Xi Cephei

Xi Cephei (ξ Cephei, abbreviated Xi Cep, ξ Cep) is a multiple star system in the constellation of Cepheus. It is approximately 86 light-years from Earth.^[6]

ξ Cephei

Location of ξ Cephei (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Cepheus
Right ascension	22h 03m 47.455s[1]
Declination	+64° 37′ 40.71″[1]
Apparent magnitude (V)	4.2[2] (4.45 + 4.60[3])
Characteristics
ξ Cephei A
Spectral type	kA2.5hF2mF2(IV)[4]
ξ Cephei B
Spectral type	F8V[5]
Astrometry
Proper motion (μ)	RA: 215.46±1.14[1] mas/yr Dec.: 91.06±0.97[1] mas/yr
Parallax (π)	38.10 ± 2.81 mas[6]
Distance	86 ± 6 ly (26 ± 2 pc)
Absolute magnitude (MV)	+1.79[7]
Orbit[8]
Period (P)	810.9 d
Eccentricity (e)	0.46
Periastron epoch (T)	2438529.8 JD
Argument of periastron (ω) (secondary)	106°
Semi-amplitude (K1) (primary)	7.1 km/s
Semi-amplitude (K2) (secondary)	19.9 km/s
Details
ξ Cephei Aa
Mass	1.045±0.031[6] M☉
ξ Cephei Ab
Mass	0.408±0.066[6] M☉
Other designations
Kurhah, 17 Cephei, BD+63°1802, CCDM J22038+2407, HIP 108917, HR 8417, SAO 19827, WDS J22038+6438
A: HD 209790
B: HD 209791
Database references
SIMBAD	ξ
	A
	B

It consists of two binary stars, designated Xi Cephei A and B, together with a more distant companion, Xi Cephei C. A's two components are themselves designated Xi Cephei Aa (officially named Kurhah /ˈkɜːrhə/, the traditional name of the system)^[9] and Ab.

Nomenclature

ξ Cephei (Latinised to Xi 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 (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).^[10]

Xi Cephei bore the traditional names Kurhah, Alkirdah or Al Kirduh,^[11] the name coming from Qazvini who gave Al Ḳurḥaḥ (القرحة al-qurhah), 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 (ألقردة al qírada "the Ape").^[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[13] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.^[14] 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.^[9]

In Chinese, 天鈎 (Tiān Gōu), 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.^[15] Consequently, the Chinese name for Xi Cephei itself is 天鈎六 (Tiān Gōu liù, English: the Sixth Star of Celestial Hook).^[16]

Properties

Xi Cephei A is a double-lined spectroscopic binary system with an orbital period of 810.9 days and an eccentricity of 0.46.^[8] The primary, component Aa, is a chemically peculiar Am star, a probable subgiant with an apparent magnitude of +4.29. Eight arcseconds away, Xi Cephei B is another spectroscopic binary. Xi Cephei C is a 13th magnitude star nearly two arcminutes away.^[3]

References

1. van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.Vizier catalog entry
2. Monet, David G.; Levine, Stephen E.; Canzian, Blaise; Ables, Harold D.; Bird, Alan R.; Dahn, Conard C.; Guetter, Harry H.; Harris, Hugh C.; Henden, Arne A.; Leggett, Sandy K.; Levison, Harold F.; Luginbuhl, Christian B.; Martini, Joan; Monet, Alice K. B.; Munn, Jeffrey A.; Pier, Jeffrey R.; Rhodes, Albert R.; Riepe, Betty; Sell, Stephen; Stone, Ronald C.; Vrba, Frederick J.; Walker, Richard L.; Westerhout, Gart; Brucato, Robert J.; Reid, I. Neill; Schoening, William; Hartley, M.; Read, M. A.; Tritton, S. B. (2003). "The USNO-B Catalog". The Astronomical Journal. 125 (2): 984–993. arXiv:astro-ph/0210694. Bibcode:2003AJ....125..984M. doi:10.1086/345888. S2CID 55896673.
3. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
4. Gray, R. O; Garrison, R. F (1989). "The early F-type stars - Refined classification, confrontation with Stromgren photometry, and the effects of rotation". The Astrophysical Journal Supplement Series. 69: 301. Bibcode:1989ApJS...69..301G. doi:10.1086/191315.
5. Gray, R. O; Napier, M. G; Winkler, L. I (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars". The Astronomical Journal. 121 (4): 2148. Bibcode:2001AJ....121.2148G. doi:10.1086/319956.
6. Farrington, C. D.; et al. (2014). "Separated Fringe Packet Observations with the CHARA Array. II. omega Andromeda, HD 178911, and xi Cephei". The Astronomical Journal. 148 (3): 48. arXiv:1407.0639. Bibcode:2014AJ....148...48F. doi:10.1088/0004-6256/148/3/48. S2CID 12909818.
7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
8. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "S_B⁹: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
9. "Naming Stars". IAU.org. Retrieved 16 December 2017.
10. Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
11. "Islamic Crescent Project: Star names". Archived from the original on 2008-02-02. Retrieved 2010-12-08.
12. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 159. ISBN 0-486-21079-0. Retrieved 2010-12-12.
13. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
14. "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
15. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
16. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 29, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.