We report the discovery of a possible planet in microlensing event MOA-2010-BLG-353. This event was only recognised 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 high cadence 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^{+1.6}_{-0.53} M_{Saturn} mass planet orbiting a 0.18^{+0.32}_{-0.11} M_{sun} red dwarf star, 6.43^{+1.09}_{-1.15} kpc away. The projected separation of the planet from the host star is 1.72^{+0.56}_{-0.48} 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.
@article{arxiv.1510.01393,
title = {MOA-2010-BLG-353Lb A Possible Saturn Revealed},
author = {N. J. Rattenbury and D. P. Bennett and T. Sumi and N. Koshimoto and I. A. Bond and A. Udalski and F. Abe and A. Bhattacharya and M. Freeman and A. Fukui and Y. Itow and M. C. A. Li and C. H. Ling and K. Masuda and Y. Matsubara and Y. Muraki and K. Ohnishi and To. Saito and A. Sharan and D. J. Sullivan and D. Suzuki and P. J. Tristram and S. Kozlowski and P. Mroz and P. Pietrukowicz and G. Pietrzynski and R. Poleski and D. Skowron and J. Skowron and I. Soszynski and M. K. Szymanski and K. Ulaczyk and L. Wyrzykowski},
journal= {arXiv preprint arXiv:1510.01393},
year = {2015}
}