Sigma Aurigae

σ Aurigae
Location of σ Aurigae (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Auriga
Right ascension 05h 24m 39.141s
Declination +37° 23′ 07.26″
Apparent magnitude (V) 4.99
Characteristics
Evolutionary stage red giant branch
Spectral type K3III CN+2
U−B color index +1.75
B−V color index +1.42
Astrometry
Radial velocity (Rv)−19.7 km/s
Proper motion (μ) RA: −0.564 mas/yr
Dec.: −10.953 mas/yr
Parallax (π)6.3543±0.0892 mas
Distance513 ± 7 ly
(157 ± 2 pc)
Absolute magnitude (MV)−0.75
Details
Radius43.72+1.08
−3.24 R☉
Luminosity496±20 L☉
Surface gravity (log g)1.75 cgs
Temperature4,120+162
−50 K
Metallicity [Fe/H]−0.03 dex
Rotational velocity (v sin i)10 km/s
Other designations
σ Aur, 21 Aurigae, BD+37°1175, GC 6636, HD 35186, HIP 25292, HR 1773, SAO 57981, PPM 70308, WDS J05247+3723A
Database references
SIMBADdata

Sigma Aurigae is a star in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from σ Aurigae, and abbreviated Sigma Aur or σ Aur. This star is faintly visible to the naked eye with an apparent visual magnitude of 4.99. With an annual parallax shift of 6.35 mas, it is approximately 530 light-years (160 parsecs) distant from the Earth. It is drifting closer to the Sun with a radial velocity of −20 km/s.

This is an evolved giant star with a stellar classification of K3III CN+2, indicating that it has exhausted the supply of hydrogen at its core. The 'CN+2' notation indicates anomalously strong lines of the CN molecule in the spectrum. This star has expanded to 44 times the radius of the Sun and is radiating nearly 500 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,120 K. There is a 12th magnitude companion at an angular separation of 8 arcseconds, as well as two fainter companions at 28 and 35" respectively. All are background objects, stars much further away than Sigma itself.[citation needed]

Sigma Aurigae, along with λ Aur and μ Aur, were Kazwini's Al Ḣibāʽ (ألحباع), the Tent. According to the catalogue of stars in the Technical Memorandum 33-507 – A Reduced Star Catalog Containing 537 Named Stars, Al Ḣibāʽ were the title for three stars: λ Aur as Al Ḣibāʽ I, μ Aur as Al Ḣibāʽ II and σ Aur as Al Ḣibāʽ III.

References

  1. 1 2 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 7 Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 4 Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133 (4): 475–493, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
  4. 1 2 Abt, H. A. (September 1985), "Visual multiples. VIII - 1000 MK types", Astrophysical Journal Supplement Series, 59: 95–112, Bibcode:1985ApJS...59...95A, doi:10.1086/191064.
  5. 1 2 Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
  6. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. 1 2 McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
  8. ↑ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
  9. ↑ "sig Aur", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-08-22.
  10. ↑ Mason, Brian D.; et al. (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.
  11. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 91, ISBN 0-486-21079-0, retrieved 2010-12-12.{{citation}}: CS1 maint: ignored ISBN errors (link)
  12. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, California Institute of Technology: Jet Propulsion Laboratory, retrieved 2025-05-16.