6 Andromedae

For the galaxy, see Andromeda VI.

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]

6 Andromedae

Location of 6 Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda[1]
Right ascension	23h 10m 27.241s[2]
Declination	+43° 32′ 38.53″[2]
Apparent magnitude (V)	5.91[1]
Characteristics
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 mas/yr[2] Dec.: −144.535 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]