"Metallic-line" A-type stars, or, for short, "Am" stars, are defined as stars which show a difference between the K-line type and the metallic-line type. The star 63 Tau is a classic example of such a star. As can be seen in the illustration, the Ca II K-line of this star is similar in strength to that of the A2 standard, while the metallic-line spectrum more closely matches that of the F3 standard. The hydrogen lines show an intermediate spectral type, estimated here to be about F0. The spectral type of this star is expressed, therefore, as kA2 hF0 mF3 (III-IV). Notice that the Sr II 4077 line is enhanced in the Am star, and the Ca I 4227 line is weak.
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