Microvariability of Line Profiles in the Spectra of OB Stars II: $\delta $Ori A

–We have studied variability of the spectral lines of the OB star δ Ori A–the brightest component of the δ Ori triple system. Forty spectra with signal-to-noise ratios ≈ 500–800 and a time resolution of four minutes were obtained. We detected variability in the HeII λ 4686, HeI λ 4713 and H β absorption and the CIII λ 5696 emission line profiles. The amplitude of the variability is ≈ (0.5–1)% of the continuum intensity. The dynamical wavelet spectrum of the profile variations reveals large-scale components in the interval 25–50 km/s that move within the - V sin i to V sin i band for the primary star of the system, Aa 1 , with a band crossing time of 4 h –5 h . However, some of the variable features go outside the band, presumably due to either imhomogeneities in the stellar wind from δ Ori Aa 1 or non-radial pulsations of the weaker components of the system, Aa 2 or Ab. The detected variability may by cyclic with a period of ≈ 4 h . We suggest that it is associated with non-radial pulsations of the primary in the sector mode ( l, m ) = (2 , − 2).