Simon Jeffery, Armagh Observatory, College Hill, Armagh, N.
Ireland
Don Pollacco, Queens University Belfast, Belfast, N. Ireland
At discovery in 1996 March, the spectrum of V4334 Sgr resembled that of a late A or early F star. It subsequently evolved rapidly to become a carbon star by 1997 April. We will review the qualitative behaviour of the spectrum during this interval as observed by others. We will also introduce a continuous sequence of optical spectra obtained with the Isaac Newton Telescope from discovery onwards. The interpretation of the evolving spectrum in terms of fundamental stellar parameters (temperature, gravity, composition) will also be examined. These data are fundamental to the debate over whether V4334 Sgr is a `final-flash' helium star and how it is related to other `post-AGB' helium stars. This object presents a unique series of problems for the quantitative analyst; we will attempt to identify those which require most urgent attention.