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6. B2

The blend near lambda 4072 is weaker than at B1. Si II 4128-4130 is fainter than in class B3. The luminosity classes were determined from the ratios lambda 3995: lambda 4009, lambda 4121: lambda 4144, lambda 4387: lambda 4552 and from the appearance of the wings of the hydrogen lines. The stars gamma Peg and zeta Cas are located between classes B2 and B3.


Star MKK a delta m HD Notes

gamma Peg...... B2.5 IV 0:08 +14°38' 2.9 B2
zeta Cas..... B2.5 IV 0:31 +53 21 3.7 B3
gamma Ori...... B2 IV 5:19 + 6 16 1.7 B2
chi2 Ori..... B2 I 5:58 +20 8 4.7 B2p
pi Sco...... B2 IV 15:52 -25 50 3.0 B2
rho Oph...... B2 V 16:19 -23 13 5.2 B5 1
theta Oph...... B2 IV 17:15 -24 54 3.4 B3
lambda Sco...... B2 IV 17:26 -37 2 1.7 B2
9 Cep...... B2 I 21:35 +61 38 4.9 B2p 2
12 Lac..... B2 III 22:37 +39 42 5.2 B2

1. The He I lines are as strong as in other B2 stars and are considerably stronger than at class B5. The H lines are strong and broad; this has been taken to be an effect of low luminosity in a B2 spectrum rather than a reason for classifying the star as B5. The H lines are somewhat weaker than in eta UMa (B3). All spectral lines are very broad.
2. The star 9 Cep is a pronounced supergiant but spectroscopic evidence (lambda 3995: lambda 4009, lambda 4387: lambda 4552, intensity of H lines) indicates that it is definitely less luminous than chi Ori.

The luminosity effects are so well marked at B2 that there is no ambiguity in the location of any of the stars in the five luminosity classes used.

Plate 11. Luminosity Effects at B2
Plate 11
High resolution image

Plate 12. The Be Stars and Phi Persei
Plate 12
High resolution image

Plate 13. The Bnn Stars
Plate 13
High resolution image

Plate 14. P Cygni
Plate 14
High resolution image

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