Astron. J., 141, 70 (2011/March-0)
Hubble space telescope imaging and spectral analysis of two brown dwarf binaries at the L dwarf/T dwarf transition.
BURGASSER A.J., BARDALEZ-GAGLIUFFI D.C. and GIZIS J.E.
Abstract (from CDS):
We present a detailed examination of the brown dwarf multiples 2MASS J08503593+1057156 and 2MASS J17281150+3948593, both suspected of harboring components that straddle the L dwarf/T dwarf transition. Resolved photometry from Hubble Space Telescope/NICMOS shows opposite trends in the relative colors of the components, with the secondary of 2MASS J0850+1057 being redder than its primary, while that of 2MASS J1728+3948 is bluer. We determine near-infrared component types by matching combined-light, near-infrared spectral data to binary templates, with component spectra scaled to resolved NICMOS and Kp photometry. Combinations of L7 + L6 for 2MASS J0850+1057 and L5 + L6.5 for 2MASS J1728+3948 are inferred. Remarkably, the primary of 2MASS J0850+1057 appears to have a later-type classification compared to its secondary, despite being 0.8-1.2 mag brighter in the near-infrared, while the primary of 2MASS J1728+3948 is unusually early for its combined-light optical classification. Comparison to absolute magnitude/spectral type trends also distinguishes these components, with 2MASS J0850+1057A being ~1 mag brighter and 2MASS J1728+3948A ~ 0.5 mag fainter than equivalently classified field counterparts. We deduce that thick condensate clouds are likely responsible for the unusual properties of 2MASS J1728+3948A, while 2MASS J0850+1057A is either an inflated young brown dwarf or a tight unresolved binary, making it potentially part of a wide, low-mass, hierarchical quintuple system.
binaries: visual - brown dwarfs - infrared: stars - stars: individual (2MASS J08503593+1057156, 2MASS J17281150+3948593) - stars: low-mass
[BBG2011] 2MASS J1728+3948 N=1, [BBG2011] 2MASS J1728+3948A (Nos A-B).
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