KMT-2024-BLG-0816/OGLE-2024-BLG-0519 -- A Microlensing Event with Candidate Free-Floating Planet Lens and Blended Light
R. Poleski, Y. -H. Ryu, A. Udalski, W. Zang, M. D. Albrow, S. -J. Chung, A. Gould, C. Han, K. -H. Hwang, Y. K. Jung, I. -G. Shin, Y. Shvartzvald, J. C. Yee, H. Yang, D. -J. Kim, C. -U. Lee, B. -G. Park, M. K. Szymański, I. Soszyński, K. Ulaczyk, P. Pietrukowicz, J. Skowron, D. Skowron, P. Mróz, K. Rybicki, P. Iwanek, M. Wrona, M. Gromadzki, M. Mróz, M. Ratajczak
TL;DR
Poleski et al. present the discovery of a microlensing event, KMT-2024-BLG-0816/OGLE-2024-BLG-0519, consistent with a free-floating planet lens that shows finite-source effects and a significant, unresolved blending flux. Through joint photometric modeling of KMTNet and OGLE data, the authors find a short Einstein timescale ($t_E \lesssim 0.5$ d) and an angular Einstein radius of about $\theta_E \sim 5\,\mu$as, characteristic of FFPs, while the blending light remains ambiguous in origin. A comprehensive astrometric analysis using Gaia and OGLE data suggests the blend is more likely bulge-related, though it does not decisively rule out a planetary host scenario; follow-up observations are proposed to test whether the blend is the host of the lens. The paper outlines a viable GRAVITY+ interferometric path to resolve the source and blend, potentially confirming a host detection if the blend is associated with the lens, and providing a key test of the FFP interpretation with implications for planet formation and the occurrence rate of wide-orbit companions.
Abstract
We present the discovery of a free-floating planet microlensing event KMT-2024-BLG-0816. The event shows finite-source effect, significant blending light, and no microlensing signal from a putative planet host. Among the free-floating planet events with finite source effects, this is the only event with unresolved blending light. We discuss how follow-up observations can be used to determine whether the blending light originates from a putative planet host.