Astronomy:Zeta Aurigae

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Short description: Binary star system in the constellation Auriga
ζ Aurigae
Location of ζ Aurigae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Auriga
Right ascension  05h 02m 28.683s[1]
Declination +41° 04′ 33.00″[1]
Apparent magnitude (V) 3.751[2] (3.70–3.97[3])
Characteristics
Spectral type K5II (or K5Ib[4]) + B7 V[5]
U−B color index +0.374[2]
B−V color index +1.293[2]
R−I color index 0.87[citation needed]
Variable type Algol[3]
Astrometry
Radial velocity (Rv)+12.11[4] km/s
Proper motion (μ) RA: +12.093[1] mas/yr
Dec.: −19.324[1] mas/yr
Parallax (π)3.791 ± 0.05[6] mas
Distance860 ± 10 ly
(264 ± 3 pc)
Absolute magnitude (MV)−3.21[7]
Orbit[8]
Period (P)972.162 d (2.66 yr)
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
Mass5.8±0.2[9] M☉
Radius148±3[9] R☉
Luminosity4,786[4] L☉
Surface gravity (log g)1.33[10] cgs
Temperature3,960±100[9] K
Metallicity [Fe/H]−0.26[10] dex
Rotational velocity (v sin i)5.7±1[4] km/s
ζ Aur B
Mass4.8±0.2[9] M☉
Radius4.5±0.5[9] R☉
Temperature15,200±200[9] K
Other designations
Saclateni, ζ Aur, Zeta Aur, 8 Aurigae, BD+40°1142, FK5 1137, GC 6137, HD 32068, HIP 23453, HR 1612, SAO 39966, PPM 47641, WDS 05025+4105[11]
Database references
SIMBADdata

Zeta Aurigae is an eclipsing binary star system in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from ζ Aurigae, and abbreviated Zeta Aur or ζ Aur. Based upon parallax measurements, this system is approximately 860 light-years (260 parsecs) distant from the Sun.[6] It has a combined apparent visual magnitude of 3.75,[2] which is bright enough to be seen with the naked eye. The system is drifting further away from the Sun with a radial velocity of +12 km/s.[4]

The two components are designated Zeta Aurigae A and B. The bright giant or supergiant component A has the official name Saclateni, pronounced /sækləˈtiːni/,[12] which is an old misspelling of "Sadatoni". Its hotter companion is a B-type dwarf. The pair orbit each other with a period of 2.66 yr.

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).[13]

The system bore the traditional names Haedus I (also Hoedus) and Sadatoni (rarely Saclateni).[14] 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.[12]

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]

Properties

A light curve for Zeta Aurigae showing the brightness change as an eclipse ends, in three photometric colors. The inset plot shows the visible band data with an expanded vertical scale. Adapted from Bennett et al. (1996)[20]

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.[21] 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.[22] In 1932 the eclipsing binary nature of the system was confirmed by Paul Guthnick, Heribert Schneller and independently by Josef Hopmann.[23]

The orbital plane of this eclipsing system is oriented close to the line of sight from the Earth, with an inclination estimated as 87.0°.[8] As a result, an eclipse of one star by the other occurs during each orbit, causing the net magnitude to decrease to +3.99. The pair have an orbital period of 972 days (2.66 years) and an eccentricity (ovalness) of 0.4.[8] The primary, component A, has been categorized as a K-type bright giant or supergiant star. Its companion, component B, is a B-type main-sequence star with a stellar classification B5 V or B7 V.[8][5] Because component B has a much hotter photosphere than component A, component B produces most of the system's ultraviolet light. This causes the brightness change seen during the eclipses (when B is obscured) to be much greater in ultraviolet light than it is in visible light.

References

  1. ↑ 1.0 1.1 1.2 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Kiyokawa, M. (1967), "Photoelectric Observation of Zeta Aurigae during the 1963-64 Eclipse", Publications of the Astronomical Society of Japan 19 (2): 209, doi:10.1093/pasj/19.2.209, Bibcode: 1967PASJ...19..209K. 
  3. ↑ 3.0 3.1 Samus, N. N. et al. (2009), "General Catalogue of Variable Stars", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1, Bibcode: 2009yCat....102025S. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Harper, Graham M. et al. (2022), "HST STIS Observations of ζ Aurigae A's Irradiated Atmosphere", The Astronomical Journal 164 (1): 16, doi:10.3847/1538-3881/ac6feb, Bibcode: 2022AJ....164...16H. 
  5. ↑ 5.0 5.1 Shenavrin, V. I. et al. (January 2011), "Search for and study of hot circumstellar dust envelopes", Astronomy Reports 55 (1): 31–81, doi:10.1134/S1063772911010070, Bibcode: 2011ARep...55...31S. 
  6. ↑ 6.0 6.1 Groenewegen, M. A. T. (January 2023), "Orbital parallax of binary systems compared to Gaia DR3 and the parallax zero-point offset at bright magnitudes", Astronomy and Astrophysics 669: A4, doi:10.1051/0004-6361/202244479, ISSN 0004-6361, Bibcode: 2023A&A...669A...4G.  Zeta Aurigae's database entry at VizieR.
  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 8.2 8.3 Eaton, Joel A. et al. (June 2008), "Orbits and Pulsations of the Classical ζ Aurigae Binaries", The Astrophysical Journal 679 (2): 1490–1498, doi:10.1086/587452, Bibcode: 2008ApJ...679.1490E. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Harper, G. M. et al. (February 2016), "Orbitally modulated photoexcited Si I emission in the eclipsing composite-spectrum binary ζ Aurigae", Monthly Notices of the Royal Astronomical Society 456 (2): 1346–1358, doi:10.1093/mnras/stv2668, ISSN 0035-8711, Bibcode: 2016MNRAS.456.1346H. 
  10. ↑ 10.0 10.1 McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants", Astrophysical Journal Supplement Series 74: 1075–1128, doi:10.1086/191527, Bibcode: 1990ApJS...74.1075M.  origin: STI
  11. ↑ "zet Aur". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=zet+Aur. 
  12. ↑ 12.0 12.1 Naming Stars, IAU.org, https://www.iau.org/public/themes/naming_stars/, retrieved 16 December 2017. 
  13. ↑ Hessman, F. V. et al. (2010), "On the naming convention used for multiple star systems and extrasolar planets", eprint, Bibcode: 2010arXiv1012.0707H. 
  14. ↑ Rumrill, H. B. (June 1936), "Star Name Pronunciation", Publications of the Astronomical Society of the Pacific (San Francisco, California) 48 (283): 139, doi:10.1086/124681, Bibcode: 1936PASP...48..139R. 
  15. ↑ Kaler, James B., Al Kab, http://stars.astro.illinois.edu/sow/alkab.html, retrieved 2017-02-02. 
  16. ↑ IAU Working Group on Star Names (WGSN), International Astronomical Union, https://www.iau.org/science/scientific_bodies/working_groups/280/, retrieved 22 May 2016. 
  17. ↑ WG Triennial Report (2015-2018) - Star Names, International Astronomical Union, p. 5, https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf, retrieved 2018-07-14. 
  18. ↑ Script error: The function "in_lang" does not exist. 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. ↑ Script error: The function "in_lang" does not exist. 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.
  20. ↑ Bennett, Philip D. et al. (November 1996), "The Masses and Radii of the Eclipsing Binary zeta Aurigae", Astrophysical Journal 471 (1): 454, doi:10.1086/177981, Bibcode: 1996ApJ...471..454B. 
  21. ↑ Campbell, W. W. (1909), "Eleven stars having variable radial velocities", The Astrophysical Journal 29: 224–228, doi:10.1086/141644, Bibcode: 1909ApJ....29..224C. 
  22. ↑ 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, https://babel.hathitrust.org/cgi/pt?id=uc1.c3225584&seq=177, retrieved 2025-05-11. 
  23. ↑ Christie, William H.; Wilson, O. C. (1935), "ζ Aurigae: the Structure of a Stellar Atmosphere", The Astrophysical Journal 81: 426–460, doi:10.1086/143645, Bibcode: 1935ApJ....81..426C. 

Coordinates: Sky map 05h 02m 28.6834s, +41° 04′ 32.995″



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