POLARIMETRIC OBSERVATIONS OF THE RV TAURI STAR AC HERCULIS

Polarimetrie observations in the band were obtained over one cycle of the 75.46-day period and on four nights in the V band. A correlation between the light and polarization changes is clearly evident. The variations in the polarization exhibit first and third harmonic behavior with an amplitude of approximately 1.0%. The maximum polarization occurs just after the primary light minimum. The path of the polarization on the equatorial Q, U plane is elongated along an axis which makes an angle 2θ = 145° ± 3° with the ⁺Q axis. This suggests either nonradial pulsations in the star or radial pulsations propagating into an asymmetrical circumstellar medium.