Journal Article

KMT-2024-BLG-3237: Another Free-floating Planet Candidate with Angular Einstein Radius Measurement

Han, Cheongho, Zang, Weicheng, Lee, Chung-Uk, Yang, Hongjing, Yee, Jennifer C, Kim, Dong-Jin, Jung, Youn Kil, Albrow, Michael D, Shvartzvald, Yossi, Park, Byeong-Gon, Ryu, Yoon-Hyun, Inyanya, Tanagodchaporn, Chung, Sun-Ju, Gould, Andrew, Shin, In-Gu, Hwang, Kyu-Ha

2026

Overview

Planet-formation theories suggest the presence of free-floating planets (FFPs) that are ejected from their formation sites. While these planets emit very little light, they can be identified through gravitational microlensing. Here, we report the discovery of a FFP candidate in the microlensing event KMT-2024-BLG-3237. The observed light curve exhibits strong finite-source effects characterized by a small amplitude (≲0.9 mag) and a short timescale (≲3 days). The analysis yields an Einstein timescale of tE = 0.54 ± 0.02 days and an angular Einstein radius of θE = 6.30 ± 0.48 μas. The measurements make it possible to estimate the lens mass as M≃102M⊕(πrel/16μas)−1 , where πrel is the relative lens-source parallax. Depending on the unknown πrel, the lens could be a Neptune-mass planet (πrel ≃ 0.1 mas) or a Saturn-mass planet (πrel ≃ 16 μas). A Bayesian analysis yields the lens mass M=67.3−42.5+103.2M⊕ and the lens distance DL=7.34−2.11+0.96kpc . This lens is thirteenth isolated microlens with a measurement of θE < 10 μas. We find that additional searches for possible signatures of a lens host do not show significant evidence for the host.

• Publisher: IOP Publishing
• Subject: Astronomy / Astrophysics / Bayesian analysis / Extrasolar planets / Gas giant planets / Gravitational lenses / Light curve / Microlenses / Parallax / Planet formation / Planets / Rogue planets / Stars & galaxies / Telescopes / Time