Brown Dwarfs

The Diversity of Cold Worlds: A Blended-light Binary Straddling The T/Y Transition In Brown Dwarfs

By Keith Cowing
Status Report
astro-ph.SR
March 7, 2025
Filed under , , , , , , ,
The Diversity of Cold Worlds: A Blended-light Binary Straddling The T/Y Transition In Brown Dwarfs
Color-magnitude diagram of late-T and Y dwarfs in Spitzer colors. Effective temperatures have been estimated using color-temperature relations from Kirkpatrick et al. (2019). Our target, W0146, is shown as a star. Its best fit single is W0535, slightly fainter and redder. The components of its best fit binary template are W0751 as a primary, and W1405 as a secondary. The addition of these two spectra would produce a blended-light template that is redder than expected for its temperature. Three other confirmed binary systems straddling the T/Y transition are shown as squares: WISE J1711+3500 (Liu et al. 2012), WISE J1217+1626 (Liu et al. 2012), and W0336AB (Calissendorff et al. 2023). — astro-ph.SR

We present the first brown dwarf spectral binary characterized with JWST: WISE J014656.66+423410.0, the coldest blended-light brown dwarf binary straddling the T/Y transition.

We obtained a moderate resolution (R∼2700) G395H spectrum of this unresolved binary with JWST/NIRSpec and we fit it to late-T and Y dwarf spectra from JWST/NIRSpec, and model spectra of comparable temperatures, both as individual spectra and pairs mimicking an unresolved binary system.

We find that this tightly-separated binary is likely composed of two unequal-brightness sources with a magnitude difference of 0.50±0.08 mag in IRAC [4.5] and a secondary 1.01±0.13 mag redder than the primary in [3.6]-[4.5]. Despite the large color difference between the best fit primary and secondary, their temperature difference is only 92±23K, a feature reminiscing of the L/T transition.

Carbon disequilibrium chemistry strongly shapes the mid-infrared spectra of these sources, as a complex function of metallicity and surface gravity. While a larger library of JWST/NIRSpec spectra is needed to conclusively examine the peculiarities of blended-light sources, this spectral binary is a crucial pathfinder to both understand the spectral features of planetary-mass atmospheres and detect binarity in unresolved, moderate-resolution spectra of the coldest brown dwarfs.

Daniella C. Bardalez Gagliuffi, Jacqueline K. Faherty, Genaro Suarez, Sherelyn Alejandro Merchan, Brianna Lacy, Ben Burningham, Klara Matuszewska, Rocio Kiman, Johanna M. Vos, Austin Rothermich, Jonathan Gagne, Caroline Morley, Melanie J. Rowland, Dan Caselden, Aaron Meisner, Adam C. Schneider, Marc J. Kuchner, Charles A. Beichman, Peter R. Eisenhardt, Christopher R. Gelino, Ehsan Gharib-Nezhad, Eileen C. Gonzales, Federico Marocco, Niall Whiteford, J. Davy Kirkpatrick

Comments: 21 pages, 7 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2503.02025 [astro-ph.SR] (or arXiv:2503.02025v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2503.02025
Focus to learn more
Submission history
From: Daniella Bardalez Gagliuffi PhD
[v1] Mon, 3 Mar 2025 19:57:39 UTC (6,598 KB)
https://arxiv.org/abs/2503.02025
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter
MORE FROM Brown Dwarfs