  Many early-type stars have been measured with high angular velocities. In
such stars, mode identification is difficult as the effects of fast and
differential rotation are not well known. Using fundamental parameters measured
by interferometry, the ESTER structure code and the TOP oscillation code, we
investigate the oscillation spectrum of Rasalhague (alpha Ophiuchi), for which
observations by the MOST satellite found 57 oscillations frequencies. Results
do not show a clear identification of the modes and highlight the difficulties
of asteroseismology for such stars with a very complex oscillation spectrum.
