We present the discovery of a wide ( 67 AU ) substellar companion to the nearby ( 21 pc ) young solar-metallicity M1 dwarf CD - 35 2722 , a member of the \approx 100 Myr AB Doradus association .
Two epochs of astrometry from the NICI Planet-Finding Campaign confirm that CD - 35 2722 B is physically associated with the primary star .
Near-IR spectra indicate a spectral type of L4 \pm 1 with a moderately low surface gravity , making it one of the coolest young companions found to date .
The absorption lines and near-IR continuum shape of CD - 35 2722 B agree especially well the dusty field L4.5 dwarf 2MASS J22244381 - 0158521 , while the near-IR colors and absolute magnitudes match those of the 5-Myr old L4 planetary-mass companion , 1RXS J160929.1 - 210524 b .
Overall , CD - 35 2722 B appears to be an intermediate-age benchmark for L-dwarfs , with a less peaked H -band continuum than the youngest objects and near-IR absorption lines comparable to field objects .
We fit Ames-Dusty model atmospheres to the near-IR spectra and find T _ { eff } = 1700–1900 K and \log ( g ) = 4.5 \pm 0.5 .
The spectra also show that the radial velocities of components A and B agree to within \pm 10 km/s , further confirming their physical association .
Using the age and bolometric luminosity of CD - 35 2722 B , we derive a mass of 31 \pm 8 M _ { Jup } from the Lyon/Dusty evolutionary models .
Altogether , young late-M to mid-L type companions appear to be overluminous for their near-IR spectral type compared to field objects , in contrast to the underluminosity of young late-L and early-T dwarfs .