Chi Pegasi

Chi Pegasi, Latinized from χ Pegasi, is a single[11] star in the northern constellation of Pegasus, along the eastern constellation border with Pisces. It has a reddish hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.80.[2] The distance to this star is approximately 368 light years based on parallax,[1] but it is drifting closer with a radial velocity of -46 km/s.[6]

Chi Pegasi
Location of χ Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension  00h 14m 36.16451s[1]
Declination 20° 12′ 24.1205″[1]
Apparent magnitude (V) 4.80[2]
Characteristics
Evolutionary stage asymptotic giant branch[3]
Spectral type M2+III[4]
U−B color index +1.91[2]
B−V color index +1.57[2]
Variable type suspected[5]
Astrometry
Radial velocity (Rv)−46.26±0.57[6] km/s
Proper motion (μ) RA: +90.76[1] mas/yr
Dec.: +1.24[1] mas/yr
Parallax (π)8.86 ± 0.22[1] mas
Distance368 ± 9 ly
(113 ± 3 pc)
Absolute magnitude (MV)−0.47[7]
Details[8]
Mass1.06±0.11 M☉
Radius52.88+1.31
−1.37 R☉
Luminosity435±23[9] L☉
Surface gravity (log g)0.80 cgs
Temperature3,842±49 K
Metallicity [Fe/H]0.00 dex
Rotational velocity (v sin i)6.0[6] km/s
Age7.70±2.01 Gyr
Other designations
χ Peg, 89 Pegasi, NSV 99, BD+19°27, FK5 1004, GC 270, HD 1013, HIP 1168, HR 45, SAO 91792[10]
Database references
SIMBADdata

This is an aging red giant star on the asymptotic giant branch[3] with a stellar classification of M2+III.[4] It is a suspected small-amplitude variable.[5] The star is about 8 billion years old with a mass 6% greater than the Sun. With the supply of hydrogen at its core exhausted, the star has cooled and expanded to 53 times the girth of the Sun. It is radiating around 435 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,842 K.[8]

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. 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.
  4. 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.
  5. Percy, John R.; Wong, Nancy; Bohme, Dietmar; Curott, David R.; Dempsey, Frank; Fortier, George L.; Ganis, Matt; Parello, Stephanie; Landis, Howard J.; Luedeke, Kenneth D.; Pray, Donald; Smith, Michael S.; Snyder, Leroy F.; Thompson, Raymond R.; Wasson, Rick; Williams, Harold O.; Walker, William S. G.; Wood, James E. (June 1994). "Photometric Surveys of Suspected Small-Amplitude Red Variables. III. an AAVSO Photoelectric Photometry Survey". Publications of the Astronomical Society of the Pacific. 106: 611. Bibcode:1994PASP..106..611P. doi:10.1086/133420.
  6. 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.
  7. 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
  8. Baines, Ellyn K.; et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155. 30. arXiv:1712.08109. Bibcode:2018AJ....155...30B. doi:10.3847/1538-3881/aa9d8b.
  9. 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.
  10. "chi Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved January 12, 2011.
  11. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
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