The upsilon Andromedae system was the first multi-planet system discovered orbiting a main sequence star .
We describe the detection of water vapor in the atmosphere of the innermost non-transiting gas giant ups And b by treating the star-planet system as a spectroscopic binary with high-resolution , ground-based spectroscopy .
We resolve the signal of the planet ’ s motion and break the mass-inclination degeneracy for this non-transiting planet via deep combined flux observations of the star and the planet .
In total , seven epochs of Keck NIRSPEC L band observations , three epochs of Keck NIRSPEC short wavelength K band observations , and three epochs of Keck NIRSPEC long wavelength K band observations of the ups And system were obtained .
We perform a multi-epoch cross correlation of the full data set with an atmospheric model .
We measure the radial projection of the Keplerian velocity ( K _ { P } = 55 \pm 9 km/s ) , true mass ( M _ { b } = 1.7 ^ { +0.33 } _ { -0.24 } M _ { J } ) , and orbital inclination ( i _ { b } = 24 \pm 4 ^ { \circ } ) , and determine that the planet ’ s opacity structure is dominated by water vapor at the probed wavelengths .
Dynamical simulations of the planets in the ups And system with these orbital elements for ups And b show that stable , long-term ( 100 Myr ) orbital configurations exist .
These measurements will inform future studies of the stability and evolution of the ups And system , as well as the atmospheric structure and composition of the hot Jupiter .