37 research outputs found

    MOA-2020-BLG-135Lb: A New Neptune-class Planet for the Extended MOA-II Exoplanet Microlens Statistical Analysis

    Full text link
    We report the light-curve analysis for the event MOA-2020-BLG-135, which leads to the discovery of a new Neptune-class planet, MOA-2020-BLG-135Lb. With a derived mass ratio of q=1.520.31+0.39×104q=1.52_{-0.31}^{+0.39} \times 10^{-4} and separation s1s\approx1, the planet lies exactly at the break and likely peak of the exoplanet mass-ratio function derived by the MOA collaboration (Suzuki et al. 2016). We estimate the properties of the lens system based on a Galactic model and considering two different Bayesian priors: one assuming that all stars have an equal planet-hosting probability and the other that planets are more likely to orbit more massive stars. With a uniform host mass prior, we predict that the lens system is likely to be a planet of mass mplanet=11.36.9+19.2Mm_\mathrm{planet}=11.3_{-6.9}^{+19.2} M_\oplus and a host star of mass Mhost=0.230.14+0.39MM_\mathrm{host}=0.23_{-0.14}^{+0.39} M_\odot, located at a distance DL=7.91.0+1.0  kpcD_L=7.9_{-1.0}^{+1.0}\;\mathrm{kpc}. With a prior that holds that planet occurrence scales in proportion to the host star mass, the estimated lens system properties are mplanet=2515+22Mm_\mathrm{planet}=25_{-15}^{+22} M_\oplus, Mhost=0.530.32+0.42MM_\mathrm{host}=0.53_{-0.32}^{+0.42} M_\odot, and DL=8.31.0+0.9  kpcD_L=8.3_{-1.0}^{+0.9}\; \mathrm{kpc}. This planet qualifies for inclusion in the extended MOA-II exoplanet microlens sample.Comment: 22 pages, 6 figures, 4 tables, submitted to the AAS Journal

    KMT-2021-BLG-1077L: The fifth confirmed multiplanetary system detected by microlensing

    Full text link
    The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the aim of revealing the nature of the anomaly. We test various models in combination with several interpretations. We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are 1.56×103\sim 1.56 \times 10^{-3} and 1.75×103\sim 1.75 \times 10^{-3}, which correspond to 1.6\sim 1.6 and 1.8\sim 1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. With the constraints of the event time-scale and angular Einstein radius, it is found that the host of the lens system is a low-mass star of mid-to-late M spectral type with a mass of Mh=0.140.07+0.19 MM_{\rm h} = 0.14^{+0.19}_{-0.07}~M_\odot, and it hosts two gas giant planets with masses of Mp1=0.220.12+0.31 MJM_{\rm p_1}=0.22^{+0.31}_{-0.12}~M_{\rm J} and Mp2=0.250.13+0.35 MJM_{\rm p_2}=0.25^{+0.35}_{-0.13}~M_{\rm J}. The planets lie beyond the snow line of the host with projected separations of a,p1=1.261.08+1.41 AUa_{\perp, {\rm p}_1}=1.26^{+1.41}_{-1.08}~{\rm AU} and a,p2=0.930.80+1.05 AUa_{\perp, {\rm p}_2}=0.93^{+1.05}_{-0.80}~{\rm AU}. The planetary system resides in the Galactic bulge at a distance of DL=8.241.16+1.02 kpcD_{\rm L}=8.24^{+1.02}_{-1.16}~{\rm kpc}. The lens of the event is the fifth confirmed multiplanetary system detected by microlensing following OGLE-2006-BLG-109L, OGLE-2012-BLG-0026L, OGLE-2018-BLG-1011L, and OGLE-2019-BLG-0468L.Comment: 9 pages, 8 figure

    KMT-2021-BLG-1150Lb: Microlensing planet detected through a densely covered planetary-caustic signal

    Full text link
    Recently, there have been reports of various types of degeneracies in the interpretation of planetary signals induced by planetary caustics. In this work, we check whether such degeneracies persist in the case of well-covered signals by analyzing the lensing event KMT-2021-BLG-1150, for which the light curve exhibits a densely and continuously covered short-term anomaly. In order to identify degenerate solutions, we thoroughly investigate the parameter space by conducting dense grid searches for the lensing parameters. We then check the severity of the degeneracy among the identified solutions. We identify a pair of planetary solutions resulting from the well-known inner-outer degeneracy, and find that interpreting the anomaly is not subject to any degeneracy other than the inner-outer degeneracy. The measured parameters of the planet separation (normalized to the Einstein radius) and mass ratio between the lens components are (s,q)in(1.297,1.10×103)(s, q)_{\rm in}\sim (1.297, 1.10\times 10^{-3}) for the inner solution and (s,q)out(1.242,1.15×103)(s, q)_{\rm out}\sim (1.242, 1.15\times 10^{-3}) for the outer solution. According to a Bayesian estimation, the lens is a planetary system consisting of a planet with a mass Mp=0.880.36+0.38 MJM_{\rm p}=0.88^{+0.38}_{-0.36}~M_{\rm J} and its host with a mass Mh=0.730.30+0.32 MM_{\rm h}=0.73^{+0.32}_{-0.30}~M_\odot lying toward the Galactic center at a distance DL=3.81.2+1.3D_{\rm L} =3.8^{+1.3}_{-1.2}~kpc. By conducting analyses using mock data sets prepared to mimic those obtained with data gaps and under various observational cadences, it is found that gaps in data can result in various degenerate solutions, while the observational cadence does not pose a serious degeneracy problem as long as the anomaly feature can be delineated.Comment: 9 pages, 8 figure

    Mass Production of 2021 KMTNet Microlensing Planets III: Analysis of Three Giant Planets

    Full text link
    We present the analysis of three more planets from the KMTNet 2021 microlensing season. KMT-2021-BLG-0119Lb is a 6MJup\sim 6\, M_{\rm Jup} planet orbiting an early M-dwarf or a K-dwarf, KMT-2021-BLG-0192Lb is a 2MNep\sim 2\, M_{\rm Nep} planet orbiting an M-dwarf, and KMT-2021-BLG-0192Lb is a 1.25MNep\sim 1.25\, M_{\rm Nep} planet orbiting a very--low-mass M dwarf or a brown dwarf. These by-eye planet detections provide an important comparison sample to the sample selected with the AnomalyFinder algorithm, and in particular, KMT-2021-BLG-2294, is a case of a planet detected by-eye but not by-algorithm. KMT-2021-BLG-2294Lb is part of a population of microlensing planets around very-low-mass host stars that spans the full range of planet masses, in contrast to the planet population at 0.1\lesssim 0.1\, au, which shows a strong preference for small planets.Comment: 17 pages, 12 figures, 7 tables. Accept for publication in The Astronomical Journa

    KMT-2022-BLG-0440Lb: A New q<104q < 10^{-4} Microlensing Planet with the Central-Resonant Caustic Degeneracy Broken

    Full text link
    We present the observations and analysis of a high-magnification microlensing planetary event, KMT-2022-BLG-0440, for which the weak and short-lived planetary signal was covered by both the KMTNet survey and follow-up observations. The binary-lens models with a central caustic provide the best fits, with a planet/host mass ratio, q=0.75q = 0.75--1.00×1041.00 \times 10^{-4} at 1σ1\sigma. The binary-lens models with a resonant caustic and a brown-dwarf mass ratio are both excluded by Δχ2>70\Delta\chi^2 > 70. The binary-source model can fit the anomaly well but is rejected by the ``color argument'' on the second source. From Bayesian analyses, it is estimated that the host star is likely a K or M dwarf located in the Galactic disk, the planet probably has a Neptune-mass, and the projected planet-host separation is 1.90.7+0.61.9^{+0.6}_{-0.7} or 4.61.7+1.44.6^{+1.4}_{-1.7} au, subject to the close/wide degeneracy. This is the third q<104q < 10^{-4} planet from a high-magnification planetary signal (A65A \gtrsim 65). Together with another such planet, KMT-2021-BLG-0171Lb, the ongoing follow-up program for the KMTNet high-magnification events has demonstrated its ability in detecting high-magnification planetary signals for q<104q < 10^{-4} planets, which are challenging for the current microlensing surveys.Comment: MNRAS accepte

    Systematic KMTNet Planetary Anomaly Search. V. Complete Sample of 2018 Prime-Field

    Full text link
    We complete the analysis of all 2018 prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 10 previously unpublished events with clear planetary solutions, 8 are either unambiguously planetary or are very likely to be planetary in nature: OGLE-2018-BLG-1126, KMT-2018-BLG-2004, OGLE-2018-BLG-1647, OGLE-2018-BLG-1367, OGLE-2018-BLG-1544, OGLE-2018-BLG-0932, OGLE-2018-BLG-1212, and KMT-2018-BLG-2718. Combined with the 4 previously published new AnomalyFinder events and 12 previously published (or in preparation) planets that were discovered by eye, thismakes a total of 24 2018 prime-field planets discovered or recovered by AnomalyFinder. Together with a paper in preparation on 2018 sub-prime planets, this work lays the basis for the first statistical analysis of the planet mass-ratio function based on planets identified in KMTNet data. By systematically applying the heuristic analysis of Hwang et al. (2022) to each event, we identify the small modification in their formalism that is needed to unify the so-called close/wide and inner/outer degeneracies, as conjectured byComment: 22 pages, 14 tables, 15 figure

    KMT-2023-BLG-1431Lb: A New q<104q < 10^{-4} Microlensing Planet from a Subtle Signature

    Full text link
    The current studies of microlensing planets are limited by small number statistics. Follow-up observations of high-magnification microlensing events can efficiently form a statistical planetary sample. Since 2020, the Korea Microlensing Telescope Network (KMTNet) and the Las Cumbres Observatory (LCO) global network have been conducting a follow-up program for high-magnification KMTNet events. Here, we report the detection and analysis of a microlensing planetary event, KMT-2023-BLG-1431, for which the subtle (0.05 magnitude) and short-lived (5 hours) planetary signature was characterized by the follow-up from KMTNet and LCO. A binary-lens single-source (2L1S) analysis reveals a planet/host mass ratio of q=(0.72±0.07)×104q = (0.72 \pm 0.07) \times 10^{-4}, and the single-lens binary-source (1L2S) model is excluded by Δχ2=80\Delta\chi^2 = 80. A Bayesian analysis using a Galactic model yields estimates of the host star mass of Mhost=0.570.29+0.33 MM_{\rm host} = 0.57^{+0.33}_{-0.29}~M_\odot, the planetary mass of Mplanet=13.56.8+8.1 MM_{\rm planet} = 13.5_{-6.8}^{+8.1}~M_{\oplus}, and the lens distance of DL=6.91.7+0.8D_{\rm L} = 6.9_{-1.7}^{+0.8} kpc. The projected planet-host separation of a=2.30.5+0.5a_\perp = 2.3_{-0.5}^{+0.5} au or a=3.20.8+0.7a_\perp = 3.2_{-0.8}^{+0.7}, subject to the close/wide degeneracy. We also find that without the follow-up data, the survey-only data cannot break the degeneracy of central/resonant caustics and the degeneracy of 2L1S/1L2S models, showing the importance of follow-up observations for current microlensing surveys.Comment: PASP submitted. arXiv admin note: text overlap with arXiv:2301.0677

    MOA-2019-BLG-008Lb : a new microlensing detection of an object at the planet/brown dwarf boundary

    Get PDF
    Funding: R.A.S. and E.B. gratefully acknowledge support from NASA grant 80NSSC19K0291. Y.T. and J.W. acknowledge the support of DFG priority program SPP 1992 “Exploring the Diversity of Extrasolar Planets” (WA 1047/11-1). K.H. acknowledges support from STFC grant ST/R000824/1. J.C.Y. acknowledges support from NSF grant No. AST-2108414. Work by C.H. was supported by the grants of the National Research Foundation of Korea (2019R1A2C2085965 and 2020R1A4A2002885). D.M.B. acknowledges the support of the NYU Abu Dhabi Research Enhancement Fund under grant RE124. This work was partly supported by the National Science Foundation of China (grant Nos. 11333003, 11390372, and 11761131004 to S.M.). The MOA project is supported by JSPS KAKENHI grant Nos. JSPS24253004, JSPS26247023, JSPS23340064, JSPS15H00781, JP16H06287, and JP17H02871.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 θE cannot be measured from the light curve alone. However, the large event duration, tE ∼ 80 days, allows a precise measurement of the microlensing parallax πE. In addition to the constraints on the angular radius θ* and the apparent brightness Is of the source, we employ the Besançon and GalMod galactic models to estimate the physical properties of the lens. We find excellent agreement between the predictions of the two galactic models: the companion is likely a resident of the brown dwarf desert with a mass Mp ∼ 30 MJup, and the host is a main-sequence dwarf star. The lens lies along the line of sight to the Galactic bulge, at a distance of ≤4 kpc. We estimate that in about 10 yr the lens and source will be separated by ∼55 mas, and it will be possible to confirm the exact nature of the lensing system by using high-resolution imaging from ground- or space-based observatories.Publisher PDFPeer reviewe

    A地区の自主防災力を高める保健師の支援

    Get PDF
    A地区における防災に関するニーズをもとに開催した防災講習会が住民の意識に与える影響および自主防災力を高めるための保健師の支援について検討した。地域の組織・団体へのインタビュー調査やA地区住民に対するアンケー結果をもとに、ニーズを反映した講習会を開催し、開催後にアンケートを実施した。各地域の組織・団体は「自主防災組織の発展」、「市や消防団との連携体制」を望んでいた。また、住民のニーズや防災講習会をとおして、①平均自立期間延伸のための取り組み、②住民組織間の連携の強化、③人材発掘、④ニーズの把握、⑤継続的かつ体験型の防災活動の実施等の保健師の支援が必要といえた

    OGLE-2019-BLG-0825: Constraints on the Source System and Effect on Binary-lens Parameters arising from a Five Day Xallarap Effect in a Candidate Planetary Microlensing Event

    Full text link
    We present an analysis of microlensing event OGLE-2019-BLG-0825. This event was identified as a planetary candidate by preliminary modeling. We find that significant residuals from the best-fit static binary-lens model exist and a xallarap effect can fit the residuals very well and significantly improves χ2\chi^2 values. On the other hand, by including the xallarap effect in our models, we find that binary-lens parameters like mass-ratio, qq, and separation, ss, cannot be constrained well. However, we also find that the parameters for the source system like the orbital period and semi major axis are consistent between all the models we analyzed. We therefore constrain the properties of the source system better than the properties of the lens system. The source system comprises a G-type main-sequence star orbited by a brown dwarf with a period of P5P\sim5 days. This analysis is the first to demonstrate that the xallarap effect does affect binary-lens parameters in planetary events. It would not be common for the presence or absence of the xallarap effect to affect lens parameters in events with long orbital periods of the source system or events with transits to caustics, but in other cases, such as this event, the xallarap effect can affect binary-lens parameters.Comment: 19 pages, 7 figures, 6 tables. Accepted by A
    corecore