Omicron Persei (ο Persei, abbreviated Omicron Per, ο Per) is a triple star system in the constellation of Perseus. From parallax measurements taken during the Hipparcos mission it is approximately 1,100 light-years (330 parsecs) from the Sun.
The system consists of a spectroscopic binary pair designated Omicron Persei A and a third companion Omicron Persei B.[9] A's two components are themselves designated Omicron Persei Aa (officially named Atik /ˈeɪtɪk/, the traditional name of the system)[10][11] and Ab.
Etymology
ο Persei (Latinised to Omicron Persei) is the system's Bayer designation. The designations of the two constituents as Omicron Persei A and B, and those of A's components - Omicron Persei Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[12]
It bore the traditional name Atik (also Ati, Al Atik), Arabic for "the shoulder". Some sources attribute the name Atik to the nearby, brighter star Zeta Persei.[13][14] 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 decided to attribute proper names to individual stars rather than entire multiple systems.[16] It approved the name Atik for the component Omicron Persei A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[11]
In Chinese, 卷舌 (Juǎn Shé), meaning Rolled Tongue, refers to an asterism consisting of Omicron Persei, Nu Persei, Epsilon Persei, Xi Persei, Zeta Persei and 40 Persei.[17] Consequently, the Chinese name for Omicron Persei itself is 卷舌五 (Juǎn Shé wu), "the Fifth Star of Rolled Tongue".[18]
Properties
Omicron Persei A is a spectroscopic binary consisting of a spectral type B1 giant and a type B2 dwarf orbiting each other every 4.4 days. The orbit is near-circular although its inclination is not precisely known. The two stars are separated by approximately 33 R☉, the exact value depending on the inclination. The primary is approximately one magnitude brighter than the secondary at visual wavelengths.[5] The binary pair forms a rotating ellipsoidal variable star, which varies in brightness from visual magnitude 3.79 to 3.88 during the orbital period.[20]
Omicron Persei lies just north of the open cluster IC 348, but is not catalogued as a member. Both IC 348 and Omicron Persei belong to the Perseus OB2 association.[21]