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 4^h–5^h. 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 ≈4^h. We suggest that it is associated with nonradial pulsations of the primary in the sector mode (l,m) = (2, ?2).