A study of the β Cephei star γ Pegasi: binarity, magnetic field, rotation, and pulsations
Butkovskaya, V. V.; Plachinda, S. I.
Ukraine, Austria
Abstract
Aims:We provide observational material to study the magnetic field variability of the classical
Methods: The observations were carried out in the He I 6678 line in the course of 23 observing nights from 1997 to 2005 with using the Coudé spectrograph in spectropolarimetric mode at the Crimean 2.6 m telescope. The behavior of stellar wind was studied in the UV region using data from the IUE satellite (the INES database).
Results: It is shown that the UV stellar wind exhibits a variability. A variation of the wind due to stellar pulsations has been detected. In the He I 6678 line, the abnormally blueshifted radial velocities (γ = -60.57 ± 0.29 km s-1) were detected during a single night in 2005. We do not confirm the 370.5-day orbital period. The most probable orbital period was estimated as P_orb = 6.81608 ± 0.00012 day. The ratio P_orb/P_puls = 44.92 appeared to be very close to integer. We have detected the presence of a weak magnetic field on the star. The longitudinal component of the field varies from -10 G to 30 G with the stellar rotation. The most probable rotational period is P_rot = 6.6538 ± 0.0016 days. Both the orbital and the rotational periods are integral multiples of the difference between them: P_orb/|P_orb - P_rot| = 42.002, and P_rot/|P_orb - P_rot| = 41.002. Variation in the longitudinal magnetic field during the pulsation period with an amplitude about 7 G was detected.