Six microlensing planets detected via sub-day signals during the 2023–2024 season

¹ Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
² Korea Astronomy and Space Science Institute, Daejon 34055, Republic of Korea
³ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
⁴ Institute of Natural and Mathematical Science, Massey University, Auckland 0745, New Zealand
⁵ University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch 8020, New Zealand
⁶ Department of Astronomy, Ohio State University, 140 West 18th Ave., Columbus, OH 43210, USA
⁷ University of Science and Technology, Daejeon 34113, Republic of Korea
⁸ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
⁹ Center for Astrophysics | Harvard & Smithsonian 60 Garden St., Cambridge, MA 02138, USA
¹⁰ Department of Astronomy and Tsinghua Centre for Astrophysics, Tsinghua University, Beijing 100084, China
¹¹ School of Space Research, Kyung Hee University, Yongin, Kyeonggi 17104, Republic of Korea
¹² Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
¹³ Villanova University, Department of Astrophysics and Planetary Sciences, 800 Lancaster Ave., Villanova, PA 19085, USA
¹⁴ Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
¹⁵ Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁶ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁷ Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁸ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
¹⁹ Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
²⁰ Department of Physics, The Catholic University of America, Washington, DC 20064, USA
²¹ Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
²² Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
²³ Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
²⁴ University of Canterbury Mt. John Observatory, P.O. Box 56, Lake Tekapo 8770, New Zealand

^★ Corresponding author: leecu@kasi.re.kr

Received: 16 March 2025
Accepted: 4 September 2025

Abstract

Aims. We present analyses of six microlensing events: KMT-2023-BLG-0548, KMT-2023-BLG-0830, KMT-2023-BLG-0949, KMT-2024-BLG-1281, KMT-2024-BLG-2059, and KMT-2024-BLG-2242. These were identified in KMTNet data from the 2023–2024 seasons, selected for exhibiting anomalies shorter than one day – potential signatures of low-mass planetary companions. Motivated by this, we conducted detailed investigations to characterize the nature of the observed perturbations.

Methods. Detailed modeling of the light curves reveals that the anomalies in all six events are caused by planetary companions to the lenses. The brief durations of the anomalies are attributed to various factors: a low planet-to-host mass ratio (KMT-2024-BLG-2059, KMT-2024-BLG-2242), a wide planet-host separation (KMT-2023-BLG-0548), small and elongated caustics restricting the source’s interaction region (KMT-2023-BLG-0830, KMT-2024-BLG-1281), and a partial caustic crossing (KMT-2023-BLG-0949).

Results. We estimated the physical parameters of the lens systems using Bayesian analysis. For KMT-2023-BLG-0548, the posterior distribution of the lens mass shows two distinct peaks: a low-mass solution indicating a sub-Jovian planet orbiting an M dwarf in the Galactic disk, and a high-mass solution suggesting a super-Jovian planet around a K-type dwarf in the bulge. KMT-2023-BLG-0830 hosts a Neptune-mass planet orbiting an M dwarf in the Galactic bulge. KMT-2023-BLG-0949 involves a super-Jovian planet orbiting a ~0.5 M_⊙ host located at ~6 kpc. KMT-2024-BLG-2059Lb is a super-Earth with a mass about seven times that of Earth, orbiting an early M dwarf of ~0.5 M_⊙. KMT-2024-BLG-1281L hosts a planet slightly more massive than Neptune, orbiting an M dwarf of ~0.3 M_⊙. The short timescale and small angular Einstein radius of KMT-2024-BLG-2242 suggest a ~0.07 M_⊙ primary, likely a brown dwarf, with a planet of Uranus- or Neptune-like mass.