Massey Research Online - Browsing by Author "Kim D"

Browsing by Author "Kim D"

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Brown dwarf companions in microlensing binaries detected during the 2016-2018 seasons
(EDP Sciences on behalf of the European Southern Observatory, 2022-11-08) Han C; Ryu Y-H; Shin I-G; Jung YK; Kim D; Hirao Y; Bozza V; Albrow MD; Zang W; Udalski A; Bond IA; Chung S-J; Gould A; Hwang K-H; Shvartzvald Y; Yang H; Cha S-M; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Yee JC; Lee Y; Park B-G; Pogge RW; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Rybicki KA; Iwanek P; Wrona M; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Silva SI; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Okamura A; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Itow Y
Aims. With the aim of finding microlensing binaries containing brown dwarf (BD) companions, we investigate the microlensing survey data collected during the 2016 2018 seasons. Methods. For this purpose, we first modeled lensing events with light curves exhibiting anomaly features that are likely to be produced by binary lenses. We then sorted out BD companion binary-lens events by applying the criterion that the companion-to-primary mass ratio is q 0.1. With this procedure, we identify six binaries with candidate BD companions: OGLE-2016-BLG-0890L, MOA-2017-BLG-477L, OGLE-2017-BLG-0614L, KMT-2018-BLG-0357L, OGLE-2018-BLG-1489L, and OGLE-2018-BLG-0360L. Results. We estimated the masses of the binary companions by conducting Bayesian analyses using the observables of the individual lensing events. According to the Bayesian estimation of the lens masses, the probabilities for the lens companions of the events OGLE-2016-BLG-0890, OGLE-2017-BLG-0614, OGLE-2018-BLG-1489, and OGLE-2018-BLG-0360 to be in the BD mass regime are very high with PBD > 80%. For MOA-2017-BLG-477 and KMT-2018-BLG-0357, the probabilities are relatively low with PBD = 61% and 69%, respectively.
Four microlensing giant planets detected through signals produced by minor-image perturbations
(EDP Sciences on behalf of The European Southern Observatory, 2024-07) Han C; Bond IA; Lee C-U; Gould A; Albrow MD; Chung S-J; Hwang K-H; Jung YK; Ryu Y-H; Shvartzvald Y; Shin I-G; Yee JC; Yang H; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Abe F; Bando K; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Silva SI; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K; Bachelet E; Rota P; Bozza V; Zielinski P; Street RA; Tsapras Y; Hundertmark M; Wambsganss J; Wyrzykowski Ł; Jaimes RF; Cassan A; Dominik M; Rybicki KA; Rabus M
Aims. We investigated the nature of the anomalies appearing in four microlensing events KMT-2020-BLG-0757, KMT-2022-BLG-0732, KMT-2022-BLG-1787, and KMT-2022-BLG-1852. The light curves of these events commonly exhibit initial bumps followed by subsequent troughs that extend across a substantial portion of the light curves. Methods. We performed thorough modeling of the anomalies to elucidate their characteristics. Despite their prolonged durations, which differ from the usual brief anomalies observed in typical planetary events, our analysis revealed that each anomaly in these events originated from a planetary companion located within the Einstein ring of the primary star. It was found that the initial bump arouse when the source star crossed one of the planetary caustics, while the subsequent trough feature occurred as the source traversed the region of minor image perturbations lying between the pair of planetary caustics. Results. The estimated masses of the host and planet, their mass ratios, and the distance to the discovered planetary systems are (Mhost/M☉, Mplanet/MJ, q/10−3, DL/kpc) = (0.58−+00.3033, 10.71−+56.6117, 17.61 ± 2.25, 6.67+−01.9330) for KMT-2020-BLG-0757, (0.53+−00.3131, 1.12+−00.6565, 2.01 ± 0.07, 6.66+−11.1984) for KMT-2022-BLG-0732, (0.42−+00.2332, 6.64−+43.9864, 15.07 ± 0.86, 7.55+−01.8930) for KMT-2022-BLG-1787, and (0.32+−00.3419, 4.98+−52.4294, 8.74 ± 0.49, 6.27+−01.9015) for KMT-2022-BLG-1852. These parameters indicate that all the planets are giants with masses exceeding the mass of Jupiter in our solar system and the hosts are low-mass stars with masses substantially less massive than the Sun.
Four sub-Jovian-mass planets detected by high-cadence microlensing surveys
(EDP Sciences on behalf of the European Southern Observatory, 2022-08-05) Han C; Kim D; Gould A; Udalski A; Bond IA; Bozza V; Jung YK; Albrow MD; Chung S-J; Hwang K-H; Ryu Y-H; Shin I-G; Shvartzvald Y; Yee JC; Zang W; Cha S-M; Kim D-J; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozaowski S; Ulaczyk K; Rybicki KA; Iwanek P; Abe F; Barry RK; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Koshimoto N; Kondo I; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Olmschenk G; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Silva SI; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H
Aims. With the aim of finding short-term planetary signals, we investigated the data collected from current high-cadence microlensing surveys. Methods. From this investigation, we found four planetary systems with low planet-to-host mass ratios, including OGLE-2017-BLG-1691L, KMT-2021-BLG-0320L, KMT-2021-BLG-1303L, and KMT-2021-BLG-1554L. Despite the short durations, ranging from a few hours to a couple of days, the planetary signals were clearly detected by the combined data of the lensing surveys. We found that three of the planetary systems have mass ratios on the order of 10-4 and the other has a mass ratio that is slightly greater than 10-3. Results. The estimated masses indicate that all discovered planets have sub-Jovian masses. The planet masses of KMT-2021-BLG-0320Lb, KMT-2021-BLG-1303Lb, and KMT-2021-BLG-1554Lb correspond to ∼0.10, ∼0.38, and ∼0.12 times the mass of the Jupiter, and the mass of OGLE-2017-BLG-1691Lb corresponds to that of the Uranus. The estimated mass of the planet host KMT-2021-BLG-1554L, Mhost ∼ 0.08 M⊙, corresponds to the boundary between a star and a brown dwarf. Besides this system, the host stars of the other planetary systems are low-mass stars with masses in the range of ∼[0.3-0.6] M⊙. The discoveries of the planets fully demonstrate the capability of the current high-cadence microlensing surveys in detecting low-mass planets.
KMT-2019-BLG-1715: Planetary microlensing event with three lens masses and two source stars
(IOP Publishing on behalf of the American Astronomical Society, 2021-06-01) Han C; Udalski A; Kim D; Jung YK; Lee C-U; Bond IA; Albrow MD; Chung S-J; Gould A; Hwang K-H; Kim H-W; Ryu Y-H; Shin I-G; Shvartzvald Y; Zang W; Yee JC; Cha S-M; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Kim C-H; Kim W-T; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Rybicki KA; Iwanek P; Wrona M; Gromadzki M; Abe F; Barry R; Bennett DP; Bhattacharya A; Donachie M; Fujii H; Fukui A; Itow Y; Hirao Y; Kirikawa R; Kondo I; Li MCA; Matsubara Y; Muraki Y; Miyazaki S; Ranc C; Rattenbury NJ; Satoh Y; Shoji H; Suematsu H; Sumi T; Suzuki D; Tanaka Y; Tristram PJ; Yamakawa T; Yamawaki T; Yonehara A
We investigate the gravitational microlensing event KMT-2019-BLG-1715, the light curve of which shows two short-term anomalies from a caustic-crossing binary-lensing light curve: one with a large deviation and the other with a small deviation. We identify five pairs of solutions, in which the anomalies are explained by adding an extra lens or source component in addition to the base binary-lens model. We resolve the degeneracies by applying a method in which the measured flux ratio between the first and second source stars is compared with the flux ratio deduced from the ratio of the source radii. Applying this method leaves a single pair of viable solutions, in both of which the major anomaly is generated by a planetary-mass third body of the lens, and the minor anomaly is generated by a faint second source. A Bayesian analysis indicates that the lens comprises three masses: a planet-mass object with ∼2.6 MJ and binary stars of K and M dwarfs lying in the galactic disk. We point out the possibility that the lens is the blend, and this can be verified by conducting high-resolution follow-up imaging for the resolution of the lens from the source.
KMT-2021-BLG-1077L: The fifth confirmed multiplanetary system detected by microlensing
(EDP Sciences on behalf of the European Southern Observatory, 2022-06-20) Han C; Gould A; Bond IA; Jung YK; Albrow MD; Chung S-J; Hwang K-H; Ryu Y-H; Shin I-G; Shvartzvald Y; Yee JC; Zang W; Cha S-M; Kim D-J; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Kim D; Abe F; Barry RK; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Koshimoto N; Kondo I; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Olmschenk G; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Silva SI; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H
Aims. The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the aim of revealing the nature of the anomaly. Methods. We test various models in combination with several interpretations: that the lens is a binary (2L1S), the source is a binary (1L2S), both the lens and source are binaries (2L2S), or the lens is a triple system (3L1S). We search for the best-fit models under the individual interpretations of the lens and source systems. Results. We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are ~1.56 A - 10a- 3 and ~1.75 A - 10a- 3, which correspond to ~1.6 and ~1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. With the constraints of the event time-scale and angular Einstein radius, it is found that the host of the lens system is a low-mass star of mid-to-late M spectral type with amass of Mh = 0.14a- 0.07+0.19 MI, and it hosts two gas giant planets with masses of Mp1 = 0.22a- 0.12+0.31 MJ and Mp2 = 0.25a- 0.13+0.35. The planets lie beyond the snow line of the host with projected separations of aap1 = 1.26a- 1.08+1.41 AU and aap2 = 0.93a- 0.80+1.05 AU. The planetary system resides in the Galactic bulge at a distance of DL = 8.24a- 1.16+1.02 kpc. The lens of the event is the fifth confirmed multiplanetary system detected by microlensing following OGLE-2006-BLG-109L, OGLE-2012-BLG-0026L, OGLE-2018-BLG-1011L, and OGLE-2019-BLG-0468L.
OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136: Microlensing events with prominent orbital effects
(EDP Sciences, 2024-06-14) Han C; Udalski A; Bond IA; Lee C-U; Gould A; Albrow MD; Chung S-J; Hwang K-H; Jung YK; Kim H-W; Ryu Y-H; Shvartzvald Y; Shin I-G; Yee JC; Yang H; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozłowski S; Rybicki KA; Iwanek P; Ulaczyk K; Wrona M; Gromadzki M; Mróz MJ; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hirao Y; Silva SI; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K
Aims. We undertake a project to reexamine microlensing data gathered from high-cadence surveys. The aim of the project is to reinvestigate lensing events whose light curves exhibit intricate anomaly features that are associated with caustics, but lack prior proposed models that would explain these features. Methods. Through detailed reanalyses considering higher-order effects, we determined that it is vital to account for the orbital motions of lenses to accurately explain the anomaly features observed in the light curves of the lensing events OGLE-2018-BLG-0971, MOA-2023-BLG-065, and OGLE-2023-BLG-0136. Results. We estimated the masses and distances to the lenses by conducting Bayesian analyses using the lensing parameters of the newly found lensing solutions. These analyses showed that the lenses of the events OGLE-2018-BLG-0971 and MOA-2023-BLG-065 are binaries composed of M dwarfs, while the lens of OGLE-2023-BLG-0136 likely is a binary composed of an early K-dwarf primary and a late M-dwarf companion. For all lensing events, the probability that the lens resides in the bulge is considerably higher than that it is located in the disk.
OGLE-2019-BLG-0825: Constraints on the Source System and Effect on Binary-lens Parameters Arising from a Five-day Xallarap Effect in a Candidate Planetary Microlensing Event
(American Astronomical Society, 2023-08-18) Satoh YK; Koshimoto N; Bennett DP; Sumi T; Rattenbury NJ; Suzuki D; Miyazaki S; Bond IA; Udalski A; Gould A; Bozza V; Dominik M; Hirao Y; Kondo I; Kirikawa R; Hamada R; Abe F; Barry R; Bhattacharya A; Fujii H; Fukui A; Fujita K; Ikeno T; Ishitani Silva S; Itow Y; Matsubara Y; Matsumoto S; Muraki Y; Niwa K; Okamura A; Olmschenk G; Ranc C; Toda T; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K; Mróz P; Poleski R; Skowron J; Szymański MK; Poleski R; Soszyński I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Rybicki KA; Iwanek P; Wrona M; Gromadzki M; Albrow MD; Chung S-J; Han C; Hwang K-H; Kim D; Jung YK; Kim HW; Ryu Y-H; Shin I-G; Shvartzvald Y; Yang H; Yee JC; Zang W; Cha S-M; Kim D-J; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Jørgensen UG; Longa-Peña P; Sajadian S; Skottfelt J; Snodgrass C; Tregloan-Reed J; Bach-Møller N; Burgdorf M; D'Ago G; Haikala L; Hitchcock J; Hundertmark M; Khalouei E; Peixinho N; Rahvar S; Southworth J; Spyratos P
We present an analysis of microlensing event OGLE-2019-BLG-0825. This event was identified as a planetary candidate by preliminary modeling. We find that significant residuals from the best-fit static binary-lens model exist and a xallarap effect can fit the residuals very well and significantly improves χ 2 values. On the other hand, by including the xallarap effect in our models, we find that binary-lens parameters such as mass ratio, q, and separation, s, cannot be constrained well. However, we also find that the parameters for the source system such as the orbital period and semimajor axis are consistent between all the models we analyzed. We therefore constrain the properties of the source system better than the properties of the lens system. The source system comprises a G-type main-sequence star orbited by a brown dwarf with a period of P ∼5 days. This analysis is the first to demonstrate that the xallarap effect does affect binary-lens parameters in planetary events. It would not be common for the presence or absence of the xallarap effect to affect lens parameters in events with long orbital periods of the source system or events with transits to caustics, but in other cases, such as this event, the xallarap effect can affect binary-lens parameters.
Probable brown dwarf companions detected in binary microlensing events during the 2018- 2020 seasons of the KMTNet survey
(EDP Sciences, 2023-07-04) Han C; Jung YK; Kim D; Gould A; Bozza V; Bond IA; Chung S-J; Albrow MD; Hwang K-H; Ryu Y-H; Shin I-G; Shvartzvald Y; Yang H; Zang W; Cha S-M; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Yee JC; Lee Y; Park B-G; Pogge RW; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Silva SI; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Okamura A; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Itow Y
Aims. We inspect the microlensing data of the KMTNet survey collected during the 2018-2020 seasons in order to find lensing events produced by binaries with brown dwarf (BD) companions. Methods. In order to pick out binary-lens events with candidate BD lens companions, we conducted systematic analyses of all anomalous lensing events observed during the seasons from 2018 to 2020. By applying a selection criterion of mass ratio between the lens components of 0.03 q 0.1, we identify four binary-lens events with candidate BD companions, namely KMT-2018-BLG-0321, KMT-2018-BLG-0885, KMT-2019-BLG-0297, and KMT-2019-BLG-0335. For the individual events, we present interpretations of the lens systems and measure the observables that can be used to constrain the physical lens parameters. Results. The masses of the lens companions estimated from the Bayesian analyses based on the measured observables indicate high probabilities that the lens companions are in the BD mass regime; that is, 59%, 68%, 66%, and 66% for the four respective events.
Three sub-Jovian-mass microlensing planets: MOA-2022-BLG-563Lb, KMT-2023-BLG-0469Lb, and KMT-2023-BLG-0735Lb
(The European Southern Observatory (ESO) for EDP Sciences, 2024-03-12) Han C; Jung YK; Bond IA; Gould A; Albrow MD; Chung S-J; Hwang K-H; Lee C-U; Ryu Y-H; Shin I-G; Shvartzvald Y; Yang H; Yee JC; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hirao Y; Silva SI; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K
Aims. We analyze the anomalies appearing in the light curves of the three microlensing events MOA-2022-BLG-563, KMT-2023BLG-0469, and KMT-2023-BLG-0735. The anomalies exhibit common short-term dip features that appear near the peak. Methods. From the detailed analyses of the light curves, we find that the anomalies were produced by planets accompanied by the lenses of the events. For all three events, the estimated mass ratios between the planet and host are on the order of 10−4: q ∼ 8 × 10−4 for MOA-2022-BLG-563L, q ∼ 2.5 × 10−4 for KMT-2023-BLG-0469L, and q ∼ 1.9 × 10−4 for KMT-2023-BLG-0735L. The interpretations of the anomalies are subject to a common inner-outer degeneracy, which causes ambiguity when estimating the projected planet-host separation. Results. We estimated the planet mass, Mp, host mass, Mh, and distance, DL, to the planetary system by conducting Bayesian analyses using the observables of the events. The estimated physical parameters of the planetary systems are (Mh/M, Mp/MJ, DL/kpc) = (0.48+−00.3630, 0.40+−00.3125, 6.53+−11.1257) for MOA-2022-BLG-563L, (0.47+−00.3526, 0.124+−00.092067, 7.07−+11.1903) for KMT-2023-BLG-0469L, and (0.62+−00.3435, 0.125+−00.068070, 6.26+−11.2767) for KMT-2023-BLG-0735L. According to the estimated parameters, all planets are cold planets with projected separations that are greater than the snow lines of the planetary systems, they have masses that lie between the masses of Uranus and Jupiter of the Solar System, and the hosts of the planets are main-sequence stars that are less massive than the Sun. In all cases, the planetary systems are more likely to be in the bulge with probabilities Pbulge = 64%, 73%, and 56% for MOA-2022-BLG-563, KMT-2023-BLG-0469, and KMT-2023-BLG-0735, respectively.

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