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 |
It is a well-studied Gamma Doradus variable,[5] and was one of the first stars to be so-classified.[17] This star type varies in luminosity due to non-radial pulsations.[17] Its apparent magnitude varies from 4.93 to 5.03 over a period of 1.25804 days.[2] For that reason it has been given the variable star designation V398 Aurigae.[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.[18][19] 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,[20] 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,[21] although Gaia astrometry places it at a similar distance and with a similar proper motion.[22] The most widely-separated companion is component E, a distant unrelated star.[21][23]