Polarization of Dwarf Novae and Novalike Variables

Extract

Linear polarization observations have been made over the past several years on several bright dwarf novae (DN) and related objects (NL). The purpose was to investigate any possible variation that could be related to outburst state (changes in the asymmetry of the disk from max to min), short time scale variability (related to flickering) and variability over the orbital cycle (related to the view of the hot spot or to cyclotron emission as in the AM Her variables). The measurements were made at Kitt Peak (KP), Lowell (L), or Battelle Obs. (B) with either the Dyck (D), Hall/Bowell (HB) or Battelle (B) polarimeters and the system was calibrated in each case by taking 30-40 measurements of the nonpolarized and known polarized standards of Serkowski. The data is summarized in the following table. AE Aqr shows the only variation in mean p between runs while the largest variations on flickering timescales are evident in V Sge, RX And and V426 Oph. VSge and RX And show orbital phase dependent variability. SS Cyg does not show any changes in mean polarization over the outburst cycle although the wavelength dependence of the polarization (U-+R) reverses from max to min.