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Paper: Disk Precession in Pleione
Volume: 361, Active OB-Stars: Laboratories For Stellar and Circumstellar Physics
Page: 267
Authors: Hirata, R.
Abstract: From the polarimetric observation of Pleione, we found that the intrinsic polarization angle varied from 60° to 130° in 1974-2003. The Hα profile also changed dramatically from the edge-on type (shell-line profile) to the surface-on type (wine-bottle profile). These facts clearly indicate the spatial motion of the disk axis.

We interpret these variations in terms of the disk precession, caused by the secondary of this spectroscopic binary with a period of 218d. We performed the Χ2 minimization for the polarization angle, assuming uniform precession with an imposed condition that the shell maximum occurred at edge-on view. The resulting precession angle is 59° with a period of 81 years. Then, we can describe chronologically the spatial motion of disk axis. We also derived the Hα disk radius from the peak separation, assuming the Keplerian disk.

The precession of the disk gives natural explanation of the mysterious longterm spectroscopic behaviors of this star.

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