HD 224801, also known asCG Andromedae, is anAlpha2 Canum Venaticorum variablestar in the constellationAndromeda. Located approximately 188 parsecs (610 ly) away, the star varies betweenapparent magnitudes 6.32 and 6.42 over a period of approximately 3.74 days.
CG Andromedae is also a chemically peculiar star with a strong magnetic field, orAp star, with aspectral type A0IIspSiSrHg. This means that it's abright giant star that shows narrowabsorption lines and unusual strong lines ofsilicium,strontium andmercury.Calcium andmanganese lines are weaker than expected instead.[4] Other sources report that the stronger lines are ofsilicium andeuropium, thus giving a spectral classification B9pSiEu, which has just a slightly different temperature for theblackbody emission in addition to the different lines.[3]
CG Andromedae's variability was detected in 1951, and announced by Sanford S. Provin in 1953.[13]
Like inAlpha2 Canum Venaticorum variable stars, CG Andromedae shows a variation of luminosity and one in the strength of spectral lines with the same period of approximately 3.74 days.[8] It is thought that this is caused by an inhomogeneous distribution of elements on the surface of the star, which cause an inhomogeneous surface brightness.
A shorter period, slightly longer than 2 hours, with an amplitude of 0.011 magnitudes has been observed in thelight curve of CG Andromedae; however, with a temperature of 11,000K, it lies outside the instability strip of theHR diagram whererapidly oscillating Ap stars are located.Magnetohydrodynamic waves propagating in the star could explain the observed variability.[4]
^abCG And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al.,CDS IDII/250 Accessed on line 2018-10-17.
^abcHøg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars".Astronomy & Astrophysics.355:L27 –L30.Bibcode:2000A&A...355L..27H.
^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.
