2001MNRAS.327.1288B

We present the results of a multisite spectroscopic and photometric campaign on the Be star ω Orionis. From the photometry and radial velocity variation of several spectral lines, we confirm that the star is a variable with period P=0.97 d. Only one period can be extracted from both the photometric and radial velocity observations. We find that the projected rotational velocity from the helium lines (vsini=173 km.s^-1) is considerably smaller than from the metal lines (vsini=226 km.s^-1). The line profiles show an excess absorption feature moving from blue to red for half the period and from red to blue for the other half of the period. Another excess absorption feature moves exactly out of phase. The excess absorption features are present in photospheric lines as well as in lines which are significantly affected by circumstellar material, such as Hβ. From this we conclude that the periodic variations are most probably associated with corotating circumstellar material.