Browsing by Author "Zhu W"

Now showing 1 - 5 of 5
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    MOA-2020-BLG-135Lb: A New Neptune-class Planet for the Extended MOA-II Exoplanet Microlens Statistical Analysis
    (IOP Publishing on behalf of the American Astronomical Society, 2022-09-01) Silva SI; Ranc C; Bennett DP; Bond IA; Zang W; Abe F; Barry R; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Muraki Y; Olmschenk G; Okamura A; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Petric A; Burdullis T; Fouqué P; Mao S; Penny MT; Zhu W; Rau G
    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 = 1.52-0.31+0.39 ´ 10-4 and separation s ≈ 1, the planet lies exactly at the break and likely peak of the exoplanet mass-ratio function derived by the Microlensing Observations in Astrophysics (MOA) Collaboration. 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 = 11.3-6.9+19.2 MÅ and a host star of mass Mhost = 0.23-0.14+0.39 M☉, located at a distance DL = 7.9-1.0+1.0 kpc. With a prior that holds that planet occurrence scales in proportion to the host-star mass, the estimated lens system properties are mplanet = 25-15+22 MÅ, Mhost = 0.53-0.32+0.42 M☉, and DL = 8.3-1.0+0.9 kpc. This planet qualifies for inclusion in the extended MOA-II exoplanet microlens sample.
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    MOA-2020-BLG-208Lb: Cool Sub-Saturn-mass Planet within Predicted Desert
    (American Astronomical Society, 2023-03) Olmschenk G; Bennett DP; Bond IA; Zang W; Jung YK; Yee JC; Bachelet E; Abe F; Barry RK; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Silva SI; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Matsubara Y; Matsumoto S; Miyazaki S; Munford B; Muraki Y; Okamura A; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Toda T; Tristram PJ; Vandorou A; Yama H; Albrow MD; Cha S-M; Chung S-J; Gould A; Han C; Hwang K-H; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge RW; Ryu Y-H; Shin I-G; Shvartzvald Y; Christie G; Cooper T; Drummond J; Green J; Hennerley S; McCormick J; Monard LAG; Natusch T; Porritt I; Tan T-G; Mao S; Maoz D; Penny MT; Zhu W; Bozza V; Cassan A; Dominik M; Hundertmark M; Jaimes RF; Kruszyńska K; Rybicki KA; Street RA; Tsapras Y; Wambsganss J; Wyrzykowski L; Zieliński P; Rau G
    We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio q=3.17-0.26+0.28×10-4, the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass mplanet=46-24+42M⊕ and a host star of mass Mhost=0.43-0.23+0.39M⊙, located at a distance DL=7.49-1.13+0.99kpc . For the second scenario, we estimate mplanet=69-34+37M⊕, Mhost=0.66-0.32+0.35M⊙, and DL=7.81-0.93+0.93kpc . The planet has a projected separation as a fraction of the Einstein ring radius s=1.3807-0.0018+0.0018 . As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models
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    OGLE-2015-BLG-0845L: a low-mass M dwarf from the microlensing parallax and xallarap effects
    (Oxford University Press, 2024-09-01) Hu Z; Zhu W; Gould A; Udalski A; Sumi T; Chen P; Calchi Novati S; Yee JC; Beichman CA; Bryden G; Carey S; Fausnaugh M; Scott Gaudi B; Henderson CB; Shvartzvald Y; Wibking B; Mroz P; Skowron J; Poleski R; Szymanski MK; Soszynski I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Rybicki KA; Iwanek P; Wrona M; Gromadzki MG; Abe F; Barry R; Bennett DP; Bhattacharya A; Bond IA; Fujii H; Fukui A; Hamada R; Hirao Y; Silva SI; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K
    We present the analysis of the microlensing event OGLE-2015-BLG-0845, which was affected by both the microlensing parallax and xallarap effects. The former was detected via the simultaneous observations from the ground and Spitzer, and the latter was caused by the orbital motion of the source star in a relatively close binary. The combination of these two effects led to a mass measurement of the lens object, revealing a low-mass (0.14 ± 0.05 M) M dwarf at the bulge distance (7.6 ± 1.0 kpc). The source binary consists of a late F-type subgiant and a K-type dwarf of ∼ 1.2 and ∼ 0.9M, respectively, and the orbital period is 70 ± 10 d. OGLE-2015-BLG-0845 is the first single-lens event in which the lens mass is measured via the binarity of the source. Given the abundance of binary systems as potential microlensing sources, the xallarap effect may not be a rare phenomenon. Our work thus highlights the application of the xallarap effect in the mass determination of microlenses, and the same method can be used to identify isolated dark lenses.
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    Systematic KMTNet Planetary Anomaly Search. II. Six New q < 2 × 10−4 Mass-ratio Planets
    (IOP Publishing on behalf of the American Astronomical Society, 2022-02-01) Hwang K-H; Zang W; Gould A; Udalski A; Bond IA; Yang H; Mao S; Albrow MD; Chung S-J; Han C; Jung YK; Ryu Y-H; Shin I-G; Shvartzvald Y; Yee JC; Cha S-M; Kim D-J; Kim H-W; Kim S-L; Lee C-U; Lee D-J; Lee Y; Park B-G; Pogge R; Mróz P; Poleski R; Skowron J; Szymański MK; Soszyński I; Pietrukowicz P; Kozłowski S; Ulaczyk K; Rybicki KA; Iwanek P; Wrona M; Gromadzki M; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Munford B; Matsubara Y; Miyazaki S; Muraki Y; Olmschenk G; Ranc C; Rattenbury NJ; Satoh YK; Shoji H; Silva SI; Sumi T; Suzuki D; Tristram PJ; Yonehara A; Zhang X; Zhu W; Penny MT; Fouqué P
    We apply the automated AnomalyFinder algorithm of Paper I to 2018-2019 light curves from the ≃13 deg2 covered by the six KMTNet prime fields, with cadences Γ ≥ 2 hr-1. We find a total of 11 planets with mass ratios q < 2 × 10-4, including 6 newly discovered planets, 1 planet that was reported in Paper I, and recovery of 4 previously discovered planets. One of the new planets, OGLE-2018-BLG-0977Lb, is in a planetary caustic event, while the other five (OGLE-2018-BLG-0506Lb, OGLE-2018-BLG-0516Lb, OGLE-2019-BLG-1492Lb, KMT-2019-BLG-0253, and KMT-2019-BLG-0953) are revealed by a "dip"in the light curve as the source crosses the host-planet axis on the opposite side of the planet. These subtle signals were missed in previous by-eye searches. The planet-host separations (scaled to the Einstein radius), s, and planet-host mass ratios, q, are, respectively, (s, q × 105) = (0.88, 4.1), (0.96 ± 0.10, 8.3), (0.94 ± 0.07, 13), (0.97 ± 0.07, 18), (0.97 ± 0.04, 4.1), and (0.74, 18), where the "± "indicates a discrete degeneracy. The 11 planets are spread out over the range . Together with the two planets previously reported with q ∼ 10-5 from the 2018-2019 nonprime KMT fields, this result suggests that planets toward the bottom of this mass-ratio range may be more common than previously believed.
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    Systematic reanalysis of KMTNet microlensing events, paper I: Updates of the photometry pipeline and a new planet candidate
    (Oxford University Press on behalf of the Royal Astronomical Society., 2024-02-01) Yang H; Yee JC; Hwang K-H; Qian Q; Bond IA; Gould A; Hu Z; Zhang J; Mao S; Zhu W; Albrow MD; Chung S-J; Kim S-L; Park B-G; Han C; Jung YK; Ryu Y-H; Shin I-G; Shvartzvald Y; Cha S-M; Kim D-J; Kim H-W; Lee C-U; Lee D-J; Lee Y; Pogge RW; Zang W; Abe F; Barry R; Bennett DP; Bhattacharya A; Donachie M; Fujii H; Fukui A; Hirao Y; Itow Y; Kirikawa R; Kondo I; Koshimoto N; Silva SI; Li MCA; Matsubara Y; Muraki Y; Suzuki D; Tristram PJ; Yonehara A; Ranc C; Miyazaki S; Olmschenk G; Rattenbury NJ; Satoh Y; Shoji H; Sumi T; Tanaka Y; Yamawaki T
    In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create a new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals.