Pi2 Pegasi

π2 Pegasi, Latinized as Pi2 Pegasi, is a single[8] star in the northern constellation Pegasus. It is yellow-white in hue and visible to the naked eye as a faint point of light with an apparent visual magnitude of +4.28.[2] The distance to this object is approximately 263 light years based on parallax,[1] and it is drifting further away with a radial velocity of +5 km/s.[2] This star is an outlying member of the Ursa Major Moving Group.[9]

π1 Pegasi (right) and π2 Pegasi (left) in optical light
For other stars with this Bayer designation see π Pegasi
π2 Pegasi
Location of π2 Pegasi (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension  22h 09m 59.24371s[1]
Declination +33° 10′ 41.5976″ [1]
Apparent magnitude (V) +4.28[2]
Characteristics
Spectral type F5 III[3]
B−V color index 0.471±0.012[2]
Astrometry
Radial velocity (Rv)+5.1±0.9[2] km/s
Proper motion (μ) RA: −12.87±0.12[1] mas/yr
Dec.: −18.95±0.16[1] mas/yr
Parallax (π)12.40 ± 0.17[1] mas
Distance263 ± 4 ly
(81 ± 1 pc)
Absolute magnitude (MV)0.21[4]
Details
Mass2.48[5] M☉
Radius8.5±0.8[6] R☉
Luminosity102.9±2.6[6] L☉
Temperature6,300+298
−263[6] K
Rotational velocity (v sin i)139.7[4] km/s
Age530[5] Myr
Other designations
π2 Peg, 29 Pegasi, BD+32°4352, FK5 835, HD 210459, HIP 109410, HR 8454, SAO 72077[7]
Database references
SIMBADdata

This object has a stellar classification of F5 III,[3] matching an aging giant star that has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. At present it has 8.5[6] times the radius of the Sun. The star is 530[5] million years old with 2.48[5] times the Sun's mass. It shows a high rotation rate considering its evolutionary status, with a projected rotational velocity of 140 km/s.[4] The star has been noted as a possible variable shell star.[10] Pi2 Pegasi is radiating 103 times the Sun's luminosity from its swollen photosphere at an effective temperature of 6,300 K.[6]

References
  1. van Leeuwen, F. (November 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
  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.
  3. Herbig, George H.; Spalding, John F., Jr. (January 1955), "Axial Rotation and Line Broadening in Stars of Spectral Types F0-K5", Astrophysical Journal, 121: 118, Bibcode:1955ApJ...121..118H, doi:10.1086/145969.
  4. Reiners, A. (January 2006), "Rotation- and temperature-dependence of stellar latitudinal differential rotation", Astronomy and Astrophysics, 446 (1): 267–277, arXiv:astro-ph/0509399, Bibcode:2006A&A...446..267R, doi:10.1051/0004-6361:20053911.
  5. Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88.
  6. 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.
  7. "pi02 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-11.
  8. 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.
  9. Chupina, N. V.; et al. (June 2006), "Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars", Astronomy and Astrophysics, 451 (3): 909–916, Bibcode:2006A&A...451..909C, doi:10.1051/0004-6361:20054009.
  10. Hauck, B.; Jaschek, C. (February 2000), "A-shell stars in the Geneva system", Astronomy and Astrophysics, 354: 157–162, Bibcode:2000A&A...354..157H.
  • Kaler, James B. "Pi Pegasi". Stars. University of Illinois. Retrieved 16 March 2016.
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