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arXiv · 2609.12743

Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516

Przemek Mróz·Klara Piotrowska·Antoine Mérand·Subo Dong·Zexuan Wu
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Abstract

Recent studies found a number of short-timescale microlensing events that are thought to be produced by free-floating or wide-orbit planets. The microlensing event KMT-2024-BLG-0792/OGLE-2024-BLG-0516 is currently the only free-floating planet candidate with a directly measured mass ($0.73^{+0.25}_{-0.15}$ Saturn masses), derived from joint ground-based and Gaia satellite observations. However, it remains unclear whether the lens is truly isolated or bound to a widely separated host star. Here, we report high-angular-resolution interferometric observations of the event obtained with the Very Large Telescope Interferometer/GRAVITY instrument two years after peak magnification. We detect no luminous host star up to a projected separation of 90 au, supporting the hypothesis that the lens is indeed a free-floating planet. We derive a 5 sigma upper limit on the mass of a putative host star of approximately 0.5-0.6 M_solar. This work demonstrates that interferometry provides a powerful method for directly searching for or constraining host stars in short-duration and planetary microlensing events.

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Przemek Mróz, Klara Piotrowska, Antoine Mérand, Subo Dong, Zexuan Wu. 2026-09-11. Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516. https://arxiv.org/abs/2609.12743

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