H-band spectroscopic classification of OB stars

We present a new spectroscopic classification for OB stars based on H-band (1.5 mu m to 1.8 mu m) observations of a sample of stars with optical spectral types. Our initial sample of nine stars demonstrates that the combination of He I 1.7002 mu m and H Brackett series absorption can be used to determine spectral types for stars between similar to O4 and B7 (to within similar to+/-2 sub-types). We find that the Brackett series exhibits luminosity effects similar to the Balmer series for the B stars. This classification scheme will be useful in studies of optically obscured high mass star forming regions. In addition, we present spectra for the OB stars near 1.1 mu m and 1.3 mu m which may be of use in analyzing their atmospheres and winds. (C) 1997 American Astronomical Society.