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]

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