Phi Cygni

Phi Cygni
Location of φ Cygni (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Cygnus
Right ascension 19h 39m 22.606s
Declination +30° 09′ 11.957″
Apparent magnitude (V) 4.70 (5.31 + 5.6)
Characteristics
Evolutionary stage red clump
Spectral type G8III + G8III
U−B color index +0.81
B−V color index +0.98
Astrometry
Radial velocity (Rv)+4.50 km/s
Proper motion (μ) RA: +1.520 mas/yr
Dec.: +35.883 mas/yr
Parallax (π)12.7786±0.1207 mas
Distance255 ± 2 ly
(78.3 ± 0.7 pc)
Absolute magnitude (MV)+0.12 (+0.77/+1.07)
Orbit
Period (P)434.208 days
Semi-major axis (a)26.9 mas″
Eccentricity (e)0.5557
Inclination (i)80.8°
Longitude of the node (Ω)251°
Periastron epoch (T)2451239.58
Argument of periastron (ω)
(secondary)		209.41°
Semi-amplitude (K1)
(primary)		26.40 km/s
Semi-amplitude (K2)
(secondary)		27.22 km/s
Details
A
Mass2.104±0.049 M☉
Radius7.46 R☉
Luminosity34.7+2.5
−2.3 L☉
Temperature5,130±120 K
Metallicity [Fe/H]−0.11 dex
Rotational velocity (v sin i)4.7 km/s
Age479+58
−52 Myr
B
Mass2.040±0.042 M☉
Radius7.04 R☉
Luminosity28±3 L☉
Temperature5,010 K
Rotational velocity (v sin i)4.8 km/s
Age562+69
−61 Myr
Other designations
φ Cygni, 12 Cygni, BD+29°3684, GC 27203, HD 185734, HIP 96683, HR 7478, SAO 68637, WDS J19394+3009AB
Database references
SIMBADdata

Phi Cygni is a binary star system in the northern constellation of Cygnus. Its name is a Bayer designation that is Latinized from φ Cygni and abbreviated Phi Cyg or φ Cyg. This system is faintly visible to the naked eye as a point of light with an apparent visual magnitude of 4.70. The annual parallax shift is 12.78 mas as measured from Earth, which yields a distance estimate of approximately 255 light years. It is moving further from the Sun with a radial velocity of +4.5 km/s.

φ Cygni is a double-lined spectroscopic binary system, which means that the absorption lines of both components are visible in the spectrum. The pair have an orbital period of 434.208 days, or 1.2 Earth years, a semimajor axis of 26.9 mas, and a high eccentricity of 0.56.

The two sets of spectral lines are almost identical and both stars are assigned a spectral type of K0III, meaning they have evolved into giants. They are considered to be red clump giants, stars that have begun core helium fusion and lie on the horizontal branch but because of their metallicity and the size of their hydrogen envelope they are found very close to the red giant branch. The two stars are assumed to have the same age, which would be around 650 million years.

Notes

  1. ↑ Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:
  2. ↑ Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K:

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 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 Fernie, J. D. (June 1969), "UBV observations of miscellaneous stars", Journal of the Royal Astronomical Society of Canada, 63: 133–135, Bibcode:1969JRASC..63..133F.
  4. 1 2 3 4 Pourbaix, D (2000), "Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses", Astronomy and Astrophysics Supplement, 145 (2): 215–222, Bibcode:2000A&AS..145..215P, doi:10.1051/aas:2000237.
  5. 1 2 Fekel, F. C (2004), "The Spectroscopic Orbit of φ Cygni, a System with Two Late-Type Giants", The Environment and Evolution of Double and Multiple Stars, 21: 63, Bibcode:2004RMxAC..21...63F.
  6. 1 2 Armstrong, J. T.; et al. (1992), "The orbit of Phi Cygni measured with long-baseline optical interferometry - Component masses and absolute magnitudes", Astronomical Journal, 104: 2217, arXiv:1304.2530, Bibcode:1992AJ....104.2217A, doi:10.1086/116396.
  7. 1 2 3 Piccotti, Luca; et al. (2020-02-01), "A study of the physical properties of SB2s with both the visual and spectroscopic orbits", Monthly Notices of the Royal Astronomical Society, 492 (2): 2709–2721, Bibcode:2020MNRAS.492.2709P, doi:10.1093/mnras/stz3616, ISSN 0035-8711. Phi Cygni's database entry at VizieR.
  8. 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.
  9. 1 2 Armstrong, J. T.; et al. (1992), "The orbit of Phi Cygni measured with long-baseline optical interferometry - Component masses and absolute magnitudes", Astronomical Journal, 104: 2217, Bibcode:1992AJ....104.2217A, doi:10.1086/116396.
  10. 1 2 3 4 5 6 7 8 9 10 Massarotti, Alessandro; et al. (2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  11. ↑ "* phi Cyg", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2016-04-10.
  12. ↑ 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 Vizier catalog entry
  13. ↑ Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121.