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Published April 20, 2009 | Published
Journal Article Open

OGLE-2005-BLG-071Lb, the Most Massive M Dwarf Planetary Companion?

Abstract

We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from the Hubble Space Telescope, as well as constraints from higher order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion, and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M = 0.46 ± 0.04 M_☉, distance D_l = 3.2 ± 0.4 kpc, and thick-disk kinematics v_LSR ~ 103 km s^(−1). From the best-fit model, the planet has mass M_p = 3.8 ± 0.4 M_(Jupiter), lies at a projected separation r_⊥ = 3.6 ± 0.2AU from its host, and so has an equilibrium temperature of T ~ 55 K, that is, similar to Neptune. A degenerate model gives similar planetary mass M_p = 3.4 ± 0.4 M_(Jupiter) with a smaller projected separation, r_⊥ = 2.1 ± 0.1AU, and higher equilibrium temperature, T ~ 71 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this primary analysis, which assumes (based on real but limited evidence) that the unlensed light coincident with the source is actually due to the lens, that is, the planetary host. However, these caveats could mostly be resolved by a single astrometric measurement a few years after the event.

Additional Information

© 2009. The American Astronomical Society. Received 2008 April 9, accepted for publication 2008 November 18. Published 2009 April 6. We thank M. Pinsonneault and D. An for providing us their unpublished isochrones. S.D. wishes to thank D. Will of Ohio State astronomy department for setting up and maintaining the Condor system, which greatly facilitates the computations for this work. S.D. is grateful to O. Pejcha and D. Heyrovsky for interesting discussions on limb-darkening. Based on observations with the NASA/ESA HST obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Support for this work was provided by NASA through grant HST-GO-10707.01-A from STScI. S.D. and A.G. were supported in part by grant AST 042758 from the NSF. S.D., A.G., D.D., and R.P. acknowledge support by NASA grant NNG04GL51G. A.G. thanks IAP, CNRS for its support. Support for OGLE project was provided by Polish MNiSW grant N20303032/4275. B.G.P. was supported by the grant (KRF-2006-311-C00072) from Korea Research Foundation. H.C. was supported by the Science Research Center from Korea Science and Engineering Foundation. The MOA project is supported by Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, Grant-in-Aid for Specially Promoted Research No. 14002006. J.P.B., P.F., A.C., C.C., S.B., J.B.M. acknowledge the financial support of ANR HOLMES. K.H.C.'s work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work was supported in part by an allocation of computing time from the Ohio Supercomputer Center.

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August 21, 2023
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