The following document lists the file abstract/DLAMBERT_DLL003.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
The SWS will be used to provide complete spectral scans of the unique variable star FG Sge. This star has always been a true puzzle as to its exact nature; however, in 1992, after nearly a century of slow brightness and spectral changes, FG Sge began undergoing extreme and rapid visual brightness declines follwed by a slower return to normal brightness. These declines are caused by mass ejection and dust condensation obscuring the underlying stellar photosphere. This behavior is similar to the R CrB type stars (RCB) and leads us to suspect that FG Sge is evolving into a new member of the RCB class. The energy distribution of the SWS spectra will be used to infer the distribution of dust with distance. Broad spectral features will betray the chemical make-up of the dust grains, while broad emission lines from a circumstellar envelope may be present. A comparison of FG Sge's IR dust and gas signature with other members of the RCBs will allow us to determine whether FG Sge is evolving into a RCB. The nature and distribution of the circumstellar dust and gas will allow us to test certain hypothesized formation mechanisms for objects like FG Sge, e.g. evolution from a 'born-again' AGB star, where a star on the white dwarf cooling track has ignited its He shell and evolved back into an object resembling a cooler supergiant star.