학술논문
OGLE-2017-BLG-0448Lb: A Low Mass-Ratio Wide-Orbit Microlensing Planet?
Document Type
Working Paper
Author
Zhai, Ruocheng; Poleski, Radosław; Zang, Weicheng; Jung, Youn Kil; Udalski, Andrzej; Kuang, Renkun; Albrow, Michael D.; Chung, Sun-Ju; Gould, Andrew; Han, Cheongho; Hwang, Kyu-Ha; Ryu, Yoon-Hyun; Shin, In-Gu; Shvartzvald, Yossi; Yang, Hongjing; Yee, Jennifer C.; Cha, Sang-Mok; Kim, Dong-Jin; Kim, Hyoun-Woo; Kim, Seung-Lee; Lee, Chung-Uk; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W.; Skowron, Jan; Szymański, Michał K.; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł; Kozłowski, Szymon; Mróz, Przemek; Rybicki, Krzysztof A.; Iwanek, Patryk; Wrona, Marcin; Gromadzki, Mariusz; Wang, Hanyue; Mao, Shude; Zhang, Jiyuan; Qian, Qiyue; Zhu, Wei
Source
Subject
Language
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, where $s$ is the planet-to-host separation normalized to the angular Einstein ring radius, $\theta_{\rm E}$. 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 with $s \sim 2.5$ and a planet-to-host mass-ratio of $q \sim 10^{-4}$ are significantly preferred, but we cannot rule out the close models with $s \sim 0.35$ and $q \sim 10^{-3}$. 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 $\sim 6$ au and the surviving close-orbit models all consist of a Jovian-mass planet at $\sim 1$ 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.
Comment: submitted to AJ
Comment: submitted to AJ