1 Pegasi

1 Pegasi (1 Peg) is a triple star[11] system in the constellation Pegasus, located approximately 156 light years away from the Sun based on parallax.[1] It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.09.[2] The system is moving closer to the Earth with a heliocentric radial velocity of −11 km/s.[4]

1 Pegasi
Location of 1 Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension  21h 22m 05.199s[1]
Declination 19° 48′ 16.24″[1]
Apparent magnitude (V) 4.09[2]
Characteristics
Spectral type K1III[3]
U−B color index +1.05[2]
B−V color index +1.11[2]
Astrometry
Radial velocity (Rv)−10.80[4] km/s
Proper motion (μ) RA: +105.35[1] mas/yr
Dec.: +63.51[1] mas/yr
Parallax (π)20.93 ± 0.17[1] mas
Distance156 ± 1 ly
(47.8 ± 0.4 pc)
Absolute magnitude (MV)0.68[5]
Details
1 Peg A
Mass1.57[6] M☉
Radius12[6] R☉
Luminosity71.78[5] L☉
Surface gravity (log g)2.59[7] cgs
Temperature4,600[8] K
Metallicity [Fe/H]+0.01[7] dex
Rotational velocity (v sin i)1.2[9] km/s
Other designations
1 Peg, BD+19°4691, FK5 804, GC 29914, HD 203504, HIP 105502, HR 8173, SAO 107073, CCDM J21221+1949A, WDS J21221+1948A[10]
Database references
SIMBADdata

The primary component is a giant with a stellar classification of K1III,[3] a star that has exhausted the hydrogen supply at its core and evolved away from the main sequence. It has 1.57[6] times the mass of the Sun and has expanded to 12[6] times the Sun's radius. The star is radiating 72[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,600 K.[8]

There are several companions in addition to the primary. The brightest, component B, is a magnitude 9.3, K-type main-sequence star with a class of K0 V orbiting at an angular separation of 36.6" from the primary; it is itself a single-lined spectroscopic binary with an orbital period of 3.042 ± 0.011 years and eccentricity of 0.290±0.022.[12] Visual companions C, with magnitude 12.9 and separation 64.7", and D, with magnitude 9.6 and separation 5.3", have been reported.[13]

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. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  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. Bakos, G. A. (1974). "Radial velocity measurements of visual binaries. 1". The Astronomical Journal. 79: 866. Bibcode:1974AJ.....79..866B. doi:10.1086/111622.
  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. Vizier catalog entry
  6. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
  7. Wu, Yue; Singh, H. P.; Prugniel, P.; Gupta, R.; Koleva, M. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014.
  8. Gontcharov, G. A. (2009). "Red giant clump in the Tycho-2 catalogue". Astronomy Letters. 34 (11): 785. arXiv:1607.00619. Bibcode:2008AstL...34..785G. doi:10.1134/S1063773708110078. Vizier catalog entry
  9. 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
  10. "1 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-10.
  11. Eggleton, P. P.; Tokovinin, A. A. (2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. Vizier catalog entry
  12. Griffin, R. F. (February 1987). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 72: 1 Pegasi B". The Observatory. 107: 1–5. Bibcode:1987Obs...107....1G.
  13. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. Vizier catalog entry
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