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OGLE-2018-BLG-1185b: A Low-mass Microlensing Planet Orbiting a Low-mass Dwarf

Kondo, Iona and Yee, Jennifer C. and Bennett, David P. and Sumi, Takahiro and Koshimoto, Naoki and Bond, Ian A. and Gould, Andrew and Udalski, Andrzej and Shvartzvald, Yossi and Jung, Youn Kil and Zang, Weicheng and Bozza, Valerio and Bachelet, Etienne and Hundertmark, Markus P. G. and Rattenbury, Nicholas J. and Abe, F. and Barry, R. and Bhattacharya, A. and Donachie, M. and Fukui, A. and Fujii, H. and Hirao, Y. and Ishitani Silva, S. and Itow, Y. and Kirikawa, R. and Li, M. C. A. and Matsubara, Y. and Miyazaki, S.` and Muraki, Y. and Olmschenk, G. and Ranc, C. and Satoh, Y. and Shoji, H. and Suzuki, D. and Tanaka, Y. and Tristram, P. J. and Yamawaki, T. and Yonehara, A. and Mróz, P. and Poleski, R. and Skowron, J. and Szymanski, M. K. and Soszyński, I. and Kozłowski, S. and Ulaczyk, P. Pietrukowicz K. and Rybicki, K. A. and Iwanek, P. and Wrona, M. and Albrow, M. D. and Chung, S.-J. and Han, C. and Hwang, K.-H. and Kim, H.-W. and Shin, I.-G. and Cha, S.-M. and Kim, D.-J. and Kim, S.-L. and Lee, C.-U. and Lee, D.-J. and Lee, Y. and Park, B.-G. and Pogge, R. W. and Ryu, Y.-H. and Beichman, C. A. and Bryden, G. and Calchi Novati, S. and Carey, S. and Gaudi, B. S. and Henderson, C. B. and Zhu, W. and Maoz, D. and Penny, M. T. and Dominik, M. and Jørgensen, U. G. and Longa-Peña, P. and Peixinho, N. and Sajadian, S. and Skottfelt, J. and Snodgrass, C. and Tregloan-Reed, J. and Burgdorf, M. J. and Campbell-White, J. and Dib, S. and Fujii, Y. I. and Hinse, T. C. and Khalouei, E. and Rahvar, S. and Rabus, M. and Southworth, J. and Tsapras, Y. and Street, R. A. and Bramich, D. M. and Cassan, A. and Horne, K. and Wambsganss, J. and Mao, S. and Saha, A. (2021) OGLE-2018-BLG-1185b: A Low-mass Microlensing Planet Orbiting a Low-mass Dwarf. Astronomical Journal, 162 (2). Art. No. 77. ISSN 0004-6256. doi:10.3847/1538-3881/ac00ba.

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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 of q = (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 be Δf_(Spz) < 4 instrumental flux units yields a host mass of M_(host) = 0.37^(+0.35)_(−0.21) M_⊙ and a planet mass of m_p = 8.4^(+7.9)_(−4.7) M_⊕. A Bayesian analysis including the full parallax constraint from Spitzer suggests smaller host star and planet masses of M_(host) = 0.091^(+0.064)_(−0.018) M_⊙ and m_p = 2.1^(+1.5)_(−0.4) M_⊕, 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kondo, Iona0000-0002-3401-1029
Yee, Jennifer C.0000-0001-9481-7123
Bennett, David P.0000-0001-8043-8413
Sumi, Takahiro0000-0002-4035-5012
Koshimoto, Naoki0000-0003-2302-9562
Udalski, Andrzej0000-0001-5207-5619
Shvartzvald, Yossi0000-0003-1525-5041
Jung, Youn Kil0000-0002-0314-6000
Zang, Weicheng0000-0001-6000-3463
Bozza, Valerio0000-0003-4590-0136
Bachelet, Etienne0000-0002-6578-5078
Rattenbury, Nicholas J.0000-0001-5069-319X
Fukui, A.0000-0002-4909-5763
Ishitani Silva, S.0000-0003-2267-1246
Miyazaki, S.`0000-0001-9818-1513
Ranc, C.0000-0003-2388-4534
Suzuki, D.0000-0002-5843-9433
Mróz, P.0000-0001-7016-1692
Poleski, R.0000-0002-9245-6368
Skowron, J.0000-0002-2335-1730
Szymanski, M. K.0000-0002-0548-8995
Soszyński, I.0000-0002-7777-0842
Kozłowski, S.0000-0003-4084-880X
Rybicki, K. A.0000-0002-9326-9329
Iwanek, P.0000-0002-6212-7221
Wrona, M.0000-0002-3051-274X
Albrow, M. D.0000-0003-3316-4012
Hwang, K.-H.0000-0002-9241-4117
Shin, I.-G.0000-0002-4355-9838
Kim, D.-J.0000-0001-8263-1006
Pogge, R. W.0000-0003-1435-3053
Ryu, Y.-H.0000-0001-9823-2907
Beichman, C. A.0000-0002-5627-5471
Bryden, G.0000-0001-5966-837X
Calchi Novati, S.0000-0002-7669-1069
Carey, S.0000-0002-0221-6871
Gaudi, B. S.0000-0003-0395-9869
Henderson, C. B.0000-0001-8877-9060
Penny, M. T.0000-0001-7506-5640
Dominik, M.0000-0002-3202-0343
Hinse, T. C.0000-0001-8870-3146
Rabus, M.0000-0003-2935-7196
Southworth, J.0000-0002-3807-3198
Tsapras, Y.0000-0001-8411-351X
Street, R. A.0000-0001-6279-0552
Wambsganss, J.0000-0002-8365-7619
Mao, S.0000-0001-8317-2788
Additional Information:© 2021. The American Astronomical Society. Received 2021 April 2; revised 2021 April 26; accepted 2021 May 11; published 2021 July 29. Work by I.K. was supported by JSPS KAKENHI grant No. 20J20633. Work by J.C.Y. was supported by Jet Propulsion Laboratory grant 1571564. Work by D.P.B., A.B., and C.R. was 5 supported by NASA through grant NASA-80NSSC18K0274. T.S. acknowledges financial support from the JSPS (JSPS23103002, JSPS24253004, and JSPS26247023). Work by N.K. is supported by JSPS KAKENHI grant No. JP18J00897. A.S. is a University of Auckland doctoral scholar. Y.T. acknowledges the support of DFG priority program SPP 1992 Exploring the Diversity of Extrasolar Planets (WA 1047/11-1). T.C.H. acknowledges financial support from the National Research Foundation (No. 2019R1I1A1A01059609). U.G.J. acknowledges support from H2020-MSCA-ITN-2019, grant No. 860470 (CHAMELEON), and the NovoNordisk Foundation grant No. NNF19OC0057374. W.Z. and S.M. acknowledge support by the National Science Foundation of China (grant Nos. 11821303 and 11761131004). Work by C.H. was supported by grants of the National Research Foundation of Korea (2020R1A4A2002885 and 2019R1A2C2085965). Funding for B.S.G. was provided by NASA grant NNG16PJ32C and the Thomas Jefferson Chair for Discovery and Space Exploration. The MOA project is supported by JSPS KAKENHI grant Nos. JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, JP16H06287, 17H02871, and 19KK0082. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute and the data were obtained at the three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. This research uses data obtained through the Telescope Access Program (TAP), which has been funded by the TAP member institutes. This work has made use of data from the European Space Agency mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Software: OGLE DIA pipeline (Udalski 2003), MOA DIA pipeline (Bond et al. 2001), KMTNet pySIS pipeline (Albrow et al. 2009), DanDIA (Bramich 2008; Bramich et al. 2013), DoPHOT (Schechter et al. 1993), ISIS (Alard & Lupton 1998; Alard 2000; Zang et al. 2018), image-centered ray-shooting method (Bennett & Rhie 1996; Bennett 2010).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)20J20633
Japan Society for the Promotion of Science (JSPS)23103002
Japan Society for the Promotion of Science (JSPS)24253004
Japan Society for the Promotion of Science (JSPS)26247023
Japan Society for the Promotion of Science (JSPS)18J00897
University of AucklandUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)SPP 1992
Deutsche Forschungsgemeinschaft (DFG)WA 1047/11-1
National Research Foundation of Korea2019R1I1A1A01059609
European Research Council (ERC)860470
NovoNordisk FoundationNNF19OC0057374
National Natural Science Foundation of China11821303
National Natural Science Foundation of China11761131004
National Research Foundation of Korea2020R1A4A2002885
National Research Foundation of Korea2019R1A2C2085965
Thomas Jefferson Chair for Discovery and Space ExplorationUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)23340064
Japan Society for the Promotion of Science (JSPS)15H00781
Japan Society for the Promotion of Science (JSPS)16H06287
Japan Society for the Promotion of Science (JSPS)17H02871
Japan Society for the Promotion of Science (JSPS)19KK0082
National Science Centre (Poland)2014/14/A/ST9/00121
TAP member institutesUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:Gravitational microlensing; Gravitational microlensing exoplanet detection; Satellite microlensing parallax
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Gravitational microlensing (672); Gravitational microlensing exoplanet detection (2147); Satellite microlensing parallax (2148)
Record Number:CaltechAUTHORS:20210603-122502635
Persistent URL:
Official Citation:Iona Kondo et al 2021 AJ 162 77
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109361
Deposited By: George Porter
Deposited On:03 Jun 2021 20:42
Last Modified:08 Aug 2022 20:47

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