at least five different frequencies. We find variability at the previously known frequencies f(1)=5.25 cycles/day (radial pulsation) and f(2)=5.38 c/d and f(3)=4.92 c/d. Additionally, we report two new frequencies f(4)=5.08 c/d and f(5)=5.42 c/d. These five frequencies are present in periodograms of the velocity moments of all of the absorption lines considered (Si III lambda 4552, 4567, 4574 and O II lambda 4591), and also in periodograms of the intensity variations in these lines.