Browsing by Author "Olmschenk, Greg"

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    Four microlensing giant planets detected through signals produced by minor-image perturbations
    (2024) Han, Cheongho; Bond, Ian A.; Lee, Chung-Uk; Gould, Andrew; Albrow, Michael D.; Chung, Sun-Ju; Hwang, Kyu-Ha; Jung, Youn Kil; Ryu, Yoon-Hyun; Shvartzvald, Yossi; Shin, In-Gu; Yee, Jennifer C.; Yang, Hongjing; Zang, Weicheng; Cha, Sang-Mok; Kim, Doeon; Kim, Dong-Jin; Kim, Seung-Lee; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W.; Abe, Fumio; Bando, Ken; Barry, Richard; Bennett, David P.; Bhattacharya, Aparna; Fujii, Hirosame; Fukui, Akihiko; Hamada, Ryusei; Hamada, Shunya; Hamasaki, Naoto; Hirao, Yuki; Ishitani Silva, Stela; Itow, Yoshitaka; Kirikawa, Rintaro; Koshimoto, Naoki; Matsubara, Yutaka; Miyazaki, Shota; Muraki, Yasushi; Nagai, Tutumi; Nunota, Kansuke; Olmschenk, Greg; Ranc, Clement; Rattenbury, Nicholas J.; Satoh, Yuki; Sumi, Takahiro; Suzuki, Daisuke; Tomoyoshi, Mio; Tristram, Paul J.; Vandorou, Aikaterini; Yama, Hibiki; Yamashita, Kansuke; Bachelet, Etienne; Rota, Paolo; Bozza, Valerio; Zielinski, Pawel; Street, Rachel A.; Tsapras, Yiannis; Hundertmark, Markus; Wambsganss, Joachim; Wyrzykowski, Lukasz; Figuera Jaimes, Roberto; Cassan, Arnaud; Dominik, Martin; Rybicki, Krzysztof A.; Rabus, Markus
    Aims. We investigated the nature of the anomalies appearing in four microlensing events KMT-2020-BLG-0757, KMT-2022-BLG-0732, KMT-2022-BLG-1787, and KMT-2022-BLG-1852. The light curves of these events commonly exhibit initial bumps followed by subsequent troughs that extend across a substantial portion of the light curves. Methods. We performed thorough modeling of the anomalies to elucidate their characteristics. Despite their prolonged durations, which differ from the usual brief anomalies observed in typical planetary events, our analysis revealed that each anomaly in these events originated from a planetary companion located within the Einstein ring of the primary star. It was found that the initial bump arouse when the source star crossed one of the planetary caustics, while the subsequent trough feature occurred as the source traversed the region of minor image perturbations lying between the pair of planetary caustics. Results. The estimated masses of the host and planet, their mass ratios, and the distance to the discovered planetary systems are (M-host/M-circle dot, M-planet/M-J, q/10(-3), D-L/kpc) = (0.58(-0.30)(+0.33), 10.71(-5.61)(+6.17), 17.61 +/- 2.25, 6.67(-1.30)(+0.93)) for KMT-2020-BLG-0757, (0.53(-0.31)(+0.31), 1.12(-0.65)(+0.65), 2.01 +/- 0.07, 6.66(-1.84)(+1.19)) for KMT-2022-BLG-0732, (0.42(-0.23)(+0.32), 6.64(-3.64)(+4.98), 15.07 +/- 0.86, 7.55(-1.30)(+0.89)) for KMT-2022-BLG-1787, and (0.32(-0.19)(+0.34), 4.98(-2.94)(+5.42), 8.74 +/- 0.49, 6.27(-1.15)(+0.90)) for KMT-2022-BLG-1852. These parameters indicate that all the planets are giants with masses exceeding the mass of Jupiter in our solar system and the hosts are low-mass stars with masses substantially less massive than the Sun.
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    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
    (2023) Satoh, Yuki; Koshimoto, Naoki; Bennett, David A.; Sumi, Takahiro; Rattenbury, Nicholas; Suzuki, Daisuke; Miyazaki, Shota; Bond, Ian; Udalski, Andrzej; Gould, Andrew; Bozza, Valerio; Dominik, Martin; Hirao, Yuki; Kondo, Iona; Kirikawa, Rintaro; Hamada, Ryusei; Abe, Fumio; Barry, Richard; Bhattacharya, Aparna; Fujii, Hirosane; Fukui, Akihiko; Fujita, Katsuki; Ikeno, Tomoya; Ishitani Silva, Stela; Itow, Yoshitaka; Matsubara, Yutaka; Matsumoto, Sho; Muraki, Yasushi; Niwa, Kosuke; Okamura, Arisa J.; Olmschenk, Greg; Ranc, Clement; Toda, Taiga; Tomoyoshi, Mio; Tristram, Paul; Vandorou, Aikaterini; Yama, Hibiki; Yamashita, Kansuke; Mroz, Przemek; Poleski, Radoslaw; Skowron, Jan; Szymanski, Michal K.; Poleski, Radek A.; Soszynski, Igor; Pietrukowicz, Pawel; Kozlowski, Szymon; Ulaczyk, Krzysztof D.; Rybicki, Krzysztof; Iwanek, Patryk; Wrona, Marcin; Gromadzki, Mariusz; Albrow, Michael; Chung, Sun-Ju; Han, Cheongho; Hwang, Kyu-Ha; Kim, Doeon; Jung, Youn Kil; Kim, Hyoun Woo C.; Ryu, Yoon-Hyun; Shin, In-Gu; Shvartzvald, Yossi; Yang, Hongjing; Yee, Jennifer; Zang, Weicheng; Cha, Sang-Mok; Kim, Dong-Jin; Kim, Seung-Lee W.; Lee, Chung-Uk G.; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard; Jorgensen, Uffe; Longa-Pena, Penelope; Sajadian, Sedighe; Skottfelt, Jesper; Snodgrass, Colin; Tregloan-Reed, Jeremy; Bach-Moller, Nanna; Burgdorf, Martin; D'Ago, Giuseppe; Haikala, Lauri; Hitchcock, James; Hundertmark, Markus; Khalouei, Elahe; Peixinho, Nuno; Rahvar, Sohrab; Southworth, John; Spyratos, Petros
    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 chi (2) values. On the other hand, by including the xallarap effect in our models, we find that binary-lens parameters such as mass ratio, q, and separation, s, cannot be constrained well. However, we also find that the parameters for the source system such as the orbital period and semimajor 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 P similar to 5 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.
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    Short-period Variables in TESS Full-frame Image Light Curves Identified via Convolutional Neural Networks
    (2024) Olmschenk, Greg; Barry, Richard K.; Silva, Stela Ishitani; Schnittman, Jeremy D.; Cieplak, Agnieszka M.; Powell, Brian P.; Kruse, Ethan; Barclay, Thomas; Solanki, Siddhant; Ortega, Bianca; Baker, John; Salinas, Mamani Yesenia Helem
    The Transiting Exoplanet Survey Satellite (TESS) mission measured light from stars in similar to 85% of the sky throughout its 2 yr primary mission, resulting in millions of TESS 30-minute-cadence light curves to analyze in the search for transiting exoplanets. To search this vast data set, we aim to provide an approach that is computationally efficient, produces accurate predictions, and minimizes the required human search effort. We present a convolutional neural network that we train to identify short-period variables. To make a prediction for a given light curve, our network requires no prior target parameters identified using other methods. Our network performs inference on a TESS 30-minute-cadence light curve in similar to 5 ms on a single GPU, enabling large-scale archival searches. We present a collection of 14,156 short-period variables identified by our network. The majority of our identified variables fall into two prominent populations, one of close-orbit main-sequence binaries and another of delta Scuti stars. Our neural network model and related code are additionally provided as open-source code for public use and extension.