D.-J. Kim

MASS MEASUREMENTS of ISOLATED OBJECTS from SPACE-BASED MICROLENSING

We report on the mass and distance measurements of two single-lens events from the 2015 Spitzer microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is very likely a brown dwarf (BD). Assuming that the source star lies behind the same amount of dust as the Bulge red clump, we find the lens is a 45 ± 7 M_J BD at 5.9 ± 1.0 kpc. The lens of of the second event, OGLE-2015-BLG-0763, is a 0.50 ± 0.04 M_M☉ star at 6.9 ± 1.0 kpc. We show that the probability to definitively measure the mass of isolated microlenses is dramatically increased once simultaneous ground- and space-based observations are conducted.

Spitzer Observations of OGLE-2015-BLG-1212 Reveal a New Path toward Breaking Strong Microlens Degeneracies

Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations.

A SUPER-JUPITER MICROLENS PLANET CHARACTERIZED BY HIGH-CADENCE KMTNET MICROLENSING SURVEY OBSERVATIONS OF OGLE-2015-BLG-0954

We report the characterization of a massive (mp = 3.9±1.4Mjup) microlensing planet (OGLE2015-BLG-0954Lb) orbiting an M dwarf host (M = 0.33 ± 0.12M ) at a distance toward the Galactic bulge of 0.6 −0.2 kpc, which is extremely nearby by microlensing standards. The planet-host projected separation is a⊥ ∼ 1.2AU. The characterization was made possible by the wide-field (4 deg) high cadence (Γ = 6hr−1) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time t∗ = 16min is among the shortest ever published. The high-cadence, wide-field observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional effects (bright lens and/or microlens parallax). When combined with the measured crossing time, these effects can yield planet/host masses and distance.

OGLE-2015-BLG-1459L: The Challenges of Exo-Moon Microlensing

Work by K.H.H. was support by KASI grant 2017-1-830-03. Work by W.Z., Y.K.J., and A.G. were supported by AST-1516842 from the US NSF. W.Z., I.G.S., and A.G. were supported by JPL grant 1500811. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. Work by C.H. was supported by the grant (2017R1A4A101517) of National Research Foundation of Korea. The OGLE Team thanks Prof. G. Pietrzynski for his contribution to the collection of the OGLE photometric data. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. The MOA project is supported by JSPS KAKENHI Grant Number JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, and JP16H06287.

The KMTNet/K2-C9 (Kepler) Data Release

We present Korea Microlensing Telescope Network (KMTNet) light curves for microlensing-event candidates in the Kepler K2 C9 field having peaks within 3 effective timescales of the Kepler observations. These include 181 clear microlensing and 84 possible microlensing events found by the KMTNet event finder, plus 56 other events found by OGLE and/or MOA that were not found by KMTNet. All data for the first two classes are immediately available for public use without restriction.

OGLE-2017-BLG-1522: A Giant Planet around a Brown Dwarf Located in the Galactic Bulge

We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of

Korea Microlensing Telescope Network Microlensing Events from 2015: Event-finding Algorithm, Vetting, and Photometry

t_{rm E} sim 7.5

OGLE-2016-BLG-0596Lb: A High-mass Planet from a High-magnification Pure-survey Microlensing Event

days. The Einstein radius is unusually small,

SPACE-BASED MICROLENS PARALLAX OBSERVATION AS A WAY to RESOLVE the SEVERE DEGENERACY between MICROLENS-PARALLAX and LENS-ORBITAL EFFECTS

theta_{rm E} = 0.065,

DESIGN OF DATA REDUCTION SYSTEM AND CONSTRUCTION OF PHOTOMETRIC DATABASE FOR KMTNet

mas, implying that the lens system either has very low mass or lies much closer to the microlensed source than the Sun, or both. A Bayesian analysis yields component masses