Hot DB White Dwarfs from the Sloan Digital Sky Survey

We present ugriz photometry and optical spectroscopy for 28 DB and DO whitedwarfs with temperatures between 28,000K and 45,000K. About 10 of these areparticularly well-observed; the remainder are candidates. These are the hottestDB stars yet found, and they populate the "DB gap" between the hotter DO starsand the familiar DB stars cooler than 30,000K. Nevertheless, after carefullymatching the survey volumes, we find that the ratio of DA stars to DB/DO starsis a factor of 2.5 larger at 30,000 K than at 20,000 K, suggesting that the "DBgap" is indeed deficient and that some kind of atmospheric transformation takesplace in roughly 10% of DA stars as they cool from 30,000 K to 20,000 K.Comment: Accepted by the Astronomical Journal. 34 pages, 10 figures, LaTe