The nearby Sun-like star HD 19467 shows a subtle radial velocity ( RV ) acceleration of -1.37 \pm 0.09 m \ > s ^ { -1 } \ > yr ^ { -1 } over an 16.9 year time baseline ( an RV trend ) , hinting at the existence of a distant orbiting companion .
We have obtained high-contrast adaptive optics images of the star using NIRC2 at Keck Observatory and report the direct detection of the body that causes the acceleration .
The companion , HD 19467 B , is \Delta K _ { s } = 12.57 \pm 0.09 mag fainter than its parent star ( contrast ratio of 9.4 \times 10 ^ { -6 } ) , has blue colors J - K _ { s } = -0.36 \pm 0.14 ( J - H = -0.29 \pm 0.15 ) , and is separated by \rho = 1.653 \pm 0.004 \arcsec ( 51.1 \pm 1.0 AU ) .
Follow-up astrometric measurements obtained over an 1.1 year time baseline demonstrate physical association through common parallactic and proper motion .
We calculate a firm lower-limit of m \geq 51.9 ^ { +3.6 } _ { -4.3 } M _ { J } for the companion mass from orbital dynamics using a combination of Doppler observations and imaging .
We estimate a model-dependent mass of m = 56.7 ^ { +4.6 } _ { -7.2 } M _ { Jup } from a gyrochronological age of 4.3 ^ { +1.0 } _ { -1.2 } Gyr .
Isochronal analysis suggests a much older age of 9 \pm 1 Gyr , which corresponds to a mass of m = 67.4 ^ { +0.9 } _ { -1.5 } M _ { J } .
HD 19467 B ’ s measured colors and absolute magnitude are consistent with a late T-dwarf [ \approx T5-T7 ] .
We may infer a low metallicity of [ Fe/H ] = -0.15 \pm 0.04 for the companion from its G3V parent star .
HD 19467 B is the first directly imaged benchmark T-dwarf found orbiting a Sun-like star with a measured RV acceleration .