The Unusual Ultraviolet Chromospheric Spectrum of the R Coronae Borealis Star, V854 Centauri (NSV 6708), at Minimum Light
Judge, P. G.; Stanford, S. A.; Clayton, Geoffrey C.; Drilling, John S.; Whitney, Barbara A.
United States
Abstract
Results are presented of IUE observations of a decline of the recently discovered R CrB star, V854 Cen. These observations are of particular interest because they include spectra taken at 7 mag below maximum light. The 'chromospheric' emission spectra show striking differences from UV spectra of other R CrB stars in decline. Strong emission appears in several lines not normally seen in R CrB emission-line spectra, in particular at semiforbidden C II 2326, Mg I 2852, and C I 2965, 2967. Spectral evolution similar to that seen in visible spectra of R CrB stars is clearly seen in the UV. It is argued that the differences between V854 Cen and other R CrB stars are related to known abundance differences or to different temperature and density conditions in the emission-line regions of the various R CrB stars. The emission may also be significantly affected by the presence of dust in or near the emitting region.