Delta Cassiopeiae is the primary or 'A' component of a multiple star system designated WDS J01258+6014. Delta Cassiopeiae's two components are therefore designated WDS J01258+6014 Aa and Ab. Aa is officially named Ruchbah/ˈrʌkbə/, the traditional name for the system.[12][13]
It also bore the traditional names Ruchbah and Ksora; the former deriving from the Arabic word ركبة rukbah meaning "knee",[9] and the latter appeared in a 1951 publication, Atlas Coeli (Skalnate Pleso Atlas of the Heavens) by Czech astronomer Antonín Bečvář. Professor Paul Kunitzch has been unable to find any clues as to the origin of the name.[14] The star Alpha Sagittarii also bore the traditional name Ruchbah (as well as Rukbat). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN approved the name Ruchbah for the component WDS J01258+6014 Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names (Alpha Sagittarii's primary was given the name Rukbat).[13]
Delta Cassiopeiae is a possible eclipsing binary star system consisting of a pair of stars that orbit about each other over a period of 759 days.[18][19] The combined apparent visual magnitude of the two stars is 2.68, making it readily observable with the naked eye. Eclipses have been reported with a period of 759 days,[18] when the brightness drops by 0.07 magnitudes.[4] Modern studies have shown no brightness variations greater than 0.01 magnitudes.[20]
The primary member of the system (WDS J01258+6014 Aa) has a stellar classification of A5 IV, with the luminosity class of IV indicating that it has exhausted the hydrogen at its core and has begun to evolve through the subgiant phase into a giant star. It is calculated that it is 4% beyond the end of its main sequence lifetime,[7] with an age of about 600 million years.[8] It has expanded to about 3.9 times the Sun's radius.[8]
Anexcess infrared emission has been observed at a wavelength of 60 μm, which suggests the presence of a circumstellar debris disk. This emission can be characterized by heat radiated from dust at a temperature of 85 K, which corresponds to an orbital radius of 88 Astronomical Units, or 88 times the distance of the Earth from the Sun.[8] For comparison, the region of the remote Kuiper belt in the Solar System extends from 30–50 AU.
^ abcJohnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
^Gray, R. O.; Garrison, R. F. (1989), "The late A-type stars - Refined MK classification, confrontation with Stromgren photometry, and the effects of rotation", Astrophysical Journal Supplement Series, 70: 623, Bibcode:1989ApJS...70..623G, doi:10.1086/191349
^ abKukarkin, B. V.; et al. (1971), "General Catalogue of Variable Stars", General Catalogue of Variable Stars (3rd ed.), Bibcode:1971GCVS3.C......0K
^Kunitzch, Paul; Smart, Tim (2006) [1986], A Dictionary of Modern Star Names: A Short Guide to 254 Star Names and Their Derivations, Cambridge, Massachusetts: Sky Publishing Corporation, p. 62, ISBN978-1-931559-44-7
