S. Namba

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.

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

Candidate gravitational microlensing events for future direct lens imaging

A_{\rm max}\sim 1.5

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

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

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

q = 0.13

Reanalyses of anomalous gravitational microlensing events in the Ogle-III early warning system database with combined data

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-2011-BLG-262Lb: A SUB-EARTH-MASS MOON ORBITING A GAS GIANT PRIMARY OR A HIGH VELOCITY PLANETARY SYSTEM IN THE GALACTIC BULGE

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

MOA-2011-BLG-322Lb: a ‘second generation survey’ microlensing planet

and

OGLE-2012-BLG-0455/MOA-2012-BLG-206: Microlensing event with ambiguity in planetary interpretations caused by incomplete coverage of planetary signal

M_{2} = 0.012 \pm 0.002~M_{\odot}

MOA-2013-BLG-220Lb: Planetary Companion to a Possible Brown Dwarf Host

, which correspond to near the hydrogen-burning and deuterium-burning mass limits, respectively. The distance to the lens is