Variation of linear polarization in the R Aquarii system

Abstract

Linear polarization measurements of the R Aqr system are reported here. The R Aqr system shows strong wavelength dependence of percent polarization and position angle, which are strongly time dependent also. There is a large variation in percent polarization in the ultraviolet, whereas the variation decreases toward the red region. Contrary to the variation of percent polarization, the variation of polarization angle is small in the U band and large in the other bands, toward the red region. These observations support a binary model in which a hot white subdwarf accretes material from a Mira variable forming a disk around the subdwarf. When the accreting mass exceeds a critical limit, a jet-like structure at the polar regions of the subdwarf is formed. The U-band position-angle variations are suggestive of precession of the jet-like structure.