UBV RI LINEAR AND CIRCULAR-POLARIZATION OF RS CVN-TYPE BINARIES

The observed sample of 15 RS CVn binaries contains 6 systems with evid ence of circumbinary dust envelopes from an IR excess, and for compari son 6 binaries which do not show any excess, the rest of the objects h ave an uncertain detection. Four of the binaries, II Peg, DK Dra, GK H ya, and UX Ari were observed with phase coverages sufficient for a sec ond order Fourier analysis. Data for II Peg from 36 nights spanning tw o observing seasons give evidence for a statistically significant seco nd harmonic in the V band with an amplitude of 0.024 +/- 0.007% in the parameter Ps. The modulation appears to be stronger (0.042 +/- 0.010% ) during the first season (1989-90) and to have a decreased amplitude (0.013 +/- 0.010%) during the second indicating possible long-term var iability. Due to the small number of observations in the R and I bands the detections are less clear. The same is true for the Fourier fits of the other observed binaries. CQ Aur, RZ Eri, and VV Mon are polariz ed at the 0.20% level (sigma similar to +/-0.01%), but the wavelength dependence for these binaries is consistent with interstellar polariza tion The mean polarizations for UX Ari and DK Dra are small (0.017 +/- 0.010% and 0.032 +/- 0.008%, respectively), but show a tendency to in crease toward the infrared, which may indicate scattering by large dus t particles in optically thin circumstellar material. No correlation b etween the IR excess and the evidence for intrinsic polarization was f ound.