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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>
Zhu, L. L.,Park, Y. J.,Gan, L.,Go, S. I.,Kim, H. N.,Kim, J. M.,Ko, J. W. Chapman and Hall 2017 Journal of materials science Materials in electron Vol. No.
<P>Highly transparent Y2O3 ceramics doped with different Zr concentrations were successfully fabricated by vacuum pre-sintering at temperatures ranging from 1600 to 1800 degrees C combined with a subsequent hot-isostatic pressing (HIP) treatment using commercial powders as the starting materials. All of the 1 mol% Zr-doped Y2O3 ceramics exhibit very good optical quality. The sample with the highest transparency level was realized by vacuum sintering at 1650 degrees C for 4 h followed by a post-HIP treatment at 1450 degrees C lasting 5 h. It has a fine microstructure and the grain size is 1.48 mu m. Furthermore, the in-line transmittance reaches 83.3% at 1100 nm (1.2 mm thickness). It was found that a relatively low vacuum sintering temperature (1650 degrees C) and relatively low Zr doping concentration (1 mol%) are more appropriate to achieve optimally transparent Y2O3 ceramics with a subsequent HIP treatment.</P>
Zhu (祝伟,), Wei,Udalski, A.,Gould, A.,Dominik, M.,Bozza, V.,Han, C.,Yee, J. C.,Novati, S. Calchi,Beichman, C. A.,Carey, S.,Poleski, R.,Skowron, J.,Kozłowski, S.,Mró,z, P.,Pietrukowicz, P.,P IOP Publishing 2015 The Astrophysical journal Vol.805 No.1
<P>We report the first mass and distance measurements of a caustic-crossing binary system OGLE-2014-BLG-1050 L using the space-based microlens parallax method. Spitzer captured the second caustic. crossing of the event, which occurred similar to 10 days before that seen from Earth. Due to the coincidence that the source-lens relative motion was almost parallel to the direction of the binary-lens axis, the fourfold degeneracy, which was known before only to occur in single-lens events, persists in this case, leading to either a lower-mass (0.2 and 0.07 M-circle dot) binary at similar to 1.1 kpc or a higher-mass (0.9 and 0.35 M-circle dot) binary at similar to 3.5 kpc. However, the latter solution is strongly preferred for reasons including blending and lensing probability. OGLE-2014-BLG-1050 L demonstrates the power of microlens parallax in probing stellar and substellar binaries.</P>
Ground-based Parallax Confirmed by<i>Spitzer</i>: Binary Microlensing Event MOA-2015-BLG-020
Wang, Tianshu,Zhu, Wei,Mao, Shude,Bond, I. A.,Gould, A.,Udalski, A.,Sumi, T.,Bozza, V.,Ranc, C.,Cassan, A.,Yee, J. C.,Han, C.,Abe, F.,Asakura, Y.,Barry, R.,Bennett, D. P.,Bhattacharya, A.,Donachie, M. American Astronomical Society 2017 The Astrophysical journal Vol.845 No.2
<P>We present the analysis of the binary gravitational microlensing event MOA-2015-BLG-020. The event has a fairly long timescale (similar to 63 days) and thus the light curve deviates significantly from the lensing model that is based on the rectilinear lens-source relative motion. This enables us to measure the microlensing parallax through the annual parallax effect. The microlensing parallax parameters constrained by the ground-based data are confirmed by the Spitzer observations through the satellite parallax method. By additionally measuring the angular Einstein radius from the analysis of the resolved caustic crossing, the physical parameters of the lens are determined. It is found that the binary lens is composed of two dwarf stars with masses M-1= 0.606 +/- 0.028M(circle dot) and M-2= 0.125 +/- 0.006 M-circle dot in the Galactic disk. Assuming that the source star is at the same distance as the bulge red clump stars, we find the lens is at a distance D-L = 2.44 +/- 0.10 kpc. We also provide a summary and short discussion of all of the published microlensing events in which the annual parallax effect is confirmed by other independent observations.</P>
OGLE-2015-BLG-1482L: The First Isolated Low-mass Microlens in the Galactic Bulge
Chung, S.-J.,Zhu, W.,Udalski, A.,Lee, C.-U.,Ryu, Y.-H.,Jung, Y. K.,Shin, I.-G.,Yee, J. C.,Hwang, K.-H.,Gould, A.,Albrow, M.,Cha, S.-M.,Han, C.,Kim, D.-J.,Kim, H.-W.,Kim, S.-L.,Kim, Y.-H.,Lee, Y.,Park, American Astronomical Society 2017 The Astrophysical Journal Vol.838 No.2
<P>We analyze the single microlensing event OGLE-2015-BLG-1482 simultaneously observed from two ground-based surveys and from Spitzer. The Spitzer data exhibit finite-source effects that are. due to the passage of the lens close to or directly over. the surface of the source star as seen from Spitzer. Such finite-source effects generally yield measurements of the angular Einstein radius, which when combined with the microlens parallax derived from a comparison between the ground-based and the Spitzer light curves. yields the lens mass and lens-source relative parallax. From this analysis, we find that the lens of OGLE-2015-BLG-1482 is a very low-mass star with a. mass 0.10 +/- 0.02 M-circle dot or a brown dwarf with a. mass 55 +/- 9MJ, which are. located at D-LS = 0.80 +/- 0.19 kpc and D-LS = 0.54 +/- 0.08 kpc, respectively,. where DLS is the distance between the lens and the source, and thus it is the first isolated low-mass microlens that has been decisively located in the Galactic bulge. The degeneracy between the two solutions is severe ( Delta chi(2) = 0.3). The fundamental reason for the degeneracy is that the finite-source effect is seen only in a single data point from Spitzer, and this single data point gives rise to two solutions for rho, the angular size of the source in units of the angular Einstein ring radius. Because the rho degeneracy can be resolved only by relatively high-cadence observations around the peak, while the Spitzer cadence is typically similar to 1 day(-1), we expect that events for which the finite-source effect is seen only in the Spitzer data may frequently exhibit this rho degeneracy. For OGLE-2015-BLG-1482, the relative proper motion of the lens and source for the low-mass star is mu(rel) = 9.0 +/- 1.9 mas yr(-1), while for the brown dwarf it is 5.5 +/- 0.5 mas yr(-1). Hence, the degeneracy can be resolved within similar to 10 years from direct-lens imaging by using next-generation instruments with high spatial resolution.</P>
OGLE-2016-BLG-1190Lb: The First<i>Spitzer</i>Bulge Planet Lies Near the Planet/Brown-dwarf Boundary
Ryu, Y.-H.,Yee, J. C.,Udalski, A.,Bond, I. A.,Shvartzvald, Y.,Zang, W.,Jaimes, R. Figuera,Jørgensen, U. G.,Zhu, W.,Huang, C. X.,Jung, Y. K.,Albrow, M. D.,Chung, S.-J.,Gould, A.,Han, C.,Hwang, K.-H.,Sh American Astronomical Society 2018 The Astronomical journal Vol.155 No.1
<P>We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/ bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source-lens baseline object. The planet's mass, M-p = 13.4 +/- 0.9 M-J, places it right at the deuteriumburning limit, i. e., the conventional boundary between 'planets' and 'brown dwarfs.' Its existence raises the question of whether such objects are really ' planets' (formed within the disks of their hosts) or 'failed stars' (lowmass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf, M-host = 0.89. +/- 0.07 M-circle dot, and the planet has a semimajor axis a similar to 2.0 au. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth-Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultradense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over < 1% of an orbital period.</P>
OGLE-2016-BLG-1469L: Microlensing Binary Composed of Brown Dwarfs
Han, C.,Udalski, A.,Sumi, T.,Gould, 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.,Soszyń,ski, American Astronomical Society 2017 The Astrophysical journal Vol.843 No.1
<P>We report the discovery of a binary composed of two brown dwarfs, based on the analysis of the microlensing event OGLE-2016-BLG-1469. Thanks to the detection of both finite-source and microlens-parallax effects, we are able to measure both the masses M-1 similar to 0.05M(circle dot) and. M-2 similar to 0.01M(circle dot), and the. distance D-L similar to 4.5 kpc, as well as the projected separation a(perpendicular to) similar to 0.33 au. This is the third brown-dwarf binary detected using the microlensing method, demonstrating the usefulness of microlensing in detecting field brown-dwarf binaries with separations of less than 1 au.</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>
OGLE-2016-BLG-0613LABb: A Microlensing Planet in a Binary System
Han, C.,Udalski, A.,A., Gould,Lee, C.-U.,Shvartzvald, Y.,Zang, W. C.,Mao, S.,Kozłowski, S.,Albrow, M. D.,Chung, S.-J.,Hwang, K.-H.,Jung, Y. K.,Kim, D.,Kim, H.-W.,Ryu, Y.-H.,Shin, I.-G.,Yee, J. C.,Zhu, American Astronomical Society 2017 The Astronomical journal Vol.154 No.6
<P>We present the analysis of OGLE-2016-BLG-0613, for which the lensing light curve appears to be that of a typical binary-lens event with two caustic spikes but with a discontinuous feature on the trough between the spikes. We find that the discontinuous feature was produced by a planetary companion to the binary lens. We find four degenerate triplelens solution classes, each composed of a pair of solutions according to the well-known wide/close planetary degeneracy. One of these solution classes is excluded due to its relatively poor fit. For the remaining three pairs of solutions, the most-likely primary mass is about M-1 similar to 0.7M(circle dot) , while the planet is a super Jupiter. In all cases, the system lies in the Galactic disk, about halfway toward the Galactic bulge. However, in one of these three solution classes, the secondary of the binary system is a low- mass brown dwarf, with relative mass ratios (1: 0.03: 0.003), while in the two others the masses of the binary components are comparable. These two possibilities can be distinguished in about 2024 when the measured lens-source relative proper motion will permit separate resolution of the lens and source.</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>