A Targeted Search for Peculiarly Red L and T Dwarfs in SDSS, 2MASS, and WISE: Discovery of a Possible L7 Member of the TW Hydrae Association

TL;DR

This study identifies peculiar red L and T dwarf candidates through cross-matching SDSS, 2MASS, and WISE data, discovering new objects including a potential low-mass member of the TW Hydrae group, highlighting ongoing survey potential.

Contribution

It presents the first results of a targeted search for peculiar brown dwarfs, discovering new objects and potential group members not previously identified.

Findings

10 candidates confirmed as peculiar or binary brown dwarfs

Discovery of a very red L7 dwarf possibly linked to TW Hydrae

Identification of a overlooked T dwarf in SDSS data

Abstract

We present first results from a targeted search for brown dwarfs with unusual red colors indicative of peculiar atmospheric characteristics. These include objects with low surface gravities or with unusual dust content or cloud properties. From a positional cross-match of SDSS, 2MASS and WISE, we have identified 40 candidate peculiar early L to early T dwarfs that are either new objects or have not been identified as peculiar through prior spectroscopy. Using low resolution spectra, we confirm that 10 of the candidates are either peculiar or potential L/T binaries. With a J-Ks color of 2.62 +/- 0.15 mag, one of the new objects --- the L7 dwarf 2MASS J11193254-1137466 --- is among the reddest field dwarfs currently known. Its proper motion and photometric parallax indicate that it is a possible member of the TW Hydrae moving group. If confirmed, it would its lowest-mass (5--6 MJup) free-floating member. We also report a new T dwarf, 2MASS J22153705+2110554, that was previously overlooked in the SDSS footprint. These new discoveries demonstrate that despite the considerable scrutiny already devoted to the SDSS and 2MASS surveys, our exploration of these data sets is not yet complete.