Chi Aurigae

Chi Aurigae (χ Aur, χ Aurigae) is the Bayer designation for a binary star in the northern constellation of Auriga. It is faintly visible to the naked eye with an apparent visual magnitude of 4.74.[2] The annual parallax shift of this object is much smaller than the measurement error, making distance estimates by that means unreliable.[1] The estimated distance to this star is approximately 3,000 light years. The brightness of the star is diminished by 1.26 in magnitude from extinction caused by intervening gas and dust.[5]

Chi Aurigae
The location of χ Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 32m 43.67312s[1]
Declination +32° 11′ 31.2753″[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]
R−I color index 0.27
Astrometry
Radial velocity (Rv)–0.2[4] km/s
Proper motion (μ) RA: –1.52[1] mas/yr
Dec.: –4.33[1] mas/yr
Distance3,000 ly
(912[5] pc)
Absolute magnitude (MV)–6.4[5]
Orbit[5]
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
Mass16.5-19 M☉
Radius42.3 R☉
Luminosity95,000 L☉
Surface gravity (log g)2.5[5] cgs
Temperature15,500[6] K
Rotational velocity (v sin i)40[7] km/s
Other designations
25 Aurigae, BD+32°1024, HD 36371, HIP 25984, HR 1843, SAO 58164.[8]
Database references
SIMBADdata

Chi Aurigae is a spectroscopic binary with an orbital period of 676.85 d and an eccentricity of 0.12.[9] The primary component of this system is a supergiant star with a stellar classification of B5 Iab.[3] 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.[6]

References
  1. 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. Note: see VizieR catalogue I/311.
  2. 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. 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, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. 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.
  6. 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.
  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. 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.
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