34 Pegasi

34 Pegasi is a triple star^[7] system in the northern constellation of Pegasus. It has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.76.^[2] The system is located at a distance of 131 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −13.5 km/s.^[2] It has been catalogued as a member of the Hyades Supercluster,^[9] although its membership status remains doubtful.

34 Pegasi

Observation data Epoch J2000      Equinox J2000
Constellation	Pegasus
Right ascension	22h 26m 37.37059s[1]
Declination	+04° 23′ 37.6056″[1]
Apparent magnitude (V)	5.76[2]
Characteristics
Spectral type	F7V[3] or F8IV−V[4] + K4[5]
B−V color index	0.519±0.005[2]
Astrometry
Radial velocity (Rv)	−13.5±0.2[2] km/s
Proper motion (μ)	RA: +307.781[1] mas/yr Dec.: +47.533[1] mas/yr
Parallax (π)	24.9028±0.1794 mas[1]
Distance	131.0 ± 0.9 ly (40.2 ± 0.3 pc)
Absolute magnitude (MV)	2.85[4]
Orbit[4]
Primary	Aa
Companion	Ab
Period (P)	929.91±0.46 d
Semi-major axis (a)	9.5±0.3" (≥58.24±0.65 Gm)
Eccentricity (e)	0.4358±0.0062
Inclination (i)	94.0±5.1°
Longitude of the node (Ω)	101.6±4.6°
Periastron epoch (T)	53,293.9±3.2 HJD
Argument of periastron (ω) (secondary)	188.5±1.1°
Semi-amplitude (K1) (primary)	5.060±0.054 km/s
Details
Aa
Mass	1.33[6] M☉
Radius	2.25+0.07 −0.08[1] R☉
Luminosity	6.7±0.1[1] L☉
Surface gravity (log g)	3.92[6] cgs
Temperature	6,200+110 −100[1] K
Metallicity [Fe/H]	−0.04±0.02[2] dex
Rotational velocity (v sin i)	8.4±1.0[4] km/s
Age	3.22[6] Gyr
Ab
Mass	0.29[4] M☉
Other designations
BU 290[7], BD+03°4705, GJ 9782, HD 212754, HIP 110785, HR 8548, SAO 127529, WDS J22266+0424, BU 290[8]
Database references
SIMBAD	data

The innermost system is a single-lined spectroscopic binary with an orbital period of 2.55 years and an eccentricity of 0.44.^[4] The orbital plane of this pair is being viewed nearly edge-on, and has an angular semimajor axis of 9.5″.^[4] A third member of the system has a poorly-constrained 420 year orbit around the main pair.^[10] This star was discovered by Burnham in 1874,^[5] and the discovery code BU 290 was given to the double. As of 2015, it lies at an angular separation of 3.90±0.02 along a position angle of 226.2°±0.8° from the inner system.^[7]

The primary member, component Aa, is an F-type main-sequence star that is starting to evolve off the main sequence,^[4] with stellar classifications of F7V^[3] or F8IV−V,^[4] depending on the source. It is around three^[6] billion years old and is spinning with a projected rotational velocity of 8 km/s,^[4] with a measured rotation period of 12 days.^[5] The star has 1.3^[6] times the mass of the Sun and 2.25^[1] times the Sun's radius. It is radiating 6.7^[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,200 K.^[1]

The secondary companion to the primary, component Ab, is most likely a red dwarf^[5] star with around 29% of the mass of the Sun.^[4] The tertiary member, component B, has 53%^[11] of the Sun's mass and a class of around K4.^[5]