CY Boötis
star in the constellation Boötes
CY Boötis (Flamsteed: 101 Virginis) is a red giant variable star in the Boötes constellation, currently on the asymptotic giant branch.
Its apparent magnitude ranges from 5.74 to 5.9, making it faintly visible to the naked eye under good observing conditions. It was originally catalogued as 101 Virginis by Flamsteed due to an error in the position. John R. Percy found it to be "marginally variable" in 1993. When it was confirmed as a variable star, it was actually within the border of the constellation Boötes and given its name.
The variability is not strongly defined but a primary period of 23 days and a secondary period of 340 days have been reported.
CY Boo is listed in the Hipparcos catalogue as a "problem binary", a star which was suspected of being multiple but for which the Hipparcos observations did not give a satisfactory solution. Further observations have always shown it to be single.
Begin with the source’s own compact description: “CY Boötis” is star in the constellation Boötes. The dossier treats that line as a proposition to test through Boötis, star and constellation, not as a finished interpretation.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Aug 23, 2026. The linked authority identifier is Q4546336. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1993.
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This entry incorporates text from “CY Boötis” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.