• DOI:10.3847/2041-8213/abbfad
• Corpus ID: 221971000

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

@article{Mrz2020ATR,
  title={A Terrestrial-mass Rogue Planet Candidate Detected in the Shortest-timescale Microlensing Event},
  author={Przemek Mr{\'o}z and Radosław Poleski and A. Gould and Andrzej Udalski and Takahiro Sumi and Michał K. Szymański and Igor Soszyński and Paweł Pietrukowicz and Szymon Kozłowski and Jan Skowron and Krzysztof Ulaczyk and Michael D. Albrow and Sun-Ju Chung and Cheongho Han and Kyu-Ha Hwang and Youn Kil Jung and Hyoun-Woo Kim and Yoon-Hyun Ryu and In-Gu Shin and Yossi Shvartzvald and Jennifer C. Yee and Weicheng Zang and Sang-Mok Cha and Dong-Jin Kim and Seung-Lee Kim and Chung-Uk Lee and Dong-Joo Lee and Yongseok Lee and B.-G. Park and Richard W. Pogge},
  journal={The Astrophysical Journal Letters},
  year={2020},
  volume={903}
}

• P. Mróz, R. Poleski, +27 authors R. Pogge
• Published 25 September 2020
• Physics, Geology
• The Astrophysical Journal Letters

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 ( ). 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 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.