Our observations confirm the presence of CS gas around eight Bootis stars, more particularly among the most rapid rotators. This is in line with the recent study of Holweger & Rentzsch-Holm (1995), who conclude that these stars are in the pre-main-sequence phase of evolution. Furthermore, our data show that the intensity of the CS component is variable on a timescale of months or years. As the actual time resolution of the observations does not cover a timescale of days we cannot arrive at a conclusion for this timescale. The analysis of the photometric data confirms that four Bootis candidates can be excluded from the Bootis group.
This research has made use of the SIMBAD database, operated at the CDS, Strasbourg, France. One of us (BH) is grateful to the Fonds National suisse de la Recherche Scientifique, which gave its support to part of the research.