Kepler K2 Campaign 9: II. First space-based discovery of an exoplanet using microlensing
Creators: name: Specht, D.
name: Poleski, R.
name: Penny, M. T.
name: Kerins, E.
name: McDonald, I.
name: Lee, Chung-Uk
name: Udalski, A.
name: Bond, I. A.
name: Shvartzvald, Y.
name: Zang, Weicheng
name: Street, R. A.
name: Hogg, D. W.
name: Gaudi, B. S.
name: Barclay, T.
name: Barentsen, G.
name: Howell, S. B.
name: Mullally, F.
name: Henderson, C. B.
name: Bryson, S. T.
name: Caldwell, D. A.
name: Haas, M. R.
name: Van Cleve, J. E.
name: Larson, K.
name: McCalmont, K.
name: Peterson, C.
name: Putnam, D.
name: Ross, S.
name: Packard, M.
name: Reedy, L.
name: Albrow, Michael D.
name: Chung, Sun-Ju
name: Jung, Youn Kil
name: Gould, Andrew
name: Han, Cheongho
name: Hwang, Kyu-Ha
name: Ryu, Yoon-Hyun
name: Shin, In-Gu
name: Yang, Hongjing
name: Yee, Jennifer C.
name: Cha, Sang-Mok
name: Kim, Dong-Jin
name: Kim, Seung-Lee
name: Lee, Dong-Joo
name: Lee, Yongseok
name: Park, Byeong-Gon
name: Pogge, Richard W.
name: Szymański, M. K.
name: Soszyński, I.
name: Ulaczyk, K.
name: Pietrukowicz, P.
name: Kozlowski, Sz.
name: Skowron, J.
name: Mróz, P.
name: Mao, Shude
name: Fouqué, Pascal
name: Zhu, Wei
name: Abe, F.
name: Barry, R.
name: Bennett, D. P.
name: Bhattacharya, A.
name: Fukui, A.
name: Fujii, H.
name: Hirao, Y.
name: Itow, Y.
name: Kirikawa, R.
name: Kondo, I.
name: Koshimoto, N.
name: Matsubara, Y.
name: Matsumoto, S.
name: Miyazaki, S.
name: Muraki, Y.
name: Olmschenk, G.
name: Ranc, C.
name: Okamura, A.
name: Rattenbury, N. J.
name: Satoh, Y.
name: Sumi, T.
name: Suzuki, D.
name: Silva, S. I.
name: Toda, T.
name: Tristram, P. J.
name: Vandorou, A.
name: Yama, H.
name: Beichman, C.
name: Bryden, G.
name: Novati, S. Calchi
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 (K2C9). 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 K2C9 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 $0.58\pm0.04 ~{\rm M}_\odot$ and a planetary mass of $1.1\pm0.1 ~{\rm M_J}$. The system lies at a distance of $5.2\pm0.2~$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 $4.2\pm0.3~$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.
description: 18 pages. Accepted for publication in MNRAS Published by Oxford University Press on behalf of the Royal Astronomical Society