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Multiple star system in the constellation Auriga From Wikipedia, the free encyclopedia
9 Aurigae (9 Aur) is a star system in Auriga (constellation). 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,[1] although individual Gaia Data Release 3 parallaxes place all three components at 88 light years.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Auriga |
| Right ascension | 05h 06m 40.62967s[1] |
| Declination | +51° 35′ 51.8025″[1] |
| Apparent magnitude (V) | 4.93 - 5.03[2] |
| Characteristics | |
| Spectral type | F2V[3] |
| U−B color index | -0.03[4] |
| B−V color index | +0.34[4] |
| Variable type | γ Dor[5] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −0.47±0.57[6] km/s |
| Proper motion (μ) | RA: −28.557[6] mas/yr Dec.: −171.822[6] mas/yr |
| Parallax (π) | 37.0551 ± 0.1371 mas[6] |
| Distance | 88.0 ± 0.3 ly (26.99 ± 0.10 pc) |
| B | |
| Proper motion (μ) | RA: −54.582[7] mas/yr Dec.: −156.009[7] mas/yr |
| Parallax (π) | 37.0796 ± 0.0631 mas[7] |
| Distance | 88.0 ± 0.1 ly (26.97 ± 0.05 pc) |
| C | |
| Radial velocity (Rv) | −1.88±0.17[7] km/s |
| Proper motion (μ) | RA: −32.386[8] mas/yr Dec.: −173.026[8] mas/yr |
| Parallax (π) | 37.2115 ± 0.0184 mas[8] |
| Distance | 87.65 ± 0.04 ly (26.87 ± 0.01 pc) |
| Orbit[9] | |
| Period (P) | 391.7 d |
| Eccentricity (e) | 0.37 |
| Semi-amplitude (K1) (primary) | 5.8 km/s |
| Details | |
| A | |
| Mass | 1.97[10] M☉ |
| Radius | 1.56[5] R☉ |
| Luminosity | 6.042[11] L☉ |
| Surface gravity (log g) | 4.07[5] cgs |
| Temperature | 7,023[5] K |
| Metallicity [Fe/H] | −0.12[5] dex |
| Rotational velocity (v sin i) | 21.0[5] km/s |
| B | |
| Mass | 0.49[10] 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 | |
| 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.[17] It is a well-studied Gamma Doradus variable,[5] and was one of the first stars to be so-classified.[18] This star type varies in luminosity due to non-radial pulsations.[18] 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.[19][2]
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.[9]
Four other companions to 9 Aurigae are listed in multiple star catalogs.[20][21] The closest companion is a 12th-magnitude red dwarf 5″ away.[5] 90″ away is component C, a 9th-magnitude star with a spectral class of K5Ve,[22] which may also be a spectroscopic binary.[10] Further-separated still is a 14th-magnitude star, component D, proposed to be a more distant red giant,[23] although Gaia astrometry places it at a similar distance and with a similar proper motion.[24] The most widely-separated companion is component E, a distant unrelated star.[23][25]
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