31 Pegasi

31 Pegasi is a single[9] star in the northern constellation of Pegasus. It is visible to the naked eye as a dim, blue-white hued point of light with a baseline apparent visual magnitude of 4.99.[2] It is located approximately 1,600 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −5.3 km/s.[4]

A light curve for IN Pegasi, plotted from Hipparcos data[10]
31 Pegasi
Location of 31 Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension 22h 21m 31.07511s[1]
Declination 12° 12′ 18.6628″[1]
Apparent magnitude (V) 4.99[2]
Characteristics
Spectral type B2IV-Ve[3]
U−B color index -0.81[2]
B−V color index -0.10[2]
Variable type γ Cas
Astrometry
Radial velocity (Rv)−5.30[4] km/s
Proper motion (μ) RA: +6.32[1] mas/yr
Dec.: +4.80[1] mas/yr
Parallax (π)2.01 ± 0.28 mas[1]
Distanceapprox. 1,600 ly
(approx. 500 pc)
Absolute magnitude (MV)−3.61[5]
Details[6]
Mass12.5±0.7 M☉
Luminosity (bolometric)27,925+4,360
−3,770 L☉
Surface gravity (log g)3.71±0.15 cgs
Temperature23,890±740 K
Rotational velocity (v sin i)98±8 km/s
Age15.4±1.3[7] Myr
Other designations
31 Peg, IN Peg, BD+11°4784, FK5 843, GC 31255, HD 212076, HIP 110386, HR 8520, SAO 107854[8]
Database references
SIMBADdata

This is a massive Be star with a stellar classification of B2IV-V.[11] It is a γ Cas variable; a type of shell star with a circumstellar disc of gas surrounding the star at the equator, and ranges from 5.05 up to 4.85 in visual magnitude.[12] It is spinning with a projected rotational velocity of 98 km/s, with the pole being inclined by an estimated angle of 26°±9° to the line of sight from the Earth.[6] The star is 15.4[7] million years old with 12.5[6] times the mass of the Sun. It is radiating around 28,000 times the luminosity of the Sun from its photosphere at an effective temperature of 23,890 K.[6]

References
  1. Van Leeuwen, F. (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. S2CID 18759600. 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". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H (5th Revised ed.). 5050. Bibcode:1995yCat.5050....0H.
  4. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  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. S2CID 119257644. Vizier catalog entry
  6. Zorec, J.; et al. (2016). "Critical study of the distribution of rotational velocities of Be stars". Astronomy & Astrophysics. 595: A132. Bibcode:2016A&A...595A.132Z. doi:10.1051/0004-6361/201628760.
  7. Tetzlaff, N.; et al. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873. Vizier catalog entry
  8. "31 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-07-01.
  9. 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. S2CID 14878976.
  10. "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  11. Lesh, Janet Rountree (December 1968). "The Kinematics of the Gould Belt: an Expanding Group?". Astrophysical Journal Supplement. 17: 371. Bibcode:1968ApJS...17..371L. doi:10.1086/190179.
  12. Samus, N. N.; Durlevich, O. V.; et al. (2009). "General Catalogue of Variable Stars". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S.
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