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1. Kepler K2Campaign 9 – II. First space-based discovery of an exoplanet using microlensing

Author

D Specht, R Poleski, M T Penny, E Kerins, I McDonald, Chung-Uk Lee, A Udalski, I A Bond, Y Shvartzvald, Weicheng Zang, R A Street, D W Hogg, B S Gaudi, T Barclay, G Barentsen, S B Howell, F Mullally, C B Henderson, S T Bryson, D A Caldwell, M R Haas, J E Van Cleve, K Larson, K McCalmont, C Peterson, D Putnam, S Ross, M Packard, L Reedy, Michael D Albrow, Sun-Ju Chung, Youn Kil Jung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Yoon-Hyun Ryu, In-Gu Shin, Hongjing Yang, Jennifer C Yee, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W Pogge, M K Szymański, I Soszyński, K Ulaczyk, P Pietrukowicz, Sz Kozłowski, J Skowron, P Mróz, Shude Mao, Pascal Fouqué, Wei Zhu, F Abe, R Barry, D P Bennett, A Bhattacharya, A Fukui, H Fujii, Y Hirao, Y Itow, R Kirikawa, I Kondo, N Koshimoto, Y Matsubara, S Matsumoto, S Miyazaki, Y Muraki, G Olmschenk, C Ranc, A Okamura, N J Rattenbury, Y Satoh, T Sumi, D Suzuki, S I Silva, T Toda, P J Tristram, A Vandorou, H Yama, C Beichman, G Bryden, and S Calchi Novati

Published
2023
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2. Precision Measurement of a Brown Dwarf Mass in A Binary System in the Microlensing Event OGLE-2019-BLG-0033/MOA-2019-BLG-035

Author

A. Herald, A. Udalski, V. Bozza, P. Rota, I. A. Bond, J. C. Yee, S. Sajadian, P. Mróz, R. Poleski, J. Skowron, M. K. Szymanski, I. Soszynski, P. Pietrukowicz, S. Kozłowsk, K. Ulaczyk, K. A. Rybicki, P. Iwanek, M. Wrona, M. Gromadzk, F. Abe, R. Barry, D. P. Bennett, A. Bhattacharya, A. Fukui, H. Fujii, Y. Hirao, Y. Itow, R. Kirikawa, I. Kondo, N. Koshimoto, Y. Matsubara, S. Matsumoto, S. Miyazaki, and Y. Muraki

Subjects
Astronomy, Astrophysics
Abstract

Context. Brown dwarfs are transition objects between stars and planets that are still poorly understood, for which several competing mechanisms have been proposed to describe their formation. Mass measurements are generally difficult to carry out for isolated objects as well as for brown dwarfs orbiting low-mass stars, which are often too faint for a spectroscopic follow-up. Aims. Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here, we present an analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is caused by a binary system composed of a brown dwarf orbiting a red dwarf. Methods. Thanks to extensive ground observations and the availability of space observations from Spitzer, it has been possible to obtain accurate estimates of all microlensing parameters, including the parallax, source radius, and orbital motion of the binary lens. Results. Following an accurate modeling process, we found that the lens is composed of a red dwarf with a mass of M(1) = 0:149 ± 0.010 M⊙� and a brown dwarf with a mass of M(2) = 0:0463 ± 0:0031 M� at a projected separation of a⊥ = 0:585 au. The system has a peculiar velocity that is typical of old metal-poor populations in the thick disk. A percent-level precision in the mass measurement of brown dwarfs has been achieved only in a few microlensing events up to now, but will likely become more common in the future thanks to the Roman space telescope.

Published
2022
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3. OGLE-2018-BLG-1185b: A Low-mass Microlensing Planet Orbiting a Low-mass Dwarf

Author

Iona Kondo, Jennifer C. Yee, David P. Bennett, Takahiro Sumi, Naoki Koshimoto, Ian A. Bond, Andrew Gould, Andrzej Udalski, Yossi Shvartzvald, Youn Kil Jung, Weicheng Zang, Valerio Bozza, Etienne Bachelet, Markus P. G. Hundertmark, Nicholas J. Rattenbury, F. Abe, R Barry, A. Bhattacharya, M. Donachie, A. Fukui, H. Fujii, Y. Hirao, S. Ishitani Silva, Y. Itow, R. Kirikawa, M. C. A. Li, Y. Matsubara, S. Miyazaki, Y. Muraki, G. Olmschenk, C. Ranc, Y. Satoh, H. Shoji, D. Suzuki, Y. Tanaka, K. Ulaczyk, P. J. Tristram, T. Yamawaki, A Yonehara, R. Poleski, J. Skowron, M. K. Szymański, K. A. Rybicki, I. Soszynski, S. Kozłowski, P. Pietrukowicz, P. Iwanek, M. Wrona, M. D. Albrow, J. Wambsganss, S. J. Chung, C. Han, K. H. Hwang, H. W. Kim, I. G. Shin, S. M. Cha, D. J. Kim, S. L. Kim, C. U. Lee, D. J. Lee, Y. Lee, B. G. Park, R. W. Pogge, Y.-H. Ryu, C. A. Beichman, G Bryden, S. Calchi Novati, S. Carey, B. S. Gaudi, C. B. Henderson, W. Zhu, D. Maoz, M. T. Penny, M. Dominik, U. G. Jorgensen, P. Longa-Pena, N. Peixinho, S. Sajadian, J. Skottfelt, C. Snodgrass, J. Tregloan-Reed, M. J. Burgdorf, J. Campbell-White, S. Dib, Y. I. Fujii, E. Khalouei, S. Rahvar, M. Rabus, J. Southworth, Y. Tsapras, R. A. Street, D. M. Bramich, A. Cassan, K. Horne, S. Mao, A. Saha, and P. Mroz

Subjects
Astronomy
Abstract

We report an analysis of the planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the Spitzer Space Telescope. The ground-based light curve indicates a low planet–host star mass ratio ofq=(6.9±0.2)×10−5, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. We estimate the host star and planet masses with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability of hosting the planet. The flux variation observed by Spitzer is marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should beΔfSpz<4 instrumental flux units yields a host mass of=-+MM0.37 host 0.210.35 and a planet mass of =-+ÅmM8.4p4.77.9. A Bayesian analysis including the full parallax constraint from Spitzer suggests smaller host star and planet masses of =-+MM0.091 host 0.0180.064 and =-+ÅmM2.1p0.41.5, respectively. Future high-resolution imaging observations with the Hubble Space Telescope or Extremely Large Telescope could distinguish between these two scenarios and help reveal the planetary system properties in more detail.

Published
2021
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4. Kepler K2 Campaign 9: II. First space-based discovery of an exoplanet using microlensing

Author

D Specht, R Poleski, M T Penny, E Kerins, I McDonald, Chung-Uk Lee, A Udalski, I A Bond, Y Shvartzvald, Weicheng Zang, R A Street, D W Hogg, B S Gaudi, T Barclay, G Barentsen, S B Howell, F Mullally, C B Henderson, S T Bryson, D A Caldwell, M R Haas, J E Van Cleve, K Larson, K McCalmont, C Peterson, D Putnam, S Ross, M Packard, L Reedy, Michael D Albrow, Sun-Ju Chung, Youn Kil Jung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Yoon-Hyun Ryu, In-Gu Shin, Hongjing Yang, Jennifer C Yee, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W Pogge, M K Szymański, I Soszyński, K Ulaczyk, P Pietrukowicz, Sz Kozłowski, J Skowron, P Mróz, Shude Mao, Pascal Fouqué, Wei Zhu, F Abe, R Barry, D P Bennett, A Bhattacharya, A Fukui, H Fujii, Y Hirao, Y Itow, R Kirikawa, I Kondo, N Koshimoto, Y Matsubara, S Matsumoto, S Miyazaki, Y Muraki, G Olmschenk, C Ranc, A Okamura, N J Rattenbury, Y Satoh, T Sumi, D Suzuki, S I Silva, T Toda, P J Tristram, A Vandorou, H Yama, C Beichman, G Bryden, and S Calchi Novati

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), micro, gravitational lensing, data analysis, Astrophysics::Instrumentation and Methods for Astrophysics, detection, FOS: Physical sciences, Astronomy and Astrophysics, telescopes, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, methods, Astrophysics - Solar and Stellar Astrophysics, surveys, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Planets and satellites, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
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 (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., 18 pages. Accepted for publication in MNRAS Published by Oxford University Press on behalf of the Royal Astronomical Society

Published
2023
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