Stellar archaeology: the evolving spectrum of FG Sagittae

  title={Stellar archaeology: the evolving spectrum of FG Sagittae},
  author={C. Jeffery and D. Scho{\^e}nberner},
  journal={Astronomy and Astrophysics},
Over an interval of 120 years, the extraordinary object FG Sge has been transformed from a hot post-AGB star to a very luminous cool supergiant. Theoretically, this evolution has been associated with the reignition of a helium-shell during the post-AGB stage. A series of studies of the chemical composition of the photosphere have suggested that this evolution has been associated with a dramatic increase of approximately 3 dex in the abundances of s-process elements between about 1960 and 1995… Expand
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