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KMT-2017-BLG-2820 and the Nature of the Free-floating Planet Population

Ryu, Yoon-Hyun and Mróz, Przemek and Gould, Andrew and Hwang, Kyu-Ha and Kim, Hyoun-Woo and Yee, Jennifer C. and Albrow, Michael D. and Chung, Sun-Ju and Jung, Youn Kil and Shin, In-Gu and Shvartzvald, Yossi and Zang, Weicheng and Cha, Sang-Mok and Kim, Dong-Jin and Kim, Seung-Lee and Lee, Chung-Uk and Lee, Dong-Joo and Lee, Yongseok and Park, Byeong-Gon and Han, Cheongho and Pogge, Richard W. and Udalski, Andrzej and Poleski, Radek and Skowron, Jan and Szymański, Michał K. and Soszyński, Igor and Pietrukowicz, Paweł and Kozłowski, Szymon and Ulaczyk, Krzysztof and Rybicki, Krzysztof A. and Iwanek, Patryk (2021) KMT-2017-BLG-2820 and the Nature of the Free-floating Planet Population. Astronomical Journal, 161 (3). Art. No. 126. ISSN 0004-6256. doi:10.3847/1538-3881/abd55f.

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We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius θ_E ≃ 6 μas, lens-source relative proper motion μ_(rel) ≃ 8 mas yr⁻¹, and Einstein timescale t_E = 6.5 hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet database and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six point-source point-lens (PSPL) FFP candidates found by Mróz et al. in the OGLE-IV database. The θ_E distribution of the FSPL FFPs implies that they are either sub-Jovian planets in the bulge or super-Earths in the disk. However, the apparent "Einstein desert" (10 ≾ θE/μas ≾ 30) would argue for the latter. Whether each of the 12 (six FSPL and six PSPL) FFP candidates is truly an FFP or simply a very wide-separation planet can be determined at first adaptive optics (AO) light on 30 m telescopes, and earlier for some. If the latter, a second epoch of AO observations could measure the projected planet–host separation with a precision of O(10 au). At the present time, the balance of evidence favors the unbound-planet hypothesis.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ryu, Yoon-Hyun0000-0001-9823-2907
Mróz, Przemek0000-0001-7016-1692
Hwang, Kyu-Ha0000-0002-9241-4117
Kim, Hyoun-Woo0000-0001-8263-1006
Yee, Jennifer C.0000-0001-9481-7123
Albrow, Michael D.0000-0003-3316-4012
Chung, Sun-Ju0000-0001-6285-4528
Jung, Youn Kil0000-0002-0314-6000
Shin, In-Gu0000-0002-4355-9838
Shvartzvald, Yossi0000-0003-1525-5041
Zang, Weicheng0000-0001-6000-3463
Cha, Sang-Mok0000-0002-7511-2950
Kim, Seung-Lee0000-0003-0562-5643
Lee, Chung-Uk0000-0003-0043-3925
Lee, Yongseok0000-0001-7594-8072
Park, Byeong-Gon0000-0002-6982-7722
Han, Cheongho0000-0002-2641-9964
Pogge, Richard W.0000-0003-1435-3053
Udalski, Andrzej0000-0001-5207-5619
Poleski, Radek0000-0002-9245-6368
Skowron, Jan0000-0002-2335-1730
Szymański, Michał K.0000-0002-0548-8995
Soszyński, Igor0000-0002-7777-0842
Pietrukowicz, Paweł0000-0002-2339-5899
Kozłowski, Szymon0000-0003-4084-880X
Ulaczyk, Krzysztof0000-0001-6364-408X
Rybicki, Krzysztof A.0000-0002-9326-9329
Iwanek, Patryk0000-0002-6212-7221
Additional Information:© 2021 The American Astronomical Society. Received 2020 October 15; revised 2020 December 8; accepted 2020 December 17; published 2021 February 19. We thank Subo Dong for stimulating discussions. 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. Work by C.H. was supported by grants from the National Research Foundation of Korea (2017R1A4A1015178 and 2019R1A2C2085965). The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to A.U.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Research Foundation of Korea2017R1A4A1015178
National Research Foundation of Korea2019R1A2C2085965
National Science Centre (Poland)MAESTRO 2014/14/A/ST9/00121
Subject Keywords:Gravitational microlensing
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Gravitational microlensing (672)
Record Number:CaltechAUTHORS:20210223-130306638
Persistent URL:
Official Citation:Yoon-Hyun Ryu et al 2021 AJ 161 126
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108154
Deposited By: Tony Diaz
Deposited On:23 Feb 2021 22:46
Last Modified:16 Nov 2021 19:09

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