1995A&A...294..763A

The R Coronae Borealis (RCB) star RY Sgr underwent a deep minimum ({DELTA}V∼7.5mag) in 1993. Here medium and low resolution observations from approximately 35 days into the decline are presented together with photometry from the early phases until some 100 days thereafter. The spectra show sharp chromospheric emission lines of Fe, TiII, ScII, BaII and YII, as well as broad emission from Na D, HeI, K and MgI. In general the broad lines are stationary or slightly blueshifted relative to the star. An absorption feature in Na D₂ corresponds to a radial velocity of -200km/s. The helium line at 587.6nm is surprisingly weak, which suggests high optical depths and electron densities. Strong emission bands due to the Swan bands of C₂ are found and two extended emission "bumps" around 390nm and 590nm still lack definite identification. I also present the first identified forbidden lines in RY Sgr and the first published detection of [CaII] in a RCB star. Other lines are tentatively ascribed to [NII] and [CI]. Comparison of calcium line ratios indicates an electron density of ∼10⁹cm^–3, but it seems like at least two different regions emit the broad lines: a high density chromospheric environment and a much less dense nebula-like region.