(April 2024) Cool Star Lab members contributed to the discovery of 13 new M dwarf + T dwarf wide binaries identified in CATWISE2020 and Backyard Worlds data. These important benchmark systems enable better understanding of the influence of age and metallicity on the evolution and atmospheres of low-temperature brown dwarfs. The sample includes at least one potentially young T dwarf that could have a mass as low as 2 Jupiter masses (read the article by Marocco et al. in Astrophysical Journal)

(April 2024) Adam Burgasser contributed to analysis of the host star of the newly-discovered mini-Neptune exoplanet TOI-4336A b. The star is part of a hierarchical M dwarf triple system with nearly identical masses, mirroring the alien host star system in the Three Body Problem. The planet, which is about twice the size of Earth and receives 50% more light than Earth, is a promising target for transmission spectroscopy of a habitable zone world (read the article by Timmermans et al. in Astronomy & Astrophysics)

(March 2024) Former Cool Star Lab graduate Dino Hsu has published a study of radial and rotational velocities of late-M and L dwarfs observed with the SDSS/APOGEE instrument. The high spectral resolution of APOGEE combined with a forward-modeling approach results in radial velocity precisions of 400 m/s. The study identified 3 new members of young moving groups, and 37 sources with significant radial velocity variations, including binaries with orbital periods measured in days. It also found an expected decline in radius (inferred from rotational velocity and variability period) with age. (read the preprint by Hsu et al.)

(Oct 2023) Undergraduate researcher Alexia Bravo worked with collaborator Adam Schneider to analyze three peculiar brown dwarf spectra obtained as part of the Backyward Worlds project. She identified two spectral blend binaries and one potentially variable brown dwarf. The binaries may prove to be closely-separated systems for which mass measurements can be made, while the variable brown dwarf allows study of cloud formation and dynamics in low temperature atmospheres (see the preprint by Bravo et al. and the AAS Nova highlight)

(Aug 2023): The Cool Star Lab obtained Keck/NIRES and Keck/NIRSPEC data for a newly-resolved L dwarf binary pair identified by citizen scientists in the Backyard Worlds: Planet 9 program. CWISE J0617+1945AB is an L2 + L4 pair at 28 pc separated by 1.3 arcseconds. Its wide separation makes it an important benchmark for comparative L dwarf studies (read the Research Note by Humphries et al.). 

(Jun 2023): Adam Burgasser and Carl Melis obtained Lick/Kast optical spectra for one of two new low-mass planet host stars identified in TESS + SPECULOOS. The star, TOI-2084, has a previously unrecognized co-moving, low-mass stellar companion 1400 AU away, giving the 6.7 Earth-mass planet a second "dim red bulb" to illuminate it (read the preprint by Barkaoui et al.). 

(Mar 2023): Cool Star Lab researchers contributed to the discovery of the first Y dwarf binary, WISE J0336-0143AB, identified with JWST/NIRCam. The close pair is separated by less than 1 AU, and the secondary has a mass near or below the deuterium fusion limit, often consider the boundary between brown dwarf and planetary masses. The article has been accepted for publication in ApJ Letters (read the paper by Calissendorff et al. at ApJ Letters).

(Jan 2023): The Cool Star Lab Machine Learning group published a Research Note demonstrating spectral binary identification with a random forest classifier. The paper was led by undergraduate researcher Malina Desai (read the paper by Desai et al. at RNAAS)

(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)