HD 8673

HD 8673 is a binary star in the northern constellation of Andromeda. It has an apparent magnitude and absolute magnitude of 6.34 and 3.56 respectively.^[2] Based upon an annual parallax shift of 26.2 mas, the system is located around 124.5 light years away. The system is moving further from the Earth with a heliocentric radial velocity of +19 km/s.^[1] A sub-stellar companion was detected in 2005; it could either be an exoplanet or a brown dwarf.

HD 8673

Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	01h 26m 08.78637s[1]
Declination	+34° 34′ 46.9318″[1]
Apparent magnitude (V)	6.34[2]
Characteristics
Spectral type	F7 V + M2 V[3]
B−V color index	0.500±0.004[2]
Astrometry
Radial velocity (Rv)	19.08±0.14[1] km/s
Proper motion (μ)	RA: 236.271±0.030 mas/yr[1] Dec.: −84.632±0.022 mas/yr[1]
Parallax (π)	26.2036±0.0370 mas[1]
Distance	124.5 ± 0.2 ly (38.16 ± 0.05 pc)
Absolute magnitude (MV)	3.56[2]
Orbit[3]
Semi-major axis (a)	35–60 AU
Eccentricity (e)	< 0.5
Inclination (i)	75–85°
Details[4]
HD 8673 A
Mass	1.36±0.20 M☉
Radius	1.521±0.049 R☉
Luminosity	3.37+0.51 −0.44 L☉
Surface gravity (log g)	4.21 cgs
Temperature	6,340 K
Metallicity [Fe/H]	0.15 dex
Rotational velocity (v sin i)	26.9 km/s
Age	1.5+2.1 −0.6 Gyr
HD 8673 B
Mass	0.33–0.45[3] M☉
Temperature	3,520-3,690[3] K
Other designations
BD+33°228, Gaia DR2 317350357498173312, HD 8673, HIP 6702, HR 410, SAO 54695, PPM 66283, WDS J01262+3435AB, IRAS 01232+3418, 2MASS J01260875+3434471[5]
Database references
SIMBAD	data

The primary component is an F-type main-sequence star with a stellar classification of F7 V.^[3] It has 1.36 times the mass of the Sun and 1.52 times the Sun's radius. The star is around 1.5 billion years old and is spinning with a projected rotational velocity of 26.9 km/s. It is radiating 3.4 times the Sun's luminosity from its photosphere at an effective temperature of 6,340 K.^[4]

Speckle interferometry measurements of this star between 2001 and 2008 showed a candidate stellar companion to this star, announced in 2011. It was unclear whether the pair formed a visual double or a binary system. The authors of the study estimated a class of K2 V, based upon a visual magnitude difference of 2.3±0.5.^[6] Subsequent observations using adaptive options did not spot this companion and it was concluded this was a false detection. However, a low mass stellar companion was detected in a wide orbit. This red dwarf star has 0.33–0.45 times the mass of the Sun and is orbiting with a semimajor axis of 35–60 AU.^[3]

Planetary system

An orbiting sub-stellar companion with a minimum mass 14 times that of Jupiter in a high-eccentricity orbit was discovered in 2005 and confirmed in 2010. This object orbits at 3 AU away from the primary star with a period of 1,634 days and an eccentricity of 0.7.^[7] In 2022, the inclination and true mass of HD 8673 Ab were measured via astrometry.^[8]

The HD 8673 A planetary system^[8]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (years)	Eccentricity	Inclination	Radius
b	13.248+1.688 −1.416 MJ	2.970+0.147 −0.171	4.503+0.030 −0.043	0.730+0.042 −0.026	95.450+19.444 −8.816°	—