Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb

Cheongho Han , Jennifer C. Yee , Andrzej Udalski , Ian A. Bond , Valerio Bozza , Arnaud Cassan (1) , Yuki Hirao , Subo Dong , Juna A. Kollmeier , Nidia Morrell , Konstantina Boutsia , Michael D. Albrow , Sun-Ju Chung , Andrew Gould , Kyu-Ha Hwang , Chung-Uk Lee , Yoon-Hyun Ryu , In-Gu Shin , Yossi Shvartzvald , Youn Kil Jung , Doeon Kim , Woong-Tae Kim , Sang-Mok Cha , Dong-Jin Kim , Hyoun-Woo Kim , Kyeongsoo Hong , Seung-Lee Kim , Dong-Joo Lee , Yongseok Lee , Byeong-Gon Park , Richard W. Pogge , Weicheng Zang , Przemek Mróz , Michał K. Szymański , Jan Skowron , Radek Poleski , Igor Soszyński , Paweł Pietrukowicz , Szymon Kozłowski , Krzysztof Ulaczyk , Krzysztof A. Rybicki , Patryk Iwanek , Marcin Wrona , Fumio Abe , Richard Barry , David P. Bennett , Aparna Bhattacharya , Martin Donachie , Akihiko Fukui , Yoshitaka Itow , Kohei Kawasaki , Iona Kondo , Naoki Koshimoto , Man Cheung Alex Li , Yutaka Matsubara , Yasushi Muraki , Shota Miyazaki , Masayuki Nagakane , Clément Ranc , Nicholas J. Rattenbury , Haruno Suematsu , Denis J. Sullivan , Takahiro Sumi , Daisuke Suzuki , Paul J. Tristram , Atsunori Yonehara

1 IAP - Institut d'Astrophysique de Paris

We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The planet is detected with a very strong signal of Δχ ² ∼ 4630, but the interpretation of the signal suffers from two types of degeneracies. One type is caused by the previously known close/wide degeneracy, and the other is caused by an ambiguity between two solutions, in which one solution requires the incorporation of finite-source effects, while the other solution is consistent with a point-source interpretation. Although difficult to be firmly resolved based on only the photometric data, the degeneracy is resolved in strong favor of the point-source solution with the additional external information obtained from astrometric and spectroscopic observations. The small astrometric offset between the source and baseline object supports that the blend is the lens and this interpretation is further secured by the consistency of the spectroscopic distance estimate of the blend with the lensing parameters of the point-source solution. The estimated mass of the host is 1.0 ± 0.1 M _⊙ and the mass of the planet is 4.5 ± 0.6 M _J (close solution) or 4.8 ± 0.6 M _J (wide solution) and the lens is located at a distance of 3.2 ± 0.5 kpc. The bright nature of the lens, with I ∼ 17.1 (V ∼ 18.2), combined with its dominance of the observed flux suggest that radial-velocity (RV) follow-up observations of the lens can be done using high-resolution spectrometers mounted on large telescopes, e.g., Very Large Telescope/ESPRESSO, and this can potentially not only measure the period and eccentricity of the planet but also probe for close-in planets. We estimate that the expected RV amplitude would be ∼ 60\sin i {{m}} {{{s}}}^-1.

Keywords: gravitational lensing: micro; planetary systems; Astrophysics - Earth and Planetary Astrophysics

Domains: Sciences of the Universe [physics]

Cheongho Han, Jennifer C. Yee, Andrzej Udalski, Ian A. Bond, Valerio Bozza, et al.. Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb. The Astronomical Journal, 2019, 158, ⟨10.3847/1538-3881/ab2df4⟩. ⟨insu-03747923⟩