Masses and orbital constraints for the OGLE-2006-BLG-109Lb,c Jupiter/Saturn analog Planetary System

We present a new analysis of the Jupiter+Saturn analog system, OGLE-2006-BLG-109Lb,c, which was the first double planet system discovered with the gravitational microlensing method. This is the only multi-planet system discovered by any method with measured masses for the star and both planets. In addition to the signatures of two planets, this event also exhibits a microlensing parallax signature and finite source effects that provide a direct measure of the masses of the star and planets, and the expected brightness of the host star is confirmed by Keck AO imaging, yielding masses of M*+=0.51 +0.05 -0.04 Mo, Mb = 231 ¡À 19 M ¨’, and Mc = 86 ¡À 7 M ¨’. The Saturn-analog planet in this system had a planetary light-curve deviation that lasted for 11 days, and as a result, the effects of the orbital motion are visible in the microlensing light curve. We find that four of the six orbital parameters are tightly constrained and that a fifth parameter, the orbital acceleration, is weakly constrained. No orbital information is available for the Jupiter-analog planet, but its presence helps to constrain the orbital motion of the Saturn-analog planet. Assuming co-planar orbits, we find an orbital eccentricity of E=0.15 =+0.17 -0.10 and an orbital inclination of I=64o +4o -7o. The 95% confidence level lower limit on the inclination of i > 49¡ã implies that this planetary system can be detected and studied via radial velocity measurements using a telescope of>~ 30 m aperture.