70 Pegasi

70 Pegasi is a binary star^[6] system in the northern constellation Pegasus. It is a faint star, visible to the naked eye under good seeing conditions, with an apparent visual magnitude of 4.56.^[2] The measured annual parallax shift measured from Earth's orbit is 18.65 mas,^[1] yielding a distance estimate of around 175 light years. The visual magnitude of the star is diminished by an extinction of 0.07±0.02 due to interstellar dust. It is moving closer to the Sun with a radial velocity of −17 km/s.^[4]

70 Pegasi

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Pegasus
Right ascension	23h 29m 09.29698s[1]
Declination	+12° 45′ 37.9918″[1]
Apparent magnitude (V)	4.56[2]
Characteristics
Spectral type	G8 IIIa[3]
B−V color index	0.940[2]
Astrometry
Radial velocity (Rv)	−16.88±0.43[4] km/s
Proper motion (μ)	RA: +61.40[1] mas/yr Dec.: +24.82[1] mas/yr
Parallax (π)	18.65 ± 0.78 mas[1]
Distance	175 ± 7 ly (54 ± 2 pc)
Absolute magnitude (MV)	0.90[5]
Orbit[6]
Period (P)	941.03±0.12 d
Eccentricity (e)	0.713±0.006
Argument of periastron (ω) (secondary)	57.0±1.2°
Semi-amplitude (K1) (primary)	3.16±0.04 km/s
Details[4]
70 Peg A
Mass	2.49±0.06 M☉
Radius	8.95±0.69[7] R☉
Luminosity	49.2±2.4[7] L☉
Surface gravity (log g)	2.92±0.05 cgs
Temperature	5,108±185[7] K
Metallicity [Fe/H]	0.05±0.03 dex
Rotational velocity (v sin i)	3.6[8] km/s
Age	590±40 Myr
Other designations
70 Peg, BD+11° 5009, FK5 885, HD 221115, HIP 115919, HR 8923, SAO 108638[9]
Database references
SIMBAD	data

This is a single-lined spectroscopic binary with an orbital period of 2.58 years (941 days) and a high eccentricity of 0.713.^[6] The visible component has a stellar classification of G8 IIIa,^[3] indicating it is an evolved G-type giant star. It is a probable red clump star, which would mean it is generating energy through helium fusion at its core.^[10] The star has 2.5 times the mass of the Sun^[4] and has expanded to nine times the Sun's radius. It is radiating about 49 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,108 K.^[7]

The secondary is most likely a low mass main sequence star with no more than 0.4 times the mass of the Sun.^[6]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
4. Maldonado, J.; et al. (June 2013), "The metallicity signature of evolved stars with planets", Astronomy & Astrophysics, 554: 18, arXiv:1303.3418, Bibcode:2013A&A...554A..84M, doi:10.1051/0004-6361/201321082, S2CID 119289111, A84
5. 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.
6. Griffin, R. F. (August 2009), "Spectroscopic binary orbits from photoelectric radial velocities. Paper 207: 58 Piscium, 31 Vulpeculae, and 70 Pegasi", The Observatory, 129: 198−218, Bibcode:2009Obs...129..198G.
7. Baines, Ellyn K.; Clark, James H., III; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.{{cite journal}}: CS1 maint: multiple names: authors list (link)
8. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
9. "70 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-20.
10. Puzeras, E.; et al. (October 2010), "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements", Monthly Notices of the Royal Astronomical Society, 408 (2): 1225−1232, arXiv:1006.3857, Bibcode:2010MNRAS.408.1225P, doi:10.1111/j.1365-2966.2010.17195.x, S2CID 44228180