We report the discovery of a planetary-mass companion , HD 106906 b , with the new Magellan Adaptive Optics ( MagAO ) + Clio2 system .
The companion is detected with Clio2 in three bands : J , K _ { S } , and L ^ { \prime } , and lies at a projected separation of 7 \farcs 1 ( 650 AU ) .
It is confirmed to be comoving with its 13 \pm 2 Myr-old F5 host using Hubble Space Telescope /Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr .
DUSTY and COND evolutionary models predict the companion ’ s luminosity corresponds to a mass of 11 \pm 2 ~ { } M _ { Jup } , making it one of the most widely separated planetary-mass companions known .
We classify its Magellan/Folded-Port InfraRed Echellette J / H / K spectrum as L 2.5 \pm 1 ; the triangular H -band morphology suggests an intermediate surface gravity .
HD 106906 A , a pre-main-sequence Lower Centaurus Crux member , was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy .
The disk emission is best fit by a single component at 95 K , corresponding to an inner edge of 15–20 AU and an outer edge of up to 120 AU .
If the companion is on an eccentric ( e > 0.65 ) orbit , it could be interacting with the outer edge of the disk .
Close-in , planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored .
Furthermore , we find no additional companions , though we could detect similar-mass objects at projected separations > 35 AU .
In situ formation in a binary-star-like process is more probable , although the companion-to-primary mass ratio , at < 1 \% , is unusually small .