Spectropolarimetry of R CrB in 1998-2003

The polarization was almost constant in the phase of maximum brightness, being consistent with past observations. We detected, however, temporary changes of the polarization (~0.5%) in 2001 March and August, which were the first detections of large polarization variability in R CrB near maximum brightness.

The amplitude and the position angle of the "transient polarization" were almost constant with wavelength in both events. There was a difference of about 20{deg} in the position angle between the two events. Each event could be explained by light scattering due to a short-lived dust puff occasionally ejected off the line of sight.