We present new radial velocity and trigonometric parallax measurements indicating that the unusually red and photometrically variable T2 dwarf 2MASS J13243553+6358281 is a member of the young ( \sim 150 Myr ) AB Doradus moving group based on its space velocity .
We estimate its model-dependent mass in the range 11–12 M _ { \mathrm { Jup } } at the age of \replaced AB Doradusthe AB Doradus moving group , and its trigonometric parallax distance of 12.7 \pm 1.5 pc makes it one of the nearest known isolated planetary-mass objects .
The \replaced peculiar spectroscopic features of 2MASS J13243553+6358281 , such as its unusually red near-infrared continuum and inflated excess flux in the K band , wereunusually red continuum of 2MASS J13243553+6358281 in the near-infrared was previously suspected to be caused by an unresolved L+T brown dwarf binary , although it was never observed with high-spatial resolution imaging .
This new evidence of youth suggests that a low surface gravity may be sufficient to explain \replaced its peculiar featuresthis peculiar feature .
Using the new parallax we find that its absolute J -band magnitude is \sim 0.4 mag fainter than equivalent-type field brown dwarfs , suggesting that the binary hypothesis is unlikely .
The fundamental properties of 2MASS J13243553+6358281 follow the spectral type sequence of other known high-likelihood members of \replaced AB Doradusthe AB Doradus moving group .
The effective temperature of 2MASS J13243553+6358281 provides the first precise constraint on the L/T transition at a known young age , and indicates that it happens at a temperature of \sim 1150 K at \sim 150 Myr , compared to \sim 1250 K for field brown dwarfs .