MOA-2011-BLG-322LB: A 'second generation survey' microlensing planet

Y. Shvartzvald*, D. Maoz, S. Kaspi, T. Sumi, A. Udalski, A. Gould, D. P. Bennett, C. Han, F. Abe, I. A. Bond, C. S. Botzler, M. Freeman, A. Fukui, D. Fukunaga, Y. Itow, N. Koshimoto, C. H. Ling, K. Masuda, Y. Matsubara, Y. MurakiS. Namba, K. Ohnishi, N. J. Rattenbury, To Saito, D. J. Sullivan, W. L. Sweatman, D. Suzuki, P. J. Tristram, K. Wada, P. C.M. Yock, J. Skowron, S. Kozłowski, M. K. Szymański, M. Kubiak, G. Pietrzyński, I. Soszyński, K. Ulaczyk, Wyrzykowski, R. Poleski, P. Pietrukowicz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Global 'second-generation' microlensing surveys aim to discover and characterize extrasolar planets and their frequency, by means of round-the-clock high-cadence monitoring of a large area of the Galactic bulge, in a controlled experiment. We report the discovery of a giant planet in microlensing event MOA-2011-BLG-322. This moderate-magnification event, which displays a clear anomaly induced by a second lensing mass, was inside the footprint of our second-generation microlensing survey, involving MOA, OGLE and the Wise Observatory. The event was observed by the survey groups, without prompting alerts that could have led to dedicated follow-up observations. Fitting a microlensing model to the data, we find that the time-scale of the event was tE=23.2 ± 0.8 d, and the mass ratio between the lens star and its companion is q=0.028 ± 0.001. Finite-source effects are marginally detected, and upper limits on them help break some of the degeneracy in the system parameters. Using a Bayesian analysis that incorporates a Galactic structure model, we estimate the mass of the lens at 0.39+0.45-0.19M⊙ at a distance of 7.56 ± 0.91 kpc. Thus, the companion is likely a planet of mass 11.6+13.4-5.6 at a projected separation of 4.3+1.5-1.2 au, rather far beyond the snow line. This is the first pure-survey planet reported from a second-generation microlensing survey, and shows that survey data alone can be sufficient to characterize a planetary model. With the detection of additional survey-only planets, we will be able to constrain the frequency of extrasolar planets near their systems' snow lines.

Original languageEnglish
Pages (from-to)604-610
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Mar 2014


  • Binaries: General
  • Galaxy: Stellar content
  • Gravitational lensing: Micro
  • Planetary systems
  • Surveys


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