Short period line profile and light variations in the Be star omega Orionis

We present the results of a multisite spectroscopic and photometric campaig n on the Be star omega Orionis. From the photometry and radial velocity var iation of several spectral lines, we confirm that the star is a variable wi th period P = 0.97 d. Only one period can be extracted from both the photom etric and radial velocity observations. We find that the projected rotation al velocity from the helium lines (v sin i = 173 km s(-1)) is considerably smaller than from the metal lines (v sin i = 226 km s(-1)). The line profil es show an excess absorption feature moving from blue to red for half the p eriod and from red to blue for the other half of the period. Another excess absorption feature moves exactly out of phase. The excess absorption featu res are present in photospheric lines as well as in lines which are signifi cantly affected by circumstellar material, such as H beta. From this we con clude that the periodic variations are most probably associated with corota ting circumstellar material.