Back to Volume
Paper: Spectropolarimetric Study of γ Peg in the He I 6678 Line
Volume: 349, Astrophysics of Variable Stars
Page: 207
Authors: Butkovskaya, V.
Abstract: We present a high-accuracy spectropolarimetric study of the small-amplitude β Cephei-type star γ Pegasi. It was found that Residual Intensity, Full Width at Half Maximum and their Equivalent Width of the line vary during the 0.15-day pulsation period and reach their maximum value at maximum compression phase when the temperature of the star is highest. The pulsation variations of the line parameters are sinusoidal with amplitudes around 1–2%. The smooth character of the observed radial velocity, radius variation and acceleration curves indicates that the pulsation motion of the star does not have any strong non-linear behavior. Therefore, in the case of γ Pegasi the variations of the line parameters due to pulsation could be explained as a temperature effect as well as in other small-amplitude β Cephei stars.
The mean values of both radial velocity (γ-axis) and all line parameters are not the same for different pulsation cycles. It was shown here that our γ-axis values vary due to the 6.83-day orbital period. We found that the fundamental pulsation mode of γ Pegasi is 0.713 day.
Estimation of reasonable mass and spectral type of the secondary component led to the conclusion that the inclination of the orbit must be very low. The maximum orbit inclination angle, i < 6°, was estimated assuming that a weak dipole magnetic field exists on γ Pegasi. The calculation of central dipole parameters has been made for the inclination angle β equal to 90° between the axes of rotation and dipole and for a polar field strength of 360 G.
Back to Volume