Spectroscopy of an unusual emission line M star

We report moderate resolution spectroscopy of an unusual late-type, faint (I≈20^m), emission-line star, PC 0025 + 0447. This object was discovered as part of a grism survey for high redshift quasars; the very strong (> 250 Å equivalent width) Ha emission line was detected by our automated line search algorithm. The spectrum has two unresolved emission lines (Hα and Hβ) near zero velocity, superposed on the absorption spectrum of a very red M dwarf which has strong K I, the strongest VO bands known, and relatively weak bands of TiO. The weakness of subordinate lines of Na I (λ 8192) and other spectral features suggest that it is definitely a cooler, and probably fainter, analog of LHS 2924. The strength of the emission lines indicates that PC 0025 + 0447 is very young; it may be a fading, predecessor brown dwarf at an estimated M_bol approaching 14^m at a distance of ≈ 60 pc.