... L dwarf spectral classification . ... In practice, a spectral classification system is defined by a number of stars (or brown dwarfs) which are selected as fiducial standards, each representing a particular spectral class (M1, M2, M3, etc.) ... Spectral class M is characterised by the presence of strong absorption bands due to the diatomic molecule titanium oxide, TiO (Morgan, Keenan \ Kellman, 1943). ... Wilson system (Joy, 1947). ... Figure L1.5: Late-type M dwarf standards in the KHM system . ...