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Title: MOA-2011-BLG-262Lb: A sub-Earth-mass moon orbiting a gas giant primary or a high velocity planetary system in the galactic Bulge

We present the first microlensing candidate for a free-floating exoplanet-exomoon system, MOA-2011-BLG-262, with a primary lens mass of M {sub host} ∼ 4 Jupiter masses hosting a sub-Earth mass moon. The argument for an exomoon hinges on the system being relatively close to the Sun. The data constrain the product M{sub L} π{sub rel} where M{sub L} is the lens system mass and π{sub rel} is the lens-source relative parallax. If the lens system is nearby (large π{sub rel}), then M{sub L} is small (a few Jupiter masses) and the companion is a sub-Earth-mass exomoon. The best-fit solution has a large lens-source relative proper motion, μ{sub rel} = 19.6 ± 1.6 mas yr{sup –1}, which would rule out a distant lens system unless the source star has an unusually high proper motion. However, data from the OGLE collaboration nearly rule out a high source proper motion, so the exoplanet+exomoon model is the favored interpretation for the best fit model. However, there is an alternate solution that has a lower proper motion and fits the data almost as well. This solution is compatible with a distant (so stellar) host. A Bayesian analysis does not favor the exoplanet+exomoon interpretation, so Occam's razormore » favors a lens system in the bulge with host and companion masses of M{sub host}=0.12{sub −0.06}{sup +0.19} M{sub ⊙} and m{sub comp}=18{sub −10}{sup +28} M{sub ⊕}, at a projected separation of a{sub ⊥}=0.84{sub −0.14}{sup +0.25} AU. The existence of this degeneracy is an unlucky accident, so current microlensing experiments are in principle sensitive to exomoons. In some circumstances, it will be possible to definitively establish the mass of such lens systems through the microlensing parallax effect. Future experiments will be sensitive to less extreme exomoons.« less
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  1. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States)
  2. Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)
  3. Institute of Natural and Mathematical Sciences, Massey University, Auckland 0745 (New Zealand)
  4. Department of Physics, Massachussets Institute of Technology, Cambridge, MA 02139 (United States)
  5. Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan)
  6. UPMC-CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98bis Boulevard Arago, F-75014 Paris (France)
  7. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)
  8. Technische Universität Wien, Wieder Hauptst. 8-10, A-1040 Vienna (Austria)
  9. Dipartimento di Fisica, Università di Salerno, Via Ponte Don Melillo 132, I-84084 Fisciano (Italy)
  10. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)
  11. Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand)
  12. Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Okayama 719-0232 (Japan)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States