Optical region elemental abundance analyses of B and A stars - II. The hot AM stars o Pegasi and Aquarii and the marginal peculiar A star Cancri

Abundance analyses using optical region data and fully line blanketed model atmospheres have been performed for two sharp-lined hot Am stars o Pegasi and σ Aquarii and for the sharp-lined marginally peculiar A star ν Cancri. The derived abundances exhibit definite anomalies compared with those of normal B-type stars and the Sun. The values for both o Peg and σ Aqr show definite similarities and differences with those of both HgMn and Am stars, which are respectively hotter and cooler types of non-magnetic chemically peculiar stars of the upper main sequence. On the other hand, the elemental abundances of ν Cnc are similar to those of the HgMn stars. As ν Cnc is photometrically non-variable, it is a member of this class. The abundance differences between σ Aqr and ν Cnc, which have similar temperatures and surface gravities, raises questions about the conventional view that the hot Am stars merge smoothly into the HgMn stars.