TY - JOUR
T1 - The Diversity of Cold Worlds: a blended-light binary straddling the T/Y transition in brown dwarfs
AU - Gagliuffi, Daniella C. Bardalez
AU - Faherty, Jacqueline K.
AU - Suarez, Genaro
AU - Merchan, Sherelyn Alejandro
AU - Lacy, Brianna
AU - Burningham, Ben
AU - Matuszewska, Klara
AU - Kiman, Rocio
AU - Vos, Johanna M.
AU - Rothermich, Austin
AU - Gagne, Jonathan
AU - Morley, Caroline
AU - Rowland, Melanie J.
AU - Caselden, Dan
AU - Meisner, Aaron
AU - Schneider, Adam C.
AU - Kuchner, Marc J.
AU - Beichman, Charles A.
AU - Eisenhardt, Peter R.
AU - Gelino, Christopher R.
AU - Gharib-Nezhad, Ehsan
AU - Gonzales, Eileen C.
AU - Marocco, Federico
AU - Whiteford, Niall
AU - Kirkpatrick, J. Davy
N1 - © 2025 The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/
PY - 2025/5/1
Y1 - 2025/5/1
N2 - 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 ± 23 K, 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 the 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.
AB - 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 ± 23 K, 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 the 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.
KW - astro-ph.SR
KW - astro-ph.EP
UR - https://www.scopus.com/pages/publications/105003950443
U2 - 10.3847/1538-4357/adb61e
DO - 10.3847/1538-4357/adb61e
M3 - Article
SN - 0004-637X
VL - 984
SP - 1
EP - 13
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 1
M1 - 74
ER -