A. Sharan

The Exoplanet Mass-Ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass

We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. Laboratory for Exoplanets and Stellar Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland, New Zealand Department of Astronomy & Astrophysics, University of Chicago, 5640 S Ellis Ave, Chicago, IL 60637, USA Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601, Japan Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232, Japan Nagano National College of Technology, Nagano 381-8550, Japan Tokyo Metropolitan College of Industrial Technology, Tokyo 116-8523, Japan School of Chemical and Physical Sciences, Victoria University, Wellington, New Zealand Mt. John University Observatory, P.O. Box 56, Lake Tekapo 8770, New Zealand Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan Sagan Fellow, Department of Earth and Planetary Science, University of California at Berkeley, 501 Campbell Hall #3411, Berkeley, CA 94720, USA ar X iv :1 61 2. 03 93 9v 1 [ as tr oph .E P] 1 2 D ec 2 01 6

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.

The First Circumbinary Planet Found by Microlensing: OGLE-2007-BLG-349L(AB)c

© 2016. The American Astronomical Society. All rights reserved.We present the analysis of the first circumbinary planet microlensing event, OGLE-2007-BLG-349. This event has a strong planetary signal that is best fit with a mass ratio of q ≈ 3.4 × 10-4, but there is an additional signal due to an additional lens mass, either another planet or another star. We find acceptable light-curve fits with two classes of models: two-planet models (with a single host star) and circumbinary planet models. The light curve also reveals a significant microlensing parallax effect, which constrains the mass of the lens system to be M L ≈ 0.7 M⊙. Hubble Space Telescope (HST) images resolve the lens and source stars from their neighbors and indicate excess flux due to the star(s) in the lens system. This is consistent with the predicted flux from the circumbinary models, where the lens mass is shared between two stars, but there is not enough flux to be consistent with the two-planet, one-star models. So, only the circumbinary models are consistent with the HST data. They indicate a planet of mass m c = 80 ± 13 M⊙, orbiting a pair of M dwarfs with masses of M A = 0.41 ± 0.07 and M B = 0.30 ± 0.07, which makes this the lowest-mass circumbinary planet system known. The ratio of the separation between the planet and the center of mass to the separation of the two stars is ∼40, so unlike most of the circumbinary planets found by Kepler, the planet does not orbit near the stability limit.

OGLE-2012-BLG-0950Lb: THE FIRST PLANET MASS MEASUREMENT FROM ONLY MICROLENS PARALLAX AND LENS FLUX

We report the discovery of a microlensing planet OGLE-2012-BLG-0950Lb with a planet/host mass ratio Periapsis Approx. = 2 x10(exp. -4). A long term distortion detected in both MOA and OGLE light curve can be explained by themicrolens parallax due to the Earths orbital motion around the Sun. Although the finite source effect is not detected, we obtain the lens flux by the high resolution Keck AO observation. Combining the microlens parallax and the lens flux reveal the nature of the lens: a planet with mass of M(sub p) = 35(+17/-)M compared to Earth is orbiting around an M-dwarf with mass of M(sub host) = 0.56(+0.12/-0.16) M compared to the Sun with a planet-host projected separation of r1 = 2.7(+0.6/-0.7) au located at Luminosity Distance = 3.0(+0.8/-1.1) kpc from us. This is the first mass measurement from only microlens parallax and the lens flux without the finite source effect. In the coming space observation-era with Spitzer, K2, Euclid, and WFIRST, we expect many such events for which we will not be able to measure any finite source effect. This work demonstrates an ability of mass measurements in such events.

MOA-2010-BLG-353Lb: a possible Saturn revealed

We report the discovery of a possible planet in microlensing event MOA-2010-BLG353. This event was only recognised as having a planetary signal after the microlensing event had nished, and following a systematic analysis of all archival data for binary lens microlensing events collected to date. Data for event MOA-2010-BLG-353 were only recorded by the high cadence observations of the OGLE and MOA survey groups. If we make the assumptions that the probability of the lens star hosting a planet of the measured mass ratio is independent of the lens star mass or distance, and that the source star is in the Galactic bulge, a probability density analysis indicates the

MOA-2016-BLG-227Lb: A Massive Planet Characterized by Combining Light-curve Analysis and Keck AO Imaging

We report the discovery of a microlensing planet—MOA-2016-BLG-227Lb—with a large planet/host mass ratio of q ≃ 9 × 10^(−3). This event was located near the K2 Campaign 9 field that was observed by a large number of telescopes. As a result, the event was in the microlensing survey area of a number of these telescopes, and this enabled good coverage of the planetary light-curve signal. High angular resolution adaptive optics images from the Keck telescope reveal excess flux at the position of the source above the flux of the source star, as indicated by the light-curve model. This excess flux could be due to the lens star, but it could also be due to a companion to the source or lens star, or even an unrelated star. We consider all these possibilities in a Bayesian analysis in the context of a standard Galactic model. Our analysis indicates that it is unlikely that a large fraction of the excess flux comes from the lens, unless solar-type stars are much more likely to host planets of this mass ratio than lower mass stars. We recommend that a method similar to the one developed in this paper be used for other events with high angular resolution follow-up observations when the follow-up observations are insufficient to measure the lens–source relative proper motion.

The lowest mass ratio planetary microlens: OGLE 2016–BLG–1195Lb

The MOA project is supported by JSPS Kakenhi grants JP24253004, JP26247023, JP16H06287, JP23340064 and JP15H00781 and by the Royal Society of New Zealand Marsden Grant MAU1104. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. NJR is a Royal Society of New Zealand Rutherford Discovery Fellow. AS is a University of Auckland Doctoral Scholar.

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.

OGLE-2013-BLG-1761Lb: A Massive Planet around an M/K Dwarf

We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely sampled. But the detailed light curve analysis ruled out all stellar binary models and shows that the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of q ∼ (7.5±1.5)×10 and q ∼ (9.3±2.9)×10 with the projected separation in Einstein radius units of s = 0.95 (close) and s = 1.19 (wide), respectively. The microlens parallax effect is not detected but the finite source effect is detected. Our Bayesian analysis indicates that the Depertment of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan Warsaw University Observatory, A1. Ujazdowski 4, 00-478 Warszawa, Poland Department of Physics, University of Notre Dame, Norte Dame, IN 46556, USA Laboratory for Exoplanets and Stellar Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland, New Zealand Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD20771, USA Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232, Japan Nagano National College of Technology, Nagano 381-8550, Japan Tokyo Metropolitan College of Aeronautics, Tokyo 116-8523, Japan School of Chemical and Physical Sciences, Victoria University, Wellington, New Zealand University of Canterbury Mt John Observatory, P.O. Box 56, Lake Tekapo 8770, New Zealand Department of Physics, Faculty of Science, Kyoto Sangyo University, Kyoto 603-8555, Japan Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK Microlensing Observations in Astrophysics (MOA) Collaboration Optical Gravitational Lens Experiment (OGLE) Collaboration

A companion on the planet/brown dwarf mass boundary on a wide orbit discovered by gravitational microlensing

We present the discovery of a substellar companion to the primary host lens in the microlensing event MOA-2012-BLG-006. The companion-to-host mass ratio is 0.016, corresponding to a companion mass of