R Cygni
Star in the constellation Cygnus
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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).[4]
| 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 | |
| Evolutionary stage | AGB[3] |
| Spectral type | S2.5,9e-S6,9e(Tc)[4] |
| 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] |
| Distance | 2,200 ± 100 ly (670 ± 40 pc) |
| Details | |
| Mass | 0.85[5] M☉ |
| Luminosity | 11,700[6] L☉ |
| Surface gravity (log g) | −0.50[5] cgs |
| Temperature | 2,538[5] K |
| Metallicity [Fe/H] | +0.50[5] dex |
| Other designations | |
| R Cyg, AAVSO 1934+49, BD+49 3064, HD 185456, HIP 31822, SAO 31822, WDS J19368+5012[7] | |
| Database references | |
| SIMBAD | data |
Stars at this mass range and evolutionary stage are pulsationally unstable, displaying a variation in their light output.[8] 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.[8] 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.[8]
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".[9]