R Cygni

R Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 36m 49.35633s[1]
Declination +50° 11′ 59.7198″[1]
Apparent magnitude (V) 6.1 - 14.4[2]
Characteristics
Spectral type S2.5,9e-S6,9e(Tc)[3]
Variable type Mira[2]
Astrometry
Proper motion (μ) RA: −3.158[1] mas/yr
Dec.: −5.755[1] mas/yr
Parallax (π)1.4835 ± 0.0963 mas[1]
Distance2,200 ± 100 ly
(670 ± 40 pc)
Details
Mass0.85[4] M☉
Luminosity11,700[5] L☉
Surface gravity (log g)−0.50[4] cgs
Temperature2,538[4] K
Metallicity [Fe/H]+0.50[4] dex
Other designations
R Cyg, BD+49 3064, HD 185456, HIP 31822, SAO 31822, WDS J19368+5012[6]
Database references
SIMBADdata
R Cygni light curve, showing the period-doubling

R Cygni is a variable star of the Mira type in the constellation Cygnus, less than 4' from θ Cygni. This is a red giant star on the asymptotic giant branch located around 2,200 light years away. It is an S-type star ranging between spectral types S2.5,9e to S6,9e(Tc).[3]

Stars at this mass range and evolutionary stage are pulsationally unstable, displaying a variation in their light output.[7] R Cygni has a maximum magnitude of 6.1 and a minimum magnitude of 14.4, with a period of 426.45 days.[2] The variation of this star was discovered by English astronomer N. R. Pogson in 1852, and it has a history of recorded brightness measurements stretching back more than a century.[7] R Cygni shows distinct period-doubling, where alternate maxima are of different brightness, hence the real period of pulsation could be considered to be twice that from one maximum to the next.[7]

The Catalog of Components of Double and Multiple Stars lists 10th magnitude BD+49 3065 as a companion to R Cygni, at a separation of 91", and both stars lie at approximately the same distance. The Washington Double Star Catalog additionally lists a 15th magnitude star as a companion at a separation of about 14".[8]

  1. ^ a b c d e Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference gcvs was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference AAVSOR was invoked but never defined (see the help page).
  4. ^ a b c d Cite error: The named reference starhorse2 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference guandalini was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Kiss2002 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference wds was invoked but never defined (see the help page).