31 Cygni

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This article is about ο1 Cygni. For other star systems with this Bayer designation, see ο Cygni.
31 Cygni
Cygnus constellation map.svg
Red circle.svg
Location of 31 Cygni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 20h 13m 37.911s[1]
Declination +46° 44′ 28.739″[1]
Apparent magnitude (V) 3.73 - 3.89[2]
Characteristics
Spectral type K4Iab + B4IV-V[2]
Variable type Algol[2]
Astrometry
Radial velocity (Rv)–7.41 ± 0.08[3] km/s
Proper motion (μ) RA: 0.133 ± 0.672[1] mas/yr
Dec.: 4.834 ± 0.633[1] mas/yr
Parallax (π)4.3432 ± 0.3464[1] mas
Distance750 ± 60 ly
(230 ± 20 pc)
Orbit[4]
Period (P)3,784.3 d
Eccentricity (e)0.2084 ± 0.0031
Periastron epoch (T)2,452,345 ± 9
Argument of periastron (ω)
(secondary)		204.5 ± 1.0°
Semi-amplitude (K1)
(primary)		13.94 ± 0.04 km/s
Semi-amplitude (K2)
(secondary)		18.0[5] km/s
Details
K supergiant
Mass6.73[5] M☉
Radius127[6] R☉
Luminosity2,512 - 2,559[6] L☉
Temperature4,043±170[6] K
B dwarf
Mass5.22[5] M☉
Radius5.2 ± 0.5[7] R☉
Temperature16,500+1,000
−2,000[8] K
Age39.8[9] Myr
Other designations
ο1 Cyg, ο2 Cyg,[10] 31 Cyg, V695 Cyg, HD 192577, BD+46°2882, HIP 99675, HR 7735, SAO 49337
Database references
SIMBADdata
31 Cygni is the close pair. The third star is 30 Cygni.

31 Cygni, also known as ο1 Cygni, Omicron1 Cygni, or V695 Cygni, is a star in the constellation Cygnus.

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.[10]

An ultraviolet band light curve for the 1982 eclipse of V695 Cygni, adapted from Stencel et al. (1984)[11]

It is an Algol-type eclipsing binary and ranges between magnitudes 3.73 and 3.89 over a period of ten years. The component stars are an orange supergiant of spectral type K4Iab and a blue-white star likely to be evolving off the main sequence with a spectral type of B4IV-V. 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.[5]

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.

References[]

  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. ^ a b c 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. ^ 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.
  4. ^ 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.
  5. ^ a b c d Bennett, Philip; Brown, Alexander; Ayres, Thomas R. (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.
  6. ^ a b c 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.
  7. ^ Eaton, Joel A. (1993). "31 Cygni: The B star and the wind". Astronomical Journal. 106: 2081. Bibcode:1993AJ....106.2081E. doi:10.1086/116787.
  8. ^ 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.
  9. ^ 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.
  10. ^ a b 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.
  11. ^ 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.
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