LONG-TERM SPECTROSCOPIC AND POLARIMETRIC MONITORING OF R-CORONAE-BOREALIS NEAR MAXIMUM LIGHT

We have obtained low-resolution visible spectroscopy and polarimetry o f R Coronae Borealis covering 8 years from 1986 to 1993 at Pine Bluff Observatory. The spectra clearly show large CN and Ct band variations correlated with pulsational phase and B-V color, similar to those prev iously seen for RY Sagittarii. During the declines of 1986, 1989 and 1 993, the measured polarization increased in a manner consistent with p revious declines. However, measurements of the position angle of the p olarization in these declines do not support the result of Stanford et al. [ApJ, 325, L9 (1988)] that there is a preferred plane for the dus t ejections. Some of the strongest band strengths of CN and C-2 are as sociated with declines or suspected dust-formation episodes. Many of t he lowest band strengths are found in years when no decline takes plac e. However, large band strengths are not only associated with declines . For instance, in 1991, the band strengths were very large throughout the observing season and significant polarization variations were als o seen even though no decline occurred that year. These variations are interpreted as being due to dust-formation episodes not along the Lin e of sight. It has been suggested that a very large pulsation observed in 1990 may be a small dust-formation episode. The molecular band str engths measured during this pulsation are the largest measured in this study. However, only small variations in polarization were measured d uring the pulsation cycle. There is also some evidence that the polari zation variations are correlated with the pulsations of R CrB in 1990.