| Résumé | Detailed analyses of high-dispersion, high signal-to-noise spectra enable astronomers to infer many stellar properties. We study nonmagnetic normal and chemically peculiar B, A, and F stars to understand the details of their optical region abundances via graphical techniques using two kinds of figures for 32 elements. By characterizing the anomalies of the mercury-manganese (HgMn) and the metallic-line (Am) stars, we provide major theoretical tests. We confirmed the known Hg dichotomy between HgMn stars, which are greatly overabundant, and the Am stars with normal abundances. Further P, Ga, Xe, Pt, and Au values were only overabundant for some HgMn stars, and lines of the rare earth elements, such as Sm and Eu, were seen only in some Am and normal stars. These observations might be due in some cases to changes in the major ionization state of atoms in the relevant stellar atmosphere. That some HgMn stars with large Ga overabundances have positions close in the H-R diagram to HgMn stars that lack Ga II lines in the optical region suggests a dichotomy similar to Hg with a boundary close to, but not identical, to that for Hg. The spread of the abundance anomalies for a given element tends to be smaller among the Am stars than among the HgMn stars. Star-to-star differences are superimposed upon abundance trends. |
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