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| Paper IPM / Astronomy / 11736 |
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| Abstract: | |||||||
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We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting
a K- or M-dwarf star in the inner Galactic disk or Galactic bulge. The high-cadence observations of the MOA-II
survey discovered thismicrolensing event and enabled its identification as a high-magnification event approximately
24 hr prior to peak magnification. As a result, the planetary signal at the peak of this light curve was observed by
20 different telescopes, which is the largest number of telescopes to contribute to a planetary discovery to date. The
microlensing model for this event indicates a planet?star mass ratio of q = (3.95 ± 0.02) à 10â4 and a separation
of d = 0.97537 ± 0.00007 in units of the Einstein radius. A Bayesian analysis based on the measured Einstein
radius crossing time, tE, and angular Einstein radius, θE, along with a standard Galactic model indicates a host star
mass of ML = 0.38+0.34
â0.18M and a planet mass of Mp = 50+44
â24 Mâ, which is half the mass of Saturn. This analysis
also yields a planet?star three-dimensional separation of a = 2.4+1.2
â0.6 AU and a distance to the planetary system of
DL = 6.1+1.1
â1.2 kpc. This separation is â¼2 times the distance of the snow line, a separation similar to most of the
other planets discovered by microlensing.
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