摘要：We present the analysis of the planetary microlensing event MOA-2011-BLG-291, which has a mass ratio ofq=(3.8±0.7)×10 −4 and a source star that is redder (or brighter) than the bulge main sequence. This event islocated at a low Galactic latitude in the survey area that is currently planned for NASA’s Wide Field InfraredSurvey Telescope (WFIRST) exoplanet microlensing survey. This unusual color for a microlensed source starimplies that we cannot assume that the source star is in the Galactic bulge. The favored interpretation is that thesource star is a lower main-sequence star at a distance of D S =4.9±1.3 kpc in the Galactic disk. However, thesource could also be a turn-off star on the far side of the bulge or a subgiant in the far side of the Galactic disk if itexperiences significantly more reddening than the bulge red clump stars. However, these possibilities have only asmall effect on our mass estimates for the host star and planet. We find host star and planet masses ofM M 0.15host 0.100.27=-+ and mM 18p 1234=-+Å from a Bayesian analysis with a standard Galactic model, under theassumption that the planet hosting probability does not depend on the host mass or distance. However, if weattempt to measure the host and planet masses with host star brightness measurements from high angular resolutionfollow-up imaging, the implied masses will be sensitive to the host star distance. The WFIRST exoplanetmicrolensing survey is expected to use this method to determine the masses for many of the planetary systems thatit discovers, so this issue has important design implications for the WFIRST exoplanet microlensing survey.
关键词：gravitational lensing: micro;planetary systems
