OGLE-2015-BLG-1649Lb: A gas giant planet around a low-mass dwarf

The MOA Collaboration, the OGLE Collaboration, The RoboNet Collaboration, the MiNDSTEp Collaboration

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We report the discovery of an exoplanet from the analysis of the gravitational
microlensing event OGLE-2015-BLG-1649 that challenges the core accretion
model of planet formation and appears to support the disk instability
model. The planet/host-star mass ratio is q = 7.2 × 10−3 and the projected
separation normalized to the angular Einstein radius is s = 0.9. We conducted
high-resolution follow-up observations using the IRCS camera on the Subaru
telescope and are able to place an upper limit on the lens flux. From these measurements we are able to exclude all host stars greater than or equal in mass to a G-type dwarf. We conducted a Bayesian analysis with these new flux constraints included as priors resulting in estimates of the masses of the host star and planet. These are ML = 0.34 ± 0.19 M⊙ and Mp = 2.5+1.5
−1.4 MJup, respectively. The distance to the system is DL = 4.23+1.51
−1.64 kpc. The projected star-planet separation is a⊥ = 2.07+0.65
−0.77 AU. The estimated relative lens-source proper motion, ∼ 7.1 mas/yr, is fairly high and thus the lens can be better constrained if additional follow-up observations are conducted several years after the event.
Original languageEnglish
JournalAstronomical Journal
Issue number5
Publication statusPublished - 1 Nov 2019


  • astro-ph.EP


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