H2O and HDO bands in the spectra of late-type dwarfs

We discuss techniques and results of computations of the infrared spectra of late-type dwarfs. Our computations of the synthetic spectra and spectral energy distributions in the infrared (λλ 1–10 µm) were carried out assuming LTE, using the grids of M-and L-dwarf model atmospheres of Allard and Hauschildt (1995) and Tsuji (1998), taking into account the opacities due to H₂O and HDO absorption bands. We discuss the use of HDO bands formed in the infrared spectra of cool dwarfs to realize the “deuterium test” recently proposed for the identi fication of substellar-mass objects and large planets and to refine scenarios for the evolution of young stars and substellar objects.