Microvariability of line profiles in the spectra of OB stars: δOri A

We have studied variability of the spectral lines of the OB star δOri A—the brightest component of the δOri 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 HeIIλ4686, HeIλ4713, and Hβ absorption and the CIIIλ5696 emission 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, Aa1, with a band crossing time of 4h–5h. However, some of the variable features go outside the band, presumably due to either imhomogeneities in the stellar wind from δOri Aa1 or nonradial pulsations of the weaker components of the system, Aa2 or Ab. The detected variability may be cyclic with a period of ≈4h. We suggest that it is associated with nonradial pulsations of the primary in the sector mode (l,m) = (2, −2).