Sigma Pegasi

σ Pegasi, Latinised as Sigma Pegasi, is a binary star[3] system in the northern constellation of Pegasus. With a combined apparent visual magnitude of 5.16,[2] it is faintly visible to the naked eye. Based upon an annual parallax shift of 36.66 mas as seen from Earth,[1] the system is located 89 light years distant from the Sun. It has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.524 arcseconds per year.[11]

Sigma Pegasi
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Pegasus
Right ascension 22h 52m 24.07496s[1]
Declination +09° 50′ 08.3791″[1]
Apparent magnitude (V) 5.16[2] + 13.5[3]
Characteristics
Spectral type F6 V[4] or F7 IV[5] + M4 V[3]
U−B color index −0.016[2]
B−V color index +0.486[2]
Astrometry
Radial velocity (Rv)+11.4[6] km/s
Proper motion (μ) RA: +521.04[1] mas/yr
Dec.: +42.65[1] mas/yr
Parallax (π)36.66 ± 0.29[1] mas
Distance89.0 ± 0.7 ly
(27.3 ± 0.2 pc)
Absolute magnitude (MV)3.01[7]
Details
σ Peg A
Mass1.275[6] M☉
Surface gravity (log g)3.69[4] cgs
Temperature6,250[4] K
Metallicity [Fe/H]−0.32[4] dex
Rotational velocity (v sin i)3[8] km/s
Age2.71±0.61[9] Gyr
Other designations
σ Peg, 49 Peg, BD+09° 5122, FK5 3828, HD 216385, HIP 112935, HR 8697, SAO 127810[10]
Database references
SIMBADdata

The primary, component A, is a yellow-white hued F-type main-sequence star with a stellar classification of F6 V.[4] However, Frasca et al. (2009) lists it as a somewhat more evolved F-type subgiant star with a class of F7 IV.[5] At the age of 2.7[9] billion years, it has an inactive chromosphere[4] and is spinning with a leisurely projected rotational velocity of 3 km/s.[8] It has a faint, magnitude 13.23[12] red dwarf companion, designated component B, at an angular separation of 248 arc seconds.[3] The system is most likely (96% chance) a member of the thin disk population of the Milky Way.[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.
  2. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. 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.
  4. Gray, R. O.; et al. (2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–70, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  5. Frasca, A.; et al. (December 2009), "REM near-IR and optical photometric monitoring of pre-main sequence stars in Orion. Rotation periods and starspot parameters", Astronomy and Astrophysics, 508 (3): 1313–1330, arXiv:0911.0760, Bibcode:2009A&A...508.1313F, doi:10.1051/0004-6361/200913327, S2CID 118361131.
  6. Ramírez, I.; et al. (February 2013), "Oxygen abundances in nearby FGK stars and the galactic chemical evolution of the local disk and halo", The Astrophysical Journal, 764 (1): 78, arXiv:1301.1582, Bibcode:2013ApJ...764...78R, doi:10.1088/0004-637X/764/1/78, S2CID 118751608.
  7. Karatas, Y.; Schuster, W. J. (October 2006), "Metallicity and absolute magnitude calibrations for UBV photometry", Monthly Notices of the Royal Astronomical Society, 371 (4): 1793–1812, Bibcode:2006MNRAS.371.1793K, doi:10.1111/j.1365-2966.2006.10800.x.
  8. Takeda, Yoichi; et al. (February 2005), "High-Dispersion Spectra Collection of Nearby F—K Stars at Okayama Astrophysical Observatory: A Basis for Spectroscopic Abundance Standards", Publications of the Astronomical Society of Japan, 57 (1): 13–25, Bibcode:2005PASJ...57...13T, doi:10.1093/pasj/57.1.13.
  9. Pace, G. (March 2013), "Chromospheric activity as age indicator. An L-shaped chromospheric-activity versus age diagram", Astronomy & Astrophysics, 551: 4, arXiv:1301.5651, Bibcode:2013A&A...551L...8P, doi:10.1051/0004-6361/201220364, S2CID 56420519, L8.
  10. "49 Peg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-10.
  11. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.
  12. Lépine, Sébastien; Bongiorno, Bethany (2007), "New Distant Companions to Known Nearby Stars. II. Faint Companions of Hipparcos Stars and the Frequency of Wide Binary Systems", The Astronomical Journal, 133 (3): 889–905, arXiv:astro-ph/0610605, Bibcode:2007AJ....133..889L, doi:10.1086/510333, S2CID 16800796.
  • Kaler, James B. (November 6, 2015), "Sigma Pegasi", STARS, University of Illinois, retrieved 2017-08-11.
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