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1. MOA-2012-BLG-505Lb: A super-Earth mass planet probably in the Galactic bulge

Author

Nagakane, Masayuki, Sumi, Takahiro, Koshimoto, Naoki, Bennett, David P., Bond, Ian A., Rattenbury, Nicholas J., Suzuki, Daisuke, Abe, Fumio, Asakura, Yuichiro, Barry, Richard K., Bhattacharya, Aparna, Donachie, M., Fukui, Akihiko, Hirao, Yuki, Itow, Yoshitaka, Li, M. C. A., Ling, C. H., Masuda, Kimiaki, Matsubara, Y., Matsuo, Taro, Muraki, Yasushi, Ohnishi, Kouji, Ranc, C., Saito, To., Sharan, A., Shibai, Hiroshi, Sullivan, Denis J., Tristram, P. J., Yamada, Touko, and Yonehara, A.

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We report the discovery of a super-Earth mass planet in the microlensing event MOA-2012-BLG-505. This event has the second shortest event timescale of $t_{\rm E}=10 \pm 1$ days where the observed data show evidence of planetary companion. Our 15 minute high cadence survey observation schedule revealed the short subtle planetary signature. The system shows the well known close/wide degeneracy. The planet/host-star mass ratio is $q =2.1 \times 10^{-4}$ and the projected separation normalized by the Einstein radius is s = 1.1 or 0.9 for the wide and close solutions, respectively. We estimate the physical parameters of the system by using a Bayesian analysis and find that the lens consists of a super-Earth with a mass of $6.7^{+10.7}_{-3.6}M_{\oplus}$ orbiting around a brown-dwarf or late M-dwarf host with a mass of $0.10^{+0.16}_{-0.05}M_{\odot}$ with a projected star-planet separation of $0.9^{+0.3}_{-0.2}$AU. The system is at a distance of $7.2 \pm 1.1$ kpc, i.e., it is likely to be in the Galactic bulge. The small angular Einstein radius ($\theta_{\rm E}=0.12 \pm 0.02$ mas) and short event timescale are typical for a low-mass lens in the Galactic bulge. Such low-mass planetary systems in the Bulge are rare because the detection efficiency of planets in short microlensing events is relatively low. This discovery may suggest that such low mass planetary systems are abundant in the Bulge and currently on-going high cadence survey programs will detect more such events and may reveal an abundance of such planetary systems., Comment: 22 pages, 8 figures, 2 tables, Accepted for publication in AJ

Published
2017
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2. OGLE-2013-BLG-1761Lb: A Massive Planet Around an M/K Dwarf

Author

Hirao, Y., Udalski, A., Sumi, T., Bennett, D. P., Bond, I. A., Rattenbury, N. J., Suzuki, D., Koshimoto, N., Abe, F., Asakura, Y., Barry, R. K., Bhattacharya, A., Donachie, M., Evans, P., Fukui, A., Itow, Y., Li, M. C. A., Ling, C. H., Masuda, K., Matsubara, Y., Matsuo, T., Muraki, Y., Nagakane, M., Ohnishi, K., Saito, To., Sharan, A., Shibai, H., Sullivan, D. J., Tristram, P. J., Yamada, T., Yonehara, A., Poleski, R., Skowron, J., Mr��z, P., Szyma��ski, M. K., Koz��owski, S., Pietrukowicz, P., Soszy��ski, I., Wyrzykowski, ��., and Ulaczyk, K.

Subjects
Physics, Earth and Planetary Astrophysics (astro-ph.EP), 010504 meteorology & atmospheric sciences, Star (game theory), FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Mass ratio, Planetary system, Light curve, Gravitational microlensing, 01 natural sciences, Einstein radius, Space and Planetary Science, Planet, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Astrophysics - Earth and Planetary Astrophysics
Abstract

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 $q \sim (7.5 \pm 1.5) \times 10^{-3}$ and $q \sim (9.3 \pm 2.9) \times 10^{-3}$ 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 lens system is located at $D_{\rm L}=6.9_{-1.2}^{+1.0} \ {\rm kpc}$ away from us and the host star is an M/K-dwarf with the mass of $M_{\rm L}=0.33_{-0.18}^{+0.32} \ M_{\odot}$ orbited by a super-Jupiter mass planet with the mass of $m_{\rm P}=2.8_{-1.5}^{+2.5} \ M_{\rm Jup}$ at the projected separation of $a_{\perp}=1.8_{-0.5}^{+0.5} \ {\rm AU}$. The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters can be constrained by the future high resolution imaging by ground large telescopes or HST. If the estimated lens distance is correct, this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge., Comment: 22pages, 7figures, 2tables, submitted to AAS Journals

Published
2017
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3. Discovery of a Gas giant Planet in Microlensing Event OGLE-2014-BLG-1760

Author

Bhattacharya, A., Bennett, D. P., Bond, I. A., Sumi, T., Udalski, A., Street, R., Tsapras, Y., Abe, F., Freeman, M., Fukui, A., Hirao, Y., Itow, Y., Koshimoto, N., Li, M. C. A., Ling, C. H., Masuda, K., Matsubara, Y., Muraki, Y., Nagakane, M., Ohnishi, K., Rattenbury, N., Saito, T., Sharan, A., Sullivan, D. J., Suzuki, D., Tristram, P. J., Skowron, J., Szymański, M. K., Soszyński, I., Poleski, R., Mróz, P., Kozlowski, S., Pietrukowicz, P., Ulaczyk, K., Wyrzykowski, L., Bachelet, E., Bramich, D. M., D’Ago, G., Dominik, M., Figuera Jaimes, R., Horne, K., Hundertmark, M., Kains, N., Menzies, J., Schmidt, R., Snodgrass, C., Steele, I. A., Wambsganss, J., University of St Andrews. School of Physics and Astronomy, and University of St Andrews. St Andrews Centre for Exoplanet Science

Subjects
Proper motion, 010504 meteorology & atmospheric sciences, NDAS, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Gravitational microlensing, 01 natural sciences, micro [Gravitational lensing], Bulge, Planet, 0103 physical sciences, QB Astronomy, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, QC, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, QB, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Astronomy and Astrophysics, Planetary system, Light curve, Stars, Planetary systems, QC Physics, Space and Planetary Science, High Energy Physics::Experiment, Astrophysics::Earth and Planetary Astrophysics, Planetary mass, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present the analysis of the planetary microlensing event OGLE-2014-BLG-1760, which shows a strong light curve signal due to the presence of a Jupiter mass-ratio planet. One unusual feature of this event is that the source star is quite blue, with $V-I = 1.48\pm 0.08$. This is marginally consistent with source star in the Galactic bulge, but it could possibly indicate a young source star in the far side of the disk. Assuming a bulge source, we perform a Bayesian analysis assuming a standard Galactic model, and this indicates that the planetary system resides in or near the Galactic bulge at $D_L = 6.9 \pm 1.1 $ kpc. It also indicates a host star mass of $M_* = 0.51 \pm 0.44 M_\odot$, a planet mass of $m_p = 180 \pm 110 M_\oplus$, and a projected star-planet separation of $a_\perp = 1.7\pm 0.3\,$AU. The lens-source relative proper motion is $\mu_{\rm rel} = 6.5\pm 1.1$ mas/yr. The lens (and stellar host star) is predicted to be very faint, so it is most likely that it can detected only when the lens and source stars are partially resolved. Due to the relatively high relative proper motion, the lens and source will be resolved to about $\sim46\,$mas in 6-8 years after the peak magnification. So, by 2020 - 2022, we can hope to detect the lens star with deep, high resolution images., Comment: Submitted to ApJ

Published
2016
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4. DETERMINING THE PHYSICAL LENS PARAMETERS OF THE BINARY GRAVITATIONAL MICROLENSING EVENT MOA-2009-BLG-016

Author

Hwang, K. -H., Han, C., Bond, I. A., Miyake, N., Abe, F., Bennett, D. P., Botzler, C. S., Fukui, A., Furusawa, K., Hayashi, F., Hearnshaw, J. B., Hosaka, S., Itow, Y., Kamiya, K., Kilmartin, P. M., Korpela, A., Lin, W., Ling, C. H., Makita, S., Masuda, K., Matsubara, Y., Muraki, Y., Nishimoto, K., Ohnishi, K., Perrott, Y. C., Rattenbury, N., Saito, To., Sako, T., Skuljan, L., Sullivan, D. J., Sumi, T., Suzuki, D., Sweatman, W. L., Tristram, J., Wada, K., L., P. C. M. Yock D., Depoy, Gaudi, B. S., Gould, A., Lee, C. -U., and Pogge, R. W.

Subjects
Physics, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Light curve, Gravitational microlensing, 01 natural sciences, law.invention, Einstein radius, Lens (optics), Gravitational lens, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, law, 0103 physical sciences, Orbital motion, Astrophysics::Earth and Planetary Astrophysics, Caustic (optics), Parallax, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract

We report the result of the analysis of the light curve of the microlensing event MOA-2009-BLG-016. The light curve is characterized by a short-duration anomaly near the peak and an overall asymmetry. We find that the peak anomaly is due to a binary companion to the primary lens and the asymmetry of the light curve is explained by the parallax effect caused by the acceleration of the observer over the course of the event due to the orbital motion of the Earth around the Sun. In addition, we detect evidence for the effect of the finite size of the source near the peak of the event, which allows us to measure the angular Einstein radius of the lens system. The Einstein radius combined with the microlens parallax allows us to determine the total mass of the lens and the distance to the lens. We identify three distinct classes of degenerate solutions for the binary lens parameters, where two are manifestations of the previously identified degeneracies of close/wide binaries and positive/negative impact parameters, while the third class is caused by the symmetric cycloid shape of the caustic. We find that, for the best-fit solution, the estimated mass of the lower-mass component of the binary is (0.04 +- 0.01) M_sun, implying a brown-dwarf companion. However, there exists a solution that is worse only by \Delta\chi^2 ~ 3 for which the mass of the secondary is above the hydrogen-burning limit. Unfortunately, resolving these two degenerate solutions will be difficult as the relative lens-source proper motions for both are similar and small (~ 1 mas/yr) and thus the lens will remain blended with the source for the next several decades., Comment: 7 pages, 2 tables, and 5 figures

Published
2010

5. THE EXTREME MICROLENSING EVENT OGLE-2007-BLG-224: TERRESTRIAL PARALLAX OBSERVATION OF A THICK-DISK BROWN DWARF

Author

Gould, A., Udalski, A., Monard, B., Horne, K., Dong, Subo, Miyake, N., Sahu, K., Bennett, D. P., Wyrzykowski, Ł., Soszyński, I., Szymański, M. K., Kubiak, M., Pietrzyński, G., Szewczyk, O., Ulaczyk, K., Allen, W., Christie, G. W., Depoy, D. L., Gaudi, B. S., Han, C., Lee, C.-U., Mccormick, J., Natusch, T., Park, B.-G., Pogge, R. W., Allan, A., Bode, M. F., Bramich, D. M., Burgdorf, M. J., Dominik, M., Fraser, S. N., Kerins, E., Mottram, C., Snodgrass, C., Steele, I. A., Street, R., Tsapras, Y., Abe, F., Bond, I. A., Botzler, C. S., Fukui, A., Furusawa, K., Hearnshaw, J. B., Itow, Y., Kamiya, K., Kilmartin, P. M., Korpela, A., Lin, W., Ling, C. H., Masuda, K., Matsubara, Y., Muraki, Y., Nagaya, M., Ohnishi, K., Okumura, T., Perrott, Y. C., Rattenbury, N., Saito, To., Sako, T., Skuljan, L., Sullivan, D. J., Sumi, T., Sweatman, W. L., Tristram, P. J., Yock, P. C. M., Albrow, M., Beaulieu, J. P., Coutures, C., Calitz, H., Caldwell, J., Fouqué, P., Martin, Roland, Williams, A., Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Astrophysics Research Institute [Liverpool] (ARI), Liverpool John Moores University (LJMU), Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astronomical Objects, Solar System, gravitational lensing, Brown dwarf, FOS: Physical sciences, Astrophysics, Gravitational microlensing, 01 natural sciences, law.invention, stars: low-mass, law, 0103 physical sciences, Thick disk, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics - Astrophysics of Galaxies, Lens (optics), Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), astrometry, Astrophysics::Earth and Planetary Astrophysics, Parallax, Event (particle physics), brown dwarfs
Abstract

Parallax is the most fundamental technique to measure distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 BCE) to measure the distance to the Moon, the baseline of the Earth is so small that terrestrial parallax can generally only be applied to objects in the Solar System. However, there exists a class of extreme gravitational microlensing events in which the effects of terrestrial parallax can be readily detected and so permit the measurement of the distance, mass, and transverse velocity of the lens. Here we report observations of the first such extreme microlensing event OGLE-2007-BLG-224, from which we infer that the lens is a brown dwarf of mass M=0.056 +- 0.004 Msun, with a distance of 525 +- 40 pc and a transverse velocity of 113 +- 21 km/s. The velocity places the lens in the thick disk, making this the lowest-mass thick-disk brown dwarf detected so far. Follow-up observations may allow one to observe the light from the brown dwarf itself, thus serving as an important constraint for evolutionary models of these objects and potentially opening a new window on sub-stellar objects. The low a priori probability of detecting a thick-disk brown dwarf in this event, when combined with additional evidence from other observations, suggests that old substellar objects may be more common than previously assumed., Comment: ApJ Letters, in press, 15 pages including 2 figures

Published
2009

6. OGLE-2013-BLG-0132Lb and OGLE-2013-BLG-1721Lb: Two Saturn-mass Planets Discovered around M-dwarfs

Author

The, OGLE Collaboration, Mroz, Przemek, Udalski, A., Bond, I. A., Skowron, J., Sumi, T., Han, C., Szymanski, M. K., Soszynski, I., Poleski, R., Pietrukowicz, P., Kozlowski, S., Wyrzykowski, L., Ulaczyk, K., The, MOA Collaboration 阿部 文雄, Asakura, Y., Barry, R. K., Bennett, D. P., Bhattacharya, A., Donachie, M., Evans, P., Hirao, Y., Koshimoto, N., Li, M. C. A., Ling, C. H., Nagakane, M., Ohnishi, K., Ranc, C., Rattenbury, N. J., Saito, To., Sharan, A., Sullivan, D. J., Tristram, P. J., Yamada, T., Yonehara, A., The, MOA Collaboration Abe Fumio, Fukui, Akihiko, Itow, Yoshitaka, Masuda, Kimiaki, Matsubara, Yutaka, Muraki, Yasushi, and Suzuki, Daisuke

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics, planets and satellites: detection, 010504 meteorology & atmospheric sciences, Saturn (rocket family), FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, gravitational lensing: micro, 01 natural sciences, Space and Planetary Science, Planet, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

著者人数: 41名, Accepted: 2017-09-25, 資料番号: SA1170174000

Published
2017

7. The Microlensing Event Rate and Optical Depth Toward the Galactic Bulge from MOA-II

Author

Sumi, T., Bennett, D. P., Bond, I. A., Abe, F., Botzler, C. S., Fukui, A., Furusawa, K., Itow, Y., Ling, C. H., Masuda, K., Matsubara, Y., Muraki, Y., Ohnishi, K., Rattenbury, N., Saito, To., Sullivan, D. J., Suzuki, D., Sweatman, W. L., Tristram, J., Wada, K., and Yock, P. C. M.

Subjects
Physics, Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Gravitational microlensing, Astrophysics - Astrophysics of Galaxies, Galaxy, Luminosity, Einstein radius, Stars, Space and Planetary Science, Bulge, Astrophysics of Galaxies (astro-ph.GA), Optical depth (astrophysics), Red clump, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present measurements of the microlensing optical depth and event rate toward the Galactic Bulge based on two years of the MOA-II survey. This sample contains ~1000 microlensing events, with an Einstein Radius crossing time of t_E < 200 days between -5, Comment: 46 pages, 14 figures, accepted for publication in ApJ

Published
2013
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8. MOA-2009-BLG-387Lb: A massive planet orbiting an M dwarf

Author

Batista, V., Gould, A., Dieters, S., Dong, S., Bond, I., Beaulieu, J. P., Maoz, D., Monard, B., Christie, G. W., Mccormick, J., Albrow, M. D., Horne, K., Tsapras, Y., Burgdorf, M. J., Calchi Novati, S., Skottfelt, J., Caldwell, J., Kozłowski, S., Kubas, D., Gaudi, B. S., Han, C., Bennett, D. P., An, J., Abe, F., Botzler, C. S., Douchin, D., Freeman, M., Fukui, A., Furusawa, K., Hearnshaw, J. B., Hosaka, S., Itow, Y., Kamiya, K., Kilmartin, P. M., Korpela, A., Lin, W., Ling, C. H., Makita, B. S., Masuda, K., Matsubara, Y., Miyake, N., Muraki, Y., Nagaya, M., Nishimoto, K., Ohnishi, K., Okumura, T., Perrott, Y. C., Rattenbury, N., Saito, T. o., Sullivan, D. J., Sumi, T., Sweatman, W. L., Tristram, P. J., von Seggern, E., Yock, P. C. M., Brillant, S., Calitz, J. J., Cassan, A., Cole, A., Cook, K., Coutures, C., Dominis Prester, D., Donatowicz, J., Greenhill, J., Hoffman, M., Jablonski, F., Kane, S. R., Kains, N., Marquette, J. B., Martin, R., Martioli, E., Meintjes, P., Menzies, J., Pedretti, E., Pollard, K., Sahu, K. C., Vinter, C., Wambsganss, J., Watson, R., Williams, A., Zub, M., Allen, W., Bolt, G., Bos, M., Depoy, D. L., Drummond, J., Eastman, J. D., Gal Yam, A., Gorbikov, E., Higgins, D., Janczak, J., Kaspi, S., Lee, C. U., Mallia, F., Maury, A., Monard, L. A. G., Moorhouse, D., Morgan, N., Natusch, T., Ofek, E. O., Park, B. G., Pogge, R. W., Polishook, D., Santallo, R., Shporer, A., Spector, O., Thornley, G., Yee, J. C., Bozza, Valerio, Browne, P., Dominik, M., Dreizler, S., Finet, F., Glitrup, M., Grundahl, F., Harpsøe, K., Hessman, F. V., Hinse, T. C., Hundertmark, M., Jørgensen, U. G., Liebig, C., Maier, G., Mancini, L., Mathiasen, M., Rahvar, S., Ricci, D., Scarpetta, Gaetano, Southworth, J., Surdej, J., Zimmer, F., Allan, A., Bramich, D. M., Snodgrass, C., Steele, I. A., and Street, R. A.

Subjects
Physics, Earth and Planetary Astrophysics (astro-ph.EP), 010308 nuclear & particles physics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Mass ratio, Gravitational microlensing, 01 natural sciences, Einstein radius, Jupiter, Settore FIS/05 - Astronomia e Astrofisica, 13. Climate action, Space and Planetary Science, Planet, 0103 physical sciences, Orbital motion, High Energy Physics::Experiment, gravitational lensing, micro methods, data analysis, planets, satellites, detection, methods, numerical, instrumentation, adaptive optics, photometers, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Planetary mass, Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the longest for any planetary event. The host is an M dwarf, with a mass in the range 0.07 M_sun < M_host < 0.49M_sun at 90% confidence. The planet-star mass ratio q = 0.0132 +- 0.003 has been measured extremely well, so at the best-estimated host mass, the planet mass is m_p = 2.6 Jupiter masses for the median host mass, M = 0.19 M_sun. The host mass is determined from two "higher order" microlensing parameters. One of these, the angular Einstein radius ��_E = 0.31 +- 0.03 mas, is very well measured, but the other (the microlens parallax ��_E, which is due to the Earth's orbital motion) is highly degenate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits. The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc < D_L < 7.9 kpc, 1.1 AU < a < 2.7AU, and 3.8 yr < P < 7.6 yr, respectively., 20 pages including 8 figures. A&A 529 102 (2011)

Published
2011
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9. A Cold Neptune-Mass Planet OGLE-2007-BLG-368Lb: Cold Neptunes Are Common

Author

Sumi, T., Bennett, D. P., Bond, I. A., Udalski, A., Batista, V., Dominik, M., Fouqu��, P., Kubas, D., Gould, A., Macintosh, B., Cook, K., Dong, S., Skuljan, L., Cassan, A., Collaboration, The MOA, Abe, F., Botzler, C. S., Fukui, A., Furusawa, K., Hearnshaw, J. B., Itow, Y., Kamiya, K., Kilmartin, P. M., Korpela, A., Lin, W., Ling, C. H., Masuda, K., Matsubara, Y., Miyake, N., Muraki, Y., Nagaya, M., Nagayama, T., Ohnishi, K., Okumura, T., Perrott, Y. C., Rattenbury, N., Saito, To., Sako, T., Sullivan, D. J., Sweatman, W. L., Yock, P. C. M., Collaboration, The PLANET, Beaulieu, J. P., Cole, A., Coutures, Ch., Duran, M. F., Greenhill, J., Jablonski, F., Marboeuf, U., Martioli, E., Pedretti, E., Pejcha, O., Rojo, P., Albrow, M. D., Brillant, S., Bode, M., Bramich, D. M., Burgdorf, M. J., Caldwell, J. A. R., Calitz, H., Corrales, E., Dieters, S., Prester, D. Dominis, Donatowicz, J., Hill, K., Hoffman, M., Horne, K., J, U. G., Kains, N., Kane, S., Marquette, J. B., Martin, R., Meintjes, P., Menzies, J., Pollard, K. R., Sahu, K. C., Snodgrass, C., Steele, I., Street, R., Tsapras, Y., Wambsganss, J., Williams, A., Zub, M., Collaboration, The OGLE, Szyma, M. K., Kubiak, M., Pietrzy, G., Soszy, I., Szewczyk, O., Ulaczyk, K., Collaboration, The microFUN, Allen, W., Christie, G. W., DePoy, D. L., Gaudi, B. S., Han, C., Janczak, J., Lee, C. -U., McCormick, J., Mallia, F., Monard, B., Natusch, T., Park, B. -G., Pogge, R. W., Santallo, R., Solar-Terrestrial Environment Laboratory [Nagoya] (STEL), Nagoya University, University of Notre Dame [Indiana] (UND), Massey University, Astronomical Observatory [Warsaw], Faculty of Physics [Warsaw] (FUW), University of Warsaw (UW)-University of Warsaw (UW), Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), SUPA School of Physics and Astronomy [University of St Andrews], University of St Andrews [Scotland]-Scottish Universities Physics Alliance (SUPA), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Astronomische Rechen-Institut [Heidelberg] (ARI), Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg] = Heidelberg University-Universität Heidelberg [Heidelberg] = Heidelberg University, Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Instituto Nacional de Pesquisas Espaciais (INPE), Ministério da Ciência, Tecnologia e Inovação, Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)

Subjects
Physics, gravitational lensing: micro, planetary systems, Earth and Planetary Astrophysics (astro-ph.EP), Stellar mass, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Gas giant, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Mass ratio, Light curve, Gravitational microlensing, 01 natural sciences, Exoplanet, Space and Planetary Science, Neptune, Planet, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q=[9.5 +/- 2.1] x 10^{-5} via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at M_l = 0.64_{-0.26}^{+0.21} M_\sun and D_l = 5.9_{-1.4}^{+0.9} kpc, respectively, so the mass and separation of the planet are M_p = 20_{-8}^{+7} M_\oplus and a = 3.3_{-0.8}^{+1.4} AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these ten cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN_{\rm pl}/d\log q \propto q^{-0.7 +/- 0.2} with a 95% confidence level upper limit of n < -0.35 (where dN_{\rm pl}/d\log q \propto q^n). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level., 39 pages, 10 figures, accepted for publication in ApJ

Published
2009
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10. A NEW TYPE OF AMBIGUITY IN THE PLANET AND BINARY INTERPRETATIONS OF CENTRAL PERTURBATIONS OF HIGH-MAGNIFICATION GRAVITATIONAL MICROLENSING EVENTS

Author

Choi, J.-Y, Shin, I.-G, Han, C., Udalski, A., Sumi, T., Gould, A., Bozza, V., Dominik, M., Fouque´, P., Horne, K., Szyman´ski, M. K., Kubiak, M., Soszyn´ski, I., Pietrzyn´ski, G., Poleski, R., Ulaczyk, K., Pietrukowicz, P., Kozłowski, S., Skowron, J., Wyrzykowski, Ł., OGLE Collaboration, Abe, F., Bennett, D. P., Bond, I. A., Botzler, C. S., Chote, P., Freeman, M., Fukui, A., Furusawa, K., Itow, Y., Kobara, S., Ling, C. H., Masuda, K., Matsubara, Y., Miyake, N., Muraki, Y., Ohmori, K., Ohnishi, K., Rattenbury, N. J., Saito, To, Sullivan, D. J., Suzuki, D., Suzuki, K., Sweatman, W. L., Takino, S., Tristram, P. J., Wada, K., Yock, P. C. M., MOA Collaboration, Bramich, D. M., Snodgrass, C., Steele, I. A., Street, R. A., Tsapras, Y., RoboNet Collaboration, Alsubai, K. A., Browne, P., Burgdorf, M. J., Calchi Novati, S., Dodds, P., Dreizler, S., Fang, X.-S, Grundahl, F., Gu, C.-H, Hardis, S., Harpsøe, K., Hinse, T. C., Hornstrup, Allan, Hundertmark, M., Jessen-Hansen, J., Jørgensen, U. G., Kains, N., Kerins, E., Liebig, C., Lund, M., Lunkkvist, M., Mancini, L., Mathiasen, M., Penny, M. T., Rahvar, S., Ricci, D., Scarpetta, G., Skottfelt, J., Southworth, J., Surdej, J., Tregloan-Reed, J., Wambsganss, J., Wertz, O., Almeida, L. A., Batista, V., Christie, G., DePoy, D. L., Dong, Subo, Gaudi, B. S., Henderson, C., Jablonski, F., Lee, C.-U, McCormick, J., McGregor, D., Moorhouse, D., Natusch, T., Ngan, H., Pogge, R. W., Tan, T.-G, Thornley, G., Yee, J. C., Albrow, M. D., Bachelet, E., Beaulieu, J.-P, Brillant, S., Cassan, A., Cole, A. A., Corrales, E., Coutures, C., Dieters, S., Dominis Prester, D., Donatowicz, J., Greenhill, J., Kubas, D., Marquette, J.-B, Menzies, J. W., Sahu, K. C., and Zub, M.

Subjects
media_common.quotation_subject, FOS: Physical sciences, Binary number, Perturbation (astronomy), gravitational lensing: micro, Astrophysics, Gravitational microlensing, 01 natural sciences, Galaxy: bulge, Settore FIS/05 - Astronomia e Astrofisica, Planet, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), media_common, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Binary Independence Model, Astronomy and Astrophysics, Ambiguity, Light curve, Galaxy: bulge, gravitational lensing: micro, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Caustic (optics), Astrophysics - Earth and Planetary Astrophysics
Abstract

High-magnification microlensing events provide an important channel to detect planets. Perturbations near the peak of a high-magnification event can be produced either by a planet or a binary companion. It is known that central perturbations induced by both types of companions can be generally distinguished due to the basically different magnification pattern around caustics. In this paper, we present a case of central perturbations for which it is difficult to distinguish the planetary and binary interpretations. The peak of a lensing light curve affected by this perturbation appears to be blunt and flat. For a planetary case, this perturbation occurs when the source trajectory passes the negative perturbation region behind the back end of an arrowhead-shaped central caustic. For a binary case, a similar perturbation occurs for a source trajectory passing through the negative perturbation region between two cusps of an astroid-shaped caustic. We demonstrate the degeneracy for 2 high-magnification events of OGLE-2011-BLG-0526 and OGLE-2011-BLG-0950/MOA-2011-BLG-336. For OGLE-2011-BLG-0526, the $\chi^2$ difference between the planetary and binary model is $\sim$ 3, implying that the degeneracy is very severe. For OGLE-2011-BLG-0950/MOA-2011-BLG-336, the stellar binary model is formally excluded with $\Delta \chi^2 \sim$ 105 and the planetary model is preferred. However, it is difficult to claim a planet discovery because systematic residuals of data from the planetary model are larger than the difference between the planetary and binary models. Considering that 2 events observed during a single season suffer from such a degeneracy, it is expected that central perturbations experiencing this type of degeneracy is common., Comment: 8 pages, 8 figures

Published
2012

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