Chung‐Uk Lee
A5044493729- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Optical Systems and Laser Technology
- Atmospheric Ozone and Climate
- Calibration and Measurement Techniques
- Neutrino Physics Research
- Space Exploration and Technology
- Spacecraft Design and Technology
- solar cell performance optimization
- Advanced optical system design
- Dark Matter and Cosmic Phenomena
- Infrared Target Detection Methodologies
Korea Astronomy and Space Science Institute
2016-2025
Chungbuk National University
2002-2023
Korea University of Science and Technology
2014-2023
Massey University
2023
Center for Astrophysics Harvard & Smithsonian
2023
Tsinghua University
2023
The Ohio State University
2023
University of Canterbury
2020-2023
Max Planck Institute for Astronomy
2018-2023
University of Salerno
2023
Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing all except Mercury. We report detection a with microlensing. identify two masses ∼0.71 and ∼0.27 times mass Jupiter orbital separations ∼2.3 ∼4.6 astronomical units orbiting primary star ∼0.50 at distance ∼1.5 kiloparsecs. This...
We present the first measurement of planet frequency beyond "snow line," for planet-to-star mass-ratio interval −4.5 < log q −2, corresponding to range ice giants gas giants. find at mean mass ratio = 5 × 10−4 with no discernible deviation from a flat (Öpik's law) distribution in log-projected separation s. The determination is based on sample six planets detected intensive follow-up observations high-magnification (A>200) microlensing events during 2005–2008. sampled host stars have typical...
The Korea Microlensing Telescope Network (KMTNet) is a wide-field photometric system installed by the Astronomy and Space Science Institute (KASI). Here, we present overall technical specifications of KMTNet observation system, test results, data transfer image processing procedure, finally, science programs. consists three 1.6 m optical telescopes equipped with mosaic CCD cameras 18k pixels. Each telescope provides 2.0 square degree field view. We have finished installing all sequentially...
Abstract We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). used Hubble Space Telescope (HST) to carry out precise astrometry source star long-duration ( t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in direction Galactic bulge. HST imaging, conducted at eight epochs over interval 6 yr, reveals a clear relativistic astrometric deflection...
We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with planet–star mass ratio q = [9.5 ± 2.1] × 10−5 via gravitational microlensing. The planetary deviation was detected in real-time thanks to high cadence Microlensing Observations Astrophysics survey, light-curve monitoring and intensive follow-up observations. A Bayesian analysis returns stellar distance at Ml 0.64+0.21−0.26 M☉ Dl 5.9+0.9−1.4 kpc, respectively, so separation are Mp 20+7−8 M⊕ 3.3+1.4−0.8 AU,...
For the very short period subdwarf B eclipsing binary HW Vir, we present new CCD photometry made from 2000 through 2008. In order to obtain consistency of parameters, our light curves, showing sharp eclipses and a striking reflection effect, were analyzed simultaneously with previously published radial velocity data. The secondary star parameters M2 = 0.14 M☉, R2 0.18 R☉, T2 3084 K are consistent those an M6-7 main-sequence star. A credibility issue regarding bolometric corrections is...
We present the first microlensing candidate for a free-floating exoplanet–exomoon system, MOA-2011-BLG-262, with primary lens mass of Mhost ∼ 4 Jupiter masses hosting sub-Earth moon. The argument an exomoon hinges on system being relatively close to Sun. data constrain product MLπrel where ML is and πrel lens–source relative parallax. If nearby (large πrel), then small (a few masses) companion sub-Earth-mass exomoon. best-fit solution has large proper motion, μrel = 19.6 ± 1.6 mas yr−1,...
We report the detection of cool, Jovian-mass planet MOA-2007-BLG-400Lb. The was detected in a high-magnification microlensing event (with peak magnification A_max = 628) which primary lens transited source, resulting dramatic smoothing event. angular extent region perturbation due to is significantly smaller than size and as result planetary signature also smoothed out by finite source size. Thus deviation from single-lens fit broad relatively weak (~ few percent). Nevertheless, we...
Aims. We report the discovery of a planet with high planet-to-star mass ratio in microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over 12-day interval, one longest for any planetary event. The host is an M dwarf, range 0.07 M⊙ < Mhost 0.49 at 90% confidence. planet-star q = 0.0132 ± 0.003 has been measured extremely well, so best-estimated mass, mp 2.6 Jupiter masses median 0.19 M⊙.
We present the first example of binary microlensing for which parameter measurements can be verified (or contradicted) by future Doppler observations. This test is made possible a confluence two relatively unusual circumstances. First, lens bright enough (I=15.6) to permit measurements. Second, we measure not only usual 7 binary-lens parameters, but also 'microlens parallax' (which yields mass) and components instantaneous orbital velocity. Thus measure, effectively, 6 'Kepler+1' parameters...
Parallax is the most fundamental technique for measuring distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 B.C.E.) measure distance Moon, baseline of Earth so small that can generally only be applied objects in Solar System. However, there exists a class extreme gravitational microlensing events which effects readily detected and permit measurement distance, mass, transverse velocity lens. Here we report observations...
We present the discovery and mass measurement of cold, low-mass planet MOA-2009-BLG-266Lb, performed with gravitational microlensing method. This has a mp = 10.4 ± 1.7 M⊕ orbits star M⋆ 0.56 0.09 M☉ at semimajor axis AU an orbital period yrs. The host measurements are enabled by parallax effect, which is seen primarily in light curve distortion due to motion Earth. But analysis also demonstrates capability measure Deep Impact (or EPOXI) spacecraft heliocentric orbit. distance similar...
Because of the development large-format, wide-field cameras, microlensing surveys are now able to monitor millions stars with sufficient cadence detect planets. These new discoveries will span full range significance levels including planetary signals too small be distinguished from noise. At present, we do not understand where threshold is for detecting MOA-2011-BLG-293Lb first planet published surveys, and it also has substantial follow-up observations. This robustly detected in...
Impolite planet ignores host's partner Many known exoplanets (planets outside our own solar system) are hosted by binary systems that contain two stars. These planets normally circle around both of their Using microlensing data taken with a worldwide network telescopes, Gould et al. found twice the mass Earth circles just one pair The same approach has potential to uncover other similar star and help illuminate some mysteries formation. Science , this issue p. 46
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,...
Exoplanets classified as super-Earths are commonly observed on short-period orbits, close to their host stars, but abundance wider orbits is poorly constrained. Gravitational microlensing sensitive exoplanets wide orbits. We the event OGLE-2016-BLG-0007, which indicates an exoplanet with a planet-to-star mass ratio roughly double Earth-Sun ratio, orbit longer than Saturn's. combined this larger sample from survey determine distribution of ratios for planets infer that there ~0.35 super-Earth...
Context.We present the observational results of multi-colour optical monitoring eight red blazars from 2003 September to 2004 February.Aims.The aim our is investigate spectral variability as well flux variations at short and long time scales.Methods.The observations were carried out using 1.0 m robotic telescope Mt. Lemmon Optical Astronomy Observatory, in Arizona, USA, 0.6 Sobaeksan Observatory 1.8 Bohyunsan Republic Korea.Results.During observations, all sources show strong with amplitudes...
The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. maximum brightness detected was R = 12.0, which represents the most luminous state thus far observed (M_B ~ -31.4). In order to follow emission behaviour of source detail, a large multiwavelength campaign organized by Whole Earth Blazar Telescope (WEBT). Continuous optical, near-IR monitoring performed several bands. ToO pointings Chandra INTEGRAL satellites provided...
Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability flux at all wavebands. Its variations polarization are quite complex therefore require intensive monitoring observations multiple wavebands to characterise interpret observed changes.
We present a new analysis of the Jupiter+Saturn analog system, OGLE-2006-BLG-109Lb,c, which was first double planet system discovered with gravitational microlensing method. This is only multi-planet by any method measured masses for star and both planets. In addition to signatures two planets, this event also exhibits parallax signature finite source effects that provide direct measure expected brightness host confirmed Keck AO imaging, yielding M_* = 0.51(+0.05-0.04) M_sun, M_b 231+-19...
We report the discovery of a planetary system from observation high-magnification microlensing event OGLE-2012-BLG-0026. The lensing light curve exhibits complex central perturbation with multiple features. find that was produced by two planets located near Einstein ring planet host star. identify four possible solutions resulting well-known close/wide degeneracy. By measuring both lens parallax and radius, we estimate physical parameters system. According to best-fit model, masses are ∼0.11...
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...