A Late-type L Dwarf at 11 pc Hiding in the Galactic Plane Characterized Using Gaia DR2

TL;DR

This paper characterizes a nearby ultracool L dwarf hidden in the Galactic plane using Gaia DR2 data, confirming its spectral type, estimating its physical properties, and discussing its detection challenges due to its location and colors.

Contribution

The study provides a detailed characterization of a late-type L dwarf at 11 parsecs, utilizing Gaia data and near-infrared spectroscopy, revealing its physical properties and detection history.

Findings

Confirmed spectral type L7 through spectroscopy

Estimated mass of approximately 53 Jupiter masses

Identified detection challenges due to location and colors

Abstract

We report on the characterization of a nearby (d = 11.2 pc) ultracool L dwarf (WISE J192512.78+070038.8; hereafter W1925) identified as a faint (G = 20.0) high proper motion (0.22"/yr) object in the Gaia Data Releases 1 and 2. A Palomar/TripleSpec near-infrared spectrum of W1925 confirms a previously estimated photometric L7 spectral type by Scholz et al. 2018, and its infrared colors and absolute magnitudes are consistent with a single object of this type. We constructed a spectral energy distribution using the Gaia parallax, literature photometry and near infrared spectrum and find a luminosity log(Lbol/LSun) = -4.443+/-0.008. Applying evolutionary models, we infer that W1925 is likely a 53+/-18 MJup brown dwarf with Teff=1404+/-71 K and log g =5.1+/-0.4 dex (cgs). While W1925 was detected in both the 2MASS and WISE infrared sky surveys, it was not detected in photographic plate sky surveys. Its combination of extreme optical-infrared colors, high proper motion, and location near the crowded Galactic plane (b = -4.2 deg) likely contributed to it having evaded detection in pre-Gaia surveys.