Spitzer Parallax of OGLE-2018-BLG-0596: A Low-mass-ratio Planet around an M Dwarf

Youn Kil Jung , Andrew Gould , Andrzej Udalski , Takahiro Sumi , Jennifer C. Yee , Yossi Shvartzvald , Weicheng Zang , Cheongho Han , Michael D. Albrow , Sun-Ju Chung , Kyu-Ha Hwang , Yoon-Hyun Ryu , In-Gu Shin , 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 , Przemek Mróz , Michał K. Szymański , Jan Skowron , Radek Poleski , Igor Soszyński , Paweł Pietrukowicz , Szymon Kozłowski , Krzystof Ulaczyk , Krzysztof A. Rybicki , Patryk Iwanek , Marcin Wrona , Charles A. Beichman , Geoffery Bryden , Sebastiano Calchi Novati , Sean Carey , B. Scott Gaudi , Calen B. Henderson , Fumio Abe , Richard Barry , David P. Bennett , Ian A. Bond , Aparna Bhattacharya , Martin Donachie , Akihiko Fukui , Yuki Hirao , Yoshitaka Itow , Iona Kondo , Naoki Koshimoto , Man Cheung Alex Li , Yutaka Matsubara , Shota Miyazaki , Yasushi Muraki , Masayuki Nagakane , Clément Ranc , Nicholas J. Rattenbury , Haruno Suematsu , Denis J. Sullivan , Daisuke Suzuki , Paul J. Tristram , Atsunori Yonehara , Savannah Jacklin , Matthew T. Penny , Keivan G. Stassun , Pascal Fouqué (1, 2) , Shude Mao , Tianshu Wang

1 CFHT - Canada-France-Hawaii Telescope Corporation
2 IRAP - Institut de recherche en astrophysique et planétologie

We report the discovery of a Spitzer microlensing planet OGLE-2018-BLG-0596Lb, with preferred planet-host mass ratio q ∼ 2 × 10^-4. The planetary signal, which is characterized by a short (∼1 day) “bump” on the rising side of the lensing light curve, was densely covered by ground-based surveys. We find that the signal can be explained by a bright source that fully envelops the planetary caustic, i.e., a “Hollywood” geometry. Combined with the source proper motion measured from Gaia, the Spitzer satellite parallax measurement makes it possible to precisely constrain the lens physical parameters. The preferred solution, in which the planet perturbs the minor image due to lensing by the host, yields a Uranus-mass planet with a mass of M _p = 13.9 ± 1.6 M _⊕ orbiting a mid M-dwarf with a mass of M _h = 0.23 ± 0.03 M _⊙. There is also a second possible solution that is substantially disfavored but cannot be ruled out, for which the planet perturbs the major image. The latter solution yields M _p = 1.2 ± 0.2 M _⊕ and M _h = 0.15 ± 0.02 M _⊙. By combining the microlensing and Gaia data together with a Galactic model, we find in either case that the lens lies on the near side of the Galactic bulge at a distance D _L ∼ 6 ± 1 kpc. Future adaptive optics observations may decisively resolve the major image/minor image degeneracy.

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

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Youn Kil Jung, Andrew Gould, Andrzej Udalski, Takahiro Sumi, Jennifer C. Yee, et al.. Spitzer Parallax of OGLE-2018-BLG-0596: A Low-mass-ratio Planet around an M Dwarf. The Astronomical Journal, 2019, 158, ⟨10.3847/1538-3881/ab237f⟩. ⟨insu-03674432⟩