A proposed new white dwarf spectral classification system

The lack of temperature distinctions among the hydrogen-dominated and helium-dominated spectral sequence of white dwarfs, the discovery of hybrid composition white dwarfs, and the many composition subclasses further complicated by variability, polarization, and other observable indicators of magnetism all speak to the need for a new system of white dwarf spectral classification. Such a new scheme is proposed and defined. It retains a link with the present system but introduces a better description of what the spectrum actually exhibits and provides quantitative temperature information. These changes are consistent with the expressed needs of investigators in the field. The combination of symbols will consist of (1) an uppercase D for degenerate; (2) an uppercase letter for primary spectroscopic type in the optical spectrum; (3) an uppercase letter for secondary spectroscopic features, if present; and (4) a temperature index from 0 to 9 defined by 10 x theta-eff (= 50,400/T).