6 Andromedae
Astrometric binary star system in the constellation Andromeda
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6 Andromedae is an astrometric binary star[8] system in the northern constellation of Andromeda.[1] The designation comes from the star catalogue of John Flamsteed, first published in 1712. Its apparent visual magnitude is 5.91,[1] which is just bright enough to be visible to the naked eye under good seeing conditions. Based upon an annual parallax shift of 35.6 mas as seen from Earth,[5] it is 92 light years from the Sun. It is moving closer to the Sun with a radial velocity of −32.4 km/s.[1] The system has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.272 arc seconds per annum.[9]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda[1] |
| Right ascension | 23h 10m 27.24121s[2] |
| Declination | +43° 32′ 38.5341″[2] |
| Apparent magnitude (V) | 5.91[1] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | F5 V[3] |
| U−B color index | −0.05[3] |
| B−V color index | +0.450±0.004[1] |
| Astrometry | |
| Radial velocity (Rv) | −32.4±0.7[1] km/s |
| Proper motion (μ) | RA: −211.689±0.211 mas/yr[2] Dec.: −144.535±0.234 mas/yr[2] |
| Parallax (π) | 35.5518±0.3115 mas[2] |
| Distance | 91.7 ± 0.8 ly (28.1 ± 0.2 pc) |
| Absolute magnitude (MV) | 3.71[1] |
| Orbit[3] | |
| Period (P) | 3,373±6 d |
| Periastron epoch (T) | 53116 ± 16 MJD |
| Argument of periastron (ω) (secondary) | 165.2±2.0° |
| Semi-amplitude (K1) (primary) | 8.75±0.09 km/s |
| Details | |
| Mass | 1.30[4] M☉ |
| Radius | 1.50+0.03 −0.06[5] R☉ |
| Luminosity | 3.090+0.018 −0.017[5] L☉ |
| Surface gravity (log g) | 4.09±0.14[4] cgs |
| Temperature | 6,425±218[4] K |
| Metallicity [Fe/H] | −0.19±0.03[1] dex |
| Rotational velocity (v sin i) | 18[6] km/s |
| Age | 2.91[4] Gyr |
| Other designations | |
| 6 And, BD+42°4592, FK5 3857, HD 218804, HIP 114430, HR 8825, SAO 52761, PPM 63896[7] | |
| Database references | |
| SIMBAD | data |
This is a single-lined spectroscopic binary with an orbital period of 9.2 years and an eccentricity of 0.3.[3] Some early observations of the star gave it a subgiant luminosity class and it was published in the Bright Star Catalogue as spectral class F5 IV. More modern measurements identify the visible component as an F-type main-sequence star with a stellar classification of F5 V.[3][10] The star is an estimated 2.9[4] billion years old with 1.3[4] times the mass of the Sun and 1.5[5] times the Sun's radius. It is radiating 3.1[5] times the Sun's luminosity from its photosphere at an effective temperature of around 6,425 K.[4] 6 Andromedae displays an infrared excess at a wavelength of 22 μm, which may indicate a circumstellar disk of warm dusty debris.[6]
The mass of the secondary component is roughly at or above that of the Sun. If it were a single, ordinary star, it should be readily visible as it would be just one magnitude fainter than the primary. The lack of conspicuous ultraviolet emission appears to rule out a white dwarf companion, so it may instead itself be a binary system consisting of two smaller stars having an orbital period between a week and a year.[3]