τ Cygni
Location of τ Cygni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension 21h 14m 47.4916s
Declination +38° 02′ 43.141″
Apparent magnitude (V) 3.65 - 3.75[1] (3.80 / 6.69[2])
Characteristics
Spectral type F2 IV + G0 V
U−B color index +0.03 / +0.09
B−V color index +0.38 / +0.60
Variable type δ Sct[1]
Astrometry
Radial velocity (Rv)-21.1 km/s
Proper motion (μ) RA: 195.75 mas/yr
Dec.: 410.03 mas/yr
Parallax (π)47.80 ± 0.61 mas
Distance68.2 ± 0.9 ly
(20.9 ± 0.3 pc)
Orbit[3]
Period (P)810 days
Semi-major axis (a)0.796 mas
Eccentricity (e)0.43
Inclination (i)92.6°
Longitude of the node (Ω)78.7°
Periastron epoch (T)2453139.5
Argument of periastron (ω)
(secondary)		90°
Details
τ Cyg A
Mass1.65[2] M☉
Radius2.48[2] R☉
Surface gravity (log g)3.87[2] cgs
Temperature6,600[2] K
Metallicity [Fe/H]0.05[2] dex
τ Cyg B
Mass1.03[2] M☉
Radius0.93[2] R☉
Surface gravity (log g)4.52[2] cgs
Temperature5,670[2] K
Other designations
τ Cygni, 65 Cygni, BD+37°4240, HD 202444, HIP 104887, HR 8130, SAO 71121, GC 29723, CCDM J21148+3803AB.
Database references
SIMBADdata
A
B

Tau Cygni, Latinised from τ Cygni, is a binary star system in the constellation Cygnus, approximately 69 light years away from Earth.[4] This visual binary system has a period of 49.6 years.[2]

The main star, 4th magnitude GJ 822.1 A, is a yellowish white subgiant star of the spectral type F2IV. It therefore has a surface temperature of 6,000 to 7,500 kelvins and is larger, hotter, and several times as bright as the Sun.[5] Its companion, 6th magnitude GJ 822.1 B, is a yellow main sequence star of the spectral type G0V. It is similar to the Sun in size, surface temperature, and luminosity.[6]

Tau Cygni is classified as a δ Scuti variable. The magnitude range is given as 3.65 to 3.75, which is the combined magnitude for both components, although the variable component is A.[1]

References

  1. 1 2 3 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  2. 1 2 3 4 5 6 7 8 9 10 11 Fuhrmann, Klaus (February 2008), "Nearby stars of the Galactic disc and halo - IV", Monthly Notices of the Royal Astronomical Society, 384 (1): 173–224, Bibcode:2008MNRAS.384..173F, doi:10.1111/j.1365-2966.2007.12671.x
  3. ↑ "Sixth Catalog of Orbits of Visual Binary Stars". Archived from the original on 2017-08-01. Retrieved 2016-12-26.
  4. ↑ "* tau Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 18, 2007.
  5. ↑ "* tau Cyg A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 18, 2007.
  6. ↑ "* tau Cyg B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 18, 2007.
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