Sun‐Ju Chung
A5049884799- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- Atmospheric Ozone and Climate
- Galaxies: Formation, Evolution, Phenomena
- Spacecraft Design and Technology
- Calibration and Measurement Techniques
- Photonic and Optical Devices
- Astrophysical Phenomena and Observations
- Advanced Frequency and Time Standards
- Photorefractive and Nonlinear Optics
- Planetary Science and Exploration
- Geochemistry and Geologic Mapping
- Pulsars and Gravitational Waves Research
- Optical Systems and Laser Technology
- Advanced Optical Imaging Technologies
- Child and Adolescent Psychosocial and Emotional Development
Korea Astronomy and Space Science Institute
2014-2024
Korea University of Science and Technology
2017-2024
Universiti Brunei Darussalam
2024
Center for Astrophysics Harvard & Smithsonian
2023-2024
Chungbuk National University
2000-2023
University of Salerno
2023
Massey University
2023
University of America
2023
Catholic University of America
2023
Max Planck Institute for Astronomy
2018-2023
We combine $Spitzer$ and ground-based KMTNet microlensing observations to identify precisely measure an Earth-mass ($1.43^{+0.45}_{-0.32} M_\oplus$) planet OGLE-2016-BLG-1195Lb at $1.16^{+0.16}_{-0.13}$ AU orbiting a $0.078^{+0.016}_{-0.012} M_\odot$ ultracool dwarf. This is the lowest-mass date. At $3.91^{+0.42}_{-0.46}$ kpc, it third consecutive case among "Galactic distribution" planets toward Galactic bulge that lies in disk as opposed itself, hinting skewed distribution of planets....
We analyze an ensemble of microlensing events from the 2015 Spitzer campaign, all which were densely monitored by ground-based high-cadence survey teams. The simultaneous observations and ground yield measurements parallax vector $\pi_{\rm E}$, compact constraints on microlens properties are derived, including $\lesssim$25\% uncertainties lens mass distance. With current sample, we demonstrate that majority microlenses indeed in range M dwarfs. planet sensitivities 41 sample calculated,...
We report the detection of sub-Saturn-mass planet MOA-2008-BLG-310Lb and argue that it is strongest candidate yet for a bulge planet. Deviations from single-lens fit are smoothed out by finite-source effects so not immediately apparent light curve. Nevertheless, we find model in which primary has planetary companion favored over \Delta\chi^2 ~ 880 an additional three degrees freedom. Detailed analysis yields planet/star mass ratio q=(3.3+/-0.3)x10^{-4} angular separation between star within...
Planet formation theories predict the existence of free-floating planets that have been ejected from their parent systems. Although they emit little or no light, can be detected during gravitational microlensing events. Microlensing events caused by rogue are characterized very short timescales $t_{\rm E}$ (typically below two days) and small angular Einstein radii $\theta_{\rm (up to several uas). Here we present discovery characterization ultra-short identified in data Optical...
Abstract We report the discovery of a giant planet in OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite relatively short event timescale t E ∼ 7.5 days. Einstein radius is unusually small, θ = 0.065 mas, implying that lens system either has very low mass or lies much closer to microlensed source than Sun, both. A Bayesian analysis yields component masses and source-lens distance , this brown-dwarf/Jupiter...
Some low-mass planets are expected to be ejected from their parent planetary systems during early stages of system formation. According planet-formation theories, such as the core accretion theory, typical masses should between 0.3 and 1.0 $M_{\oplus}$. Although in practice objects do not emit any light, they may detected using gravitational microlensing via light-bending gravity. Microlensing events due terrestrial-mass rogue have extremely small angular Einstein radii (< 1 uas) short...
Abstract In order to exhume the buried signatures of “missing planetary caustics” in Korea Microlensing Telescope Network (KMTNet) data, we conducted a systematic anomaly search residuals from point-source point-lens fits, based on modified version KMTNet EventFinder algorithm. This revealed lowest-mass-ratio caustic date microlensing event OGLE-2019-BLG-1053, for which signal had not been noticed before. The system has planet–host mass ratio q = (1.25 ± 0.13) × 10 −5 . A Bayesian analysis...
Abstract We apply the automated AnomalyFinder algorithm of Paper I to 2018–2019 light curves from ≃13 deg 2 covered by six KMTNet prime fields, with cadences Γ ≥ hr −1 . find a total 11 planets mass ratios q < × 10 −4 , including 6 newly discovered planets, 1 planet that was reported in I, and recovery 4 previously planets. One new OGLE-2018-BLG-0977Lb, is planetary caustic event, while other five (OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, KMT-2019-BLG-0253,...
ABSTRACT We report the complete statistical planetary sample from prime fields (Γ ≥ 2 h−1) of 2019 Korea Microlensing Telescope Network (KMTNet) microlensing survey. develop optimized KMTNet AnomalyFinder algorithm and apply it to fields. find a total 13 homogeneously selected planets analysis three events, KMT-2019-BLG-(1042,1552,2974). The planet–host mass ratios, q, for events are 6.34 × 10−4, 4.89 10−3, 6.18 respectively. A Bayesian indicates all cold giant beyond snow line their host...
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 Korea Microlensing Telescope Network (KMTNet) AnomalyFinder algorithm to 2016–2019 KMTNet events. A Bayesian indicates that all lens systems consist a cold super-Earth orbiting an M or K dwarf. Together 17...
Abstract We complete the analysis of planetary candidates found by KMT AnomalyFinder for 2017 prime fields that cover ∼13 deg 2 . report three unambiguous planets: OGLE-2017-BLG-0640, OGLE-2017-BLG-1275, and OGLE-2017-BLG-1237. The first two these were not previously identified, while last was published due to technical complications induced a nearby variable. further fourth anomalous event, recognized OGLE-2017-BLG-1777, is very likely be planetary, although its light curve requires...
Abstract Traditional microlensing event vetting methods require highly trained human experts, and the process is both complex time consuming. This reliance on manual inspection often leads to inefficiencies constrains ability scale for widespread exoplanet detection, ultimately hindering discovery rates. To address limits of traditional vetting, we have developed LensNet, a machine learning pipeline specifically designed distinguish legitimate events from false positives caused by...
We present microlensing events in the 2015 Korea Microlensing Telescope Network (KMTNet) data and our procedure for identifying these events. In particular, candidates were detected with a novel "completed event" event-finder algorithm. The algorithm works by making linear fits to (t0,teff,u0) grid of point-lens models. This approach is rendered computationally efficient restricting u0 just two values (0 1), which we show quite adequate. implementation presented here specifically tailored...
We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be first Spitzer microlensing planet in Galactic bulge/bar, an assignation that can confirmed by two epochs high-resolution imaging combined source-lens baseline object. The planet's mass M_p= 13.4+-0.9 M_J places it right at deuterium burning limit, i.e., conventional boundary between "planets" and "brown dwarfs". Its existence raises question whether such objects are really (formed within disks their hosts) or "failed...
We present microlensing planet OGLE-2017-BLG-0173Lb, with planet-host mass ratio either $q\simeq 2.5\times 10^{-5}$ or 6.5\times 10^{-5}$, the lowest among ever detected. The planetary perturbation is strongly detected, $\Delta\chi^2\sim 10,000$, because it arises from a bright (therefore, large) source passing over and enveloping caustic: so-called "Hollywood" event. factor $\sim 2.5$ offset in $q$ of previously unrecognized discrete degeneracy between Hollywood events which caustic fully...
We present the analysis of OGLE-2016-BLG-0613, for which lensing light curve appears to be that a typical binary-lens event with two caustic spikes but discontinuous feature on trough between spikes. find was produced by planetary companion binary lens. 4 degenerate triple-lens solution classes, each composed pair solutions according well-known wide/close degeneracy. One these classes is excluded due its relatively poor fit. For remaining three pairs solutions, most-likely primary mass about...
High-cadence observations of the Galactic bulge by microlensing surveys led to discovery a handful extremely short-timescale events that can be attributed free-floating or wide-orbit planets. Here, we report another strong planet candidate, which was found from analysis gravitational event OGLE-2019-BLG-0551. The light curve is characterized very short duration (<3 d) and small amplitude (< 0.1 mag). From modeling curve, find Einstein timescale, tE = 0.381 +/- 0.017 d, much shorter, angular...
Abstract We present the analyses of two microlensing events, OGLE-2018-BLG-0567 and OGLE-2018-BLG-0962. In both short-lasting anomalies were densely continuously covered by high-cadence surveys. The light-curve modeling indicates that are generated source crossings over planetary caustics induced companions to hosts. estimated planet/host separation (scaled angular Einstein radius θ E ) mass ratio ( s , q × 10 3 = (1.81 ± 0.02, 1.24 0.07) (1.25 0.03, 2.38 0.08), respectively. From Bayesian...
Abstract We report the analysis of OGLE-2019-BLG-0960, which contains smallest mass-ratio microlensing planet found to date ( q = 1.2–1.6 × 10 −5 at 1 σ ). Although there is substantial uncertainty in satellite parallax measured by Spitzer, measurement annual effect combined with finite source allows us determine mass host star M L 0.3–0.6 ⊙ ), its m p 1.4–3.1 ⊕ projected separation between and a ⊥ 1.2–2.3 au), distance lens system D 0.6–1.2 kpc). The plausibly blend, could be checked...
We complete the analysis of all 2018 prime-field microlensing planets identified by Korea Microlensing Telescope Network (KMTNet) Anomaly Finder. Among ten previously unpublished events with clear planetary solutions, eight are either unambiguously or very likely to be in nature: OGLE-2018-BLG-1126, KMT-2018-BLG-2004, OGLE-2018-BLG-1647, OGLE-2018-BLG-1367, OGLE-2018-BLG-1544, OGLE-2018-BLG-0932, OGLE-2018-BLG-1212, and KMT-2018-BLG-2718. Combined four published new Finder 12 (or...
ABSTRACT In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create a new, mostly automated, TLC pipeline. We then start project systematically apply the new pipeline historic microlensing events, search buried planetary signals. report discovery of such planet candidate event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either around lens star or orbital motion source star. For interpretation, despite many...
We examined the anomalies in light curves of lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT-2023-BLG-1896. conducted detailed modeling to uncover nature anomalies. This revealed that all signals originated from planetary companions primary lens. The planet-to-host mass ratios are very low: $q\sim 7.5\times 10^{-5}$ for 3.6\times 10^{-4}$ 6.9\times occurred as source passed through negative deviation region behind central caustic along planet-host axis. solutions subject a common...
We examined the anomalies in light curves of lensing events MOA-2022-BLG-033, KMT-2023-BLG-0119, and KMT-2023-BLG-1896. These share similar traits: they occur near peak moderately to highly magnified display a distinct short-term dip feature. conducted detailed modeling uncover nature anomalies. This revealed that all signals originated from planetary companions primary lens. The planet-to-host mass ratios are very low: q∼ 7.5 for $q∼ 3.6 $ 6.9 occurred as source passed through negative...
Abstract Interferometric observations of gravitational microlensing events offer an opportunity for precise, efficient, and direct mass distance measurements lensing objects, especially those isolated neutron stars black holes. However, such have previously been possible only a handful extremely bright events. The recent development dual-field interferometer, GRAVITY Wide, has made it to reach out significantly fainter objects increase the pool amenable interferometric by 2 orders magnitude....
The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor future near-infrared surveys Shvartzvald2017 . Focusing on stars in Galactic center and utilizing passbands, identified approximately one thousand events, 27 which displayed anomalies their light curves Wen2023 This paper presents an analysis these anomalous aiming uncover underlying causes observed anomalies. events were analyzed under...