engleski

A Cold Neptune-Mass Planet OGLE-2007-BLG-368Lb: Cold Neptunes Are Common

We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q = [9.5 ± 2.1] × 10−5 via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive follow- up observations. A Bayesian analysis returns the stellar mass and distance at Ml = 0.64+0.21 M and Dl = 5.9+0.9 kpc, respectively, so the mass and separa- −0.26 −1.4 tion of the planet are Mp = 20+7 M⊕ and a = 3.3+1.4 AU, respectively. This −8 −0.8 discovery adds another cold Neptune-mass planet to the planetary sample dis- covered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet that could be a cold Neptune or Super-Earth. The discovery of these ten cold exoplanets by the mi- crolensing method implies that the mass function of cold exoplanets scales as Ψ(q) ∝ q −1.7±0.2 with a 95% confidence level upper limit of n < −1.35 (where Ψ(q) ∝ q n ). The microlensing sensitivity region is largely beyond the snow-line, so this implies that Neptune-mass planets are at least three times more common than Jupiters, beyond the snow-line at the 95% confidence level.

gravitational lensing: micro; planetary systems

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