W Cygni

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
Location of W Cygni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension  21h 36m 02.49619s[1]
Declination +44° 22′ 28.5292″[1]
Apparent magnitude (V) 5.10 - 6.83[2]
Characteristics
Spectral type M4e-M6e(Tc:)III[3]
U−B color index +1.24[4]
B−V color index +1.59[4]
Variable type SRb[5]
Astrometry
Radial velocity (Rv)−12.87[6] km/s
Proper motion (μ) RA: 65.17 ± 0.42[1] mas/yr
Dec.: 1.74 ± 0.30[1] mas/yr
Parallax (π)5.72 ± 0.38[1] mas
Distance570 ± 40 ly
(170 ± 10 pc)
Absolute magnitude (MV)−0.43[7]
Details
Mass0.98[8] M☉
Radius227[8] R☉
Luminosity5,888[8] L☉
Temperature3,373[8] K
Other designations
W Cyg, HR 8262, HD 205730, BD+44°3877, HIP 106642
Database references
SIMBADdata

Discovery
Visual light curve of W Cygni from 2014 to 2017

W Cygni is, at times, a naked-eye star but it was not given a Bayer or Flamsteed designation. It was discovered to be variable by John Ellard Gore, and first published in 1885.[9]

Variability

W Cygni has a maximum magnitude of 5.10 and a minimum magnitude 6.83. It 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.[10][9] It is believed to be pulsating in the first overtone.[8]

Properties

W Cygni is a 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]

Companion

W Cygni has been proposed as a binary star with a hotter main sequence companion, but it has not been confirmed.[11]

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References
  1. Van Leeuwen, Floor (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. Vizier catalog entry
  2. "W Cygni". AAVSO Website. American Association of Variable Star Observers. 10 July 2017. Retrieved 31 December 2013.
  3. Shenavrin, V. I.; Taranova, O. G.; Nadzhip, A. E. (2011). "Search for and study of hot circumstellar dust envelopes". Astronomy Reports. 55: 31. Bibcode:2011ARep...55...31S. doi:10.1134/S1063772911010070.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. Shears, Jeremy (2012). "John Ellard Gore: Of immensity and minuteness". 1203: arXiv:1203.6467. arXiv:1203.6467. Bibcode:2012arXiv1203.6467S. Cite journal requires |journal= (help)
  10. Glass, I. S.; Van Leeuwen, F. (2007). "Semiregular variables in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 378 (4): 1543. arXiv:0704.3150. Bibcode:2007MNRAS.378.1543G. doi:10.1111/j.1365-2966.2007.11903.x.
  11. 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.
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