The Discontinuous Drop in B Giant X-ray Emission at Spectra Type B1

B supergiants display a discontinuous drop in Xray emission along a dividingline in the HR diagram (analogous to the one for K giants) which is clearlyrelated to the bistability jump (BSJ) at spectral type B1. Our study revealedseveral interesting and unexpected results, but some uncertainties have arisensince B supergiant winds are thick to soft Xrays. We now have observationalevidence that the BSJ extends to the lower luminosity B giants which have lowerwind densities, i.e., they do not have the B supergiant Xray optical depthproblem. We are requesting XMMNewton EPIC observations of 2 B giants tocomplement our 2 AO6 B giant observations which will enhance our understandingof this Bstar dividing line. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]