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A Terrestrial-mass Rogue Planet Candidate Detected in the Shortest-timescale Microlensing Event

Mróz, Przemek and Poleski, R. and Gould, A. and Udalski, A. and Sumi, T. and Szymanski, M. K. and Soszyński, I. and Pietrukowicz, P. and Kozlowski, S. and Skowron, J. and Ulaczyk, K. and Albrow, M. D. and Chung, S.-J. and Han, C. and Hwang, K.-H. and Jung, Y. K. and Kim, H.-W. and Ryu, Y.-H. and Shin, I.-G. and Shvartzvald, Y. and Yee, J. C. and Zang, W. 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. (2020) A Terrestrial-mass Rogue Planet Candidate Detected in the Shortest-timescale Microlensing Event. Astrophysical Journal Letters, 903 (1). Art. No. L11. ISSN 2041-8213.

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Some low-mass planets are expected to be ejected from their parent planetary systems during early stages of planetary system formation. According to planet formation theories, such as the core accretion theory, typical masses of ejected planets should be between 0.3 and 1.0 M_⊕. Although in practice such objects do not emit any light, they may be detected using gravitational microlensing via their light-bending gravity. Microlensing events due to terrestrial-mass rogue planets are expected to have extremely small angular Einstein radii (≾1 μas) and extremely short timescales (≾0.1 day). Here, we present the discovery of the shortest-timescale microlensing event, OGLE-2016-BLG-1928, identified to date (t_E ≈ 0.0288 day = 41.5min). Thanks to the detection of finite-source effects in the light curve of the event, we were able to measure the angular Einstein radius of the lens θ_E = 0.842±0.064 μas, making the event the most extreme short-timescale microlens discovered to date. Depending on its unknown distance, the lens may be a Mars- to Earth-mass object, with the former possibility favored by the Gaia proper motion measurement of the source. The planet may be orbiting a star but we rule out the presence of stellar companions up to the projected distance of ~8.0 au from the planet. Our discovery demonstrates that terrestrial-mass free-floating planets can be detected and characterized using microlensing.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Mróz, Przemek0000-0001-7016-1692
Poleski, R.0000-0002-9245-6368
Udalski, A.0000-0001-5207-5619
Szymanski, M. K.0000-0002-0548-8995
Soszyński, I.0000-0002-7777-0842
Pietrukowicz, P.0000-0002-2339-5899
Kozlowski, S.0000-0003-4084-880X
Skowron, J.0000-0002-2335-1730
Ulaczyk, K.0000-0001-6364-408X
Albrow, M. D.0000-0003-3316-4012
Chung, S.-J.0000-0001-6285-4528
Han, C.0000-0002-2641-9964
Hwang, K.-H.0000-0002-9241-4117
Jung, Y. K.0000-0002-0314-6000
Ryu, Y.-H.0000-0001-9823-2907
Shin, I.-G.0000-0002-4355-9838
Shvartzvald, Y.0000-0003-1525-5041
Yee, J. C.0000-0001-9481-7123
Zang, W.0000-0001-6000-3463
Kim, D.-J.0000-0001-8263-1006
Pogge, R. W.0000-0003-1435-3053
Additional Information:© 2020 The American Astronomical Society. Received 2020 September 25; revised 2020 October 6; accepted 2020 October 9; published 2020 October 29. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to A.U. R.P. was supported by the Polish National Agency for Academic Exchange via Polish Returns 2019 grant. Work by A.G. was supported by JPL grant 1500811. Work by C.H. was supported by the grants of National Research Foundation of Korea (2017R1A4A1015178 and 2020R1A4A2002885). This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia.
Funding AgencyGrant Number
National Science Centre (Poland)MAESTRO 2014/14/A/ST9/00121
Polish National Agency for Academic ExchangeUNSPECIFIED
National Research Foundation of Korea2017R1A4A1015178
National Research Foundation of Korea2020R1A4A2002885
Subject Keywords:Gravitational microlensing ; Gravitational microlensing exoplanet detection ; Finite-source photometric effect ; Free floating planets
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Gravitational microlensing (672); Gravitational microlensing exoplanet detection (2147); Finite-source photometric effect (2142); Free floating planets (549)
Record Number:CaltechAUTHORS:20201019-094839181
Persistent URL:
Official Citation:Przemek Mróz et al 2020 ApJL 903 L11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106138
Deposited By: Tony Diaz
Deposited On:20 Oct 2020 17:57
Last Modified:29 Oct 2020 22:06

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