Regular patterns in the acoustic spectrum of rapidly rotating stars

4 pages, 3 figures, 2 tables, accepted for publication in A&AInternational audienceContext: Rapid rotation modifies the structure of the frequency spectrum of pulsating stars, thus making mode identification difficult. Aims: We look for new forms of organisation for the frequency spectrum that can provide a basis for mode identification at high rotation rates. Methods: Acoustic modes in uniformly rotating polytropic models of stars are computed using a numerical code that fully takes the effects of rotation (centrifugal distortion and Coriolis acceleration) into account. All low-degree modes, ? = 0 to 3, with radial orders n = 1-10 and 21-25 for N = 3 polytropic models and n = 1-10 for N = 1.5 polytropic models are followed from a zero rotation rate up to 59% of the break-up velocity. Results: We find an empirical formula that gives a good description of the high-frequency range of the computed acoustic spectrum for high rotation rates. Differences between this formula and complete eigenmode calculations are shown to be substantially smaller than those obtained with a 3rd order perturbative method valid at low rotation rates