K.-H. Hwang

THE SECOND MULTIPLE-PLANET SYSTEM DISCOVERED BY MICROLENSING: OGLE-2012-BLG-0026Lb, c-A PAIR OF JOVIAN PLANETS BEYOND THE SNOW LINE

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 ~0.11 M J and 0.68 M J and they are orbiting a G-type main-sequence star with a mass ~0.82 M ☉. The projected separations of the individual planets are beyond the snow line in all four solutions, being ~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.

A terrestrial planet in a ~1-AU orbit around one member of a ∼15-AU binary

Impolite planet ignores hosts partner Many known exoplanets (planets outside our own solar system) are hosted by binary systems that contain two stars. These planets normally circle around both of their stars. Using microlensing data taken with a worldwide network of telescopes, Gould et al. found a planet twice the mass of Earth that circles just one of a pair of stars. The same approach has the potential to uncover other similar star systems and help to illuminate some of the mysteries of planet formation. Science, this issue p. 46 Microlensing observations reveal an exoplanet twice the mass of Earth circling just one member of a binary system. Using gravitational microlensing, we detected a cold terrestrial planet orbiting one member of a binary star system. The planet has low mass (twice Earth’s) and lies projected at ~0.8 astronomical units (AU) from its host star, about the distance between Earth and the Sun. However, the planet’s temperature is much lower, <60 Kelvin, because the host star is only 0.10 to 0.15 solar masses and therefore more than 400 times less luminous than the Sun. The host itself orbits a slightly more massive companion with projected separation of 10 to 15 AU. This detection is consistent with such systems being very common. Straightforward modification of current microlensing search strategies could increase sensitivity to planets in binary systems. With more detections, such binary-star planetary systems could constrain models of planet formation and evolution.

Spitzer as a microlens parallax satellite : mass and distance measurements of the binary lens system OGLE-2014-BLG-1050L

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 ~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_☉) binary at ~1.1 kpc or a higher-mass (0.9 and 0.35 M_☉) binary at ~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.

Gravitational binary-lens events with prominent effects of lens orbital motion

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.

OGLE-2013-BLG-0102LA,B: MICROLENSING BINARY WITH COMPONENTS AT STAR/BROWN DWARF AND BROWN DWARF/PLANET BOUNDARIES

We present the analysis of the gravitational microlensing event OGLE-2013-BLG-0102. The light curve of the event is characterized by a strong short-term anomaly superposed on a smoothly varying lensing curve with a moderate magnification

A VENUS-MASS PLANET ORBITING A BROWN DWARF: A MISSING LINK BETWEEN PLANETS AND MOONS

A_{\rm max}\sim 1.5

OGLE-2005-BLG-153: Microlensing Discovery and Characterization of a Very Low Mass Binary

. It is found that the event was produced by a binary lens with a mass ratio between the components of

Candidate gravitational microlensing events for future direct lens imaging

q = 0.13

Interpretation of a short-term anomaly in the gravitational microlensing event MOA-2012-BLG-486

and the anomaly was caused by the passage of the source trajectory over a caustic located away from the barycenter of the binary. From the analysis of the effects on the light curve due to the finite size of the source and the parallactic motion of the Earth, the physical parameters of the lens system are determined. The measured masses of the lens components are

MOA-2013-BLG-220Lb : massive planetary companion to galactic-disk host

M_{1} = 0.096 \pm 0.013~M_{\odot}