The Balmer discontinuities of 09-B2 supergiants

New energy distributions of supergiants at 50 A resolution from lambdalambda3200--8000 show that the Balmer discontinuities are poorly correlated with spectral types. A particularly good example is epsilon Ori, whose Balmer discontinuity is 0.1 mag larger than other 09.5 Ia and B0.5 Ia supergiants. Analysis of available four-color and Hβ photometry shows that whereas Hβ correlates well with luminosity as indicated by MK luminosity class, the Balmer discontinuity does not. Our energy distributions show that several 09.5--B0.5 Ia supergiants have Balmer discontinuities in emission on the Palomar system of absolute calibration. They appear to be continuous across the Balmer discontinuity on the calibration of Hayes. (U.S.)