Zeta Horologii

Zeta Horologii, Latinized from ζ Horologii, is a yellow-white-hued binary star system in the southern constellation of Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 5.20.^[2] Based upon an annual parallax shift of 20.37 mas as seen from Earth,^[1] it is located around 160 light-years from the Sun.

Zeta Horologii

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Horologium
Right ascension	02h 40m 39.61286s[1]
Declination	−54° 32′ 59.6836″[1]
Apparent magnitude (V)	5.20[2]
Characteristics
Spectral type	F6 V[3] (F2 V + F5 V)[4]
B−V color index	+0.42[2]
Astrometry
Radial velocity (Rv)	5.8[3] km/s
Proper motion (μ)	RA: +32.86[1] mas/yr Dec.: +4.96[1] mas/yr
Parallax (π)	20.37±0.21 mas[1]
Distance	160 ± 2 ly (49.1 ± 0.5 pc)
Absolute magnitude (MV)	+1.76[5]
Orbit[4]
Period (P)	12.9274 d
Eccentricity (e)	0.25
Periastron epoch (T)	7.361±0.046
Argument of periastron (ω) (secondary)	78.6±0.13°
Semi-amplitude (K1) (primary)	58.1±1.37 km/s
Semi-amplitude (K2) (secondary)	66.1±1.56 km/s
Details
ζ Hor A
Mass	1.43[6] M☉
Luminosity	16.7[5] L☉
Surface gravity (log g)	3.74[7] cgs
Temperature	6,702[7] K
Metallicity [Fe/H]	−0.07[7] dex
Rotational velocity (v sin i)	8.0±1.2[3] km/s
Age	1.50[7] Gyr
ζ Hor B
Mass	1.26[6] M☉
Other designations
ζ Hor, CPD−55°446, FK5 1076, HD 16920, HIP 12484, HR 802, SAO 232857[8]
Database references
SIMBAD	data

This system was determined to be a double-lined spectroscopic binary by J. H. Moore in 1911−12. The first orbital elements were published by J. Sahade and C. A. Hernández in 1964, who found it consisted of two F-type main-sequence stars of probable stellar classifications F2 V and F5 V. The pair orbit each other with a period of 12.9274 days and an eccentricity of 0.25.^[4] The system displays an infrared excess at a wavelength of 24 μm but not at 70 μm, yielding a derived temperature of 260 K. This suggests a circumbinary debris disk orbiting at a distance of less than 4.8 AU from the star system.^[9]