Parallaxes and physical properties of 11 mid-to-late T dwarfs

TL;DR

This study measures parallaxes of 11 mid-to-late T dwarfs to test model predictions, calibrate magnitudes, and estimate their luminosities and temperatures, revealing model limitations in predicting colors of the coolest T dwarfs.

Contribution

It provides new parallax measurements and evaluates model reliability for late T dwarfs, highlighting the need for improved atmospheric opacities.

Findings

Models cannot accurately predict colors of the latest T dwarfs.

Effective temperature ranges were estimated for all targets.

The study offers a new magnitude-spectral type calibration.

Abstract

We present parallaxes of 11 mid-to-late T dwarfs observed in the UKIRT Infrared Deep Sky Survey. We use these results to test the reliability of model predictions in magnitude-color space, determine a magnitude-spectral type calibration, and, estimate a bolometric luminosity and effective temperature range for the targets. We used observations from the UKIRT WFCAM instrument pipeline processed at the Cambridge Astronomical Survey Unit. The parallaxes and proper motions of the sample were calculated using standard procedures. The bolometric luminosity was estimated using near- and mid-infrared observations with two different methods. The corresponding effective temperature ranges were found adopting a large age-radius range. We show the models are unable to predict the colors of the latest T dwarfs indicating the incompleteness of model opacities for NH3, CH4 and H2 as the temperature declines. We report the effective temperature ranges obtained.