On the relationship between the mercury-manganese stars and the metallic-lined stars

An HR diagram indicating the positions of the HgMn and the Am stars analyzed by the senior author and his collaborators shows that the coolest HgMn stars and the hottest Am stars are found on the same stellar evolutionary tracks and hence the former must evolve into the later. The explanation of the dividing line between these two types of nonmagnetic chemically peculiar stars where the Hg abundances suddenly change their degree of overabundance is a major test of the theories which try to explain the anomalous abundances of such stars. Some other important relationships are found which can also serve as tests of theories which purport to explain the properties of these stars.