Brown Dwarf Discovery
The Cool Star Lab team is engaged in the search and characterization of the coldest, oldest, and weirdest cool stars and brown dwarfs in the Milky Way. We partner with the Backyard Worlds: Planet 9 project, a citizen-science program that uses multi-epoch WISE/NEOWISE data to find faint, infrared, moving sources. Our team focuses on spectroscopic follow-up using facilities such as Lick Observatory, NASA's IRTF Observatory, and Keck Observatory to confirm, classify, and characterize the spectral properties of our faint neighbors. We also search for cold and distant brown dwarfs in HST and JWST survey, remnants for the Milky Way's distant past.
Recent Results
A Bevy of Brown Dwarf Companions
(March 2024) Cool Star Lab members contributed to a massive haul of benchmark ultracool dwarf companions to nearby stars identified by the Backyard Worlds Team. CUNY graduate student Austin Rothermich identified 89 new systems with G2-M9 primaries and M7-T9 companions with diverse spectral properties, and many of these systems appear to be triples and quadruples. These systems span exceptionally wide separations and low mass ratios, in the latter case with similar values as exoplanet systems. (read the preprint by Rothermich et al. and watch his AAS 243 press conference)
An unusual and cold brown dwarf
(Oct 2023) Cool Star Lab members contributed to the discovery of a new Y dwarf identified by the Backyard Worlds Team. The source, CWISE J105512.11+544328.3, was confirmed and classified with Keck/NIRES near-infrared spectroscopy, and has an estimated temperature of 500 K. It's extremely blue mid-infrared color suggests it may have an unusual, possibly metal-poor atmosphere. The publication was led by U. Florida undergraduate Grady Robbins (see the preprint by Robbins et al.)
JWST Uncovers Distant Brown Dwarfs on the Outskirts of the Milky Way
(Sep 2023) Adam Burgasser and Roman Gerasimov led an article analyzing JWST/NIRSpec data of three distant T dwarfs identified in the UNCOVER survey of the Abell 2744 lensing field. The NIRSpec prism data allowed full analysis of the 1-5 µm spectra, revealing all three to be T dwarfs at kiloparsec distances, two with evidence of subsolar metallicities. The coldest of the three, previously identified photometrically as GLASS-BD-1, shows evidence of phosphine in its infrared spectra, a potential new indicator of subsolar metallicity in cool brown dwarf spectra (read the preprint by Burgasser et al.).
First brown dwarf discovery in JWST
(Jan 2023) Adam Burgasser contributed to the discovery of the first brown dwarf to be found with JWST, a late T dwarf 570-720 pc from the Sun (read the paper by Nonino et al. at ApJ Letters)
Discovery of a young planetary mass object
(Jan 2023): The Cool Star Lab contributed to the discovery of an extremely red L/T dwarf by the Backyard Worlds program, which is likely a planetary mass object in the 22 Myr-old Beta Pic moving group. The CSL team obtained the spectrum of this unique young source with the NIRES spectrograph at Keck Observatory (read the paper by Schneider et al. in ApJ Letters).
The M dwarf companion to µ Virgenes
(Dec 2022) Summer research student and Lamat Institute scholar Julissa Villalobos Valencia led a spectroscopic study of the M5 dwarf companion to the bright star µ Virgenes, which is visible to the naked eye (read the paper by Villalobos Valencia et al. at AAS Research Notes)