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

We have obtained low-resolution visible spectroscopy and polarimetry of 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 previously seen for RY Sagittarii. During the declines of 1986, 1989 and 1993, the measured polarization increased in a manner consistent with previous declines. However, measurements of the position angle of the polarization in these declines do not support the result of Stanford et al. [ApJ, 325, L9 (1988)] that there is a preferred plane for the dust ejections. Some of the strongest band strengths of CN and C-2 are associated with declines or suspected dust-formation episodes. Many of the lowest band strengths are found in years when no decline takes place. 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 also seen even though no decline occurred that year. These variations are interpreted as being due to dust-formation episodes not along the Line of sight. It has been suggested that a very large pulsation observed in 1990 may be a small dust-formation episode. The molecular band strengths measured during this pulsation are the largest measured in this study. However, only small variations in polarization were measured during the pulsation cycle. There is also some evidence that the polarization variations are correlated with the pulsations of R CrB in 1990.