Psi Cygni

ψ Cygni, Latinised as Psi Cygni, is a triple star[3] system in the constellation called Cygnus. With a combined apparent visual magnitude of 4.92,[2] it is visible to the naked eye. As of 2002, the inner pair, components Aa and Ab, had an angular separation of 0.10 arc seconds along a position angle of 77.6°.[12] Their combined visual magnitude is 5.05.[3] Relative to this pair, the third member of the system, magnitude 7.61[3] component B, had an angular separation of 2.87 arc seconds along a position angle of 175.6° as of 2010.[13] Based upon an annual parallax shift of 11.59 mas,[1] Psi Cygni is located around 281 light years from the Sun.

Psi Cygni
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 19h 55m 37.78622s[1]
Declination +52° 26′ 20.2116″[1]
Apparent magnitude (V) 4.92[2] (5.05 + 7.61)[3]
Characteristics
A
Spectral type A4 Vn[4]
U−B color index +0.05[2]
B−V color index +0.13[2]
B
Spectral type F4 V[5]
Astrometry
Radial velocity (Rv)−10[6] km/s
Proper motion (μ) RA: −37.62[1] mas/yr
Dec.: −31.13[1] mas/yr
Parallax (π)11.59 ± 0.38[1] mas
Distance281 ± 9 ly
(86 ± 3 pc)
Absolute magnitude (MV)+0.23[7]
Orbit[8]
PrimaryAa
CompanionAb
Period (P)54.08 yr
Semi-major axis (a)0.141″
Eccentricity (e)0.484
Inclination (i)112.0°
Details
ψ Cyg Aa
Luminosity62[9] L☉
Temperature7,971[9] K
Rotational velocity (v sin i)207[4] km/s
ψ Cyg B
Rotational velocity (v sin i)120[10] km/s
Other designations
ψ Cyg, 24 Cygni, BD+52° 2572, HD 189037, HIP 98055, HR 7619, SAO 32114, WDS 19556+5226.[11]
Database references
SIMBADdata

The brighter member of the system, presumably component Aa, displays the spectrum of an A-type main sequence star with a stellar classification of A4 Vn,[4] where the 'n' notation indicates "nebulous" absorption lines due to rapid rotation. It appears to be a spinning with a projected rotational velocity of 207.[4] The component is radiating 62 times the solar luminosity from its outer atmosphere at an effective temperature of 7,971 K.[9]

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. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data: 0, Bibcode:1986EgUBV........0M.
  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. Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
  5. Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879.
  6. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and Their Applications. 30. p. 57. Bibcode:1967IAUS...30...57E.
  7. 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.
  8. Tokovinin, Andrei (2018). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235: 6. arXiv:1712.04750. doi:10.3847/1538-4365/aaa1a5. S2CID 119047709.
  9. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  10. Uesugi, Akira; Fukuda, Ichiro (1970). Catalogue of rotational velocities of the stars. Contributions from the Institute of Astrophysics and Kwasan Observatory. Bibcode:1970crvs.book.....U.
  11. "* psi Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-21.
  12. Roberts, Lewis C., Jr. (May 2011), "Astrometric and photometric measurements of binary stars with adaptive optics: observations from 2002", Monthly Notices of the Royal Astronomical Society, 413 (2): 1200–1205, arXiv:1012.3383, Bibcode:2011MNRAS.413.1200R, doi:10.1111/j.1365-2966.2011.18205.x, S2CID 118398949.
  13. Mason, Brian D.; et al. (August 2011), "Speckle Interferometry at the U.S. Naval Observatory. XVII.", The Astronomical Journal, 142 (2): 4, Bibcode:2011AJ....142...46M, doi:10.1088/0004-6256/142/2/46, 46.
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