Pi2 Cygni

Pi2 Cygni
Location of π2 Cygni (circled in red)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 21h 46m 47.610s
Declination +49° 18′ 34.454″
Apparent magnitude (V) 4.24
Characteristics
Spectral type B2.5 III
U−B color index −0.79
B−V color index −0.125
Variable type β Cep
Astrometry
Radial velocity (Rv)−12.3 km/s
Proper motion (μ) RA: +5.478 mas/yr
Dec.: −3.121 mas/yr
Parallax (π)2.2801±0.1353 mas
Distance1,430 ± 80 ly
(440 ± 30 pc)
Absolute magnitude (MV)−3.39
Orbit
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 M☉
Radius7.1 R☉
Luminosity (bolometric)8,442 L☉
Surface gravity (log g)3.69±0.16 cgs
Temperature20,815±1,057 K
Metallicity [Fe/H]0.04±0.09 dex
Rotational velocity (v sin i)50±5 km/s
Age33.2±5.8 Myr
Other designations
π2 Cyg, 81 Cyg, BD+48°3504, FK5 821, HD 207330, HIP 107533, HR 8335, SAO 51293
Database references
SIMBADdata

Pi2 Cygni is a candidate triple star system in the northern constellation of Cygnus. Is name is a Bayer designation that is Latinized from π2 Cygni and abbreviated Pi2 Cyg or π2 Cyg. This system is visible to the naked eye as a point of light about 2.5° east-northeast of the open cluster M39, having an apparent visual magnitude of 4.24. Based upon an annual parallax shift of 2.28 mas, it is located at a distance of approximately 1,430 light years from the Sun.

Pi2 Cygni has been described as a single-lined spectroscopic binary with an orbital period of 72.0162 days and an eccentricity of 0.34. However, a 2020 paper found no radial velocity variations on the timescale of the published orbit.

The purported primary, component A, is a B-type giant star with a stellar classification of B2.5 III. It is a Beta Cephei variable with an estimated 8.4 times the mass of the Sun and around 7.1 times the Sun's radius. The star is roughly 33 million years old and is spinning with a projected rotational velocity of 50 km/s. It is radiating 8,442 times the solar luminosity from its outer atmosphere at an effective temperature of around 20,815 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.

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).

References

  1. 1 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 4 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  4. 1 2 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, Bibcode:1971ApJS...23..257W, doi:10.1086/190239.
  5. 1 2 3 4 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, arXiv:0906.1575, Bibcode:2009MNRAS.398.1505S, doi:10.1111/j.1365-2966.2009.15208.x, S2CID 16169939.
  6. ↑ 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.
  7. 1 2 Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  8. 1 2 3 4 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, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  9. 1 2 Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics, 367 (3rd ed.): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  10. 1 2 Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  11. 1 2 3 4 Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439.
  12. ↑ "pi.02 Cyg", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-02-19.
  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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  14. ↑ O'Meara, Stephen James (2016), Deep-Sky Companions: The Caldwell Objects (2nd ed.), Cambridge University Press, p. 92, ISBN 978-1316033531.
  15. ↑ Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  16. ↑ Heyne, T.; et al. (2020), "Spectroscopic characterization of nine binary star systems as well as HIP 107136 and HIP 107533", Astronomische Nachrichten, 341 (1): 99, arXiv:1912.05343, Bibcode:2020AN....341...99H, doi:10.1002/asna.202013683.
  17. ↑ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  18. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日 Archived 2011-05-21 at the Wayback Machine