Spectrophotometry of R CrB during the minimum of 1974.

Spectrophotometric observations of R Coronae Borealis were obtained as the star returned to normal brightness during the minimum of 1974. Absolute flux distributions and extinction optical thicknesses were determined for those nights on which observations were made. The optical thicknesses were found to be consistent with extinction by spherical graphite particles having radii of about 0.07 . No trend toward either an increase or a decrease in particle size was detected. A close fit to the rising branch of the visual light curve of R CrB was obtained using a simple model in which the return to maximum brightness of R CrB is caused by the radiation pressure dispersal of a cloud of graphite particles. Subject headings: spectrophotometry - stars: circumstellar shells - stars: individual - stars: R Coronae Borealis