Chi Aurigae
Binary star system in the constellation Auriga
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Chi Aurigae is a binary star system in the northern constellation of Auriga. Its name is a Bayer designation that is Latinized from χ Aurigae, and abbreviated Chi Aur or χ Aur. This star is visible to the naked eye with an apparent visual magnitude of 4.74.[2] The brightness of the star is diminished by 1.26 in magnitude from extinction caused by intervening gas and dust.[5] It is a member of the Aur OB1 association of co-moving stars.[5]
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| 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) | 7.27±5.21[1] 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] |
| Distance | 3,910±420 ly (1,200±130 pc)[4] |
| 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 | |
| Mass | 21.1±0.2[4] M☉ |
| Radius | 68±8[4] R☉ |
| Luminosity | 190,500+49,300 −39,200[4] L☉ |
| Surface gravity (log g) | 2.11±0.06[4] cgs |
| Temperature | 14,600±300[4] K |
| Rotational velocity (v sin i) | 40[6] km/s |
| Age | 8.7[4] Myr |
| Other designations | |
| χ Aur, 25 Aurigae, BD+32°1024, GC 6849, HD 36371, HIP 25984, HR 1843, SAO 58164, PPM 70517[7] | |
| Database references | |
| SIMBAD | data |
Chi Aurigae is a single-lined spectroscopic binary with an orbital period of 676.85 d and an eccentricity of 0.116.[5] 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 than the Sun. The photosphere has an effective temperature of 14,600 K.[4] Its stellar wind 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.[8]
The distance of Chi Aurigae is determined at 3,900 light-years based on spectroscopic observations.[4] 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 3,590±750 ly.[1]