OGLE-2015-BLG-1771Lb: A Microlens Planet Orbiting an Ultracool Dwarf?

Creators: Zhang, Xiangyu; Zang, Weicheng; Udalski, Andrzej; Gould, Andrew; Ryu, Yoon-Hyun; Wang, Tianshu; Yang, Hongjing; Mao, Shude; Mróz, Przemek; Skowron, Jan; Poleski, Radoslaw; Szymański, Michał K.; Soszyński, Igor; Pietrukowicz, Paweł; Kozłowski, Szymon; Ulaczyk, Krzysztof; Albrow, Michael D.; Chung, Sun-Ju; Han, Cheongho; Hwang, Kyu-Ha; Jung, Youn Kil; Shin, In-Gu; Shvartzvald, Yossi; Yee, Jennifer C.; Zhu, Wei; 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.; OGLE Collaboration; KMTNet Collaboration

Abstract

We report the discovery and the analysis of the short (t_E < 5 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 Δχ² ~ 3. The last model is strongly disfavored by Δχ² ~ 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.

Additional Information

© 2020 The American Astronomical Society. Received 2019 November 6; revised 2020 January 16; accepted 2020 January 17; published 2020 February 20. We thank Chris W. Ormel and Xuening Bai for fruitful discussions. X.Z., W.Z., W.T., H.Y., and S.M. acknowledge support by the National Science Foundation of China (grant No. 11821303 and 11761131004). The OGLE has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. Work by A.G. was supported by AST-1516842 and by JPL grant 1500811. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. A.G. received support from the European Research Council under the European Unions Seventh Framework Programme (FP 7) ERC grant Agreement No. [321035]. Work by C.H. was supported by the grants (2017R1A4A1015178 and 2019R1A2C2085965) of National Research Foundation of Korea. W.Z. was supported by the Beatrice and Vincent Tremaine Fellowship at CITA. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.

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