47 Cygni

47 Cygni

A light curve for V2125 Cygni, plotted from Hipparcos data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	20^h 33^m 54.18809^s[2]
Declination	+35° 15′ 03.0390″[2]
Apparent magnitude (V)	4.61[3] (4.84 + 7.30)[4]
Characteristics
Spectral type	K6: Ib + B2.5:[3]
B−V color index	1.593±0.023[5]
Variable type	Lc[6]
Astrometry
Radial velocity (Rv)	−4.6±0.3[7] km/s
Proper motion (μ)	RA: −6.12 mas/yr[2] Dec.: −4.166 mas/yr[2]
Parallax (π)	0.8792 ± 0.196 mas[2]
Distance	4072+965 −773 ly (1249+296 −237 pc)[8]
Absolute magnitude (MV)	−4.1 (−4 + −1.5)[3]
Orbit[9]
Period (P)	1117±11 d
Eccentricity (e)	0.00 (assumed)
Periastron epoch (T)	2,447,088±10 JD
Semi-amplitude (K1) (primary)	2.0±0.1 km/s
Details
47 Cyg Aa
Mass	12.1±0.2[10] 19.4±3.9[11] M☉
Radius	601[12] R☉
Surface gravity (log g)	1.23[13] cgs
Temperature	4,217[13] K
Metallicity [Fe/H]	0.13[13] dex
Age	17.6±0.6[10] Myr
47 Cyg Ab
Mass	0.57[14] M☉
47 Cyg B
Mass	10.96[14] M☉
Other designations
47 Cyg, V2125 Cyg, BD+34°4079, GC 28630, HD 196093/196094, HIP 101474, HR 7866, SAO 70203, WDS J20339+3515, 2MASS J20335419+3515031[15]
Database references
SIMBAD	data

47 Cygni is a triple star^[4][16] system in the northern constellation of Cygnus, and is located around 4,000 light years from the Earth. It is visible to the naked eye with a combined apparent visual magnitude of 4.61.^[3] The system is moving closer to the Earth with a heliocentric radial velocity of −4.6 km/s.^[7]

The dual nature of this system was recognized by Annie Cannon in 1912, and she assigned the pair separate Henry Draper Catalogue identifiers.^[9] They orbit each other with a period of around 143.69 yr.^[14] The primary component is itself a spectroscopic binary in a near circular orbit with a period of around 3.06 yr. The a sin i value for the primary is 30.8 ± 1.6 Gm (0.206 ± 0.011 AU), where a is the semimajor axis and i is the orbital inclination. It has been repeatedly resolved by speckle interferometery since 1973. Radio emission was detected from this system in 1985/86.^[9]

The supergiant primary is a slow irregular variable with an amplitude of about 0.1 magnitudes.^[6] Its angular diameter has been measured at 4.472±0.017 milliarcseconds using interferometry by the Navy Precision Optical Interferometer.^[17] At the distance of 1,249 parsecs,^[8] it yield a radius of 601 R_☉.^[12] Its close companion has 57% of the mass of the Sun.^[14] The secondary is a hot B-type main-sequence star, but still 2.5 magnitudes fainter than the primary.^[4]

References

1. "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved October 15, 2022.
2. 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. Ginestet, N.; Carquillat, J. M. (December 2002). "Spectral Classification of the Hot Components of a Large Sample of Stars with Composite Spectra, and Implication for the Absolute Magnitudes of the Cool Supergiant Components". The Astrophysical Journal Supplement Series. 143 (2): 513–537. Bibcode:2002ApJS..143..513G. doi:10.1086/342942.
4. 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.
5. 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.
6. 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.
7. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
8. Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (March 1, 2021). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Gaia eDR3 source for this star.
9. Griffin, R. F. (June 1992). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 104: 47 Cygni". The Observatory. 112: 111–120. Bibcode:1992Obs...112..111G.
10. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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.
11. Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (January 1, 2022). "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs". Astronomy and Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. ISSN 0004-6361. 47 Cygni's database entry at VizieR.
12. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

    ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(10^{-3}\cdot 1,249\cdot 4.472)\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&1,201.4\cdot R_{\bigodot }\end{aligned}}}$

13. Soubiran, Caroline; et al. (2016). "The PASTEL catalogue: 2016 version". Astronomy and Astrophysics. 591: A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497. S2CID 119258214.
14. Tokovinin, A. (2008). "Comparative statistics and origin of triple and quadruple stars". Monthly Notices of the Royal Astronomical Society. 389 (2): 925–938. arXiv:0806.3263. Bibcode:2008MNRAS.389..925T. doi:10.1111/j.1365-2966.2008.13613.x. S2CID 16452670.
15. "47 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved January 14, 2019.
16. Mason, Brian D.; et al. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
17. Baines, Ellyn K.; Clark III, James H.; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (December 1, 2023). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.