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Star in the constellation Aquarius
FO Aquarii
The visual bandlight curve of FO Aquarii. The main plot shows the dimming which occurred in 2016, and the inset plot shows the short-term variation that occurs during an orbital period. Adapted from Littlefield et al. (2016)
FO Aquarii is an intermediate polarstar system in the constellationAquarius. The white dwarf and companion star orbit each other with a period of approximately 4.85 hours. The system is famous for a very strong optical pulsation which occurs every 20.9 minutes, corresponding with the rotational period of the accreting white dwarf. Prior to 2016, the system's long-term optical brightness varied between apparent magnitude 12.7 and 14.2, but in early 2016, it faded to magnitude 15.8 and thereafter began a slow recovery to its normal brightness, behavior which is indicative of a temporary dropoff in the mass-transfer rate between the two stars.
The variable nature of FO Aquarii was discovered in 1983 by Joseph Patterson and João Evangelista Steiner. It was given its variable star designation in 1985.
References
Littlefield, Colin; Garnavich, Peter; Kennedy, Mark R.; Aadland, Erin; Terndrup, Donald M.; Calhoun, Grace V.; Callanan, Paul; Abe, Lyu; Bendjoya, Philippe; Rivet, Jean-Pierre; Vernet, David; Devogèle, Maxime; Shappee, Benjamin; Holoien, Thomas; Heras, Teófilo Arranz; Bonnardeau, Michel; Cook, Michael; Coulter, Daniel; Debackère, André; Dvorak, Shawn; Foster, James R.; Goff, William; Hambsch, Franz-Josef; Harris, Barbara; Myers, Gordon; Nelson, Peter; Popov, Velimir; Solomon, Rob; Stein, William L.; Stone, Geoff; Vietje, Brad (December 2016). "Return of the King: Time-Series Photometry of FO Aquarii's Initial Recovery from its Unprecedented 2016 Low State". The Astrophysical Journal. 833 (1): 93. arXiv:1609.01026. Bibcode:2016ApJ...833...93L. doi:10.3847/1538-4357/833/1/93. S2CID54662277.
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