FIRE Spectroscopy of the ultra-cool brown dwarf, UGPS J072227.51-054031.2: Kinematics, Rotation and Atmospheric Parameters

TL;DR

This study provides high-resolution near-infrared spectroscopy of the T9 brown dwarf UGPS J072227.51-054031.2, analyzing its atmospheric composition, kinematics, and rotation to better understand its physical properties and evolutionary status.

Contribution

First detailed spectral analysis of this nearby ultra-cool brown dwarf using BT-Settl models, revealing atmospheric parameters and kinematic properties.

Findings

Effective temperature ~ 500-600 K

Radial velocity ~ 47 km/s, rotational velocity ~ 40 km/s

Indicates a young, planetary-mass brown dwarf with a thin disk orbit

Abstract

We present {\lambda}/{\Delta}{\lambda} ~ 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 NH3 absorption features by comparing the spectrum to recently published line lists. The spectrum is fit with BT-Settl models, indicating Teff ~ 500-600 K and log g ~ 4.3-5.0. This corresponds to a mass of ~ 10-30 MJup and an age of 1-5 Gyr, 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 \pm 2.5 and 40 \pm 10 km/s, respectively, reflecting a thin disk Galactic orbit and fast rotation similar to other T dwarfs, suggesting a young, possibly planetary-mass brown dwarf.