9 Aurigae
Multiple star system in the constellation Auriga
From Wikipedia, the free encyclopedia
9 Aurigae (9 Aur) is a star system in the constellation Auriga. It has an apparent magnitude of about 5, making it visible to the naked eye in many suburban skies.[15] Parallax estimates made by the Hipparcos spacecraft put it at about 86 light-years (26 parsecs) from the Solar System,[16] although individual Gaia Data Release 3 parallaxes place all three components at 88 light-years.
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Auriga |
| 9 Aurigae A | |
| Right ascension | 05h 06m 40.63060s[1] |
| Declination | +51° 35′ 51.7990″[1] |
| Apparent magnitude (V) | 4.93 - 5.03[2] |
| 9 Aurigae B | |
| Right ascension | 05h 06m 41.12083s[3] |
| Declination | 51° 35′ 53.2333″[3] |
| Apparent magnitude (V) | 12.2[4] |
| 9 Aurigae C | |
| Right ascension | 05h 06m 49.17489s[5] |
| Declination | 51° 36′ 34.5112″[5] |
| Apparent magnitude (V) | 9.49[6] |
| Characteristics | |
| A | |
| Evolutionary stage | main sequence[1] |
| Spectral type | F2V[7] |
| U−B color index | −0.01[8] |
| B−V color index | +0.34[8] |
| Variable type | γ Dor[9] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −0.47±0.57[1] km/s |
| Proper motion (μ) | RA: −28.557[1] mas/yr Dec.: −171.822[1] mas/yr |
| Parallax (π) | 37.0551±0.1371 mas[1] |
| Distance | 88.0 ± 0.3 ly (26.99 ± 0.10 pc) |
| B | |
| Proper motion (μ) | RA: −54.582[3] mas/yr Dec.: −156.009[3] mas/yr |
| Parallax (π) | 37.0796±0.0631 mas[3] |
| Distance | 88.0 ± 0.1 ly (26.97 ± 0.05 pc) |
| C | |
| Radial velocity (Rv) | −1.88±0.17[5] km/s |
| Proper motion (μ) | RA: −32.386[5] mas/yr Dec.: −173.026[5] mas/yr |
| Parallax (π) | 37.2115±0.0184 mas[5] |
| Distance | 87.65 ± 0.04 ly (26.87 ± 0.01 pc) |
| Orbit[10] | |
| Period (P) | 391.7 d |
| Eccentricity (e) | 0.37 |
| Semi-amplitude (K1) (primary) | 5.8 km/s |
| Details | |
| A | |
| Mass | 1.97[4] M☉ |
| Radius | 1.56[9] R☉ |
| Luminosity | 6.042[11] L☉ |
| Surface gravity (log g) | 4.07[9] cgs |
| Temperature | 7,023[9] K |
| Metallicity [Fe/H] | −0.12[9] dex |
| Rotational velocity (v sin i) | 21.0[9] km/s |
| B | |
| Mass | 0.49[4] M☉ |
| Temperature | 4,947[12] K |
| C | |
| Mass | 0.751[13] M☉ |
| Radius | 0.756[13] R☉ |
| Luminosity | 0.162[14] L☉ |
| Temperature | 4,633[14] K |
| Other designations | |
| V398 Aur, BD+51°1024, GJ 187.2, GJ 9174, HD 32537, HIP 23783, HR 1637, SAO 25019 | |
| Database references | |
| SIMBAD | 9 Aur A |
| 9 Aur B | |
| 9 Aur C | |
Kevin Krisciunas and Edward Francis Guinan discovered that the star is a variable star in 1990.[18] It is a well-studied Gamma Doradus variable,[9] and was one of the first stars to be so-classified.[19] This star type varies in luminosity due to non-radial pulsations.[19] Its apparent magnitude varies from 4.93 to 5.03 over a period of 1.25804 days.[2] For that reason it was given the variable star designation V398 Aurigae in 1995.[2][20]
9 Aurigae is a multiple star system. The naked-eye component A is a single-lined spectroscopic binary. Only the signature of an F-type main-sequence star can be seen in the spectrum, but the periodic Doppler shift of the absorption lines demonstrates that there is a hidden companion in a 391.7-day orbit. The gravitational interaction of the two bodies produces variations in their respective motions, which is what creates the Doppler shift.[10]
Four other companions to 9 Aurigae are listed in multiple star catalogs.[21][22] The closest companion is a 12th-magnitude red dwarf 5″ away.[9] Ninety arcseconds away is component C, a 9th-magnitude star with a spectral class of K5Ve,[23] which may also be a spectroscopic binary.[4] Further separated still is a 14th-magnitude star, component D, proposed to be a more distant red giant,[24] although Gaia astrometry places it at a similar distance and with a similar proper motion.[25] The most widely separated companion is component E, a distant, unrelated star.[24][26]