Sub-Saturn Planet MOA-2008-BLG-310Lb: Likely To Be In The Galactic Bulge
Julia Janczak, A. Fukui, Subo Dong, B. Monard, Szymon Kozlowski, A. Gould, J. P. Beaulieu, Daniel Kubas, J. B. Marquette, T. Sumi, I. A. Bond, D. P. Bennett, th… 展开作者
Julia Janczak, A. Fukui, Subo Dong, B. Monard, Szymon Kozlowski, A. Gould, J. P. Beaulieu, Daniel Kubas, J. B. Marquette, T. Sumi, I. A. Bond, D. P. Bennett, the MOA collaboration, the MicroFUN collaboration, the MiNDSTEp collaboration, the PLANET collaboration
We report the detection of sub-Saturn-mass planet MOA-2008-BLG-310Lb and argue that it is the strongest candidate yet for a bulge planet. Deviations from the single-lens fit are smoothed out by finite-source effects and so are not immediately apparent from the light curve. Nevertheless, we find that a model in which the primary has a planetary companion is favored over the single-lens model by Δχ^2 ~ 880 for an additional three degrees of freedom. Detailed analysis yields a planet/star mass ratio q=(3.3+/-0.3)x10^{-4} and an angular separation between the planet and star within 10% of the angular Einstein radius. The small angular Einstein radius, θ_E=0.155+/-0.011 mas, constrains the distance to the lens to be D_L>6.0 kpc if it is a star (M_L>0.08 M_sun). This is the only microlensing exoplanet host discovered so far that must be in the bulge if it is a star. By analyzing VLT NACO adaptive optics images taken near the baseline of the event, we detect additional blended light that is aligned to within 130 mas of the lensed source. This light is plausibly from the lens, but could also be due to a companion to lens or source, or possibly an unassociated star. If the blended light is indeed due to the lens, we can estimate the mass of the lens, M_L=0.67+/-0.14 M_sun, planet mass m=74+/-17 M_Earth, and projected separation between the planet and host, 1.25+/-0.10 AU, putting it right on the "snow line". If not, then the planet has lower mass, is closer to its host and is colder. To distinguish among these possibilities on reasonable timescales would require obtaining Hubble Space Telescope images almost immediately, before the source-lens relative motion of μ=5 mas yr^{-1} causes them to separate substantially.
MOA-2006-BLG-074 was selected as one of the most promising planetary candidates in a retrospective analysis of the MOA collaboration: its asymmetric high-magnification peak can be perfectly explained by a source passing across a central caustic deformed by a small planet. However, after a detailed analysis of the residuals, we have realized that a single lens and a source orbiting with a faint companion provides a more satisfactory explanation for all the observed deviations from a Paczynski curve and the only physically acceptable interpretation. Indeed the orbital motion of the source is con…
High-magnification gravitational microlensing events provide an important channel of detecting planetary systems with multiple giants located at their birth places. In order to investigate the potential existence of additional planets, we reanalyze the light curves of the eight high-magnification microlensing events for each of which a single planet was previously detected. The analyzed events include OGLE-2005-BLG-071, OGLE-2005-BLG-169, MOA-2007-BLG-400, MOA-2008-BLG-310, MOA-2009-BLG-319, MOA-2009-BLG-387, MOA-2010-BLG-477, and MOA-2011-BLG-293. We find that including an additional planet i…
We report the discovery of a possible planet in microlensing event MOA-2010-BLG-353. This event was only recognised as having a planetary signal after the microlensing event had finished, 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 st…
We present the MOA Collaboration light curve data for planetary microlensing event OGLE-2015-BLG-0954, which was previously announced in a paper by the KMTNet and OGLE Collaborations. The MOA data cover the caustic exit, which was not covered by the KMTNet or OGLE data, and they provide a more reliable measurement of the finite source effect. The MOA data also provide a new source color measurement that reveals a lens-source relative proper motion of $μ_{\rm rel} = 11.8\pm 0.8\,$mas/yr, which compares to the value of $μ_{\rm rel} = 18.4\pm 1.7\,$mas/yr reported in the KMTNet-OGLE paper. This n…
We present Keck/NIRC2 adaptive optics imaging of planetary microlensing event MOA-2007-BLG-400 that resolves the lens star system from the source. We find that the MOA-2007-BLG-400L planetary system consists of a $1.71\pm 0.27 M_{\rm Jup}$ planet orbiting a $0.69\pm 0.04M_{\odot}$ K-dwarf host star at a distance of $6.89\pm 0.77\,$kpc from the Sun. So, this planetary system probably resides in the Galactic bulge. The planet-host star projected separation is only weakly constrained due to the close-wide light curve degeneracy; the 2$σ$ projected separation range is 0.6--$7.2\,$AU. This host mas…
Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169
The University of Osaka（大阪大学）；Ohio State University（俄亥俄州立大学）；Massey University（梅西大学）；Università di Salerno（萨莱诺大学）；Istituto Nazionale di Fisica Nucleare（意大利国家核物理研究所）；Nagoya University（名古屋大学）；NASA Goddard Space Flight Center（NASA戈达德太空飞行中心）；University of Maryland, College Park（马里兰大学帕克分校）
Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516
University of Warsaw（华沙大学）；École Normale Supérieure, Paris（巴黎高等师范学院）；European Southern Observatory（欧洲南方天文台）；Peking University（北京大学）；National Astronomical Observatories, Chinese Academy of Science（中国科学院国家天文台）
We present the discovery of two planetary systems consisting of a Saturn-mass planet orbiting an M-dwarf, which were detected in faint microlensing events OGLE-2013-BLG-0132 and OGLE-2013-BLG-1721. The planetary anomalies were covered with high cadence by OGLE and MOA photometric surveys. The light curve modeling indicates that the planet-to-host mass ratios are $(5.15 \pm 0.28)\times 10^{-4}$ and $(13.18 \pm 0.72)\times 10^{-4}$, respectively. Both events were too short and too faint to measure a reliable parallax signal and hence the lens mass. We therefore used a Bayesian analysis to estima…
We present the discovery of a Neptune-mass planet orbiting a 0.8 +- 0.3 M_Sun star in the Galactic bulge. The planet manifested itself during the microlensing event MOA 2011-BLG-028/OGLE-2011-BLG-0203 as a low-mass companion to the lens star. The analysis of the light curve provides the measurement of the mass ratio: (1.2 +- 0.2) x 10^-4, which indicates the mass of the planet to be 12-60 Earth masses. The lensing system is located at 7.3 +- 0.7 kpc away from the Earth near the direction to Baade's Window. The projected separation of the planet, at the time of the microlensing event, was 3.1-5…
Context. Brown dwarfs are poorly understood transition objects between stars and planets, with several competing mechanisms having been proposed for their formation. Mass measurements are generally difficult for isolated objects but also for brown dwarfs orbiting low-mass stars, which are often too faint for spectroscopic follow-up. Aims. Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here we present the analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is due to a binary system composed of a brown dwarf orbiting…
We present the details of the Bayesian analysis on the planetary microlensing event MOA-2016-BLG-227, whose excess flux is likely due to a source/lens companion or an unrelated ambient star, as well as of the assumed prior distributions. Furthermore, we apply this method to four reported planetary events, MOA-2008-BLG-310, MOA-2011-BLG-293, OGLE-2012-BLG-0527, and OGLE-2012-BLG-0950, where adaptive optics observations have detected excess flux at the source star positions. For events with small angular Einstein radii, our lens mass estimates are more uncertain than those of previous analyses w…
New Method to Measure Proper Motions of Microlensed Sources: Application to Candidate Free-Floating-Planet Event MOA-2011-BLG-262
我们开发了一种新的方法来测量源自行微透镜事件，它可以部分克服由于混合的问题。它利用了这样一个事实，即从微透镜事件本身可以精确地知道源位置。我们将这种方法应用于MOA-2011-BLG-262事件，该事件具有短时标t_E=3.8天，伴星质量比q=0.0047，透镜-源相对自行μ_rel=20 mas/yr或12 mas/yr（对于两种可能的模型）。这三个特征意味着透镜可能是一颗褐矮星或一颗拥有大约地球质量的“月亮”的大质量行星。如果能证明高的透镜-光源相对自行主要是由于透镜而不是光源，那么这种解释的可能性将大大增加。根据光学引力透镜实验（OGLE）对银河系核球的长期观测资料，我们测量了在（北，东）银河系坐标系中，源的自行很小，μ s =（-2.3，-0.9）+-（2.8，2.6）mas/yr。然后，这些值是重要的输入到贝叶斯分析的事件中提出的一个配套文件由贝内特等人。
We present an adaptive optics (AO) analysis of images from the Keck-II telescope NIRC2 instrument of the planetary microlensing event MOA-2009-BLG-319. The $\sim$10 year baseline between the event and the Keck observations allows the planetary host star to be detected at a separation of $66.5\pm 1.7\,$mas from the source star, consistent with the light curve model prediction. The combination of the host star brightness and light curve parameters yield host star and planet masses of M_host = 0.514 $\pm$ 0.063M_Sun and m_p = 66.0 $\pm$ 8.1M_Earth at a distance of $D_L = 7.0 \pm 0.7\,$kpc. The st…
MOA-2020-BLG-108Lb: A Giant Planet Beyond the Snow Line of a Low-Mass Lens Near the Lower Boundary of the Mass-Ratio Desert
Kanto Gakuin University（关东学院大学）；Nippon Institute of Technology（日本工业大学）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；University of Maryland, College Park（马里兰大学帕克分校）；The University of Osaka（大阪大学）；Massey University（梅西大学）；University of Auckland（奥克兰大学）；Institute of Space and Astronautical Science（宇宙科学研究所）
High resolution Hubble Space Telescope (HST) image analysis of the MOA-2008-BLG-310 microlens system indicates that the excess flux at the location of the source found in the discovery paper cannot primarily be due to the lens star because it does not match the lens-source relative proper motion, $μ_{\rm rel}$, predicted by the microlens models. This excess flux is most likely to be due to an unrelated star that happens to be located in close proximity to the source star. Two epochs of HST observations indicate proper motion for this blend star that is typical of a random bulge star, but is no…
We present the analysis of high-resolution images of MOA-2013-BLG-220, taken with the Keck adaptive optics system 6 years after the initial observation, identifying the lens as a solar-type star hosting a super-Jupiter mass planet. The masses of planets and host-stars discovered by microlensing are often not determined from light curve data, while the star-planet mass-ratio and projected separation in units of Einstein ring radius are well measured. High-resolution follow-up observations after the lensing event is complete can resolve the source and lens. This allows direct measurements of flu…
We present the analysis of MOA-2007-BLG-197Lb, the first brown dwarf companion to a Sun-like star detected through gravitational microlensing. The event was alerted and followed-up photometrically by a network of telescopes from the PLANET, MOA, and uFUN collaborations, and observed at high angular resolution using the NaCo instrument at the VLT. From the modelling of the microlensing light curve, we derived the binary lens separation in Einstein radius units (s~1.13) and a mass ratio of (4.732+/-0.020)x10^{-2}. Annual parallax, lens orbital motion and finite source effects were included in th…
We report on the observations, analysis and interpretation of the microlensing event MOA-2019- BLG-008. The observed anomaly in the photometric light curve is best described through a binary lens model. In this model, the source did not cross caustics and no finite source effects were observed. Therefore the angular Einstein ring radius cannot be measured from the light curve alone. However, the large event duration, t E about 80 days, allows a precise measurement of the microlensing parallax. In addition to the constraints on the angular radius and the apparent brightness I s of the source, w…
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 …
We report the discovery of a microlensing planet --- MOA-2016-BLG-227Lb --- with a large planet/host mass ratio of $q \simeq 9 \times 10^{-3}$. 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 mode…
With the aim of finding microlensing binaries containing brown-dwarf (BD) companions, we investigate the microlensing survey data collected during the 2016--2018 seasons. For this purpose, we first conducted modeling of lensing events with light curves exhibiting anomaly features that are likely to be produced by binary lenses. We then sorted out BD-companion binary-lens events by applying the criterion that the companion-to-primary mass ratio is $q \lesssim 0.1$. From this procedure, we identify 6 binaries with candidate BD companions, including OGLE-2016-BLG-0890L, MOA-2017-BLG-477L, OGLE-20…
We present the analysis of the planetary microlensing event MOA-2016-BLG-319. The event light curve is characterized by a brief ($\sim 3$ days) anomaly near the peak produced by minor-image perturbations. From modeling, we find two distinct solutions that describe the observed light curve almost equally well. From the investigation of the lens-system configurations, we find that the confusion in the lensing solution is caused by the degeneracy between the two solutions resulting from the source passages on different sides of the planetary caustic. These degeneracies can be severe for major-ima…
We present the analysis of planetary microlensing event MOA-2011-BLG-291, which has a mass ratio of $q=(3.8\pm0.7)\times10^{-4}$ and a source star that is redder (or brighter) than the bulge main sequence. This event is located at a low Galactic latitude in the survey area that is currently planned for NASA's WFIRST exoplanet microlensing survey. This unusual color for a microlensed source star implies that we cannot assume that the source star is in the Galactic bulge. The favored interpretation is that the source star is a lower main sequence star at a distance of $D_S=4.9\pm1.3\,$kpc in the…
We report the discovery and the analysis of the short timescale binary-lens microlensing event, MOA-2015-BLG-337. The lens system could be a planetary system with a very low mass host, around the brown dwarf/planetary mass boundary, or a brown dwarf binary. We found two competing models that explain the observed light curves with companion/host mass ratios of q~0.01 and ~0.17, respectively. From the measurement of finite source effects in the best-fit planetary model, we find a relatively small angular Einstein radius of theta_E ~ 0.03 mas which favors a low mass lens. We conduct a Bayesian an…
We announce the discovery of a microlensing planetary system, in which a sub-Saturn planet is orbiting an ultracool dwarf host. We detect the planetary system by analyzing the short-timescale ($t_{\rm E}\sim 4.4$~days) lensing event KMT-2018-BLG-0748. The central part of the light curve exhibits asymmetry due to the negative deviations in the rising part and the positive deviations in the falling part. We find that the deviations are explained by a binary-lens model with a mass ratio between the lens components of $q\sim 2\times 10^{-3}$. The short event timescale together with the small angul…
We present the discovery of the first Neptune analog exoplanet or super-Earth with Neptune-like orbit, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune or a super-Earth and it orbits at $9\sim 14$ times the expected position of the snow-line, $a_{\rm snow}$, which is similar to Neptune's separation of $ 11\,a_{\rm snow}$ from the Sun. The planet/host-star mass ratio is $q=(3.6\pm0.7)\times 10^{-4}$ and the projected separation normalized by the Einstein radius is $s=2.39\pm0.05$. There are three degenerate physical solutions and two of these are due to a new type of degene…
We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a planetary event, the anomaly was well covered thanks to high cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio $q=(1.58\pm0.15)\times10^{-3}$. By conducting a Bayesian analysis, we estimate that the host star is an M-dwarf star with a mass of $M_{\rm L}=0.29_{-0.16}^{+0.33} \ M_{\odot}$ located at $D_{\rm L}=6.7_{-1.2}^{+1…
KMT-2016-BLG-1337L: A Saturn-mass planet orbiting within a binary system of low-mass stars
Chungbuk National University（忠北国立大学）；Korea Astronomy and Space Science Institute（韩国天文与空间科学研究所）；Massey University（梅西大学）；University of Warsaw（华沙大学）；University of Canterbury（坎特伯雷大学）；Ohio State University（俄亥俄州立大学）；University of Science and Technology（科学技术大学）
Three Saturn-mass Microlensing Planets Identified through Signals from Peripheral-caustic Perturbations
Chungbuk National University（忠北国立大学）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；Astronomical Observatory, University of Warsaw（华沙大学天文台）；Massey University（梅西大学）；University of Canterbury（坎特伯雷大学）；Ohio State University（俄亥俄州立大学）；University of Science and Technology（科学技术大学）
As a part of the ``Systematic KMTNet Planetary Anomaly Search" series, we report five new planets (namely, OGLE-2016-BLG-1635Lb, MOA-2016-BLG-532Lb, KMT-2016-BLG-0625Lb, OGLE-2016-BLG-1850Lb, and KMT-2016-BLG-1751Lb) and one planet candidate (KMT-2016-BLG-1855), which were found by searching $2016$ KMTNet prime fields. These $buried$ planets show a wide range of masses from Earth--class to Super--Jupiter--class, and are located in both the disk and the bulge. The ultimate goal of this series is to build a complete planet sample. Because our work provides a complementary sample to other planet …
Characterizing a planet detected by microlensing is hard if the planetary signal is weak or the lens-source relative trajectory is far from caustics. However, statistical analyses of planet demography must include those planets to accurately determine occurrence rates. As part of a systematic modeling effort in the context of a $>10$-year retrospective analysis of MOA's survey observations to build an extended MOA statistical sample, we analyze the light curve of the planetary microlensing event MOA-2014-BLG-472. This event provides weak constraints on the physical parameters of the lens, as a…
We report the discovery of a sub-Jovian-mass planet, OGLE-2014-BLG-0319Lb. The characteristics of this planet will be added into a future extended statistical analysis of the Microlensing Observations in Astrophysics (MOA) collaboration. The planetary anomaly of the light curve is characterized by MOA and OGLE survey observations and results in three degenerate models with different planetary mass-ratios of $q=(10.3,6.6,4.5)\times10^{-4}$, respectively. We find that the last two models require unreasonably small lens-source relative proper motions of $μ_{\rm rel}\sim1\;{\rm mas/yr}$. Consideri…
