Browsing by Author "Rattenbury, Nicholas"

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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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    The high optical brightness of the BlueWalker 3 satellite
    (2023) Nandakumar, Sangeetha; Eggl, Siegfried; Tregloan-Reed, Jeremy; Adam, Christian; Anderson-Baldwin, Jasmine; Bannister, Michele T.; Battle, Adam; Benkhaldoun, Zouhair; Campbell, Tanner; Colque, J. P.; Damke, Guillermo; Plauchu Frayn, Ilse; Ghachoui, Mourad; Guillén, Pedro F.; Kaeouach, Aziz Ettahar; Krantz, Harrison R.; Langbroek, Marco; Rattenbury, Nicholas; Reddy, Vishnu; Kim, Sam
    Large constellations of bright artificial satellites in low Earth orbit pose significant challenges to ground-based astronomy1. Current orbiting constellation satellites have brightnesses between apparent magnitudes 4 and 6, whereas in the near-infrared Ks band, they can reach magnitude 2 (ref. 2). Satellite operators, astronomers and other users of the night sky are working on brightness mitigation strategies3,4. Radio emissions induce further potential risk to ground-based radio telescopes that also need to be evaluated. Here we report the outcome of an international optical observation campaign of a prototype constellation satellite, AST SpaceMobile’s BlueWalker 3. BlueWalker 3 features a 64.3 m2 phased-array antenna as well as a launch vehicle adaptor (LVA)5. The peak brightness of the satellite reached an apparent magnitude of 0.4. This made the new satellite one of the brightest objects in the night sky. Additionally, the LVA reached an apparent V-band magnitude of 5.5, four times brighter than the current International Astronomical Union recommendation of magnitude 7 (refs. 3,6); it jettisoned on 10 November 2022 (Universal Time), and its orbital ephemeris was not publicly released until 4 days later. The expected build-out of constellations with hundreds of thousands of new bright objects1 will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes.