Super-Fast Line-Profile Variability in the Spectra of OBA Stars. IV: ζ Ori A

Absctract—The present study continues the investigation of the super-fast variability of line profiles in the spectra of stars of early spectral types. We studied the line-profile variability in the spectrum of the binary (O9.7Ib+B0III) star \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\zeta $$\end{document} Ori A using the MSS spectrograph of the 6-m BTA telescope based on observations carried out on February 19, 2019. Short-period regular variations of the hydrogen Balmer lines and He I lines with periods from 89 to 295 minutes were found. The presence of short-period variations in the period interval of 10–20 minutes is also possible. An analysis of the stellar brightness variations from observations by the TESS satellite showed the presence of seven regular components, one of which is probably the second harmonic of the rotation period of the main component of the Aa star \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\zeta $$\end{document} Ori A. The magnetic field of the star was determined for the whole series of observations. The longitudinal component of the root-mean-square magnetic field measured by the regression method over the whole observation period is \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$49$$\end{document} G.