Search for: All records

Abstract The gravitational microlensing technique is most sensitive to planets in a Jupiter-like orbit and has detected more than 200 planets. However, only a few wide-orbit (s> 2) microlensing planets have been discovered, wheresis the planet-to-host separation normalized to the angular Einstein ring radius,θ_E. Here, we present the discovery and analysis of a strong candidate wide-orbit microlensing planet in the event OGLE-2017-BLG-0448. The whole light curve exhibits long-term residuals to the static binary-lens single-source model, so we investigate the residuals by adding the microlensing parallax, microlensing xallarap, an additional lens, or an additional source. For the first time, we observe a complex degeneracy between all four effects. The wide-orbit models withs∼ 2.5 and a planet-to-host mass ratio ofq∼ 10⁻⁴are significantly preferred, but we cannot rule out the close models withs∼ 0.35 andq∼ 10⁻³. A Bayesian analysis based on a Galactic model indicates that, despite the complicated degeneracy, the surviving wide-orbit models all contain a super-Earth-mass to Neptune-mass planet at a projected planet-host separation of ∼6 au and the surviving close-orbit models all consist of a Jovian-mass planet at ∼1 au. The host star is probably an M or K dwarf. We discuss the implications of this dimension-degeneracy disaster on microlensing light-curve analysis and its potential impact on statistical studies.