OGLE-2015-BLG-1771Lb: A Microlens Planet Orbiting an Ultracool Dwarf?
Xiangyu Zhang, Weicheng Zang, A. Udalski, Andrew Gould, Yoon-Hyun Ryu, Tianshu Wang, Hongjing Yang, Shude Mao, (Leading Authors), P. Mróz, J. Skowron, Radoslaw Poleski, M. K. Szymański, I. Soszyński, P. Pietrukowicz, S. Kozłowski, K. Ulaczyk, Michael D. Albrow, Sun‐Ju Chung, Cheongho Han, Kyu‐Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Wei Zhu, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung‐Lee Kim, Chung‐Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge
Abstract
Abstract We report the discovery and the analysis of the short ( days) planetary microlensing event, OGLE-2015-BLG-1771. The event was discovered by the Optical Gravitational Lensing Experiment, and the planetary anomaly (at I ∼ 19) was captured by The Korea Microlensing Telescope Network. The event has three surviving planetary models that explain the observed light curves, with planet-host mass ratio q ∼ 5.4 × 10 −3 , 4.5 × 10 −3 and 4.5 × 10 −2 , respectively. The first model is the best-fit model, while the second model is disfavored by Δ χ 2 ∼ 3. The last model is strongly disfavored by Δ χ 2 ∼ 15 but not ruled out. A Bayesian analysis using a Galactic model indicates that the first two models are probably composed of a Saturn-mass planet orbiting a late M dwarf, while the third one could consist of a super-Jovian planet and a mid-mass brown dwarf. The source-lens relative proper motion is μ rel ∼ 9 mas yr −1 , so the source and lens could be resolved by current adaptive-optics instruments in 2020 if the lens is luminous.