An Atlas of Stellar Spectra 6. The blend near 4072 is weaker than at B1. Si II 4128-4130 is fainter than in class B3. The stars Peg and Cas are located between classes B2 and B3. The He I lines are as strong as in other B2 stars and are considerably stronger than at class B5.
All spectral lines are very broad.
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. Luminosity Effects at B2 Plate 12. The Be Stars and Phi Persei Plate 13. The Bnn Stars Plate 14.