The radiation emitted by GP Andromedae is a typical stellar blackbody with absorption lines from various elements, which gives to the star a spectral type A2pSrCrEu, meaning that unusually strong lines of strontium, chromium and europium can be observed.[3] GP Andromedae is thus classified as an Ap star. The intensity and profile of the spectral lines varies within a cycle with the same period as the brightness variations.[8]
Photometric and spectral variability of GR Andromedae is typical of a star with a strong and variable magnetic field. This way, the 518.2 days periodicity can be identified as the rotation period of the star.[8] It's among the slowest rotators in the category of magnetic chemically peculiar stars, with a calculated equatorial rotation rate of only 0.2 km/s.[1]
^ abcdeGR And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250 Accessed on line 2018-10-17.
^ 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.
^ abcdCatalano, F. A.; Leone, F. (June 1990). "Photoelectric photometry of chemically peculiar stars at the Catania astrophysical observatory. Observatory of HD 2453, HD 71866, HD 72968 and HD 126515". Astronomy and Astrophysics Supplement Series. 83: 491. Bibcode:1990A&AS...83..491C.
