The two stars share a mildly eccentric orbit with a semimajor axis of 16.725″ and a period of 975 years. Their separation has closed from 21.1″ when they were discovered by F. G. W. Struve in 1821 to 16.9″ in 2019. Struve also documented two much fainter stars about 3′ from the two red dwarfs.[11]
ADS 7251 A is 0.06 magnitudes (six percent) brighter than ADS 7251 B. A catalogue of MK spectral classes lists both stars as secondary standards, with ADS 7251 A being class M0V and ADS 7251 B being class K7V, noted as being unusual in the brighter star having a later spectral type.[5] Other publications have described the stars as being both K7V, both M0V, or the primary being K7V and the secondary M0V.[12][10]
Planetary system
ADS 7251 B, also known as Gliese 338 B or HD 79211, is orbited by one known planet discovered in 2020 by radial velocity. Though described as a super-Earth by its discovery paper, it is closer in mass to Uranus.[10] An independent confirmation of the planet was published in 2022.[13]
The ADS 7251 B (Gliese 338 B) planetary system[13]
^ abcdefCutri, 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.
^ abBobylev, V. V.; Goncharov, G. A.; Bajkova, A. T. (2007). "VizieR Online Data Catalog: Orion Spiral Arm CAtalogue (OSACA) (Bobylev+, 2006)". VizieR On-line Data Catalog. Bibcode:2007yCat..90830821B.
^Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S.