OGLE-2019-BLG-0960 Lb: The Smallest Microlensing Planet

Jennifer C. Yee, Weicheng Zang, Andrzej Udalski, Yoon Hyun Ryu, Jonathan Green, Steve Hennerley, Andrew Marmont, Takahiro Sumi, Shude Mao, Mariusz Gromadzki, Przemek Mróz, Jan Skowron, Radoslaw Poleski, Michal K. Szymanski, Igor Soszynski, Pawel Pietrukowicz, Szymon Kozlowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk IwanekMarcin Wrona, Michael D. Albrow, Sun Ju Chung, Andrew Gould, Cheongho Han, Kyu Ha Hwang, Youn Kil Jung, Hyoun Woo Kim, In Gu Shin, Yossi Shvartzvald, Sang Mok Cha, Dong Jin Kim, Seung Lee Kim, Chung Uk Lee, Dong Joo Lee, Yongseok Lee, Byeong Gon Park, Richard W. Pogge, Etienne Bachelet, Grant Christie, Markus P.G. Hundertmark, Dan Maoz, Jennie McCormick, Tim Natusch, Matthew T. Penny, Rachel A. Street, Yiannis Tsapras, Charles A. Beichman, Geoffery Bryden, Sebastiano Calchi Novati, Sean Carey, B. Scott Gaudi, Calen B. Henderson, Samson Johnson, Wei Zhu, Ian A. Bond, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Martin Donachie, Hirosane Fujii, Akihiko Fukui, Yuki Hirao, Stela Ishitani Silva, Yoshitaka Itow, Rintaro Kirikawa, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Hikaru Shoji, Daisuke Suzuki, Yuzuru Tanaka, Paul J. Tristram, Tsubasa Yamawaki, Atsunori Yonehara

Research output: Contribution to journalArticlepeer-review


We report the analysis of OGLE-2019-BLG-0960, which contains the smallest mass-ratio microlensing planet found to date (q = 1.2-1.6 × 10-5 at 1s). Although there is substantial uncertainty in the satellite parallax measured by Spitzer, the measurement of the annual parallax effect combined with the finite source effect allows us to determine the mass of the host star (M L = 0.3-0.6 M o?), the mass of its planet (m p = 1.4-3.1 M ?), the projected separation between the host and planet (a ? = 1.2-2.3 au), and the distance to the lens system (D L = 0.6-1.2 kpc). The lens is plausibly the blend, which could be checked with adaptive optics observations. As the smallest planet clearly below the break in the mass-ratio function, it demonstrates that current experiments are powerful enough to robustly measure the slope of the mass-ratio function below that break. We find that the cross-section for detecting small planets is maximized for planets with separations just outside of the boundary for resonant caustics and that sensitivity to such planets can be maximized by intensively monitoring events whenever they are magnified by a factor A > 5. Finally, an empirical investigation demonstrates that most planets showing a degeneracy between (s > 1) and (s < 1) solutions are not in the regime (log s| » 0) for which the "close"/"wide"degeneracy was derived. This investigation suggests that there is a link between the "close"/"wide"and "inner/outer"degeneracies and also that the symmetry in the lens equation goes much deeper than symmetries uncovered for the limiting cases.

Original languageEnglish
Article number180
JournalAstronomical Journal
Issue number5
StatePublished - 1 Nov 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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