THE OPTICAL-SPECTRUM OF FG SAGITTAE DURING ITS RECENT DECLINE IN BRIGHTNESS

We describe low- and intermediate-resolution optical spectra of the pe culiar variable star FG Sagittae that were obtained during the later s tages of its current episode of sharply diminished optical luminosity. In the region from lambda5600 to lambda6700 angstrom, the line spectr um is essentially the same as it was in 1983: it contains lines of Fe- peak elements typical of luminous stars of spectral type G or early K, together with a forest of lines due to heavy elements associated with traditional s-process species, e.g., Zr, Ba, Ce, La, Sm, Y, etc. Esti mates of (B-V), derived from these flux-calibrated spectra, show that from early November 1992 onward, the continuum grew progressively redd er until by the end of 1992, the color of the central star became even redder than it was before the onset of the current episode. We cautio n that colors derived from aperture photometry may be seriously contam inated by the flux from emission lines of the planetary nebula surroun ding FG Sge, and may cause the observed colors to appear anomalously t oo negative. The present results are compatible with a model in which the diminution in optical luminosity is the result of the ejection of a semitransparent dust shell by the central star, as proposed by Woodw ard et al. (1993, ApJL, in press). There is no compelling evidence to suggest that the central star is returning to its pre-1960 state withi n the domain of hot stars.