2008A&A...487..659R

The line profile variability and photometric variability of the O9.5Vp star HD93521 are examined in order to establish the properties of the non-radial pulsations in this star. Fourier techniques are used to characterize the modulations of the HeI λλ5876, 6678 and Hα lines in several spectroscopic time series and to search for variations in a photometric time series. Our spectroscopic data confirm the existence of two periods of 1.75 and 2.89 h. The line profiles, especially those affected by emission wings, exhibit also modulations on longer time scales, but these are epoch-dependent and change from line to line. Unlike previous claims, we find no unambiguous signature of the rotational period in our data, nor of a third pulsation period (corresponding to a frequency of 2.66d^–1). HD93521 very likely exhibits non-radial pulsations with periods of 1.75 and 2.89h with l≃8±1 and l≃4±1 respectively. No significant signal is found in the first harmonics of these two periods. The 2.89h mode is seen at all epochs and in all lines investigated, while the visibility of the 1.75h mode is clearly epoch-dependent. Whilst light variations are detected, their connection to these periodicities is not straightforward.