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A brown dwarf orbiting an M-dwarf: MOA 2009–BLG–411L
Bachelet, E.,Fouqué,, P.,Han, C.,Gould, A.,Albrow, M. D.,Beaulieu, J.-P.,Bertin, E.,Bond, I. A.,Christie, G. W.,Heyrovský,, D.,Horne, K.,Jørgensen, U. G.,Maoz, D.,Mathiasen, M.,Matsunaga, EDP Sciences 2012 Astronomy and astrophysics Vol.547 No.-
Bachelet, E.,Shin, I.-G.,Han, C.,Fouqué,, P.,Gould, A.,Menzies, J. W.,Beaulieu, J.-P.,Bennett, D. P.,Bond, I. A.,Dong, Subo,Heyrovský,, D.,Marquette, J.-B.,Marshall, J.,Skowron, J.,Street, IOP Publishing 2012 The Astrophysical journal Vol.754 No.1
<P>Microlensing detections of cool planets are important for the construction of an unbiased sample to estimate the frequency of planets beyond the snow line, which is where giant planets are thought to form according to the core accretion theory of planet formation. In this paper, we report the discovery of a giant planet detected from the analysis of the light curve of a high-magnification microlensing event MOA 2010-BLG-477. The measured planet-star mass ratio is q = (2.181 +/- 0.004) x 10(-3) and the projected separation is s = 1.1228 +/- 0.0006 in units of the Einstein radius. The angular Einstein radius is unusually large theta(E) = 1.38 +/- 0.11 mas. Combining this measurement with constraints on the 'microlens parallax' and the lens flux, we can only limit the host mass to the range 0.13 < M/M-circle dot < 1.0. In this particular case, the strong degeneracy between microlensing parallax and planet orbital motion prevents us from measuring more accurate host and planet masses. However, we find that adding Bayesian priors from two effects (Galactic model and Keplerian orbit) each independently favors the upper end of this mass range, yielding star and planet masses of M-* = 0.67(-0.13)(+0.33) M-circle dot and m(p) = 1.5(-0.3)(+0.8) M-JUP at a distance of D = 2.3 +/- 0.6 kpc, and with a semi-major axis of a = 2(-1)(+3) AU. Finally, we show that the lens mass can be determined from future high-resolution near-IR adaptive optics observations independently from two effects, photometric and astrometric.</P>
Shin, I.-G.,Udalski, A.,Han, C.,Gould, A.,Dominik, M.,Fouqué,, P.,Kubiak, M.,Szymań,ski, M. K.,Pietrzyń,ki, G.,Soszyń,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>
Measurement of Source Star Colors with the <i>K</i>2C9-CFHT Multi-color Microlensing Survey
Zang, Weicheng,Penny, Matthew T.,Zhu, Wei,Mao, Shude,Fouqué,, Pascal,Udalski, Andrzej,Hwang, Kyu-Ha,Wang, Tianshu,Huang, Chelsea,Boyajian, Tabetha. S.,Barentsen, Geert Astronomical Society of the Pacific 2018 Publications of the Astronomical Society of the Pa Vol.130 No.992
Shin, I.-G.,Han, C.,Choi, J.-Y.,Udalski, A.,Sumi, T.,Gould, A.,Bozza, V.,Dominik, M.,Fouqué,, P.,Horne, K.,Szymań,ski, M. K.,Kubiak, M.,Soszyń,ski, I.,Pietrzyń,ski, G.,Poleski, R. IOP Publishing 2012 The Astrophysical journal Vol.755 No.2
<P>Despite the astrophysical importance of binary star systems, detections are limited to those located in small ranges of separations, distances, and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar multiplicity across a broad range of physical parameters. In this paper, we report the detections and measurements of two binaries discovered from observations of microlensing events MOA-2011-BLG-090 and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by simultaneously measuring the Einstein radius and the lens parallax. The measured masses of the binary components are 0.43M(circle dot) and 0.39M(circle dot) for MOA-2011-BLG-090 and 0.57M(circle dot) and 0.17M(circle dot) for OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of microlensing in detecting binaries composed of low-mass components. From modeling of the light curves considering full Keplerian motion of the lens, we also measure the orbital parameters of the binaries. The blended light of OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible to check the microlensing orbital solution by follow-up radial-velocity observation. For both events, the caustic-crossing parts of the light curves, which are critical for determining the physical lens parameters, were resolved by high-cadence survey observations and thus it is expected that the number of microlensing binaries with measured physical parameters will increase in the future.</P>
A COLD NEPTUNE-MASS PLANET OGLE-2007-BLG-368Lb: Cold neptunes are common
Sumi, T.,Bennett, D. P.,Bond, I. A.,Udalski, A.,Batista, V.,Dominik, M.,Fouqué,, P.,Kubas, D.,Gould, A.,Macintosh, B.,Cook, K.,Dong, S.,Skuljan, L.,Cassan, A.,Abe, F.,Botzler, C. S.,Fukui, A.,Fu IOP Publishing 2010 The Astrophysical journal Vol.710 No.2
<P>We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q = [9.5 +/- 2.1] x 10(-5) via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the Microlensing Observations in Astrophysics survey, real-time light-curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at M(l) = 0.64(-0.26)(+0.21) M(circle dot) and D(l) = 5.9(-1.4)(+ 0.9) kpc, respectively, so the mass and separation of the planet are M(p) = 20(-8)(+7) M(circle plus) and a = 3.3(-0.8)(+1.4) AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprises four cold Neptune/super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these 10 cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN(pl)/d log q alpha q(-0.7+/-0.2) with a 95% confidence level upper limit of n < -0.35 ( where dN(pl)/d log q alpha q(n)). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.</P>
Choi, J.-Y.,Shin, I.-G.,Han, C.,Udalski, A.,Sumi, T.,Gould, A.,Bozza, V.,Dominik, M.,Fouqué,, P.,Horne, K.,Szymań,ski, M. K.,Kubiak, M.,Soszyń,ski, I.,Pietrzyń,ski, G.,Poleski, R. IOP Publishing 2012 The Astrophysical journal Vol.756 No.1
<P>High-magnification microlensing events provide an important channel to detect planets. Perturbations near the peak of a high-magnification event can be produced either by a planet or a binary companion. It is known that central perturbations induced by both types of companions can be generally distinguished due to the essentially different magnification pattern around caustics. In this paper, we present a case of central perturbations for which it is difficult to distinguish the planetary and binary interpretations. The peak of a lensing light curve affected by this perturbation appears to be blunt and flat. For a planetary case, this perturbation occurs when the source trajectory passes the negative perturbation region behind the back end of an arrowhead-shaped central caustic. For a binary case, a similar perturbation occurs for a source trajectory passing through the negative perturbation region between two cusps of an astroid-shaped caustic. We demonstrate the degeneracy for two high-magnification events of OGLE-2011-BLG-0526 and OGLE-2011-BLG-0950/MOA-2011-BLG-336. For OGLE-2011-BLG-0526, the chi(2) difference between the planetary and binary model is similar to 3, implying that the degeneracy is very severe. For OGLE-2011-BLG-0950/MOA-2011-BLG-336, the stellar binary model is formally excluded with Delta chi(2) similar to 105 and the planetary model is preferred. However, it is difficult to claim a planet discovery because systematic residuals of data from the planetary model are larger than the difference between the planetary and binary models. Considering that two events observed during a single season suffer from such a degeneracy, it is expected that central perturbations experiencing this type of degeneracy is common.</P>
Bozza, V.,Dominik, M.,Rattenbury, N. J.,Jørgensen, U. G.,Tsapras, Y.,Bramich, D. M.,Udalski, A.,Bond, I. A.,Liebig, C.,Cassan, A.,Fouqué,, P.,Fukui, A.,Hundertmark, M.,Shin, I.‐,G.,Lee, S. Blackwell Publishing Ltd 2012 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.424 No.2
<P><B>ABSTRACT</B></P><P>The microlensing event OGLE‐2008‐BLG‐510 is characterized by an evident asymmetric shape of the peak, promptly detected by the Automated Robotic Terrestrial Exoplanet Microlensing Search (ARTEMiS) system in real time. The skewness of the light curve appears to be compatible both with binary‐lens and binary‐source models, including the possibility that the lens system consists of an M dwarf orbited by a brown dwarf. The detection of this microlensing anomaly and our analysis demonstrate that: (1) automated real‐time detection of weak microlensing anomalies with immediate feedback is feasible, efficient and sensitive, (2) rather common weak features intrinsically come with ambiguities that are not easily resolved from photometric light curves, (3) a modelling approach that finds all features of parameter space rather than just the ‘favourite model’ is required and (4) the data quality is most crucial, where systematics can be confused with real features, in particular small higher order effects such as orbital motion signatures. It moreover becomes apparent that events with weak signatures are a silver mine for statistical studies, although not easy to exploit. Clues about the apparent paucity of both brown‐dwarf companions and binary‐source microlensing events might hide here.</P>
MOA-2007-BLG-197: Exploring the brown dwarf desert
Ranc, C.,Cassan, A.,Albrow, M. D.,Kubas, D.,Bond, I. A.,Batista, V.,Beaulieu, J.-P.,Bennett, D. P.,Dominik, M.,Dong, Subo,Fouqué,, P.,Gould, A.,Greenhill, J.,Jørgensen, U. G.,Kains, N.,Menzies, EDP Sciences 2015 Astronomy and astrophysics Vol.580 No.-