Astronomy:X Cygni

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Short description: Variable star in the constellation Cygnus
X Cygni
XCygLightCurve.png
A light curve for X Cygni, plotted from TESS data[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Cygnus
Right ascension  20h 43m 24.192s[2]
Declination 35° 35′ 16.08″[2]
Apparent magnitude (V) 5.85 to 6.91[3]
Characteristics
Spectral type F7 Ib to G8 Ib[4]
Variable type δ Cep[3]
Astrometry
Radial velocity (Rv)8.1±0.2[5] km/s
Proper motion (μ) RA: −6.673[2] mas/yr
Dec.: −5.108[2] mas/yr
Parallax (π)0.8842 ± 0.0199[2] mas
Distance3,690 ± 80 ly
(1,130 ± 30 pc)
Absolute magnitude (MV)−4.53[6]
Details
Mass7.9–8.9[7] M☉
Radius95.9±1.6[8] R☉
Luminosity5,202[9] L☉
Surface gravity (log g)1.601[10] cgs
Temperature5,315±80[8] K
Metallicity [Fe/H]0.10±0.08[8] dex
Rotational velocity (v sin i)8[7] km/s
Age31[6] Myr
Other designations
X Cyg, BD+35°4234, GC 28886, HD 197572, HIP 102276, HR 7932, SAO 70423[11]
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.[3] At it brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 628 light years based on parallax measurements.[2] It is drifting further away with a radial velocity of 8.1 km/s.[5] This star is a likely member of the open cluster Ruprecht 173.[12]

The variable luminosity of this star was discovered by S. C. Chandler, Jr. in 1886.[13] 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.[14] M. Luizet in 1912 found a cyclical pulsation period of 16.38543 days for the variation.[15] 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.[16] 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.[17]

In 1954, R. P. Kraft found a stellar classification of F7 Ib at peak brightness,[18] 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.[4] 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.[19] Unlike most cepheid variables that undergo a single shock per cycle, X Cyg has been found to undergo a double shock.[20]

No orbiting companion has been identified with a period of ten years or less.[21] The star shows cirrus with tentative evidence for extended emission of infrared.[22]

References

  1. ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html, retrieved 30 December 2022. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  4. ↑ 4.0 4.1 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, doi:10.1086/426339, Bibcode: 2005AJ....129..433K. 
  5. ↑ 5.0 5.1 Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  6. ↑ 6.0 6.1 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, doi:10.1111/j.1365-2966.2011.20161.x, Bibcode: 2012MNRAS.420.1590A. 
  7. ↑ 7.0 7.1 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. ↑ 8.0 8.1 8.2 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, doi:10.1051/0004-6361/202141680, A102, Bibcode: 2021A&A...656A.102T. 
  9. ↑ Groenewegen, M. A. T. (2020), "The flux-weighted gravity-luminosity relation of Galactic classical Cepheids", Astronomy and Astrophysics 640: A113, doi:10.1051/0004-6361/202038292, Bibcode: 2020A&A...640A.113G. 
  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, doi:10.3847/1538-3881/ac4de7, ISSN 0004-6256, Bibcode: 2022AJ....163..152S. 
  11. ↑ "X Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=X+Cyg. 
  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, doi:10.1093/mnras/stt1160, Bibcode: 2013MNRAS.434.2238A. 
  13. ↑ Chandler, S. C. (December 1886), "On a new short-period variable in Cygnus", Astronomical Journal 7 (148): 32, doi:10.1086/100855, Bibcode: 1886AJ......7...32C. 
  14. ↑ Frost, E. B. (1907), "Nine stars having variable radial velocities", Astrophysical Journal 25: 59–65, doi:10.1086/141465, Bibcode: 1907ApJ....25R..59F. 
  15. ↑ Luizet, Michel (November 1912), "Nouveaux éléments et courbes de lumière des étoiles X Cygni et RU Camelopardalis" (in Fr), Astronomische Nachrichten 193 (6): 83, doi:10.1002/asna.19121930603, Bibcode: 1912AN....193...83L, https://zenodo.org/record/1970880. 
  16. ↑ Jordan, F. C. (October 1919), "The color changes of certain variable stars of short period", Astrophysical Journal 50: 174–205, doi:10.1086/142495, Bibcode: 1919ApJ....50..174J. 
  17. ↑ "Photoelectric Studies. V. Magnitudes and Colors of Classical Cepheid Variable Stars", Astrophysical Journal 113: 367, March 1951, doi:10.1086/145405, Bibcode: 1951ApJ...113..367E. 
  18. ↑ Kraft, Robert P. (June 1954), "Changes in the Spectrum of X Cygni", Publications of the Astronomical Society of the Pacific 66 (390): 136, doi:10.1086/126679, Bibcode: 1954PASP...66..136K. 
  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, doi:10.1086/126897, Bibcode: 1956PASP...68..137K. 
  20. ↑ Gillet, D. (August 2014), "Atmospheric dynamics in long-period Cepheids. Hα profile variations", Astronomy & Astrophysics 568, doi:10.1051/0004-6361/201423486, A72, Bibcode: 2014A&A...568A..72G, https://www.aanda.org/10.1051/0004-6361/201423486/pdf. 
  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, doi:10.3847/1538-3881/ac167f, 149, Bibcode: 2021AJ....162..149H. 
  22. ↑ Barmby, P. et al. (February 2011), "Galactic Cepheids with Spitzer. II. Search for Extended Infrared Emission", The Astronomical Journal 141 (2): 42, doi:10.1088/0004-6256/141/2/42, 42, Bibcode: 2011AJ....141...42B. 

Further reading

  • Wallerstein, G. et al. (September 2019), "The Behavior of the Paschen and Calcium Triplet Lines in Cepheid Variables II: The 16-day Variable X Cygni", Publications of the Astronomical Society of the Pacific 131 (1003): 094203, doi:10.1088/1538-3873/ab1ec2, Bibcode: 2019PASP..131i4203W. 
  • Meyer, Ralf (December 2005), "X Cyg: observations from 1886 until today", Open European Journal on Variable Stars 13: 1, Bibcode: 2005OEJV...13....1M. 
  • Turner, David G. (July 1998), "A Search for Stars Physically Associated with the 16 Day Cepheid X Cygni. II. Clusters in the Field", The Astronomical Journal 116 (1): 274–283, doi:10.1086/300438, Bibcode: 1998AJ....116..274T. 
  • Wallerstein, G. et al. (August 1984), "A search for evidence of the neon-sodium cycle in the Cepheid X Cygni", Publications of the Astronomical Society of the Pacific 96: 613–617, doi:10.1086/131392, Bibcode: 1984PASP...96..613W. 
  • Evans, N. R. (June 1984), "X Cygni: duplicity, period stability and atmospheric velocity structure", Astrophysical Journal 281: 760–765, doi:10.1086/162154, Bibcode: 1984ApJ...281..760E. 
  • Wallerstein, G. (July 1983), "The behavior of H alpha in the 16-day cepheid X Cygni", Publications of the Astronomical Society of the Pacific 95: 422–426, doi:10.1086/131187, Bibcode: 1983PASP...95..422W. 
  • Turner, D. G. (May 1983), "A search for stars physically associated with the 16-day Cepheid X Cygni. I. Luminous Stars in the field", Astronomical Journal 88: 650–654, doi:10.1086/113353, Bibcode: 1983AJ.....88..650T. 
  • Benz, W.; Mayor, M. (July 1982), "Turbulence variations for the three cepheids SV Vul, X CYG and del Cep", Astronomy and Astrophysics 111: 224–228, Bibcode: 1982A&A...111..224B. 
  • Davis, C. G. et al. (June 1981), "On the mass of the cepheid X Cyg", Astrophysical Journal 246: 914–918, doi:10.1086/158984, Bibcode: 1981ApJ...246..914D. 
  • Abt, H. A. (June 1978), "Radial velocities of the cepheid X Cygni", Publications of the Astronomical Society of the Pacific 90: 309–311, doi:10.1086/130332, Bibcode: 1978PASP...90..309A. 
  • Masani, A. et al. (February 1968), "The Masses of BM Cas, X Cyg, RT Aur, RR Lyr", Information Bulletin on Variable Stars 258: 1, Bibcode: 1968IBVS..258....1M. 
  • Masani, A. et al. (October 1966), "Determination of the Mass and the Model of the Variables: RT Aurigae, Eta Aquilae, X Cygni, Mira Ceti and BM Cassiopeiae of Pop.I, and RR Lyrae and Two Typical Variables of Pop. II", Information Bulletin on Variable Stars 162: 1, Bibcode: 1966IBVS..162....1M. 
  • Duncan, J. C. (January 1921), "The spectroscopic orbit of the cepheid variable X Cygni", Astrophysical Journal 53: 95–98, doi:10.1086/142585, Bibcode: 1921ApJ....53...95D. 




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