Psi Pegasi

Psi Pegasi, which is Latinized from ψ Pegasi, is a binary star system within the great square[11] in the northern constellation of Pegasus. It has a red hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.66.[2] This object is located at a distance of approximately 476 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −6.6 km/s.[5]

Psi Pegasi
Location of ψ Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension  23h 57m 45.52681s[1]
Declination 25° 08′ 29.0480″[1]
Apparent magnitude (V) 4.66[2]
Characteristics
Spectral type M3III[3]
U−B color index +1.66[2]
B−V color index +1.59[2]
Variable type suspected[4]
Astrometry
Radial velocity (Rv)−6.59±0.23[5] km/s
Proper motion (μ) RA: −35.24[1] mas/yr
Dec.: −31.60[1] mas/yr
Parallax (π)6.85 ± 0.24[1] mas
Distance480 ± 20 ly
(146 ± 5 pc)
Absolute magnitude (MV)–1.19[6]
Orbit[7]
Period (P)55.06±11.31 yr
Semi-major axis (a)0.170±0.016″
Eccentricity (e)0.19±0.10
Inclination (i)65.6±2.2°
Longitude of the node (Ω)46.6±2.3°
Periastron epoch (T)2,001.83±8.81
Argument of periastron (ω)
(secondary)		159.7±11.9°
Details
Radius98±6[8] R☉
Luminosity960[6] L☉
Temperature3,882[9] K
Other designations
ψ Peg, 84 Pegasi, NSV 14777, BD+24°4865, FK5 1629, GC 33230, HD 224427, HIP 118131, HR 9064, SAO 91611, WDS J23578+2508AB[10]
Database references
SIMBADdata

The orbital elements for this system were computed for the first time in 2004 based on interferometric observations, yielding an orbital period of roughly 55 years and an eccentricity of about 0.19.[7][12][13] The visible component is an aging red giant star on the asymptotic giant branch[14] with a stellar classification of M3III.[3] It is a suspected variable, probably semiregular, with its magnitude varying from 4.63 to 4.69[4][15] over periods of 37.4 and 118.9 days.[16] With the supply of hydrogen exhausted at its core, the star has cooled and expanded to around 98[8] times the Sun's radius. It is radiating 960[6] times the luminosity of the Sun from its bloated photosphere at an effective temperature of 3,882 K.[9]

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. 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. 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. Bibcode:2009yCat....1.2025S.
  5. 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.
  6. 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
  7. Olevic, D.; Cvetkovic, Z. (2004). "Orbits of 6 Binaries". Serbian Astronomical Journal. 168: 25. Bibcode:2004SerAJ.168...25O.
  8. Arroyo-Torres, B.; et al. (June 2014), "VLTI/AMBER observations of cold giant stars: atmospheric structures and fundamental parameters", Astronomy & Astrophysics, 566: 11, arXiv:1404.7384, Bibcode:2014A&A...566A..88A, doi:10.1051/0004-6361/201323264, A88.
  9. Martínez, M. Isabel Pérez; et al. (2011). "The basal chromospheric Mg ii h+k flux of evolved stars: Probing the energy dissipation of giant chromospheres". Monthly Notices of the Royal Astronomical Society. 414: 418. arXiv:1102.4832. Bibcode:2011MNRAS.414..418P. doi:10.1111/j.1365-2966.2011.18421.x. Vizier catalog entry
  10. "psi Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-26.
  11. Harrington, Philip S. (2010). Cosmic Challenge: The Ultimate Observing List for Amateurs. Cambridge University Press. p. 50. ISBN 9781139493680.
  12. Malkov, O. Yu.; Tamazian, V. S.; Docobo, J. A.; Chulkov, D. A. (2012). "Dynamical masses of a selected sample of orbital binaries". Astronomy & Astrophysics. 546: A69. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. Vizier catalog entry
  13. Mason, Brian D.; et al. (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
  14. Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
  15. Watson, C. L. (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25. 25: 47. Bibcode:2006SASS...25...47W.
  16. Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (December 2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–1961. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x.
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