X Cygni

Not to be confused with χ Cygni.
X Cygni

A light curve for X Cygni, plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
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 mas/yr[2]
Dec.: −5.108 mas/yr[2]
Parallax (π)0.8842 ± 0.0199 mas[2]
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]

  1. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Samus_et_al_2017 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Kovtyukh_et_al_2005 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov_2006 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference acharova2012 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Breitfellner_Gillet_1993 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference Trahin_et_al_2021 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference groenewegen2020 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference apogee was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Anderson_et_al_2013 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Chandler_1886 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Frost_1907 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Luizet_1912 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Jordan_1919 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Eggen_1951 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Kraft_1954 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Kraft_1956 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Gillet_2014 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Hintz_et_al_2021 was invoked but never defined (see the help page).
  22. ^ Cite error: The named reference Barmby_et_al_2011 was invoked but never defined (see the help page).