Astronomy:Xi Cephei

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Short description: Star in the constellation Cepheus
ξ Cephei
Cepheus constellation map.svg
Red circle.svg
Location of ξ Cephei (circled)
Observation data
Equinox J2000.0]] (ICRS)
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[6] mas
Distance86 ± 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
Mass1.045±0.031[6] M☉
ξ Cephei Ab
Mass0.408±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
SIMBADξ
A
B

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]

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. ↑ 1.0 1.1 1.2 1.3 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. http://www.aanda.org/articles/aa/full/2007/41/aa8357-07/aa8357-07.html. 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. et al. (2003). "The USNO-B Catalog". The Astronomical Journal 125 (2): 984–993. doi:10.1086/345888. Bibcode: 2003AJ....125..984M. 
  3. ↑ 3.0 3.1 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. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M. 
  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. doi:10.1086/191315. Bibcode: 1989ApJS...69..301G. 
  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. doi:10.1086/319956. Bibcode: 2001AJ....121.2148G. 
  6. ↑ 6.0 6.1 6.2 6.3 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. doi:10.1088/0004-6256/148/3/48. Bibcode: 2014AJ....148...48F. 
  7. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  8. ↑ 8.0 8.1 Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I. et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics 424 (2): 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P. 
  9. ↑ 9.0 9.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  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". http://www.icoproject.org/star.html. 
  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. https://archive.org/details/starnamestheirlo00alle/page/159. Retrieved 2010-12-12. 
  13. ↑ IAU Working Group on Star Names (WGSN), International Astronomical Union, https://www.iau.org/science/scientific_bodies/working_groups/280/, retrieved 22 May 2016. 
  14. ↑ "WG Triennial Report (2015-2018) - Star Names". p. 5. https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf. 
  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 , Hong Kong Space Museum. Accessed on line November 23, 2010.



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