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	22^h 26^m 37.37059^s[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[1] mas
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[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]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
4. Willmarth, Daryl W.; et al. (August 2016), "Spectroscopic Orbits for 15 Late-type Stars" (PDF), The Astronomical Journal, 152 (2): 13, Bibcode:2016AJ....152...46W, doi:10.3847/0004-6256/152/2/46, 46.
5. Griffin, R. F. (February 2010), "Spectroscopic binary orbits from photoelectric radial velocities - Paper 210: Psi2 Aurigae and 34 Pegasi", The Observatory, 130 (1): 17–32, Bibcode:2010Obs...130...17G.
6. Luck, R. Earle (January 2017), "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants", The Astronomical Journal, 153 (1): 19, arXiv:1611.02897, Bibcode:2017AJ....153...21L, doi:10.3847/1538-3881/153/1/21, S2CID 119511744, 21.
7. Roberts, Lewis C., Jr.; et al. (March 2017), "Continued Kinematic and Photometric Investigations of Hierarchical Solar-type Multiple Star Systems", The Astronomical Journal, 153 (3): 7, arXiv:1701.05865, Bibcode:2017AJ....153..100R, doi:10.3847/1538-3881/153/3/100, S2CID 119013557, 100.
8. "34 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-12-01.
9. Eggen, Olin J. (October 1992), "The Hyades Supercluster in FK5", Astronomical Journal, 104: 1482, Bibcode:1992AJ....104.1482E, doi:10.1086/116333.
10. Tokovinin, Andrei; Horch, Elliott P. (November 2016), "Speckle Interferometry of Secondary Components in Nearby Visual Binaries", The Astronomical Journal, 152 (5): 7, arXiv:1608.06586, Bibcode:2016AJ....152..116T, doi:10.3847/0004-6256/152/5/116, S2CID 119270753, 116.
11. Tokovinin, Andrei (2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 87, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, S2CID 56066740.