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Han, C.,Udalski, A.,Choi, J.-Y.,Yee, J. C.,Gould, A.,Christie, G.,Tan, T.-G.,Szymań,ski, M. K.,Kubiak, M.,Soszyń,ski, I.,Pietrzyń,ski, G.,Poleski, R.,Ulaczyk, K.,Pietrukowicz, P.,Kozłow IOP Publishing 2013 ASTROPHYSICAL JOURNAL LETTERS - Vol.762 No.2
<P>We report the discovery of a planetary system from observation of the high-magnification microlensing event OGLE-2012-BLG-0026. The lensing light curve exhibits a complex central perturbation with multiple features. We find that the perturbation was produced by two planets located near the Einstein ring of the planet host star. We identify four possible solutions resulting from the well-known close/wide degeneracy. By measuring both the lens parallax and the Einstein radius, we estimate the physical parameters of the planetary system. According to the best-fit model, the two planet masses are similar to 0.11 M-J and 0.68 M-J and they are orbiting a G-type main-sequence star with a mass similar to 0.82 M-circle dot. The projected separations of the individual planets are beyond the snow line in all four solutions, being similar to 3.8 AU and 4.6 AU in the best-fit solution. The deprojected separations are both individually larger and possibly reversed in order. This is the second multi-planet system with both planets beyond the snow line discovered by microlensing. This is the only such system (other than the solar system) with measured planet masses without sin i degeneracy. The planetary system is located at a distance 4.1 kpc from the Earth toward the Galactic center. It is very likely that extra light from stars other than the lensed star comes from the lens itself. If this is correct, it will be possible to obtain detailed information about the planet host star from follow-up observation.</P>
MOA-2011-BLG-293Lb: A TEST OF PURE SURVEY MICROLENSING PLANET DETECTIONS
Yee, J. C.,Shvartzvald, Y.,Gal-Yam, A.,Bond, I. A.,Udalski, A.,Kozłowski, S.,Han, C.,Gould, A.,Skowron, J.,Suzuki, D.,Abe, F.,Bennett, D. P.,Botzler, C. S.,Chote, P.,Freeman, M.,Fukui, A.,Furusawa, K. IOP Publishing 2012 The Astrophysical journal Vol.755 No.2
<P>Because of the development of large-format, wide-field cameras, microlensing surveys are now able to monitor millions of stars with sufficient cadence to detect planets. These new discoveries will span the full range of significance levels including planetary signals too small to be distinguished from the noise. At present, we do not understand where the threshold is for detecting planets. MOA-2011-BLG-293Lb is the first planet to be published from the new surveys, and it also has substantial follow-up observations. This planet is robustly detected in survey+follow-up data (Delta chi(2) similar to 5400). The planet/host mass ratio is q = (5.3 similar to 0.2) x 10(-3). The best-fit projected separation is s = 0.548 +/- 0.005 Einstein radii. However, due to the s <-> s(-1) degeneracy, projected separations of s-1 are only marginally disfavored at Delta chi(2) = 3. A Bayesian estimate of the host mass gives M-L = 0.43(-0.17)(+0.27) M-circle dot, with a sharp upper limit of M-L < 1.2 M-circle dot from upper limits on the lens flux. Hence, the planet mass is m(p) = 2.4(-0.9)(+1.5) M-Jup, and the physical projected separation is either r(perpendicular to) similar or equal to 1.0 AU or r(perpendicular to) similar or equal to 3.4 AU. We show that survey data alone predict this solution and are able to characterize the planet, but the Delta chi(2) is much smaller (Delta chi(2) similar to 500) than with the follow-up data. The Delta chi(2) for the survey data alone is smaller than for any other securely detected planet. This event suggests a means to probe the detection threshold, by analyzing a large sample of events like MOA-2011-BLG-293, which have both follow-up data and high-cadence survey data, to provide a guide for the interpretation of pure survey microlensing data.</P>
C. S. Kim,J. H. Kim,H. K. Kwon,H. S. Lee,J. S. Park,이기주,K. J. Yee 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.4
We demonstrate that photocurrent spectroscopy can be used to study optical absorption in the active layer of InGaN-based light-emitting diodes. The temperature dependence of the photocurrent spectrum was compared with that of the photoluminescence, clearly showing the effect of carrier localizations at low temperatures below 70 K. The photocurrent spectrum investigated by applying reverse biases revealed that type-II optical transitions between the InGaN quantum well and the GaN barrier were considerable at high reverse voltages.
MOA-2013-BLG-220Lb: MASSIVE PLANETARY COMPANION TO GALACTIC-DISK HOST
Yee, J. C.,Han, C.,Gould, A.,Skowron, J.,Bond, I. A.,Udalski, A.,Hundertmark, M.,Monard, L. A. G.,Porritt, I.,Nelson, P.,Bozza, V.,Albrow, M. D.,Choi, J.-Y.,Christie, G. W.,DePoy, D. L.,Gaudi, B. S.,H IOP Publishing 2014 The Astrophysical journal Vol.790 No.1
<P>We report the discovery of MOA-2013-BLG-220Lb, which has a super-Jupiter mass ratio q = 3.01 +/- 0.02 x 10(-3) relative to its host. The proper motion, mu = 12.5 +/- 1 mas yr(-1), is one of the highest for microlensing planets yet discovered, implying that it will be possible to separately resolve the host within similar to 7 yr. Two separate lines of evidence imply that the planet and host are in the Galactic disk. The planet could have been detected and characterized purely with follow-up data, which has important implications for microlensing surveys, both current and into the Large Synoptic Survey Telescope (LSST) era.</P>
Yee, J. C.,Udalski, A.,Sumi, T.,Dong, Subo,Kozłowski, S.,Bird, J. C.,Cole, A.,Higgins, D.,McCormick, J.,Monard, L. A. G.,Polishook, D.,Shporer, A.,Spector, O.,Szymań,ski, M. K.,Kubiak, M.,Pietrzy IOP Publishing 2009 The Astrophysical journal Vol.703 No.2
<P>We analyze the extreme high-magnification microlensing event OGLE-2008-BLG-279, which peaked at a maximum magnification of A similar to 1600 on 2008 May 30. The peak of this event exhibits both finite-source effects and terrestrial parallax, from which we determine the mass of the lens, M-l = 0.64 +/- 0.10 M-circle dot, and its distance, D-l = 4.0 +/- 0.6 kpc. We rule out Jupiter-mass planetary companions to the lens star for projected separations in the range 0.5-20 AU. More generally, we find that this event was sensitive to planets with masses as small as 0.2 M-circle dot similar or equal to 2 (MMars) with projected separations near the Einstein ring (similar to 3 AU).</P>
Han, C.,Udalski, A.,Gould, A.,Zhu, Wei,Street, R. A.,Yee, J. C.,Beichman, C.,Bryden, C.,Novati, S. Calchi,Carey, S.,Fausnaugh, M.,Gaudi, B. S.,Henderson, Calen B.,Shvartzvald, Y.,Wibking, B.,Szyma American Astronomical Society 2016 The Astrophysical journal Vol.828 No.1
<P>We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ground and from space exhibit a time offset of similar to 13 days between the caustic spikes, indicating that the relative lens-source positions seen from the two places are displaced by parallax effects. From modeling the light curves, we measure the space-based microlens parallax. Combined with the angular Einstein radius measured by analyzing the caustic crossings, we determine the mass and distance of the lens. We find that the lens is a binary composed of two G-type stars with masses of similar to 1.0 M-circle dot and similar to 0.9 M-circle dot located at a distance. of similar to 3 kpc. In addition, we are able to constrain the complete orbital parameters of the lens thanks to the precise measurement of the microlens parallax derived from the joint analysis. In contrast to the binary event OGLE-2014-BLG-1050, which was also observed by Spitzer, we find that the interpretation of OGLE-2015-BLG-0479 does not suffer from the degeneracy between (+/-, +/-) and (+/-, -/+) solutions, confirming that the four-fold parallax degeneracy in single-lens events collapses into the two-fold degeneracy for the general case of binary-lens events. The location of the blend in the color-magnitude diagram is consistent with the lens properties, suggesting that the blend is the lens itself. The blend is bright enough for spectroscopy and thus this possibility can be checked from future follow-up observations.</P>
Han, C.,Udalski, A.,Gould, A.,Bond, I. A.,Albrow, M. D.,Chung, S.-J.,Jung, Y. K.,Ryu, Y.-H.,Shin, I.-G.,Yee, J. C.,Zhu, W.,Cha, S.-M.,Kim, S.-L.,Kim, D.-J.,Lee, C.-U.,Lee, Y.,Park, B.-G.,Skowron, J.,M American Astronomical Society 2017 The Astronomical journal Vol.154 No.4
<P>We report the discovery of a planet-mass companion to the microlens OGLE-2016-BLG-0263L. Unlike most low-mass companions that were detected through perturbations to the smooth and symmetric light curves produced by the primary, the companion was discovered through the channel of a repeating event, in which the companion itself produced its own single-mass light curve after the event produced by the primary had ended. Thanks to the continuous coverage of the second peak by high-cadence surveys, the possibility of the repeating nature due to source binarity is excluded with a 96% confidence level. The mass of the companion estimated by a Bayesian analysis is Mp = 4.1(-2.5)(+6.5) M-j. The projected primary-companion separation is a(perpendicular to) = 6.5(-1.9)(+1.3) au. The ratio of the separation to the snow-line distance of a(perpendicular to/)a(s1) similar to 15.4 corresponds to the region beyond Neptune, the outermost planet of the solar system. We discuss the importance of high-cadence surveys in expanding the range of microlensing detections of low-mass companions and future space-based microlensing surveys.</P>
로터 블레이드 제빙 시스템 설계를 위한 예측 코드 개발 및 결빙 풍동 시험
우철훈(C.H. Woo),김경삼(K.S. Kim),이석준(S.J. Yee),이재복(J.B. Yi),임태균(T.G. Lim),김정일(J.I. Kim),박남은(N.E. Park) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
When the helicopter is flighting through icing condition, the ice could be accreted on fuselage and blades. The ice on blade could deform the blade configuration and increase the weight of blade. The unstable motions of blade make decreasing of performance, handling quality and structural stability due to the abnormal weight increase and configuration change. The helicopter deicing system is required to avoid risk by icing. To protect the icing, the anti-icing system or the deicing system is used. Generally, the intake, the pitot sensor are adapted the anti-icing system, but the rotor blade uses deicing system because the large size heater mat of blade needs a lot of power consumption. The anti-icing system always actives heater mat in icing condition; the deicing system is run alternately by on/off time sequence to avoid ice accretion on blade. The design concepts of deicing system are needed estimation of heater mat location, scheduling on/off time sequence to avoid ice accretion, fixing of power consumption of heater mat. First of all, the icing region estimation on blade is needed to design of rotor blade deicing system. In this paper, air flow field and multi-phase fluid analysis was performed by the commercial CFD s/w, SC/Tetra to calculate the collection efficiency around objects. The ice accretion analysis was performed by developed in-house code, ASTROD based on Messinger thermodynamic model. The computation results show good estimation of ice accretion shape and ice thickness. The development of computational tool for icing/deicing is just one part of deicing system design process. The understanding of physical phenomenon of icing and deicing on blade surface is needed for design of deicing system. The icing/deicing wind tunnel test was performed to evaluate the function of deicing system of rotor blade that showed the phase changing on blade surface from ice to water at 0℃. And the deicing system design information was acquired from experimental results by on/off time scheduling.
Han, C.,Udalski, A.,Gould, A.,Zhu, Wei,Szymań,ski, M. K.,Soszyń,ski, I.,Skowron, J.,Mró,z, P.,Poleski, R.,Pietrukowicz, P.,Kozłowski, S.,Ulaczyk, K.,Pawlak, M.,Yee, J. C.,Beichman, C. American Astronomical Society 2017 The Astrophysical journal Vol.834 No.1
<P>In this paper, we present an analysis of the binary gravitational microlensing event OGLE-2015-BLG-0196. The event lasted for almost a year, and the light curve exhibited significant deviations from the lensing model based on the rectilinear lens-source relative motion, enabling us to measure the microlens parallax. The ground-based microlens parallax is confirmed by the data obtained from space-based microlens observations using the Spitzer telescope. By additionally measuring the angular Einstein radius from the analysis of the resolved caustic crossing, the physical parameters of the lens are determined up to the twofold degeneracy, u(0) < 0 and u(0) > 0, solutions caused by the well-known 'ecliptic' degeneracy. It is found that the binary lens is composed of two M dwarf stars with similar masses, M-1 = 0.38 +/- 0.04M(circle plus) (0.50 +/- 0.05M(circle plus)) and M-2 = 0.38 +/- 0.04M(circle plus) (0.55 +/- 0.06M(circle plus)), and the distance to the lens is D-L = 2.77. +/- 0.23 kpc (3.30 +/- 0.29 kpc). Here the physical parameters outside and inside the parentheses are for the u(0) < 0 and u(0) > 0 solutions, respectively.</P>