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Hwang, K.x2010,H.,Han, C.,Udalski, A.,Sumi, T.,Gould, A.,Jaroszyx144,ski, M.,Kubiak, M.,Szymax144,ski, M. K.,Pietrzyń,ski, G.,Soszyx144,ski, I.,Szewczyk, O.,Ulaczyk, K.,Wyrzykowski, x13 Blackwell Publishing Ltd 2011 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.413 No.2
<P><B>ABSTRACT</B></P><P>We report the result of the analysis of the light curve of a caustic‐crossing binary‐lens microlensing event OGLE‐2009‐BLG‐023/MOA‐2009‐BLG‐028. Even though the event was observed solely by survey experiments, we could uniquely determine the mass of the lens and distance to it by simultaneously measuring the Einstein radius and lens parallax. From this, we find that the lens system is composed of M‐type dwarfs with masses (0.50 ± 0.07) and (0.15 ± 0.02) M<SUB>⊙</SUB> located in the Galactic disc with a distance of ∼1.8 kpc toward the Galactic bulge direction. The event demonstrates that physical lens parameters of binary‐lens events can be routinely determined from future high‐cadence lensing surveys and thus microlensing can provide a new way to study Galactic binaries.</P>
Han, C.,Udalski, A.,Choi, J.-Y.,Yee, J. C.,Gould, A.,Christie, G.,Tan, T.-G.,Szymax144,ski, M. K.,Kubiak, M.,Soszyx144,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>
Poleski, Radosław,Zhu, Wei,Christie, Grant W.,Udalski, Andrzej,Gould, Andrew,Bachelet, Etienne,Skottfelt, Jesper,Novati, Sebastiano Calchi,Szymax144,ski, M. K.,Soszyx144,ski, I.,Pietrzyń,ski, American Astronomical Society 2016 The Astrophysical journal Vol.823 No.1
<P>The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 (mu(cl) (N, E) = (+0.36 +/- 0.10, +1.42 +/- 0.10) mas yr(-1)) as well as the source and show that the lens is not a cluster member. Even though this particular event does not probe the distribution of planets in globular clusters, other potential cluster lens events can be verified using our methodology. Additionally, we find that microlens parallax measured using Optical Gravitational Lens Experiment (OGLE) photometry is consistent with the value found based on the light curve displacement between the Earth and Spitzer.</P>
GRAVITATIONAL BINARY-LENS EVENTS WITH PROMINENT EFFECTS OF LENS ORBITAL MOTION
Park, H.,Udalski, A.,Han, C.,Gould, A.,Beaulieu, J.-P.,Tsapras, Y.,Szymax144,ski, M. K.,Kubiak, M.,Soszyx144,ski, I.,Pietrzyń,ski, G.,Poleski, R.,Ulaczyk, K.,Pietrukowicz, P.,Kozłowski, S.,Sk IOP Publishing 2013 The Astrophysical journal Vol.778 No.2
<P>Gravitational microlensing events produced by lenses composed of binary masses are important because they provide a major channel for determining physical parameters of lenses. In this work, we analyze the light curves of two binary-lens events, OGLE-2006-BLG-277 and OGLE-2012-BLG-0031, for which the light curves exhibit strong deviations from standard models. From modeling considering various second-order effects, we find that the deviations are mostly explained by the effect of the lens orbital motion. We also find that lens parallax effects can mimic orbital effects to some extent. This implies that modeling light curves of binary-lens events not considering orbital effects can result in lens parallaxes that are substantially different from actual values and thus wrong determinations of physical lens parameters. This demonstrates the importance of routine consideration of orbital effects in interpreting light curves of binary-lens events. It is found that the lens of OGLE-2006-BLG-277 is a binary composed of a low-mass star and a brown dwarf companion.</P>
Shin, I.-G.,Udalski, A.,Han, C.,Gould, A.,Dominik, M.,Fouqué,, P.,Kubiak, M.,Szymax144,ski, M. K.,Pietrzyń,ki, G.,Soszyx144,ski, I.,Ulaczyk, K.,Wyrzykowski, Ł.,DePoy, D. L.,Dong, S.,Gau IOP Publishing 2011 The Astrophysical journal Vol.735 No.2
<P>We present the result of the analysis of the gravitational binary-lensing event OGLE-2005-BLG-018. The light curve of the event is characterized by two adjacent strong features and a single weak feature separated from the strong features. The light curve exhibits noticeable deviations from the best-fit model based on standard binary parameters. To explain the deviation, we test models including various higher-order effects of the motions of the observer, source, and lens. From this, we find that it is necessary to account for the orbital motion of the lens in describing the light curve. From modeling the light curve considering the parallax effect and Keplerian orbital motion, we are able to not only measure the physical parameters but also to find a complete orbital solution of the lens system. It is found that the event was produced by a binary lens located in the Galactic bulge with a distance of 6.7 +/- 0.3 kpc from the Earth. The individual lens components with masses 0.9 +/- 0.3 M-circle dot and 0.5 +/- 0.1 M-circle dot are separated with a semi-major axis of a = 2.5 +/- 1.0 AU and orbiting each other with a period P = 3.1 +/- 1.3 yr. This event demonstrates that it is possible to extract detailed information about binary lens systems from well-resolved lensing light curves.</P>
TRIPLE MICROLENS OGLE-2008-BLG-092L: BINARY STELLAR SYSTEM WITH A CIRCUMPRIMARY URANUS-TYPE PLANET
Poleski, Radosław,Skowron, Jan,Udalski, Andrzej,Han, Cheongho,Kozłowski, Szymon,Wyrzykowski, Łukasz,Dong, Subo,Szymax144,ski, Michał K.,Kubiak, Marcin,Pietrzyń,ski, Grzegorz,Soszyx144,ski, Ig IOP Publishing 2014 The Astrophysical journal Vol.795 No.1
<P>We present the gravitational microlensing discovery of a 4 M-Uranus planet that orbits a 0.7 M circle dot star at approximate to 18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main-sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only about three times smaller than that of the companion star, suggesting significant dynamical interactions.</P>
OGLE-2005-BLG-071Lb, THE MOST MASSIVE M DWARF PLANETARY COMPANION?
Dong, Subo,Gould, Andrew,Udalski, Andrzej,Anderson, Jay,Christie, G. W.,Gaudi, B. S.,Jaroszyx144,ski, M.,Kubiak, M.,Szymax144,ski, M. K.,Pietrzyń,ski, G.,Soszyx144,ski, I.,Szewczyk, O.,Ulac IOP Publishing 2009 The Astrophysical journal Vol.695 No.2
Han, C.,Hwang, K.-H.,Kim, D.,Udalski, A.,Abe, F.,Monard, L. A. B.,McCormick, J.,Szymax144,ski, M. K.,Kubiak, M.,Pietrzyń,ski, G.,Soszyx144,ski, I.,Szewczyk, O.,Wyrzykowski, Ł.,Ulaczyk, K.,Bon IOP Publishing 2009 The Astrophysical journal Vol.705 No.2
<P>To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007- BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.</P>
A VENUS-MASS PLANET ORBITING A BROWN DWARF: A MISSING LINK BETWEEN PLANETS AND MOONS
Udalski, A.,Jung, Y. K.,Han, C.,Gould, A.,Kozłowski, S.,Skowron, J.,Poleski, R.,Soszyx144,ski, I.,Pietrukowicz, P.,Mró,z, P.,Szymax144,ski, M. K.,Wyrzykowski, Ł.,Ulaczyk, K.,Pietrzyń,sk IOP Publishing 2015 The Astrophysical journal Vol.812 No.1
<P>The co-planarity of solar system planets led Kant to suggest that they formed from an accretion disk, and the discovery of hundreds of such disks around young stars as well as hundreds of co-planar planetary systems by the Kepler satellite demonstrate that this formation mechanism is extremely widespread. Many moons in the solar system, such as the Galilean moons of Jupiter, also formed out of the accretion disks that coalesced into the giant planets. Here we report the discovery of an intermediate system, OGLE-2013-BLG-0723LB/Bb, composed of a Venus-mass planet orbiting a brown dwarf, which may be viewed either as a scaled-down version of a planet plus a star or as a scaled-up version of a moon plus a planet orbiting a star. The latter analogy can be further extended since they orbit in the potential of a larger, stellar body. For ice-rock companions formed in the outer parts of accretion disks, like Uranus and Callisto, the scaled masses and separations of the three types of systems are similar, leading us to suggest that the formation processes of companions within accretion disks around stars, brown dwarfs, and planets are similar.</P>
OGLE-2013-BLG-0578 L: A MICROLENSING BINARY COMPOSED OF A BROWN DWARF AND AN M DWARF
Park, H.,Udalski, A.,Han, C.,Poleski, R.,Skowron, J.,Kozłowski, S.,Wyrzykowski, Ł.,Szymax144,ski, M. K.,Pietrukowicz, P.,Pietrzyń,ski, G.,Soszyx144,ski, I.,Ulaczyk, K. IOP Publishing 2015 The Astrophysical journal Vol.805 No.2
<P>Determining the physical parameters of binary microlenses is hampered by the lack of information about the angular Einstein radius due to the difficulty involved in resolving caustic crossings. In this paper, we present an analysis of the binary microlensing event OGLE-2013-BLG-0578, for which the caustic exit was precisely predicted in advance from real-time analysis, enabling us to densely resolve the caustic crossing and to measure the Einstein radius. From the mass measurement of the lens system based on the Einstein radius, combined with additional information about the lens parallax, we determine that the lens is a binary composed of a late-type M dwarf primary and a substellar brown dwarf companion. This event demonstrates the capability of current real-time microlensing modeling and the usefulness of microlensing for detecting and characterizing faint or dark objects in the Galaxy.</P>