Observation of mass loss in R CrB during the visual light minimum

Visual light minima of R CrB stars are thought to be caused by the formation of circumstellar dust. It has been observed at the time of the light minimum that there is difference in the reddening between the descending and the rising branches of the light curves. The extinction during the descending branch tends to be neutral with not much of colour change, while there occurs redder colours during the recovery part of the light curve (Forrest 1974). It is probable that the gas causing the broad emission lines with Ne approximately 5 x 1011 cm-3 also produces the neutral extinction due to electron scattering. An extinction of 4.5 mag can result if this region is assumed to extend to 2R. (Auth.)