The discovery of the T8.5 dwarf UGPS J0521+3640

TL;DR

This paper reports the discovery and characterization of a new T8.5 dwarf, UGPS J0521+3640, using UKIDSS data and infrared observations, providing insights into its properties and potential for further companion searches.

Contribution

The paper presents the first identification and detailed analysis of the T8.5 dwarf UGPS J0521+3640, including spectral classification, distance estimation, and physical properties derived from infrared data.

Findings

UGPS J0521+3640 is a T8.5 dwarf at 7-9 pc.

Estimated temperature between 600K and 650K.

Mass range between 14 and 32 Jupiter masses.

Abstract

We have carried out a search for late-type T dwarfs in the UKIDSS Galactic Plane Survey 6th Data Release. The search yielded two persuasive candidates, both of which have been confirmed as T dwarfs. The brightest, UGPS J0521+3640 has been assigned the spectral type T8.5 and appears to lie at a distance of 7-9 pc. The fainter of the two, UGPS J0652+0324, is classified as a T5.5 dwarf, and lies at an estimated distance of 28-37 pc. Warm-Spitzer observations in IRAC channels 1 and 2, taken as part of the GLIMPSE360 Legacy Survey, are available for UGPS J0521+3640 and we used these data with the near-infrared spectroscopy to estimate its properties. We find best fitting solar metallicity BT-Settl models for Teff = 600K and 650K and log g = 4.5 and 5.0. These parameters suggest a mass of between 14 and 32 MJup for an age between 1 and 5 Gyr. The proximity of this very cool T dwarf, and its location in the Galactic plane makes it an ideal candidate for high resolution adaptive optics imaging to search for cool companions.