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13. A0

The lines of He I are faint or absent in the dwarfs. The strongest enhanced lines of iron are faintly present in main-sequence stars and increase in strength with increasing luminosity. The hydrogen lines show a marked negative absolute-magnitude effect.


Star MKK a delta m HD Note

C Hya.... A0 V 08:20 -03°35' 4.0 A0
gamma UMa.... A0 V 11:48 +54 15 2.5 A0
a CrB.... A0 V 15:30 +27 03 2.3 A0
a Lyr...... A0 V 18:33 +38 41 0.1 A0
delta Cyg..... A0 III 19:41 +44 53 3.0 A0 1

1. The hydrogen lines in delta Cygni have less pronounced wings than in the other stars listed. Dr. Kuiper has found that the measures of the visual system made during the last 30 years indicate a dynamical parallax of 0".013-0".018.

The luminosity classification was made on the basis of the wings of the hydrogen lines.

Plate 21. Luminosity Effects at A0
Plate 21
High resolution image

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