Astronomy:Pi2 Cygni

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Short description: Triple star system in the constellation Cygnus


For other stars with this Bayer designation, see π Cygni.
Pi2 Cygni
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cygnus
Right ascension  21h 46m 47.60832s[1]
Declination +49° 18′ 34.4511″[1]
Apparent magnitude (V) 4.24[2]
Characteristics
Spectral type B2.5 III[3]
U−B color index −0.79[2]
B−V color index −0.125[2]
Variable type β Cep[4]
Astrometry
Radial velocity (Rv)−12.3[5] km/s
Proper motion (μ) RA: +2.77[1] mas/yr
Dec.: −2.00[1] mas/yr
Parallax (π)2.95 ± 0.34[1] mas
Distanceapprox. 1,100 ly
(approx. 340 pc)
Absolute magnitude (MV)−3.39[6]
Orbit[7]
Period (P)72.0162 d
Eccentricity (e)0.34
Periastron epoch (T)2428410.6 JD
Argument of periastron (ω)
(secondary)		238.1°
Semi-amplitude (K1)
(primary)		7.8 km/s
Details
π2 Cyg A
Mass8.4±0.4[8] M☉
Radius7.1[9] R☉
Luminosity (bolometric)8,442[10] L☉
Surface gravity (log g)3.69±0.16[11] cgs
Temperature20,815±1,057[11] K
Metallicity [Fe/H]0.04±0.09[11] dex
Rotational velocity (v sin i)50±5[4] km/s
Age33.2±5.8[8] Myr
Other designations
π2 Cyg, 81 Cygni, BD+48° 3504, FK5 821, HD 207330, HIP 107533, HR 8335, SAO 51293.[12]
Database references
SIMBADdata

Pi2 Cygni, Latinized from π2 Cygni, is a triple star[13] system in the northern constellation of Cygnus. It is visible to the naked eye about 2.5° east-northeast of the open cluster M39,[14] having an apparent visual magnitude of 4.24.[2] Based upon an annual parallax shift of 2.95 mas,[1] it is located at a distance of roughly 1,100 light years from the Sun.

The inner pair of stars in this system form a single-lined[15] spectroscopic binary with an orbital period of 72.0162 days and an eccentricity of 0.34.[7] The primary, component A, is a B-type giant star with a stellar classification of B2.5 III.[3] It is a Beta Cephei variable[4] with an estimated 8.4[8] times the mass of the Sun and around 7.1[9] times the Sun's radius. The star is roughly 33[8] million years old and is spinning with a projected rotational velocity of 50[4] km/s. It is radiating 8,442[10] times the solar luminosity from its outer atmosphere at an effective temperature of around 20,815[11] K.

The third member of this system is a magnitude 5.98 star at an angular separation of 0.10 arc seconds along a position angle of 129°, as of 1996.[16]

Historical names

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of π2 Cygni, α Lacertae, 4 Lacertae, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ψ Andromedae and ι Andromedae. Consequently, the Chinese name for π2 Cygni itself is 螣蛇三 (Téng Shé sān, English: the Third Star of Flying Serpent)[17]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data (SIMBAD), Bibcode: 1986EgUBV........0M. 
  3. ↑ 3.0 3.1 Walborn, N. R. (1971), "Some Spectroscopic Characteristics of the OB Stars: An Investigation of the Space Distribution of Certain OB Stars and the Reference Frame of the Classification", The Astrophysical Journal Supplement Series 23: 257, doi:10.1086/190239, Bibcode: 1971ApJS...23..257W. 
  4. ↑ 4.0 4.1 4.2 4.3 Silvester, J. et al. (September 2009), "On the incidence of magnetic fields in slowly pulsating B, β Cephei and B-type emission-line stars", Monthly Notices of the Royal Astronomical Society 398 (3): 1505–1511, doi:10.1111/j.1365-2966.2009.15208.x, Bibcode: 2009MNRAS.398.1505S. 
  5. ↑ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication (Washington: Carnegie Institution of Washington), Bibcode: 1953GCRV..C......0W. 
  6. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Pourbaix, D. et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics 424 (2): 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P. 
  8. ↑ 8.0 8.1 8.2 8.3 Tetzlaff, N. et al. (January 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T. 
  9. ↑ 9.0 9.1 Pasinetti Fracassini, L. E. et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics 367: 521–524, doi:10.1051/0004-6361:20000451, Bibcode: 2001A&A...367..521P. 
  10. ↑ 10.0 10.1 Hohle, M. M. et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, doi:10.1002/asna.200911355, Bibcode: 2010AN....331..349H. 
  11. ↑ 11.0 11.1 11.2 11.3 Prugniel, Ph. et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics 531: A165, doi:10.1051/0004-6361/201116769, Bibcode: 2011A&A...531A.165P. 
  12. ↑ "pi.02 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=pi.02+Cyg. 
  13. ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  14. ↑ O'Meara, Stephen James (2016), Deep-Sky Companions: The Caldwell Objects (2nd ed.), Cambridge University Press, p. 92, ISBN 978-1316033531, https://books.google.com/books?id=evkODQAAQBAJ&pg=PA92. 
  15. ↑ Abt, Helmut A. et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 
  16. ↑ Mason, B. D. et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal 122 (6): 3466–3471, doi:10.1086/323920, Bibcode: 2001AJ....122.3466M. 
  17. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日



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