In 1985, Jeffrey Hopkinset al. discovered that HR 9024 is a variable star, with a period of ~23.3 days.[7] It was given thevariable star designation OU Andromedae in 1986.[8] Paola Testaet al. reported that the star showedX-ray flare activity, in 2007.[9]
The spin rate of OU Andromedae is unusually high for anevolved star of this type, showing aprojected rotational velocity of 21.5 km/s. One possible explanation is that it may have engulfed a nearbygiant planet, such as ahot Jupiter, since aninfrared excess has been observed.[5] Another explanation relies on its strongmagnetic field; if OU Andromedae was anAp star during itsmain sequence stage of evolution, it could have retained both the strong magnetic field and the fast rotation of Ap stars.[4]
OU Andromedae is a bright X-ray source, due to the activity of itscorona; it's estimated that solar-like active regions cover 30% of the surface. This is another effect of the strong magnetic field, which produces an uninterrupted flaring activity that generates a large volume of hot plasma at coronal temperatures (~7.5×106K).[10]
^abcdBorisova, A.; Aurière, M.; Petit, P.; Konstantinova-Antova, R.; Charbonnel, C.; Drake, N. A. (June 2016). "The different origins of magnetic fields and activity in the Hertzsprung gap stars, OU Andromedae and 31 Comae".Astronomy & Astrophysics.591: 15.arXiv:1604.07647.Bibcode:2016A&A...591A..57B.doi:10.1051/0004-6361/201526726.S2CID55676875. A57.
^abcCutri, 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.
