Abstract
Abstract We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely sampled. However, the detailed light-curve analysis ruled out all stellar binary models and shows the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of q ∼ (7.0 ± 2.0) × 10−3 and q ∼ (8.1 ± 2.6) × 10−3 with the projected separation in Einstein radius units of s = 0.95 (close) and s = 1.18 (wide), respectively. The microlens parallax effect is not detected, but the finite source effect is detected. Our Bayesian analysis indicates that the lens system is located away from us and the host star is an M/K dwarf with a mass of orbited by a super-Jupiter mass planet with a mass of at the projected separation of . The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters may be constrained by the future high-resolution imaging by large ground telescopes or HST. If the estimated lens distance is correct, then this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge.
Highlights
Gravitational microlensing is a unique technique to find exoplanets (Moa & Paczyński 1991) down to low masses (Bennett & Rhie 1996) just beyond the snow line (Gould & Loeb 1992), which plays an important role in the core accretion theory of planet formation (Ida & Lin 2005)
Most planetary systems, which are likely to be located in the Galactic bulge, have their distance estimated by a Bayesian analysis with somewhat uncertain priors because the microlensing parallax is not detected
We report the analysis of a planetary microlensing event Optical Gravitational Lens Experiment (OGLE)-2013-BLG-1761
Summary
Gravitational microlensing is a unique technique to find exoplanets (Moa & Paczyński 1991) down to low masses (Bennett & Rhie 1996) just beyond the snow line (Gould & Loeb 1992), which plays an important role in the core accretion theory of planet formation (Ida & Lin 2005). Sensitive to planets orbiting around faint stars like M-dwarfs and brown dwarfs, and can even detect free-floating planets (Sumi et al 2011) because it does not rely on the host’s light. Penny et al (2016) suggested that there exists a possible paucity of planets in the Galactic bulge from the sample of observed microlensing planets, though it appears that they have overestimated the detection efficiency for planets orbiting bulge stars. Distances to the planetary system are determined when either a microlensing parallax signal or lens star flux is measured from high-resolution follow-up observations. Most planetary systems, which are likely to be located in the Galactic bulge, have their distance estimated by a Bayesian analysis with somewhat uncertain priors because the microlensing parallax is not detected.
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