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

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

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 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.

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 (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). 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).

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