72 Pegasi

72 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye as a faint, orange-hued point of light with a combined apparent visual magnitude of 4.97.[2] The system is located approximately 550 light years away from the Sun, based on parallax,[1] but is drifting closer with a radial velocity of −25 km/s.[6]

72 Pegasi
Location of 72 Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension  23h 33m 57.18791s[1]
Declination 31° 19′ 31.0058″[1]
Apparent magnitude (V) 4.97[2]
Characteristics
Spectral type K4IIIb[3]
U−B color index +1.63[4]
B−V color index +1.39[4]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)−24.71[6] km/s
Proper motion (μ) RA: +50.81[1] mas/yr
Dec.: −17.46[1] mas/yr
Parallax (π)5.94 ± 0.45[1] mas
Distance550 ± 40 ly
(170 ± 10 pc)
Absolute magnitude (MV)−1.15[2]
Orbit[7]
Period (P)492.30 ± 75.96 a (179,811 ± 27,745 d)
Semi-major axis (a)0.568 ± 0.065″
Eccentricity (e)0.322 ± 0.047
Inclination (i)21.7 ± 8.3°
Longitude of the node (Ω)56.2 ± 6.0°
Periastron epoch (T)MJD 16818 ± 3658
Argument of periastron (ω)
(secondary)		293 ± 15°
Details
Mass2 / 2[7] M☉
Luminosity554[2] L☉
Surface gravity (log g)2.00[8] cgs
Temperature4,379[9] K
Metallicity [Fe/H]+0.06[2] dex
Rotational velocity (v sin i)1.4[10] km/s
Other designations
72 Peg, NSV 14617, BD+30°4978, GC 32772, HD 221673, HIP 114155, HR 8943, SAO 73341, CCDM J23340+3120AB, WDS J23340+3120AB[11]
Database references
SIMBADdata

This is a visual binary with an orbital period of roughly 492 years and an eccentricity of 0.32. The two stars are relatively similar and are about twice the mass of the Sun each. The primary star, 72 Pegasi A, is an evolved K-type giant with a visual magnitude of 5.67. The companion, 72 Pegasi B, is another K-type giant with an apparent magnitude of 6.11, and a separation of about 0.568″ from the primary. 72 Pegasi B is thought to be a binary itself, with a brown dwarf companion in a 4.2-year period.[7]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  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. Vizier catalog entry
  3. Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  4. Mermilliod, J. C. (2006). "VizieR Online Data Catalog: Homogeneous Means in the UBV System (Mermilliod 1991)". VizieR On-line Data Catalog: II/168. Originally Published in: Institut d'Astronomie. 2168. Bibcode:2006yCat.2168....0M.Vizier catalog entry
  5. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  6. Famaey, B.; et al. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data". Astronomy & Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272.
  7. Muterspaugh, Matthew W.; et al. (2010). "The Phases Differential Astrometry Data Archive. V. Candidate Substellar Companions to Binary Systems". The Astronomical Journal. 140 (6): 1657. arXiv:1010.4048. Bibcode:2010AJ....140.1657M. doi:10.1088/0004-6256/140/6/1657.
  8. Soubiran, Caroline; Le Campion, Jean-François; Brouillet, Nathalie; Chemin, Laurent (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497.
  9. McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427: 343. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. Vizier catalog entry
  10. De Medeiros, J. R.; Mayor, M. (1999). "A catalog of rotational and radial velocities for evolved stars". Astronomy and Astrophysics Supplement Series. 139 (3): 433. arXiv:astro-ph/0608248. Bibcode:1999A&AS..139..433D. doi:10.1051/aas:1999401. Vizier catalog entry
  11. "72 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-07-05.
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