The Hδ line for a number of B8 stars illustrates our criterion for assigning luminosity class. Compare to the B3 stars in Fig. 4. By this late type, there is a very large gap between stars close to the main sequence and the supergiants (see discussion in Sect. 5.2.3). The stars shown here are the same as in Fig. A.12, except for α Leo, which has replaced π Cet in order to demonstrate the effect of fast rotation on the central part of the line profiles.