Astronomy:W Cygni

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Short description: Semi-regular variable star in the constellation Cygnus
W Cygni
Location of W Cygni (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cygnus
Right ascension  21h 36m 02.49619s[1]
Declination +44° 22′ 28.5292″[1]
Apparent magnitude (V) 5.10 - 6.83[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M4e-M6e(Tc:)III[4]
U−B color index +1.24[5]
B−V color index +1.59[5]
Variable type SRb[6]
Astrometry
Radial velocity (Rv)−12.87[7] 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[8]
Details
Mass0.98[9] M☉
Radius227[9] R☉
Luminosity5,888[9] L☉
Temperature3,373[9] K
Other designations
W Cyg, BD+44°3877, HD 205730, HIP 106642, HR 8262
Database references
SIMBADdata

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.[10]

Visual light curve of W Cygni from 2014 to 2017

W Cygni was discovered to be variable by John Ellard Gore, and first published in 1885.[11] 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.[12][11] It is believed to be pulsating in the first overtone.[9] 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.[13]

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.[9] 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.[9]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Van Leeuwen, Floor (2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V.  Vizier catalog entry
  2. ↑ 2.0 2.1 "W Cygni". AAVSO Website. American Association of Variable Star Observers. 10 July 2017. http://www.aavso.org/vsx/index.php?view=detail.top&oid=10926. 
  3. ↑ Lebzelter, T.; Hron, J. (2003). "Technetium and the third dredge up in AGB stars. I. Field stars". Astronomy and Astrophysics 411 (3): 533. doi:10.1051/0004-6361:20031458. Bibcode: 2003A&A...411..533L. 
  4. ↑ 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. doi:10.1134/S1063772911010070. Bibcode: 2011ARep...55...31S. 
  5. ↑ 5.0 5.1 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. 
  6. ↑ 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. 
  7. ↑ 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. doi:10.1051/0004-6361/200810698. Bibcode: 2009A&A...498..627F. 
  8. ↑ Cardini, D. (January 2005). "Mg II chromospheric radiative loss rates in cool active and quiet stars". Astronomy and Astrophysics 430: 303–311. doi:10.1051/0004-6361:20041440. Bibcode: 2005A&A...430..303C. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 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. doi:10.1093/pasj/65.3.60. Bibcode: 2013PASJ...65...60T. 
  10. ↑ 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. doi:10.1093/mnras/stw1547. Bibcode: 2016MNRAS.461.3036O. 
  11. ↑ 11.0 11.1 Shears, Jeremy (2012). "John Ellard Gore: Of immensity and minuteness". Journal of the British Astronomical Association 123: 85. Bibcode: 2013JBAA..123...85S. 
  12. ↑ Glass, I. S.; Van Leeuwen, F. (2007). "Semiregular variables in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society 378 (4): 1543–1549. doi:10.1111/j.1365-2966.2007.11903.x. Bibcode: 2007MNRAS.378.1543G. 
  13. ↑ 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. doi:10.1086/588612. Bibcode: 2008PASP..120..523P. 



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