Three-dimensional spectral classification of WN stars: One too many?

A "three-dimensional'' classification for WN stars has been introduced by Smith, Shara, and Moffat (MNRAS 281, 163, 1996). In addition to the well known "one-dimensional'' ionization subclasses (e.g., WN6, WN7, WN8, etc.) they have added subscripts of "h'', "a'', "b'' and "o'' to refer, respectively, to the connotation of hydrogen being present (from the Balmer/ Pickering emission line decrement), the presence of absorption lines, the appearance of broad emission lines, or no evidence of hydrogen (in stars without a "b''). I will critically evaluate the appropriateness of the latter two subscripts, utilizing the observed distribution functions of line width and line strength for Galactic and LMC WN stars. A "two-dimensional'' classification, providing information about the hydrogen in addition to the ionization is probably warranted. (C) 1999 Elsevier Science B.V. All rights reserved.