S Vulpeculae

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S Vulpeculae
Observation data
Epoch J2000      Equinox J2000
Constellation Vulpecula
Right ascension 19h 48m 23.8064s[1]
Declination 27° 17′ 11.4265″[1]
Apparent magnitude (V) 8.974[2] (8.69 - 9.42[3])
Spectral type G0-K2(M1)[4]
U−B color index +1.3 - +2.0[5]
B−V color index +1.7 - +2.1[5]
Variable type δ Cep[3]
Radial velocity (Rv)0.0 ± 2[6] km/s
Proper motion (μ) RA: −3.401±0.058[1] mas/yr
Dec.: −5.923±0.059[1] mas/yr
Parallax (π)0.3050 ± 0.0406[1] mas
Distanceapprox. 11,000 ly
(approx. 3,300 pc)
Absolute magnitude (MV)−6.08[2]
Mass14.2 M
Radius382[7] R
Diameter382[7] D
Luminosity28,840 L
Temperature4,477 K
Metallicity [Fe/H]−0.01[8] dex
Age12.6 Myr
Other designations
S Vulpeculae, SAO 87743, HD 338867, BD+26°3674, AAVSO 1944+27
Database references

S Vulpeculae is a star located in the constellation Vulpecula. A supergiant star,[9] it is around 382 times the diameter of the Sun.[7]

S Vulpeculae was first suspected of varying in brightness in 1836 and this was confirmed by 1862. A pulsating variable that grows and shrinks as it changes in brightness, it has been variously classified as an RV Tauri variable, a semiregular variable star, or a Cepheid variable.[10][4]

S Vulpeculae is now confirmed as a classical Cepheid variable with one of the longest known periods at 68 days,[2] although the period has changed several times.[11] As such, it is also one of the cooler and more luminous of the Cepheids, and it lies close to the zone where semiregular variable stars are found. The shape and amplitude of the light curve varies significantly from cycle to cycle and secularly. The apparent magnitude ranges from 8.69 to 9.42.[3] The spectrum varies from early G to late K as it pulsates, with TiO bands typical of an M1 star when the star is coolest.[4]


  1. 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. arXiv:1804.09365. Bibcode 2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. 2.0 2.1 2.2 2.3 Turner, David G. (2014). "Towards a Determination of Definitive Parameters for the Long Period Cepheid S Vulpeculae". Odessa Astronomical Publications 26: 115. arXiv:1403.1968. Bibcode 2013OAP....26..115T.
  3. 3.0 3.1 3.2 Samus, N. N.Expression error: Unrecognized word "etal". (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.
  4. 4.0 4.1 4.2 Joy, Alfred H. (1952). "The Semiregular Variable Stars of the RV Tauri and Related Classes". Astrophysical Journal 115: 25. Bibcode 1952ApJ...115...25J. doi:10.1086/145506.
  5. 5.0 5.1 Berdnikov, L. N.; Ivanov, G. R. (1986). "On the Type of Variability of S Vul". Information Bulletin on Variable Stars 2856: 1. Bibcode 1986IBVS.2856....1B.
  6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode 1953GCRV..C......0W.
  7. 7.0 7.1 Gieren, Wolfgang P.; Fouque, Pascal; Gomez, Matias (1998). "Cepheid Period‐Radius and Period‐Luminosity Relations and the Distance to the Large Magellanic Cloud". The Astrophysical Journal 496: 17. arXiv:astro-ph/9710161. Bibcode 1998ApJ...496...17G. doi:10.1086/305374.
  8. Marsakov, V. A.; Koval', V. V.; Kovtyukh, V. V.; Mishenina, T. V. (2013). "Properties of the population of classical Cepheids in the Galaxy". Astronomy Letters 39 (12): 851. Bibcode 2013AstL...39..851M. doi:10.1134/S1063773713120050.
  9. Buscombe, W. (1974). "Supergiants in the Milky Way". Perem. Zvezdy 2: 127. Bibcode 1974PZP.....2..127B.
  10. Nassau, J. J.; Ashbrook, J. (1943). "S Vulpeculae". Astronomical Journal 50: 97. Bibcode 1943AJ.....50...97N. doi:10.1086/105732.
  11. Heiser, Arnold M. (1996). "BV Observations of the Long-Period Cepheid S Vulpeculae". Publications of the Astronomical Society of the Pacific 108: 603. Bibcode 1996PASP..108..603H. doi:10.1086/133771.

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