31 Cygni

Short description: Triple star system in the constellation Cygnus

31 Cygni

Location of 31 Cygni (circled)

Observation data
{{#ifeq:J2000.0|J2000.0 (ICRS)|Epoch J2000.0 Equinox J2000.0 (ICRS)| Epoch J2000.0 [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0}}
Constellation | Cygnus
31 Cygni A
Right ascension |  20h 13m 37.908s[1]
Declination | +46° 44′ 28.76″[1]
Apparent magnitude (V) | 3.73 - 3.89[2]
HD 192379
Right ascension |  20h 13m 39.199s[3]
Declination | +46° 42′ 42.70″[3]
Apparent magnitude (V) | 6.99[4]
Characteristics
31 Cygni A
Spectral type | K3Ib + B2IV-V[5]
Variable type | Algol[2]
HD 192579
Evolutionary stage | main sequence[4][3]
Spectral type | B5V[4]
Astrometry
31 Cygni A
Radial velocity (Rv)| −7.41±0.08[6] km/s
Proper motion (μ)|  RA: 1.744[1] mas/yr
Dec.: 3.390[1] mas/yr
Parallax (π)| 2.9167 ± 0.1327[1] mas
Distance| 1,120 ± 50 ly
(340 ± 20 pc)
HD 192579
Proper motion (μ)|  RA: 3.906[3] mas/yr
Dec.: 1.978[3] mas/yr
Parallax (π)| 2.9160 ± 0.0336[3] mas
Distance| 1,120 ± 10 ly
(343 ± 4 pc)
Orbit[7]
Primary| 31 Cygni Aa
Companion| 31 Cygni Ab
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[8] km/s
Details
K supergiant
Mass| 6.73[8] M☉
Radius| 127[9] R☉
Luminosity| 2,512 - 2,559[9] L☉
Temperature| 4,043±170[9] K
B dwarf
Mass| 5.22[8] M☉
Radius| 5.2±0.5[10] R☉
Temperature| 16,500+1,000
−2,000[11] K
Age| 39.8[12] Myr
HD 192579
Mass| 4.1[3] M☉
Radius| 3.3[3] R☉
Luminosity| 373[3] L☉
Surface gravity (log g)| 4.04[3] cgs
Temperature| 13,949[3] K
Metallicity [Fe/H]| +0.68[3] dex
Other designations

ο1 Cyg, ο2 Cyg,[13] 31 Cyg, ADS 13554, WDS J20136+4644

31 Cygni A (HD 192577): V695 Cyg, HD 192577, BD+46°2882, HIP 99675, HR 7735, SAO 49337
HD 192579: HD 192579, BD+46°2883, HIP 99676, SAO 49338
Database references
SIMBAD| data
| HD 192579

31 Cygni is the close pair, with 30 Cygni towards top left. (north is to the left)

31 Cygni, also known as ο1 Cygni, Omicron1 Cygni, or V695 Cygni, is a triple star system about 750 light years away 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.[13]

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.[14] The 13th-magnitude star is likely to be an unrelated background object.[15]

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.[4][3]

An ultraviolet band light curve for the 1982 eclipse of V695 Cygni, adapted from Stencel et al. (1984)[16]

31 Cygni A is an Algol-type eclipsing binary and ranges between magnitudes 3.73 and 3.89 over a period of ten years.[7] 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.[8]

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. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
2. ↑ 2.0 2.1 Samus, N. N. 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. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
4. ↑ 4.0 4.1 4.2 4.3 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. doi:10.1086/309425. Bibcode: 2000ApJ...541..298W.
6. ↑ Eaton, Joel A. et al. (2008). "Orbits and Pulsations of the Classical ζ Aurigae Binaries". The Astrophysical Journal 679 (2): 1490–1498. doi:10.1086/587452. Bibcode: 2008ApJ...679.1490E.
7. ↑ 7.0 7.1 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.
8. ↑ 8.0 8.1 8.2 8.3 Bennett, Philip; Brown, Alexander; Ayres, Thomas R. (2018). "An Accurate Mass of the 31 Cygni Red Supergiant". Cambridge Workshop on Cool Stars: 46. doi:10.5281/zenodo.1467958. Bibcode: 2018csss.confE..46B.
9. ↑ 9.0 9.1 9.2 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. doi:10.3847/1538-3881/ab1cbd. Bibcode: 2019AJ....158...20M.
10. ↑ Eaton, Joel A. (1993). "31 Cygni: The B star and the wind". Astronomical Journal 106: 2081. doi:10.1086/116787. Bibcode: 1993AJ....106.2081E.
11. ↑ 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.
12. ↑ 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. doi:10.1111/j.1365-2966.2010.17434.x. Bibcode: 2011MNRAS.410..190T.
13. ↑ 13.0 13.1 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.
14. ↑ Mason, B. D. et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal 122 (6): 3466–3471. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M.
15. ↑ Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
16. ↑ 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. doi:10.1086/162153. Bibcode: 1984ApJ...281..751S. https://ui.adsabs.harvard.edu/abs/1984ApJ...281..751S. Retrieved 21 December 2021.

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* t
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Constellation of Cygnus

* List of stars in Cygnus

Stars|

| Bayer|

* α (Deneb)
* β (Albireo)
* γ (Sadr)
* δ (Fawaris)
* ε (Aljanah)
* ζ
* η
* θ
* ι1
* ι2
* κ
* λ
* μ
* ν
* ξ
* π1 (Azelfafage)
* π2
* ρ
* σ
* τ
* υ
* φ
* χ
* ψ
* ω1
* ω2
* P
* Q

|

Flamsteed|

* 2
* 4
* 8
* 9
* 14
* 15
* 16 (c)
* 17
* 20 (d)
* 22
* 23
* 26 (e)
* 27 (b1)
* 28 (b2)
* 29 (b3)
* 30
* 31
* 32
* 33
* 35
* 39
* 41
* 47
* 52
* 55
* 56
* 57
* 59 (f1)
* 61
* 63 (f2)
* 68 (A)
* 71 (g)
* 72
* 74
* 75

Variable|

* R
* T
* W
* RW
* SS
* TT
* BC
* BI
* CH
* KY
* V404
* V476
* V1057
* V1143
* V1191
* V1489
* V1500
* V1668
* V1974
* V2513

HR|

* 7633
* 7912
* 8193

HD|

* 185269
* 185435
* 187123
* 188753
* 191806

Gliese|

* 777
* 806
* 1245

Kepler|

* 5
* 6
* 11
* 15
* 16
* 17
* 18
* 22
* 23
* 27
* 28
* 29
* 31
* 32
* 33
* 34
* 35
* 36
* 39
* 40
* 41
* 42
* 43
* 44
* 45
* 47
* 51
* 56
* 61
* 66
* 67
* 68
* 69
* 70
* 78
* 80
* 84
* 86
* 89
* 107
* 182
* 186
* 223
* 371
* 419
* 432
* 451
* 452
* 1229
* 1520
* 1625

Other|

* AFGL 2591
* BD+40° 4210
* BD+43 3654
* Cygnus OB2 #8A
* Cygnus OB2 #12
* Cygnus X-1
* Cygnus X-3
* G 208-44
* G 208-45
* HAT-P-7
* HAT-P-11
* HAT-P-17
* KELT-9
* KIC 8462852
* KIC 9832227
* KIC 11026764
* KOI-74
* KOI-81
* KOI-256
* KPD 1930+2752
* MWC 349
* N6946-BH1
* NML Cygni
* PH1
* PSR J2032+4127
* W75N(B)-VLA2
* WISE J2000+3629
* WR 134
* WR 135
* WR 136
* WR 137
* WR 140
* WR 142
* WR 147
* WR 148

Former|

* 3

Star
clusters|

| Association|

* Cygnus OB2
* Cygnus OB7

|

Open|

* DR 6
* IC 5146
* Messier 29
* Messier 39
* NGC 6811
* NGC 6819
* NGC 6834
* NGC 6866
* NGC 6871
* NGC 6910

Molecular
clouds|

* Cygnus X (including DR 21)

Nebulae|

| Dark|

* Barnard 146
* Barnard 147
* IC 5146
* L1014

|

H II|

* NGC 6914
* North America Nebula
* Pelican Nebula
* Sadr Region
* Sh2-101
* Sh2-106

Planetary|

* Abell 78
* Egg Nebula
* IRAS 19475+3119
* Kronberger 61
* M1-92
* NGC 6826
* NGC 6881
* NGC 6884
* NGC 7008
* NGC 7026
* NGC 7027
* NGC 7048
* Soap Bubble Nebula

WR|

* Crescent Nebula

SNR|

* Cygnus Loop (including Veil Nebula)

Galaxies|

| NGC|

* 6801
* 6946
* 7013

|

Other|

* 3C 438
* Cygnus A

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