Turitea Observatory

Palmerston North, New Zealand

Turitea Observatory

Palmerston North, New Zealand

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Tsapras Y.,Las Cumbres Observatory Global Telescope Network | Tsapras Y.,Queen Mary, University of London | Choi J.-Y.,Chungbuk National University | Street R.A.,Las Cumbres Observatory Global Telescope Network | And 139 more authors.
Astrophysical Journal | Year: 2014

We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the light curve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a 2.73 ± 0.43 M J planet orbiting a 0.44 ± 0.07 M early M-type star. The distance to the lens is 4.97 ± 0.29 kpc and the projected separation between the host star and its planet at the time of the event is 3.45 ± 0.26 AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens. © 2014. The American Astronomical Society. All rights reserved..


Yee J.C.,Ohio State University | Yee J.C.,Harvard - Smithsonian Center for Astrophysics | Han C.,Chungbuk National University | Gould A.,Ohio State University | And 77 more authors.
Astrophysical Journal | Year: 2014

We report the discovery of MOA-2013-BLG-220Lb, which has a super-Jupiter mass ratio q = 3.01 ± 0.02 × 10-3 relative to its host. The proper motion, μ = 12.5 ± 1 mas yr-1, is one of the highest for microlensing planets yet discovered, implying that it will be possible to separately resolve the host within ∼7 yr. Two separate lines of evidence imply that the planet and host are in the Galactic disk. The planet could have been detected and characterized purely with follow-up data, which has important implications for microlensing surveys, both current and into the Large Synoptic Survey Telescope (LSST) era. © 2014. The American Astronomical Society. All rights reserved..


Zhu W.,Ohio State University | Calchi Novati S.,California Institute of Technology | Calchi Novati S.,University of Salerno | Calchi Novati S.,Instituto Internazionale per Gli Alti Studi Scientifici IIASS | And 93 more authors.
Astrophysical Journal | Year: 2016

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 BD at 5.9 ±1.0 kpc. The lens of of the second event, OGLE-2015-BLG-0763, is a 0.50 ±0.04 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. © 2016. The American Astronomical Society. All rights reserved.


Park H.,Chungbuk National University | Udalski A.,University of Warsaw | Han C.,Chungbuk National University | Gould A.,Ohio State University | And 61 more authors.
Astrophysical Journal | Year: 2013

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. © 2013. The American Astronomical Society. All rights reserved.


Han C.,Chungbuk National University | Jung Y.K.,Chungbuk National University | Udalski A.,University of Warsaw | Sumi T.,Osaka University | And 70 more authors.
Astrophysical Journal | Year: 2013

Observations of accretion disks around young brown dwarfs (BDs) have led to the speculation that they may form planetary systems similar to normal stars. While there have been several detections of planetary-mass objects around BDs (2MASS 1207-3932 and 2MASS 0441-2301), these companions have relatively large mass ratios and projected separations, suggesting that they formed in a manner analogous to stellar binaries. We present the discovery of a planetary-mass object orbiting a field BD via gravitational microlensing, OGLE-2012-BLG-0358Lb. The system is a low secondary/primary mass ratio (0.080 ± 0.001), relatively tightly separated (0.87 AU) binary composed of a planetary-mass object with 1.9 ± 0.2 Jupiter masses orbiting a BD with a mass 0.022 M. The relatively small mass ratio and separation suggest that the companion may have formed in a protoplanetary disk around the BD host in a manner analogous to planets. © 2013. The American Astronomical Society. All rights reserved..


Han C.,Chungbuk National University | Udalski A.,University of Warsaw | Choi J.-Y.,Chungbuk National University | Yee J.C.,Ohio State University | And 34 more authors.
Astrophysical Journal Letters | Year: 2013

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 MJ 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. © 2013. The American Astronomical Society. All rights reserved.


Poleski R.,Ohio State University | Poleski R.,University of Warsaw | Zhu W.,Ohio State University | Christie G.W.,Auckland Observatory | And 98 more authors.
Astrophysical Journal | Year: 2016

The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 ((μcl (N, E) = +0.36 ± 0.10, +1.42 ± 0.10 mas yr-1) as well as the source and show that the lens is not a cluster member. Even though this particular event does not probe the distribution of planets in globular clusters, other potential cluster lens events can be verified using our methodology. Additionally, we find that microlens parallax measured using Optical Gravitational Lens Experiment (OGLE) photometry is consistent with the value found based on the light curve displacement between the Earth and Spitzer. © 2016. The American Astronomical Society. All rights reserved.


PubMed | University of Notre Dame, Korea Astronomy and Space Science Institute, Turitea Observatory, Tel Aviv University and 23 more.
Type: Journal Article | Journal: Science (New York, N.Y.) | Year: 2014

Using gravitational microlensing, we detected a cold terrestrial planet orbiting one member of a binary star system. The planet has low mass (twice Earths) and lies projected at ~0.8 astronomical units (AU) from its host star, about the distance between Earth and the Sun. However, the planets 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.

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