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

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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