* Astronomy

Title: Confirmation of the OGLE-2005-BLG-169 planet signature and characteristics with lens-source proper motion detection
Author: V. Batista, J.-P. Beaulieu, D. P. Bennett, A. Gould, J.-B. Marquette, A. Fukui, A. Bhattacharya

We present Keck NIRC2 high angular resolution adaptive optics observations of the microlensing event OGLE-2005-BLG-169, 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, mu_{{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 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 mu_{{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 earth masses) orbiting a K5-type main sequence star (M_*=0.65±0.05 solar masses) separated by a_perp=3.4±0.3 AU, at the distance D_L=4.0±0.4 kpc from us.

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