Zeta Aurigae

Zeta Aurigae (ζ Aurigae, abbreviated Zeta Aur, ζ Aur), traditionally known as Sadatoni /sædəˈtoʊni/[12] (among other names), is a binary star in the northern constellation of Auriga. Based upon parallax measurements made during the Hipparcos mission, this system is approximately 790 light-years (240 parsecs) distant from the sun. It has a combined apparent visual magnitude of 3.75,[2] which is bright enough to be seen with the naked eye.

ζ Aurigae
Location of ζ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension  05h 02m 28.68739s[1]
Declination +41° 04′ 33.0200″[1]
Apparent magnitude (V) 3.751[2] (3.70 - 3.97[3])
Characteristics
Spectral type K5 II + B7 V[4]
U−B color index +0.374[2]
B−V color index +1.293[2]
R−I color index 0.87
Variable type Algol[3]
Astrometry
Radial velocity (Rv)+12.8[5] km/s
Proper motion (μ) RA: +9.45[1] mas/yr
Dec.: -20.71[1] mas/yr
Parallax (π)4.15 ± 0.29[1] mas
Distance790 ± 50 ly
(240 ± 20 pc)
Absolute magnitude (MV)−3.21[6]
Orbit[7]
Period (P)972.162 d
Semi-major axis (a)905 R☉
Eccentricity (e)0.3973 ± 0.0007
Inclination (i)87.0°
Periastron epoch (T)RJD 53039.9 ± 0.10
Argument of periastron (ω)
(secondary)		328.9° ± 0.13°
Semi-amplitude (K1)
(primary)		23.17 ± 0.02 km/s
Details
ζ Aur A
Mass4.94 ± 0.79[8] M☉
Luminosity3,254[8] L☉
Surface gravity (log g)1.33[9] cgs
Temperature3,920[9] K
Metallicity [Fe/H]–0.26[9] dex
Rotational velocity (v sin i)68[10] km/s
ζ Aur B
Mass4.8[7] M☉
Other designations
Saclateni, ζ Aur, 8 Aurigae, BD+40°1142, FK5 1137, HD 32068, HIP 23453, HR 1612, SAO 39966, WDS 05025+4105.[11]
Database references
SIMBADdata

The two components are designated Zeta Aurigae A (officially named Saclateni /sækləˈtiːni/, an old misspelling of "Sadatoni")[13] and B.

Nomenclature

ζ Aurigae (Latinised to Zeta Aurigae) is the system's Bayer designation. The designations of the two components as ζ Aurigae A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[14]

The system bore the traditional names Haedus I (also Hoedus) and Sadatoni (rarely Saclateni). It was one of the two haedi (Latin: 'kids') of the she-goat Capella, the other being Haedus II, Eta Aurigae. The name Sadatoni is from the Arabic الساعد الثاني as-sācid aθ-θānī "the second arm (of the charioteer)". The rare traditional name Azaleh is shared (in the form Hassaleh) with Iota Aurigae.[15] In 2016, the IAU organized a Working Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] It approved the names Saclateni for the component Zeta Aurigae A and Haedus for Eta Aurigae on 30 June 2017 and they are both now so included in the List of IAU-approved Star Names.[13]

In Chinese, 柱 (Zhù), meaning Pillars, refers to an asterism consisting of Zeta Aurigae, Epsilon Aurigae, Eta Aurigae, Upsilon Aurigae, Nu Aurigae, Tau Aurigae, Chi Aurigae and 26 Aurigae.[18] Consequently, the Chinese name for Zeta Aurigae itself is 柱二 (Zhù èr, English: the Second Star of Pillars.)[19]

Binary system

Zeta Aurigae was first recognized as a spectroscopic binary by William Hammond Wright while analyzing photographic plates taken at Lick Observatory between 1898 and 1908. This star is among those earlier described by Antonia Maury as having a composite spectrum.[20] The first orbit was determined in 1924 by William Edmund Harper using measurements taken at Dominion Observatory, his orbital elements are very similar to the most recent determinations. Harper also noticed that the composite nature of the spectrum had disappeared on the one plate when the K type primary was nearest the sun indicating a possible eclipse.[21] In 1932 the eclipsing binary nature of the system was confirmed by Paul Guthnick, Heribert Schneller and independently Josef Hopmann.[22]

Properties

Zeta Aurigae is an eclipsing binary with the orbital plane being oriented close to the line of sight from the Earth; the inclination of this system is estimated as 87.0°.[7] As a result, an eclipse of one star by the other occurs during each orbit, causing the magnitude to decrease to +3.99. The pair have an orbital period of 972 days (2.66 years) and an eccentricity of 0.4.[7] The primary component, Zeta Aurigae A, has been categorized as a K-type bright giant or supergiant star. Its companion, Zeta Aurigae B, is a B-type main sequence star of stellar classification B5 V or B7 V.[7][4]

References
  1. van Leeuwen, F. (November 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.
  2. Kiyokawa, M. (1967), "Photoelectric Observation of Zeta Aurigae during the 1963-64 Eclipse", Publications of the Astronomical Society of Japan, 19: 209, Bibcode:1967PASJ...19..209K.
  3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (January 2011), "Search for and study of hot circumstellar dust envelopes", Astronomy Reports, 55 (1): 31–81, Bibcode:2011ARep...55...31S, doi:10.1134/S1063772911010070.
  5. Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  6. 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.
  7. Eaton, Joel A.; Henry, Gregory W.; Odell, Andrew P. (June 2008), "Orbits and Pulsations of the Classical ζ Aurigae Binaries", The Astrophysical Journal, 679 (2): 1490–1498, arXiv:0802.2238, Bibcode:2008ApJ...679.1490E, doi:10.1086/587452.
  8. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
  9. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants" (PDF), Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527. origin: STI
  10. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B.
  11. "zet Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-19.
  12. Rumrill, H. B. (June 1936). "Star Name Pronunciation". Publications of the Astronomical Society of the Pacific. San Francisco, California. 48 (283).
  13. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  14. 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].
  15. "Al Kab". stars.astro.illinois.edu. Retrieved 2017-02-02.
  16. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  17. "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  18. (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.
  19. (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.
  20. Campbell, W. W. (1909). "Eleven stars having variable radial velocities". The Astrophysical Journal. 29: 224–228. Bibcode:1909ApJ....29..224C. doi:10.1086/141644.
  21. Harper, W. E. (1924). "The Orbit of the spectroscopic binary Zeta Aurigae". Publications of the Dominion Observatory Ottawa. 3: 151–157. Bibcode:1924PDAO....3..151H.
  22. Christie, William H.; Wilson, O. C. (1935). "ζ Aurigae: the Structure of a Stellar Atmosphere". The Astrophysical Journal. 81: 426–460. Bibcode:1935ApJ....81..426C. doi:10.1086/143645.
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