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W Cygni
	Location of W Cygni (circled)
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Cygnus
Right ascension	21h 36m 02.49619s
Declination	+44° 22′ 28.5292″
Apparent magnitude (V)	5.10 - 6.83
Characteristics
Spectral type	M4e-M6e(Tc:)III
U−B color index	+1.24
B−V color index	+1.59
Variable type	SRb
Astrometry
Radial velocity (Rv)	−12.87 km/s
Proper motion (μ)	RA: 65.17 ± 0.42 mas/yr ; Dec.: 1.74 ± 0.30 mas/yr
Parallax (π)	5.72 ± 0.38 mas
Distance	570 ± 40 ly ; (170 ± 10 pc)
Absolute magnitude (MV)	−0.43
Details
Mass	0.98 M☉
Radius	227 R☉
Luminosity	5,888 L☉
Temperature	3,373 K
Other designations
	W Cyg, BD+44°3877, HD 205730, HIP 106642, HR 8262
Database references
SIMBAD	data

W Cygni is a semi-regular variable star in the constellation Cygnus, located 570 light-years from Earth. It lies less than half a degree southeast of ρ Cygni. W Cygni is, at times, a naked-eye star but it was not given a Bayer or Flamsteed designation. It has been proposed as a binary star system with a hotter main sequence companion, but this has not been confirmed.^[9]

W Cygni was discovered to be variable by John Ellard Gore, and first published in 1885.^[10] It has a maximum magnitude of 5.10 and a minimum magnitude 6.83. The star is catalogued as having a primary period of 131.7 days, but shows variations with a variety of periods around 131 days as well as 234 days.^[11]^[10] It is believed to be pulsating in the first overtone.^[8] There is some evidence of additional very slow and small variations in the light curve on a time scale of 3,000–5,000 days.^[12]

This star is an aging red giant on the asymptotic giant branch (AGB). Its spectral type ranges between M4e and M6e, and it shows possible elevated levels of Technetium.^[2] The masses of AGB stars are poorly known, but using the pulsation properties of W Cygni, it mass is calculated to be slightly less than the sun's.^[8] It has expanded to 227 times the girth of the Sun and is radiating 5,888 times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,373 K.^[8]

References

^ ^a ^b ^c ^d ^e van Leeuwen, Floor (13 August 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. eISSN 1432-0746. ISSN 0004-6361. Vizier catalog entry
^ ^a ^b "W Cygni". AAVSO Website. American Association of Variable Star Observers. 10 July 2017. Retrieved 31 December 2013.
^ Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55 (1): 31–81. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070. S2CID 122700080.
^ ^a ^b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
^ 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.
^ Famaey, B.; Pourbaix, D.; Frankowski, A.; Van Eck, S.; Mayor, M.; Udry, S.; Jorissen, A. (2009). "Spectroscopic binaries among Hipparcos M giants,. I. Data, orbits, and intrinsic variations". Astronomy and Astrophysics. 498 (2): 627. arXiv:0901.0934. Bibcode:2009A&A...498..627F. doi:10.1051/0004-6361/200810698. S2CID 18739721.
^ Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440, S2CID 12136256.
^ ^a ^b ^c ^d ^e ^f ^g Takeuti, Mine; Nakagawa, Akiharu; Kurayama, Tomoharu; Honma, Mareki (2013). "A Method to Estimate the Masses of Asymptotic Giant Branch Variable Stars". Publications of the Astronomical Society of Japan. 65 (3): 60. Bibcode:2013PASJ...65...60T. doi:10.1093/pasj/65.3.60.
^ Ortiz, Roberto; Guerrero, Martín A. (2016). "Ultraviolet emission from main-sequence companions of AGB stars". Monthly Notices of the Royal Astronomical Society. 461 (3): 3036. arXiv:1606.09086. Bibcode:2016MNRAS.461.3036O. doi:10.1093/mnras/stw1547. S2CID 118619933.
^ ^a ^b Shears, Jeremy (2012). "John Ellard Gore: Of immensity and minuteness". Journal of the British Astronomical Association. 123: 85. arXiv:1203.6467. Bibcode:2013JBAA..123...85S.
^ Glass, I. S.; Van Leeuwen, F. (2007). "Semiregular variables in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 378 (4): 1543–1549. arXiv:0704.3150. Bibcode:2007MNRAS.378.1543G. doi:10.1111/j.1365-2966.2007.11903.x. S2CID 14332208.
^ Percy, John R.; Mashintsova, M.; Nasui, C. O.; Palaniappan, R.; Seneviratne, R.; Henry, Gregory W. (May 2008). "Further Studies of the Photometric Variability of Bright Pulsating Red Giants". Publications of the Astronomical Society of the Pacific. 120 (867): 523. Bibcode:2008PASP..120..523P. doi:10.1086/588612. S2CID 123722836.