A Photometric Study of Selected R Coronae Borealis Variables.

Abstract

view Abstract Citations (59) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Photometric Study of Selected R Coronae Borealis Variables. Fernie, J. D. ; Sherwood, Vicki ; DuPuy, David L. Abstract UB V observations of 10 possible R CrB variables are presented. For eight of these only a few observations are available, and average values are presented. More extensive observations are available for p Cas and R CrB. The star p Cas was found to show low-amplitude quasi-periodic variability of the type previously observed by Brodskaya. R CrB was observed during its emergence from a prolonged major minimum. During this time the colors changed in a manner which, allowing for an ultraviolet excess and some reddening, mimicked those of supergiants from G8 to F8. Also during this rise R CrB followed a linear relation on the color- magnitude diagram of slope V/A(B - V) = +3.6. Superposed on this rise toward maximum was a sharp minimum, during which the V-magnitude was observed to decline through more than 3 mag without any corresponding reddening in the color indices. Throughout the emergence from the extended minimum the star showed irregular fluctuations of up to 0.2 mag on a timescale of weeks. Detailed observations at maximum light show that R CrB exhibits a sinusoidal variability of period about 44 and amplitude about 0.15 mag. The light curve suggests RV Tauri-like behavior. The B - V color curve seems irregular with an amplitude of about 0.04 mag, while the radial-velocity at maximum is also slightly variable by about 4 km 2 Isolated VRI observations indicate that R CrB has a small color excess of between 0.0 and 0.1 mag. If it is assumed that the star is pulsating at maximum, the 44d period may be combined with Searle's spectroscopic determination of its surface gravity to indicate a mass of about 2 and a radius of about 100R0. Publication: The Astrophysical Journal Pub Date: March 1972 DOI: 10.1086/151357 Bibcode: 1972ApJ...172..383F full text sources ADS | data products SIMBAD (13) GCPD (1)