X Cygni

X Cygni

A light curve for X Cygni, plotted from TESS data
Observation data
Epoch J2000      Equinox ICRS
Constellation Cygnus
Right ascension 20h 43m 24.192s
Declination +35° 35′ 16.08″
Apparent magnitude (V) 5.85 to 6.91
Characteristics
Spectral type F7 Ib to G8 Ib
Variable type δ Cep
Astrometry
Radial velocity (Rv)8.1±0.2 km/s
Proper motion (μ) RA: −6.673 mas/yr
Dec.: −5.108 mas/yr
Parallax (π)0.8842±0.0199 mas
Distance3,690 ± 80 ly
(1,130 ± 30 pc)
Absolute magnitude (MV)−4.53
Details
Mass7.9–8.9 M☉
Radius95.9±1.6 R☉
Luminosity5,202 L☉
Surface gravity (log g)1.601 cgs
Temperature5,315±80 K
Metallicity [Fe/H]0.10±0.08 dex
Rotational velocity (v sin i)8 km/s
Age31 Myr
Other designations
X Cyg, BD+35°4234, GC 28886, HD 197572, HIP 102276, HR 7932, SAO 70423
Database references
SIMBADdata

X Cygni is a variable star in the northern constellation of Cygnus, abbreviated X Cyg. This is a Delta Cephei variable that ranges in brightness from an apparent visual magnitude of 5.85 down to 6.91 with a period of 16.386332 days. At it brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 3,690 light years based on parallax measurements. It is drifting further away with a radial velocity of 8.1 km/s. This star is a likely member of the open cluster Ruprecht 173.

The variable luminosity of this star was discovered by S. C. Chandler, Jr. in 1886. In 1907, E. B. Frost showed that X Cyg is an F-type star with a varying radial velocity, behaving analogous to a Delta Cephei variable. M. Luizet in 1912 found a cyclical pulsation period of 16.38543 days for the variation. In 1919, F. C. Jordan determined that the color index of the star changed over the course of each cycle, becoming redder as the star grew fainter. It came to be identified as a member of the benchmark class of stars termed Classical Cepheid variables that satisfy a simple period–luminosity relation.

In 1954, R. P. Kraft found a stellar classification of F7 Ib at peak brightness, matching the spectrum of an F-type supergiant star. The class of the star varies over the course of a pulsation cycle, ranging down to G8 Ib at minimum brightness. R. P. Kraft in 1956 identified a doubling of certain spectral lines, which he explained as the result of a falling shell of matter from a prior pulsation cycle that is colliding with the photosphere. Unlike most cepheid variables that undergo a single shock per cycle, X Cyg has been found to undergo a double shock.

No orbiting companion has been identified with a period of ten years or less. The star shows cirrus with tentative evidence for extended emission of infrared.

References

  1. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 30 December 2022.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. 1 2 3 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  4. 1 2 Kovtyukh, V. V.; et al. (January 2005), "Phase-dependent Variation of the Fundamental Parameters of Cepheids. II. Periods Longer than 10 Days", The Astronomical Journal, 129 (1): 433–453, Bibcode:2005AJ....129..433K, doi:10.1086/426339, S2CID 120666782.
  5. 1 2 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 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.
  6. 1 2 Acharova, I. A.; et al. (2012), "Galactic restrictions on iron production by various types of supernovae", Monthly Notices of the Royal Astronomical Society, 420 (2): 1590, arXiv:1111.2152, Bibcode:2012MNRAS.420.1590A, doi:10.1111/j.1365-2966.2011.20161.x, S2CID 118404944.
  7. 1 2 Breitfellner, M. G.; Gillet, D. (October 1993), "Atmospheric motions in classical cepheid stars. III. A very large amplitude star : X Cygni", Astronomy and Astrophysics, 277: 553, Bibcode:1993A&A...277..553B.
  8. 1 2 3 Trahin, B.; et al. (December 2021), "Inspecting the Cepheid parallax of pulsation using Gaia EDR3 parallaxes. Projection factor and period-luminosity and period-radius relations", Astronomy & Astrophysics, 656, arXiv:2111.09125, Bibcode:2021A&A...656A.102T, doi:10.1051/0004-6361/202141680, S2CID 244173657, A102.
  9. ↑ Groenewegen, M. A. T. (2020), "The flux-weighted gravity-luminosity relation of Galactic classical Cepheids", Astronomy and Astrophysics, 640: A113, arXiv:2007.02148, Bibcode:2020A&A...640A.113G, doi:10.1051/0004-6361/202038292, S2CID 220364506.
  10. ↑ Sprague, Dani; et al. (March 8, 2022), "APOGEE Net: An Expanded Spectral Model of Both Low-mass and High-mass Stars", The Astronomical Journal, 163 (4): 152, arXiv:2201.03661, Bibcode:2022AJ....163..152S, doi:10.3847/1538-3881/ac4de7, eISSN 1538-3881, ISSN 0004-6256.
  11. ↑ "X Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-12-28.
  12. ↑ Anderson, Richard I.; et al. (September 2013), "Cepheids in open clusters: an 8D all-sky census", Monthly Notices of the Royal Astronomical Society, 434 (3): 2238–2261, arXiv:1212.5119, Bibcode:2013MNRAS.434.2238A, doi:10.1093/mnras/stt1160.
  13. ↑ Chandler, S. C. (December 1886), "On a new short-period variable in Cygnus", Astronomical Journal, 7 (148): 32, Bibcode:1886AJ......7...32C, doi:10.1086/100855.
  14. ↑ Frost, E. B. (1907), "Nine stars having variable radial velocities", Astrophysical Journal, 25: 59–65, Bibcode:1907ApJ....25R..59F, doi:10.1086/141465.
  15. ↑ Luizet, Michel (November 1912), "Nouveaux éléments et courbes de lumière des étoiles X Cygni et RU Camelopardalis", Astronomische Nachrichten (in French), 193 (6): 83, Bibcode:1912AN....193...83L, doi:10.1002/asna.19121930603.
  16. ↑ Jordan, F. C. (October 1919), "The color changes of certain variable stars of short period", Astrophysical Journal, 50: 174–205, Bibcode:1919ApJ....50..174J, doi:10.1086/142495, hdl:2027/mdp.39015086631564.
  17. ↑ Eggen, Olin J. (March 1951), "Photoelectric Studies. V. Magnitudes and Colors of Classical Cepheid Variable Stars", Astrophysical Journal, 113: 367, Bibcode:1951ApJ...113..367E, doi:10.1086/145405.
  18. ↑ Kraft, Robert P. (June 1954), "Changes in the Spectrum of X Cygni", Publications of the Astronomical Society of the Pacific, 66 (390): 136, Bibcode:1954PASP...66..136K, doi:10.1086/126679, S2CID 123620740.
  19. ↑ Kraft, Robert P. (April 1956), "Double Lines in the Spectrum of the Classical Cepheid X Cygni", Publications of the Astronomical Society of the Pacific, 68 (401): 137, Bibcode:1956PASP...68..137K, doi:10.1086/126897, S2CID 122849355.
  20. ↑ Gillet, D. (August 2014), "Atmospheric dynamics in long-period Cepheids. Hα profile variations", Astronomy & Astrophysics, 568, Bibcode:2014A&A...568A..72G, doi:10.1051/0004-6361/201423486, A72.
  21. ↑ Hintz, Eric G.; et al. (October 2021), "An Examination of Pulsational Changes in the Classical Cepheid X Cygni", The Astronomical Journal, 162 (4): 149, Bibcode:2021AJ....162..149H, doi:10.3847/1538-3881/ac167f, S2CID 237553133, 149.
  22. ↑ Barmby, P.; et al. (February 2011), "Galactic Cepheids with Spitzer. II. Search for Extended Infrared Emission", The Astronomical Journal, 141 (2): 42, arXiv:1011.3386, Bibcode:2011AJ....141...42B, doi:10.1088/0004-6256/141/2/42, S2CID 118581168, 42.

Further reading