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OGLE-2016-BLG-0596Lb: A High-mass Planet from a High-magnification Pure-survey Microlensing Event
Mró,z, P.,Han, C.,Udalski, A.,Poleski, R.,Skowron, J.,Szymań,ski, M. K.,Soszyń,ski, I.,Pietrukowicz, P.,Kozłowski, S.,Ulaczyk, K.,Wyrzykowski, Ł.,Pawlak, M.,Albrow, M. D.,Cha, S.-M.,Ch American Institute of Physics 2017 The Astronomical journal Vol.153 No.4
<P>We report the discovery of a high mass ratio planet, q = 0.012, i.e., 13 times higher than the Jupiter/Sun ratio. The host mass has not yet been measured but can be determined or strongly constrained from adaptive optics imaging. The planet was discovered in a small archival study of high-magnification events in pure-survey microlensing data, which was unbiased by the presence of anomalies. The fact that it was previously unnoticed may indicate that more such planets lie in archival data and could be discovered by a similar systematic study. In order to understand the transition from predominantly survey+followup to predominately survey-only planet detections, we conduct the first analysis of these detections in the observational (s, q) plane. Here s is the projected separation in units of the Einstein radius. We find some evidence that survey+followup is relatively more sensitive to planets near the Einstein ring, but that there is no statistical difference in sensitivity by mass ratio.</P>
A Neptune-mass Free-floating Planet Candidate Discovered by Microlensing Surveys
Mró,z, Przemek,Ryu, Y.-H.,Skowron, J.,Udalski, A.,Gould, A.,Szymań,ski, M. K.,Soszyń,ski, I.,Poleski, R.,Pietrukowicz, P.,Kozłowski, S.,Pawlak, M.,Ulaczyk, K.,Albrow, M. D.,Chung, S.-J American Astronomical Society 2018 The Astronomical journal Vol.155 No.3
OGLE-2013-BLG-0132Lb and OGLE-2013-BLG-1721Lb: Two Saturn-mass Planets Discovered around M-dwarfs
Mró,z, Przemek,Udalski, A.,Bond, I. A.,Skowron, J.,Sumi, T.,Han, C.,Szymań,ski, M. K.,Soszyń,ski, I.,Poleski, R.,Pietrukowicz, P.,Kozłowski, S.,Wyrzykowski, Ł.,Ulaczyk, K.,Abe, F.,Asak American Astronomical Society 2017 The Astronomical journal Vol.154 No.5
<P>We present the discovery of two planetary systems consisting of a Saturn-mass planet orbiting an M-dwarf, which were detected in faint microlensing events OGLE-2013-BLG-0132 and OGLE-2013-BLG-1721. The planetary anomalies were covered with high cadence by Optical Gravitational Lensing Experiment (OGLE) and Microlensing Observations in Astrophysics (MOA) photometric surveys. The light curve modeling indicates that the planet-to-host mass ratios are (5.15 +/- 0.28) x 10(-4) and (13.18 +/- 0.72) x 10(-4), respectively. Both events were too short and too faint to measure a reliable parallax signal and hence the lens mass. We therefore used a Bayesian analysis to estimate the masses of both planets: 0.29(-0.13) (+0.16) M-Jup (OGLE-2013-BLG-0132Lb) and 0.64(-0.31)(+0.35) M-Jup (OGLE-2013-BLG-1721Lb). Thanks to a high relative proper motion, OGLE-2013-BLG-0132 is a promising candidate for the high-resolution imaging follow-up. Both planets belong to an increasing sample of sub-Jupiter-mass planets orbiting M-dwarfs beyond the snow line.</P>
OGLE-2014-BLG-0289: Precise Characterization of a Quintuple-peak Gravitational Microlensing Event
Udalski, A.,Han, C.,Bozza, V.,Gould, A.,Bond, I. A.,Mró,z, P.,Skowron, J.,Wyrzykowski, Ł.,Szymań,ski, M. K.,Soszyń,ski, I.,Ulaczyk, K.,Poleski, R.,Pietrukowicz, P.,Kozłowski, S.,Abe, F American Astronomical Society 2018 The Astrophysical journal Vol.853 No.1
<P>We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits five very unusual peaks, four of which were produced by caustic crossings and the other by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax pi(E). Furthermore, the three resolved caustics allow us to measure the angular Einstein radius theta(E). From the combination of pE and qE, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses M-1 = 0.52 +/- 0.04 M-circle dot and M-2 = 0.42 +/- 0.03 M-circle dot separated in projection by a(perpendicular to) = 6.4 +/- 0.5 au. The lens is located in the disk with a distance of D-L = 3.3 +/- 0.3 kpc. The reason for the absence of a lensing signal in the Spitzer data is that the time of observation corresponds to the flat region of the light curve.</P>
OGLE-2017-BLG-0373Lb: A Jovian Mass-Ratio Planet Exposes A New Accidental Microlensing Degeneracy
Skowron, J.,Ryu, Y.-H.,Hwang, K.-H.,Udalski, A.,Mró,z, P.,Kozłowski, S.,Soszyń,ski, I.,Pietrukowicz, P.,Szymań,ski, M. K.,Poleski, R. COPERNICUS FOUNDATION FOR POLISH ASTRONOMY 2018 Acta astronomica Vol.68 No.1
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>
Han, C.,Udalski, A.,Bozza, V.,Szymań,ski, M. K.,Soszyń,ski, I.,Skowron, J.,Mró,z, P.,Poleski, R.,Pietrukowicz, P.,Kozłowski, S.,Ulaczyk, K.,Wyrzykowski, Ł.,Novati, S. Calchi,D’Ago, G. American Astronomical Society 2017 The Astrophysical journal Vol.843 No.2
<P>Due to the nature of the gravitational field, microlensing, in principle, provides an important tool for detecting faint and even dark brown dwarfs. However, the number of identified brown dwarfs is limited due to the difficulty of the lens mass measurement that is needed to check the substellar nature of the lensing object. In this work, we report a microlensing brown dwarf discovered from an analysis of the gravitational binary-lens event OGLE-2014-BLG1112. We identify the brown dwarf nature of the lens companion by measuring the lens mass from the detections of both microlens-parallax and finite-source effects. We find that the companion has a mass of. ' ( 3.03 +/- 0.78) 10(-2) M-circle dot and it is orbiting a solar-type primary star with a mass of 1.07 +/- 0.28 M-circle dot. The estimated projected separation between the lens components is 9.63 +/- 1.33 au and the distance to the lens is 4.84 +/- 0.67 kpc. We discuss the usefulness of space-based microlensing observations for detecting brown dwarfs through the channel of binary-lens events.</P>
Shin, I.-G.,Udalski, A.,Yee, J. C.,Novati, S. Calchi,Han, C.,Skowron, J.,Mró,z, P.,Soszyń,ski, I.,Poleski, R.,Szymań,ski, M. K.,Kozłowski, S.,Pietrukowicz, P.,Ulaczyk, K.,Pawlak, M.,Al American Astronomical Society 2017 The Astronomical journal Vol.154 No.5
<P>The microlens parallax is a crucial observable for conclusively identifying the nature of lens systems in microlensing events containing or composed of faint (even dark) astronomical objects such as planets, neutron stars, brown dwarfs, and black holes. With the commencement of a new era of microlensing in collaboration with space-based observations, the microlens parallax can be routinely measured. In addition, space-based observations can provide opportunities to verify the microlens parallax measured from ground-only observations and to find a unique solution to the lensing light-curve analysis. Furthermore, since most space-based observations cannot cover the full light curves of lensing events, it is also necessary to verify the reliability of the information extracted from fragmentary space-based light curves. We conduct a test based on the microlensing event OGLE-2016-BLG-0168, created by a binary lens system consisting of almost equal mass M-dwarf stars, to demonstrate that it is possible to verify the microlens parallax and to resolve degeneracies using the space-based light curve even though the observations are fragmentary. Since space-based observatories will frequently produce fragmentary light curves due to their short observing windows, the methodology of this test will be useful for next-generation microlensing experiments that combine space-based and ground-based collaboration.</P>
OGLE-2016-BLG-1045: A Test of Cheap Space-based Microlens Parallaxes
Shin, I.-G.,Udalski, A.,Yee, J. C.,Novati, S. Calchi,Christie, G.,Poleski, R.,Mró,z, P.,Skowron, J.,Szymań,ski, M. K.,Soszyń,ski, I.,Pietrukowicz, P.,Kozłowski, S.,Ulaczyk, K.,Pawlak, American Astronomical Society 2018 The Astrophysical journal Vol.863 No.1