Fire spectroscopy of the ultra-cool brown dwarf, UGPS J072227.51-054031.2: Kinematics, rotation and atmospheric parameters

Abstract

We present λ/Δλ 6000 near-infrared spectroscopy of the nearby T9 dwarf, UGPS J072227.51-054031.2, obtained during the commissioning of the Folded-Port Infrared Echellette Spectrograph on the Baade Magellan telescope at Las Campanas Observatory. The spectrum is marked by significant absorption from H2O, CH4, and H2. We also identify NH 3 absorption features by comparing the spectrum to recently published line lists. The spectrum is fit with BT-Settl models, indicating T eff 500-600 K and log g 4.3-5.0. This corresponds to a mass of 10-30 and an age of 1-5Gyr, however, there are large discrepancies between the model and observed spectrum. The radial and rotational velocities of the brown dwarf are measured as 46.9 2.5 and 40 10kms-1, respectively, reflecting a thin disk Galactic orbit and fast rotation similar to other T dwarfs, suggesting a young, possibly planetary-mass brown dwarf. © 2011. The American Astronomical Society. All rights reserved.