2014ApJ...780..123S

We report on the analysis of the high microlensing event MOA-2008-BLG-379, which has a strong microlensing anomaly at its peak due to a massive planet with a mass ratio of q = 6.9x10^–3. Because the faint source star crosses the large resonant caustic, the planetary signal dominates the light curve. This is unusual for planetary microlensing events, and as a result, the planetary nature of this light curve was not immediately noticed. The planetary nature of the event was found when the Microlensing Observations in Astrophysics (MOA) Collaboration conducted a systematic study of binary microlensing events previously identified by the MOA alert system. We have conducted a Bayesian analysis based on a standard Galactic model to estimate the physical parameters of the lens system. This yields a host star mass of M_L = 3.3_–1.2^+1.7 M_☉ orbited by a planet of mass m_p = 0.56_–0.27^+0.24 M_Jup at an orbital separation of a = 3.3_–1.2^+1.3 AU at a distance of DL = 4.1_–1.9^+1.7 kpc. The faint source magnitude of I_S= 21.30 and relatively high lens-source relative proper motion of µ_rel = 7.6±1.6 mas/yr imply that high angular resolution adaptive optics or Hubble Space Telescope observations are likely to be able to detect the source star, which would determine the masses and distance of the planet and its host star.