Kepler K2 Campaign 9 – II. First space-based discovery of an exoplanet using microlensing. Issue 4 (31st January 2023)

• Record Type: Journal Article
• Authors: Specht, D; Poleski, R; Penny, M T; Kerins, E; McDonald, I; Lee, Chung-Uk; Udalski, A; Bond, I A; Shvartzvald, Y; Zang, Weicheng; Street, R A; Hogg, D W; Gaudi, B S; Barclay, T; Barentsen, G; Howell, S B; Mullally, F; Henderson, C B; Bryson, S T; Caldwell, D A; Haas, M R; Van Cleve, J E; Larson, K; McCalmont, K; Peterson, C; Putnam, D; Ross, S; Packard, M; Reedy, L; Albrow, Michael D; Chung, Sun-Ju; Kil Jung, Youn; Gould, Andrew; Han, Cheongho; Hwang, Kyu-Ha; Ryu, Yoon-Hyun; Shin, In-Gu; Yang, Hongjing; Yee, Jennifer C; Cha, Sang-Mok; Kim, Dong-Jin; Kim, Seung-Lee; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W; Szymański, M K; Soszyński, I; Ulaczyk, K; Pietrukowicz, P; Kozłowski, Sz; Skowron, J; Mróz, P; Mao, Shude; Fouqué, Pascal; Zhu, Wei; Abe, F; Barry, R; Bennett, D P; Bhattacharya, A; Fukui, A; Fujii, H; Hirao, Y; Itow, Y; Kirikawa, R; Kondo, I; Koshimoto, N; Matsubara, Y; Matsumoto, S; Miyazaki, S; Muraki, Y; Olmschenk, G; Ranc, C; Okamura, A; Rattenbury, N J; Satoh, Y; Sumi, T; Suzuki, D; Silva, S I; Toda, T; Tristram, P J; Vandorou, A; Yama, H; Beichman, C; Bryden, G; Calchi Novati, S;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 520:Issue 4(2023)
• Page Start: 6350
• Page End: 6366
• Publication Date: 2023-01-31
• Subjects: gravitational lensing: micro -- methods: data analysis -- telescopes -- surveys -- planets and satellites: detection; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stad212
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present K2-2016-BLG-0005Lb, a densely sampled, planetary binary caustic-crossing microlensing event found from a blind search of data gathered from Campaign 9 of the Kepler K2 mission ( K2 C9). K2-2016-BLG-0005Lb is the first bound microlensing exoplanet discovered from space-based data. The event has caustic entry and exit points that are resolved in the K2 C9 data, enabling the lens-source relative proper motion to be measured. We have fitted a binary microlens model to the Kepler data and to simultaneous observations from multiple ground-based surveys. Whilst the ground-based data only sparsely sample the binary caustic, they provide a clear detection of parallax that allows us to break completely the microlensing mass-position-velocity degeneracy and measure the planet's mass directly. We find a host mass of 0.58 ± 0.04 M⊙ and a planetary mass of 1.1 ± 0.1 MJ . The system lies at a distance of 5.2 ± 0.2 kpc from Earth towards the Galactic bulge, more than twice the distance of the previous most distant planet found by Kepler . The sky-projected separation of the planet from its host is found to be 4.2 ± 0.3 au which, for circular orbits, deprojects to a host separation $a = 4.4^{+1.9}_{-0.4}$ au and orbital period $P = 13^{+9}_{-2}$ yr. This makes K2-2016-BLG-0005Lb a close Jupiter analogue orbiting a low-mass host star. According to current planet formation models, this system is very close to the host mass threshold below which Jupiters are not expected to form. Upcoming space-based exoplanet microlensing surveys by NASA's Nancy Grace Roman Space Telescope and, possibly, ESA's Euclid mission, will provide demanding tests of current planet formation models.