Xi Cephei


Xi Cephei is a multiple star system in the constellation of Cepheus. It is approximately 102 light-years from Earth and has an apparent magnitude for all the components combined of 4.29.
It consists of a binary star, designated Xi Cephei A, together with a more distant companion, Xi Cephei B. A's two components are themselves designated Xi Cephei Aa and Ab.

Nomenclature

ξ Cephei is the system's Bayer designation. The designations of the three constituents as ξ Cephei A, B and C, and those of A's components - ξ Cephei Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog for multiple star systems, and adopted by the International Astronomical Union.
Xi Cephei bore the traditional names Kurhah, Alkirdah or Al Kirduh, the name coming from Qazvini who gave Al Ḳurḥaḥ, an Arabic word Ideler translated as a white spot, or blaze, in the face of a horse. Allen indicates that Ideler felt this was not a proper name for a star, and suggested the name Al Ḳirdah. In 2016, the International Astronomical Union organized a Working Group on Star Names to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Kurhah for the component Xi Cephei Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, 天鈎, meaning Celestial Hook, refers to an asterism consisting of Xi Cephei, 4 Cephei, HD 194298, Eta Cephei, Theta Cephei, Alpha Cephei, 26 Cephei, Iota Cephei and Omicron Cephei. Consequently, the Chinese name for Xi Cephei itself is 天鈎六.

Properties

Xi Cephei A is a double-lined spectroscopic binary system with an orbital period of 820 days and an eccentricity of 0.5. The primary, component Aa, is a chemically peculiar Am star with an apparent magnitude of +4.61. The spectroscopic secondary, component Ab, is an F-type star.
Eight arcseconds away from Xi Cephei A, Xi Cephei B is a 6th-magnitude main sequence star.
Xi Cephei C is a 13th magnitude star nearly two arcminutes away. It has a small parallax and is an unrelated background star only accidentally in line with Xi Cephei.