MOA-2010-BLG-353Lb: A possible Saturn revealed

Abstract

We report the discovery of a possible planet in microlensing event MOA-2010-BLG-353. This event was only recognized as having a planetary signal after the microlensing event had finished, and following a systematic analysis of all archival data for binary lens microlensing events collected to date. Data for event MOA-2010-BLG-353 were only recorded by the highcadence observations of the OGLE and MOA survey groups. If we make the assumptions that the probability of the lens star hosting a planet of the measured mass ratio is independent of the lens star mass or distance, and that the source star is in the Galactic bulge, a probability density analysis indicates the planetary system comprises a 0.9-0.53+1.6 MSaturn mass planet orbiting a 0.18-0.11+0.32 M⊙ red dwarf star, 6.43-1.15+1.09 kpc away. The projected separation of the planet from the host star is 1.72-0.48+0.56 au. Under the additional assumption that the source is on the far side of the Galactic bulge, the probability density analysis favours a lens system comprising a slightly lighter planet.