Photometry of R Coronae Borealis

Extract

Photoelectric photometry of R CrB was obtained during the years 1966–71. During this time the star emerged from a prolonged minimum, showing a change in colour indices which was very like those of the supergiant sequence between G 8 and F 8 if allowance is made for an ultraviolet excess and some interstellar reddening. Superimposed on this rise towards maximum was a sharp minimum, during which the V magnitude was observed to decline through more than 3 magnitudes without any corresponding reddening in the colour indices. Throughout the emergence from the extended minimum the star showed irregular fluctuations of up to 0.2 mag. on a timescale of weeks.