Abstract
We have combined multi-epoch images from the Infrared Side Port Imager on the
CTIO 4-meter telescope to derive a 3-sigma limit of J=21.7 for the ultra cool
brown dwarf companion to WD 0806-661 (GJ 3483). We find that J-4.5>4.95,
redder than any other brown dwarf known to date. With theoretical evolutionary
models and ages 1.5-2.7 Gyr, we estimate the brown dwarf companion to have mass
<10-13 Jupiter masses and temperature <400 K, providing evidence that this is
among the coolest brown dwarfs currently known. The range of masses for this
object is consistent with that anticipated from Jeans-mass fragmentation and we
present this as the likely formation mechanism. However, we find that
substellar companions of similar mass (~7-17 Jupiter masses) are distributed
over a wide range of semi-major axes, which suggests that giant planet and
low-mass brown dwarf formation overlap in this mass range.
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