New spectrophotometry of the extremely cool proper motion star LHS 2924

Improved spectrophotometric scans are presented for this very faint, red, large-proper motion star which has a peculiar spectrum. The Palomar Observatory 5 meter CCD spectrum shows the clear presence of VO λ7400 and λ7900. However, the TiO and hydride bands and the Na I and K I lines appear relatively weaker over the spectrum of LHS 2924 than they do in the benchmark low-luminosity star VB 10. A high-resolution observation with the MMT echelle spectrograph shows very weak Hα emission, at best. These and other recent results eliminate all previously considered explanations of the nature of LHS 2924 other than a very cool, main-sequence star or sub-stellar-mass "brown dwarf." The weakness of Hα emission tends to indicate that the star is an old, main-sequence object.