KMT-2025-BLG-0975Lb and KMT-2025-BLG-1160Lb: Two Uranus-Mass Planets Beyond the Snow Line Discovered by Microlensing

Abstract

We present the analysis of two planetary microlensing events, KMT-2025-BLG-0975 and KMT-2025-BLG-1160, discovered during the 2025 Galactic bulge microlensing season through high-cadence survey observations. In both events, short-duration anomalies near the peaks of the lensing light curves reveal the presence of planetary companions. Light-curve modeling yields planet-to-host mass ratios of $q=8.6\times 10^{-4}$ for KMT-2025-BLG-0975 and $1.3\times 10^{-4}$ for KMT-2025-BLG-1160. For KMT-2025-BLG-0975, finite-source effects are detected, enabling a measurement of the angular Einstein radius, whereas only a lower limit on this quantity is obtained for KMT-2025-BLG-1160. We estimate the physical parameters of the lens systems through Bayesian analyses constrained by the measured microlensing observables. The results indicate that the planetary companions have masses of $M_{\mathrm{p}}=29.8_{-16.0}^{+50.5}{M}_{\oplus }$ for KMT-2025-BLG-0975Lb and $25.4_{-14.1}^{+15.5}{M}_{\oplus }$ for KMT-2025-BLG-1160Lb. Both planets have masses comparable to that of Uranus. The host stars are inferred to be a low-mass M dwarf with a mass of $M_{\mathrm{h}}=0.10_{-0.06}^{+0.18}{M}_{\odot }$ for KMT-2025-BLG-0975L and a late K dwarf with a mass of $M_{\mathrm{h}}=0.58_{-0.32}^{+0.35}{M}_{\odot }$ for KMT-2025-BLG-1160L. The projected planet--host separations are $a_{\perp }=0.81_{-0.11}^{+0.10}$~au for KMT-2025-BLG-0975Lb and $a_{\perp }=2.56_{-0.71}^{+0.48}$~au and $3.29_{-0.92}^{+0.61}$~au for the inner and wide solutions, respectively, of KMT-2025-BLG-1160Lb. In both systems, the planets are located beyond the expected snow-line distances of their hosts, placing them in the cold ice-giant regime.

11 pages, 7 figures