We have used high-resolution spectroscopy to observe the Kepler-16 eclipsing binary as a double-lined system , and measure precise radial velocities for both stellar components .
These velocities yield a dynamical mass-ratio of q = 0.2994 \pm 0.0031 .
When combined with the inclination , i = 90 ^ { \circ } .3401 ^ { +0.0016 } _ { -0.0019 } , measured from the Kepler photometric data by Doyle et al .
( 11 ) , we derive dynamical masses for the Kepler-16 components of \mathrm { M _ { A } = 0.654 \pm 0.017 \mathit { M _ { \odot } } } and \mathrm { M _ { B } = 0.1959 \pm 0.0031 \mathit { M _ { \odot } } } , a precision of 2.5 % and 1.5 % respectively .
Our results confirm at the \sim 2 % level the mass-ratio derived by D11 with their photometric-dynamical model , q = 0.2937 \pm 0.0006 .
These are among the most precise spectroscopic dynamical masses ever measured for low-mass stars , and provide an important direct test of the results from the photometric-dynamical modeling technique .