More Like this

1. Systematic KMTNet Planetary Anomaly Search. X. Complete Sample of 2017 Prime-field Planets

   https://doi.org/10.3847/1538-3881/ad1888  

   Ryu, Yoon-Hyun; Udalski, Andrzej; Yee, Jennifer C; Zang, Weicheng; Shvartzvald, Yossi; Han, Cheongho; Gould, Andrew; Albrow, Michael D; Chung, Sun-Ju; Hwang, Kyu-Ha; et al (February 2024, The Astronomical Journal)

   Abstract We complete the analysis of planetary candidates found by the KMT AnomalyFinder for the 2017 prime fields that cover ∼13 deg². We report three unambiguous planets: OGLE-2017-BLG-0640, OGLE-2017-BLG-1275, and OGLE-2017-BLG-1237. The first two of these were not previously identified, while the last was not previously published due to technical complications induced by a nearby variable. We further report that a fourth anomalous event, the previously recognized OGLE-2017-BLG-1777, is very likely to be planetary, although its light curve requires unusually complex modeling because the lens and source both have orbiting companions. One of the three unambiguous planets, OGLE-2017-BLG-1275, is the first AnomalyFinder discovery that has a Spitzer microlens parallax measurement,π_E≃ 0.045 ± 0.015, implying that this planetary system almost certainly lies in the Galactic bulge. In the order listed, the four planetary events have planet-host mass ratiosqand normalized projected separationssof $(\log q,s)=(-2.31,0.61)$, (−2.06, 0.63/1.09), (−2.10, 1.04), and (−2.86, 0.72). Combined with previously published events, the 2017 prime fields contain 11 unambiguous planets with well-measuredqand one very likely candidate, of which three are AnomalyFinder discoveries. In addition to these 12, there are three other unambiguous planets with large uncertainties inq. 

   more » « less
2. Systematic KMTNet Planetary Anomaly Search. VII. Complete Sample of q < 10 ⁻⁴ Planets from the First 4 yr Survey

   https://doi.org/10.3847/1538-3881/acb34b  

   Zang, Weicheng; Jung, Youn Kil; Yang, Hongjing; Zhang, Xiangyu; Udalski, Andrzej; Yee, Jennifer C.; Gould, Andrew; Mao, Shude; Albrow, Michael D.; Chung, Sun-Ju; et al (February 2023, The Astronomical Journal)

   Abstract We present the analysis of seven microlensing planetary events with planet/host mass ratios q < 10 −4 : KMT-2017-BLG-1194, KMT-2017-BLG-0428, KMT-2019-BLG-1806, KMT-2017-BLG-1003, KMT-2019-BLG-1367, OGLE-2017-BLG-1806, and KMT-2016-BLG-1105. They were identified by applying the Korea Microlensing Telescope Network (KMTNet) AnomalyFinder algorithm to 2016–2019 KMTNet events. A Bayesian analysis indicates that all the lens systems consist of a cold super-Earth orbiting an M or K dwarf. Together with 17 previously published and three that will be published elsewhere, AnomalyFinder has found a total of 27 planets that have solutions with q < 10 −4 from 2016–2019 KMTNet events, which lays the foundation for the first statistical analysis of the planetary mass-ratio function based on KMTNet data. By reviewing the 27 planets, we find that the missing planetary caustics problem in the KMTNet planetary sample has been solved by AnomalyFinder. We also find a desert of high-magnification planetary signals ( A ≳ 65), and a follow-up project for KMTNet high-magnification events could detect at least two more q < 10 −4 planets per year and form an independent statistical sample. 

   more » « less
3. KMT-2023-BLG-1431Lb: A New q < 10 ⁻⁴ Microlensing Planet from a Subtle Signature

   https://doi.org/10.1088/1538-3873/ad48b8  

   Bell, Aislyn; Zhang, Jiyuan; Zang, Weicheng; Jung, Youn Kil; Yee, Jennifer C; Yang, Hongjing; Sumi, Takahiro; Udalski, Andrzej; Albrow, Michael D; Chung, Sun-Ju; et al (May 2024, Publications of the Astronomical Society of the Pacific)

   Abstract The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here, we report the detection and analysis of a microlensing planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 mag) and short-lived (5 hr) planetary signature was characterized by the follow-up from KMTNet and LCO. A binary-lens single-source (2L1S) analysis reveals a planet/host mass ratio ofq= (0.72 ± 0.07) × 10⁻⁴, and the single-lens binary-source (1L2S) model is excluded by Δχ²= 80. A Bayesian analysis using a Galactic model yields estimates of the host star mass of $M_{\mathrm{host}}={0.57}_{-0.29}^{+0.33}{M}_{\odot }$, the planetary mass of $M_{\mathrm{planet}}={13.5}_{-6.8}^{+8.1}{M}_{\oplus }$, and the lens distance of $D_{\mathrm{L}}={6.9}_{-1.7}^{+0.8}$kpc. The projected planet-host separation of $a_{\perp }={2.3}_{-0.5}^{+0.5}$au or $a_{\perp }={3.2}_{-0.8}^{+0.7}$au, subject to the close/wide degeneracy. We also find that without the follow-up data, the survey-only data cannot break the degeneracy of central/resonant caustics and the degeneracy of 2L1S/1L2S models, showing the importance of follow-up observations for current microlensing surveys. 

   more » « less
4. OGLE-2019-BLG-1180Lb: Discovery of a Wide-orbit Jupiter-mass Planet around a Late-type Star

   https://doi.org/10.3847/1538-3881/ad0723  

   Chung, Sun-Ju; Udalski, Andrzej; Yee, Jennifer C.; Gould, Andrew; Leading Authors; Albrow, Michael D.; Jung, Youn Kil; Hwang, Kyu-Ha; Han, Cheongho; Ryu, Yoon-Hyun; et al (November 2023, The Astronomical Journal)

   Abstract We report on the discovery and analysis of the planetary microlensing event OGLE-2019-BLG-1180 with a planet-to-star mass ratioq∼ 0.003. The event OGLE-2019-BLG-1180 has unambiguous cusp-passing and caustic-crossing anomalies, which were caused by a wide planetary caustic withs≃ 2, wheresis the star–planet separation in units of the angular Einstein radiusθ_E. Thanks to well-covered anomalies by the Korea Micorolensing Telescope Network (KMTNet), we measure both the angular Einstein radius and the microlens parallax in spite of a relatively short event timescale oft_E= 28 days. However, because of a weak constraint on the parallax, we conduct a Bayesian analysis to estimate the physical lens parameters. We find that the lens system is a super-Jupiter-mass planet of $M_{\mathrm{p}}={1.75}_{-0.51}^{+0.53}{M}_{\mathrm{J}}$orbiting a late-type star of $M_{\mathrm{h}}={0.55}_{-0.26}^{+0.27}{M}_{\odot }$at a distance $D_{\mathrm{L}}={6.1}_{-1.3}^{+0.9}\mathrm{kpc}$. The projected star–planet separation is $a_{\perp }={5.19}_{-1.23}^{+0.90}\mathrm{au}$, which means that the planet orbits at about four times the snow line of the host star. Considering the relative lens–source proper motion ofμ_rel= 6 mas yr⁻¹, the lens will be separated from the source by 60 mas in 2029. At that time one can measure the lens flux from adaptive optics imaging of Keck or a next-generation 30 m class telescope. OGLE-2019-BLG-1180Lb represents a growing population of wide-orbit planets detected by KMTNet, so we also present a general investigation into prospects for further expanding the sample of such planets. 

   more » « less
5. Systematic KMTNet Planetary Anomaly Search. XI. Complete Sample of 2016 Subprime Field Planets

   https://doi.org/10.3847/1538-3881/ad3ba3  

   Shin, In-Gu; Yee, Jennifer_C; Zang, Weicheng; Han, Cheongho; Yang, Hongjing; Gould, Andrew; Lee, Chung-Uk; Udalski, Andrzej; Sumi, Takahiro; Leading_authors; et al (May 2024, The Astronomical Journal)

   Abstract Following Shin et al. (2023b), which is a part of the “Systematic KMTNet Planetary Anomaly Search” series (i.e., a search for planets in the 2016 KMTNet prime fields), we conduct a systematic search of the 2016 KMTNet subprime fields using a semi-machine-based algorithm to identify hidden anomalous events missed by the conventional by-eye search. We find four new planets and seven planet candidates that were buried in the KMTNet archive. The new planets are OGLE-2016-BLG-1598Lb, OGLE-2016-BLG-1800Lb, MOA-2016-BLG-526Lb, and KMT-2016-BLG-2321Lb, which show typical properties of microlensing planets, i.e., giant planets orbit M-dwarf host stars beyond their snow lines. For the planet candidates, we find planet/binary or 2L1S/1L2S degeneracies, which are an obstacle to firmly claiming planet detections. By combining the results of Shin et al. (2023b) and this work, we find a total of nine hidden planets, which is about half the number of planets discovered by eye in 2016. With this work, we have met the goal of the systematic search series for 2016, which is to build a complete microlensing planet sample. We also show that our systematic searches significantly contribute to completing the planet sample, especially for planet/host mass ratios smaller than 10⁻³, which were incomplete in previous by-eye searches of the KMTNet archive. 

   more » « less