Mystery of lithium in FS CMa stars.

FS CMa type stars are B-type emission-line stars, whose effective temperatures (from 9 000 to 30 000 K) are too high for neutral lithium with a low ionization threshold of 5.39 eV to exist in their atmospheres. However, about half of stars from the FS CMa group shows the Li I doublet 6708 Å. The presence of lithium lines has been considered a proof of binarity. Here we discuss spectral properties of FS CMa stars that show a slight indication of a possibility that lithium lines may be formed in the circumstellar disk.

Based on data from Perek 2 m telescope, Ondřejov, Czech Republic.

Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientique of France, and the University of Hawaii. The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site.