31 Cygni

31 Cygni
Location of 31 Cygni (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Cygnus
31 Cygni A
Right ascension 20h 13m 37.908s
Declination +46° 44′ 28.76″
Apparent magnitude (V) 3.73 to 3.89
HD 192579
Right ascension 20h 13m 39.199s
Declination +46° 42′ 42.70″
Apparent magnitude (V) 6.99
Characteristics
31 Cygni A
Spectral type K3Ib + B2IV-V
Variable type Algol
HD 192579
Evolutionary stage main sequence
Spectral type B5V
Astrometry
31 Cygni A
Radial velocity (Rv)−7.41±0.08 km/s
Proper motion (μ) RA: 1.744 mas/yr
Dec.: 3.390 mas/yr
Parallax (π)2.9167±0.1327 mas
Distance1,120 ± 50 ly
(340 ± 20 pc)
HD 192579
Proper motion (μ) RA: 3.906 mas/yr
Dec.: 1.978 mas/yr
Parallax (π)2.9160±0.0336 mas
Distance1,120 ± 10 ly
(343 ± 4 pc)
Orbit
Primary31 Cygni Aa
Secondary31 Cygni Ab
Period (P)10.301+0.030
−0.037 years
Eccentricity (e)0.203+0.007
−0.008
Inclination (i)101.007+28.772
−18.623°
Longitude of the node (Ω)307.271+9.802
−11.253°
Periastron epoch (T)1950.508+0.171
−0.129
Argument of periastron (ω)
(secondary)		198.619+2.771
−1.963°
Semi-amplitude (K1)
(primary)		13.94±0.04 km/s
Semi-amplitude (K2)
(secondary)		18.0 km/s
Details
K supergiant
Mass9.44+1.51
−1.39 M☉
Radius127 R☉
Luminosity2,512 to 2,559 L☉
Temperature4,043±170 K
B dwarf
Mass6.475 M☉
Radius5.2±0.5 R☉
Temperature16,500+1,000
−2,000 K
Age39.8 Myr
HD 192579
Mass4.1 M☉
Radius3.3 R☉
Luminosity373 L☉
Surface gravity (log g)4.04 cgs
Temperature13,949 K
Metallicity [Fe/H]+0.68 dex
Other designations
ο1 Cyg, ο2 Cyg, 31 Cyg, ADS 13554, WDS J20136+4644
31 Cygni A (HD 192577): V695 Cyg, BD+46°2882, HD 192577, HIP 99675, HR 7735, SAO 49337
HD 192579: BD+46°2883, HD 192579, HIP 99676, SAO 49338
Database references
SIMBADdata
HD 192579
31 Cygni is the close pair, with 30 Cygni towards top left. (north is to the left)

31 Cygni is a ternary star system in the constellation of Cygnus. Alternatively, it is known as ο1 Cygni, Omicron1 Cygni, ο2 Cygni or V695 Cygni. Based on parallax measurements, it is located at a distance of approximately 1,120 light years.

The Bayer designation ο (omicron) has been variously applied to two or three of the stars 30, 31, and 32 Cygni. 31 Cygni has been designated, variously, as ο1 or ο2 Cygni — therefore for clarity, it is preferred to use the Flamsteed designation 31 Cygni.

31 Cygni consists of a visible pair of stars 109″ apart as of 2016, and the brighter of the two is also a spectroscopic binary. 31 Cygni A is also designated HD 192577 and HR 7735, while its 7th-magnitude visual companion is designated HD 192579. Some multiple star catalogues designate a 13th-magnitude star 36″ from 31 Cygni A as 31 Cygni B, and HD 192579 as 31 Cygni C. The 13th-magnitude star is likely to be an unrelated background object.

The spectroscopic pair are an orange supergiant of spectral type K3Ib and a blue-white star likely to be evolving off the main sequence with a spectral type of B2IV-V. The visible companion is a 7th-magnitude B5 main sequence star.

An ultraviolet band light curve for the 1982 eclipse of V695 Cygni, adapted from Stencel et al. (1984)

31 Cygni A is an Algol-type eclipsing binary and ranges between magnitudes 3.73 and 3.89 over a period of ten years. The eclipsing system has been studied in attempts to determine an accurate direct mass for a red supergiant. The value 6.73 M☉ is believed to be accurate to about 2%, but there are some discrepancies in the orbital fit.

30 Cygni is another naked eye star a tenth of a degree away, forming a bright triple.

32 Cygni is about a degree away to the north, also a detached eclipsing binary system. It comprises a large cool evolved star and a small hot main sequence or subgiant companion.

Notes

  1. ↑ from primary mass and mass ratio

References

  1. 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.
  2. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 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.
  4. 1 2 3 4 Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  5. ↑ Weaver, Wm. Bruce (2000). "Spectral Classification of Unresolved Binary Stars with Artificial Neural Networks". The Astrophysical Journal. 541 (1): 298–305. Bibcode:2000ApJ...541..298W. doi:10.1086/309425.
  6. ↑ Eaton, Joel A.; et al. (2008). "Orbits and Pulsations of the Classical ζ Aurigae Binaries". The Astrophysical Journal. 679 (2): 1490–1498. arXiv:0802.2238. Bibcode:2008ApJ...679.1490E. doi:10.1086/587452. S2CID 2079219.
  7. 1 2 3 Videla, Miguel; et al. (April 2022). "Bayesian Inference in Single-line Spectroscopic Binaries with a Visual Orbit". The Astronomical Journal. 163 (5): 220. arXiv:2203.07438. Bibcode:2022AJ....163..220V. doi:10.3847/1538-3881/ac5ab4. ISSN 1538-3881.
  8. 1 2 Griffin, R. F. (2008). "Spectroscopic binary orbits from photoelectric radial velocities - Paper 202: 31 and 32 Cygni". The Observatory. 128: 362. Bibcode:2008Obs...128..362G.
  9. 1 2 Bennett, Philip; et al. (2018). "An Accurate Mass of the 31 Cygni Red Supergiant". Cambridge Workshop on Cool Stars: 46. Bibcode:2018csss.confE..46B. doi:10.5281/zenodo.1467958.
  10. 1 2 3 Messineo, M.; Brown, A. G. A. (2019). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal. 158 (1): 20. arXiv:1905.03744. Bibcode:2019AJ....158...20M. doi:10.3847/1538-3881/ab1cbd. S2CID 148571616.
  11. ↑ Eaton, Joel A. (1993). "31 Cygni: The B star and the wind". Astronomical Journal. 106: 2081. Bibcode:1993AJ....106.2081E. doi:10.1086/116787.
  12. ↑ Di Benedetto, G. P.; Ferluga, S. (1990). "Angular diameters of Zeta Aurigae-type supergiants by Michelson interferometry". Astronomy and Astrophysics. 236: 449. Bibcode:1990A&A...236..449D.
  13. ↑ 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.
  14. 1 2 Kostjuk, N. D. (2004). "VizieR Online Data Catalog: HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)". VizieR On-line Data Catalog: IV/27A. Originally Published in: Institute of Astronomy of Russian Academy of Sciences (2002). 4027. Bibcode:2004yCat.4027....0K.
  15. ↑ 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.
  16. ↑ 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.
  17. ↑ Stencel, Robert E.; Hopkins, Jeffrey L.; Hagen, Wendy; Fried, Robert; Schmidtke, Paul C.; Kondo, Yoji; Chapman, Robert D. (June 1984). "The 1982 eclipse of 31 Cygni". The Astrophysical Journal. 281: 751–759. Bibcode:1984ApJ...281..751S. doi:10.1086/162153. Retrieved 21 December 2021.