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)[1]
FO Aquarii is an intermediate polar[4]star system in the constellationAquarius. The white dwarf and companion star orbit each other with a period of approximately 4.85 hours.[5] 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.[6] Prior to 2016, the system's long-term optical brightness varied between apparent magnitude 12.7 and 14.2,[7] 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.[8]
The variable nature of FO Aquarii was discovered in 1983 by Joseph Patterson and João Evangelista Steiner.[6] It was given its variable star designation in 1985.[9]
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.
^ abcdefgCutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
^Samus’, N. N.; Goranskii, V. P.; Durlevich, O. V.; Zharova, A. V.; Kazarovets, E. V.; Kireeva, N. N.; Pastukhova, E. N.; Williams, D. B.; Hazen, M. L. (2003). "An electronic version of the second volume of the General Catalogue of Variable Stars with improved coordinates". Astronomy Letters. 29 (7): 468–479. Bibcode:2003AstL...29..468S. doi:10.1134/1.1589864. S2CID16299532.