MOA 2010-BLG-477Lb: constraining the mass of a microlensing planet from microlensing parallax, orbital motion, and detection of blended light

Microlensing detections of cool planetsare important for the construction of an unbiased sample to estimate the frequency of planetsbeyond the snow line, which is where giant planetsare thought to form according to the core accretion theory of planetformation. In this paper, we report the discovery of a giant planetdetected from the analysis of the light curve of a high-magnification microlensing event MOA 2010-BLG-477. The measured planet-star mass ratio is q = (2.181 {+-} 0.004) Multiplication-Sign10{sup -3} and the projected separation is s = 1.1228 {+-} 0.0006 in units of the Einstein radius. The angular Einstein radiusis unusually large {theta}{sub E} = 1.38 {+-} 0.11 mas. Combining this measurement with constraints on the ' microlens parallax' and the lens flux, we can only limit the host mass to the range 0.13 < M/M{sub Sun} < 1.0. In this particular case, the strong degeneracy between microlensing parallaxand planet orbital motionprevents us from measuring more accurate host and planetmasses. However, we find that adding Bayesian priors from two effects (Galactic model and Keplerian orbit) each independently favors the upper end of this mass range, yielding star and planetmasses of M{sub *} = 0.67{supmore » +0.33}{sub -0.13} M{sub Sun} and m{sub p} = 1.5{sup +0.8}{sub -0.3} M{sub JUP} at a distance of D = 2.3 {+-} 0.6 kpc, and with a semi-major axisof a = 2{sup +3}{sub -1} AU. Finally, we show that the lens mass can be determined from future high-resolution near-IR adaptive optics observations independently from two effects, photometric and astrometric.« less