Chi Aurigae

Chi Aurigae
The location of χ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 32m 43.67437s[1]
Declination +32° 11′ 31.2805″[1]
Apparent magnitude (V) 4.74[2]
Characteristics
Spectral type B5 Iab[3]
U−B color index –0.44[2]
B−V color index +0.32[2]
Astrometry
Radial velocity (Rv)–0.2[4] km/s
Proper motion (μ) RA: −0.812 mas/yr[1]
Dec.: −3.15 mas/yr[1]
Parallax (π)0.9087 ± 0.1906 mas[1]
Distance3910±420 ly
(1,200±130 pc)[5]
Absolute magnitude (MV)–6.4[6]
Orbit[6]
Period (P)676.85 ± 0.21 d
Eccentricity (e)0.116 ± 0.048
Longitude of the node (Ω)181.7° ± 24.3°
Periastron epoch (T)2422754.2 ± 46.1 HJD
Semi-amplitude (K1)
(primary)		22.0 ± 2.9 km/s
Details
Mass21.1±0.2[5] M☉
Radius68±8[5] R☉
Luminosity190,500+49,300
−39,200[5] L☉
Surface gravity (log g)2.11±0.06[5] cgs
Temperature14,600±300[5] K
Rotational velocity (v sin i)40[7] km/s
Age8.7[5] Myr
Other designations
χ Aur, 25 Aurigae, BD+32°1024, HD 36371, HIP 25984, HR 1843, SAO 58164[8]
Database references
SIMBADdata

Chi Aurigae, Latinized from χ Aurigae, is the Bayer designation for a binary star system in the northern constellation of Auriga. It is visible to the naked eye with an apparent visual magnitude of 4.74.[2] The distance of Chi Aurigae is determined at 3,900 ly based on spectroscopic observations.[5] Parallax measurements by the Hipparcos spacecraft were unsuccessful because the parallax error was bigger than the value itself,[9] while the Gaia spacecraft measured the parallax with a 22% error, giving a distance of 3590±750 ly.[1] The brightness of the star is diminished by 1.26 in magnitude from extinction caused by intervening gas and dust.[6]

Chi Aurigae is a spectroscopic binary with an orbital period of 676.85 d and an eccentricity of 0.12.[10] The primary component of this system is a supergiant star with a stellar classification of B5 Iab.[3] It is over 190,000 times more luminous, around 20 times more massive and around 70 times larger. Its surface has an effective temperature of 14,600 K.[5] It has a stellar wind that is causing mass loss at the rate of 0.38–0.46 × 10−9 solar masses per year, or the equivalent of the Sun's mass every 2.4 billion years.[11]

References

  1. ^ a b c d e 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.
  2. ^ a b c d Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
  3. ^ a b Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
  4. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. ^ a b c d e f g h i Weßmayer, D.; Przybilla, N.; Butler, K. (2022-12-01), "Quantitative spectroscopy of B-type supergiants", Astronomy & Astrophysics, 668: A92, arXiv:2208.02692, Bibcode:2022A&A...668A..92W, doi:10.1051/0004-6361/202243973, ISSN 0004-6361
  6. ^ a b c Raja, Tomas; Wolf, Marek (March 1998), "Hα variability of the B-type binary chi Aurigae", Astronomy and Astrophysics, 331: 550–556, Bibcode:1998A&A...331..550R.
  7. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  8. ^ "* chi Aur". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-23.
  9. ^ van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600. Note: see VizieR catalogue I/311.
  10. ^ Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  11. ^ Prinja, R. K.; Massa, D. L. (October 2010), "Signature of wide-spread clumping in B supergiant winds", Astronomy and Astrophysics, 521: L55, arXiv:1007.2744, Bibcode:2010A&A...521L..55P, doi:10.1051/0004-6361/201015252, S2CID 59151633.

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