A High-Resolution H- and K-Band Spectroscopic Sequence of Ultracool Dwarf Stars

Brown dwarfs are substellar objects too low mass to initiate the hydrogen fusion necessary to be considered stars. We have obtained high-resolution near-infrared spectra in the H and K bands of a sequence of brown dwarfs and low mass stars (known as ultracool dwarfs). All data were obtained using the Immersion Grating INfrared Spectrometer (IGRINS) on the 4.3 m Discovery Channel Telescope at a resolving power of R~45,000. Our sequence spans the spectral types from M6V to T2, covering the temperature range from 1300-3000K. We are performing model comparisons between our data and a new generation of model atmospheres created by Marley and collaborators. This will allow us to measure specific properties including temperature, surface gravity and cloud properties of our objects. Surface gravity is a measurement of the gravitational acceleration at the surface of a star, and allows the estimation of a star’s mass. By observing objects with different surface gravities, we are also able to empirically search our spectra for features that are especially sensitive to changes in brown dwarf surface gravity.