A sub-Saturn mass planet, MOA-2009-BLG-319Lb

Miyake, N.; Sumi, T.; Dong, S.B.; Jørgensen, U.G.; et al. (2011) .

Astrophysical Journal

. 728: A120.

Link to Publication:

http://arxiv.org/abs/1010.1809

Download Publication:

1010.1809v3.pdf

Abstract:

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 this microlensing event and enabled its identification as a high magnification event approximately 24 hours 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) x 10^-4 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, t_E, and angular Einstein radius, θ_E, along with a standard Galactic model indicates a host star mass of M_L = 0.38^+0.34_-0.18 M_sun and a planet mass of M_p = 50⁺⁴⁴_-24 M_Earth, which is half the mass of Saturn. This analysis also yields a planet-star three-dimensional separation of a = 2.4^+1.2_-0.6 AU and a distance to the planetary system of D_L = 6.1^+1.1_-1.2 kpc. This separation is ~ 2 times the distance of the snow line, a separation similar to most of the other planets discovered by microlensing.