1995A&A...303..819H

We present results of a high-S/N search for circumstellar Ca K lines in two classes of A stars: (i) metal-deficient stars of the λBootis type whose surface anomalies are believed to be due to accretion of depleted gas, and (ii) stars known to possess circumstellar dust disks, including Vega and βPictoris. We derive T_eff and logg and combine model-atmosphere analysis with spectrum synthesis to determine projected rotational velocities, calcium abundances, and the motion of circumstellar gas with respect to the star. Narrow components in Ca K are present in five of the eleven λBoo stars studied. This exceptional high incidence suggests that the λBoo phenomenon is related to the presence of circumstellar gas. Specific topics discussed (Sect. 6) include: (1) a connection between rotation, the presence of detectable amounts of CS gas, and metal deficiency, (2) Vega and βPic as suspected λBoo stars, (3) λBoo stars as probable pre-main-sequence objects, and (4) episodes of massive accretion in βPic and in the λBoo star HR4881.