Confirmation of the OGLE-2005-BLG-169 Planet Signature and Its Characteristics with Lens-Source Proper Motion Detection
Bennett, D. P.; Gould, A.; Fukui, A.; Beaulieu, J. -P.; Marquette, J. -B.; Bhattacharya, A.; Batista, V.
France, United States, Japan
Abstract
We present Keck NIRC2 high angular resolution adaptive optics observations of the microlensing event OGLE-2005-BLG-169Lb, taken 8.21 years after the discovery of this planetary system. For the first time for a microlensing planetary event, the source and the lens are completely resolved, providing a precise measurement of their heliocentric relative proper motion, {μ }{rel,{helio}}=7.44+/- 0.17 mas yr-1. This confirms and refines the initial model presented in the discovery paper and rules out a range of solutions that were allowed by the microlensing light curve. This is also the first time that parameters derived from a microlensing planetary signal are confirmed, both with the Keck measurements, presented in this paper, and independent measurements obtained with the Hubble Space Telescope in I,V and B bands, presented in a companion paper. Hence, this new measurement of {μ }{rel,{helio}}, as well as the measured brightness of the lens in H band, enabled the mass and distance of the system to be updated: a Uranus-mass planet ({m}{{p}}=13.2+/- 1.3{M}\oplus ) orbiting a K5-type main sequence star ({M}*=0.65+/- 0.05{M}⊙ ) separated by {a}\perp =3.4+/- 0.3 AU, at the distance {D}{{L}}=4.0+/- 0.4 kpc from us.