59 Cygni

This article is about f¹ Cygni. For other stars with this Bayer designation, see f Cygni.

59 Cygni is a multiple^[7] star system in the northern constellation of Cygnus, located roughly 1,300 light years away from Earth. It is visible to the naked eye as a blue-white hued star with a combined apparent visual magnitude of 4.74.^[3]

59 Cygni

A visual band light curve of V832 Cygni. The main plot shows the long-term variability, and the inset plot shows the variation over a single orbital period. Adapted from Harmanec et al. (2002)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	20h 59m 49.55164s[2]
Declination	+47° 31′ 15.3789″[2]
Apparent magnitude (V)	4.74[3]
Characteristics
Spectral type	B1.5Vnne[4] + sdO + A3V + A8III + ?[5]
B−V color index	−0.084±0.004[3]
Variable type	γ Cas[6]
Astrometry
Radial velocity (Rv)	1.4±4.2[3] km/s
Proper motion (μ)	RA: +9.534[2] mas/yr Dec.: +3.090[2] mas/yr
Parallax (π)	2.5088±0.3226 mas[2]
Distance	approx. 1,300 ly (approx. 400 pc)
Absolute magnitude (MV)	−3.37[3]
Orbit[7]
Period (P)	28.1871±0.0011 d
Eccentricity (e)	0.141±0.008
Periastron epoch (T)	45677.6±0.3 HJD
Argument of periastron (ω) (secondary)	257±4°
Semi-amplitude (K1) (primary)	11.7±0.9 km/s
Semi-amplitude (K2) (secondary)	121.3±1.1 km/s
Details[7]
59 Cyg Aa – Be star
Mass	6.3–9.4 M☉
Radius	5.5–7.0 R☉
Luminosity	7,943 L☉
Surface gravity (log g)	3.78±0.09 cgs
Temperature	21,800±700 K
Rotational velocity (v sin i)	379±27 km/s
59 Cyg Aa – sdO
Mass	0.62–0.91 M☉
Radius	0.34–0.43 R☉
Luminosity	1,000 L☉
Surface gravity (log g)	5.0±1.0 cgs
Temperature	52,100±4,800 K
Rotational velocity (v sin i)	< 40 km/s
Other designations
f1 Cyg, 59 Cyg, V832 Cyg, BD+46°3133, FK5 1551, HD 200120, HIP 103632, HR 8047, SAO 50335, WDS J20598+4731[8]
Database references
SIMBAD	data

The primary component and brightest member of this system, designated 59 Cyg Aa, is a rapidly rotating Be star with a stellar classification of B1.5 Vnne.^[4] This is a well-studied star thanks to pronounced spectral variations that have been observed since 1916, and two short-term shell star phases that were observed in 1973 and 1974–5.^[9] It is actually a confirmed spectroscopic binary system with a high temperature subdwarf O-type companion in a 28-day orbital period. The latter is heating the nearest side of the circumstellar gaseous disk that surrounds the primary.^[7]

Orbiting the primary pair is 59 Cyg Ab, a magnitude 7.64 A-type main-sequence star of class A3V, located at an angular separation of 0.200″. A fourth component is a magnitude 9.8 A-type giant star of class A8III at a separation of 20.2″ along a position angle (PA) of 352°, as of 2008. The fifth companion is magnitude 11.7 at a separation of 26.7″ and a PA of 141°.^[5] Gaia Data Release 2 suggests that the companions at 20.2″ and 26.7″ are respectively 382 pc and 366 pc away and moving in approximately the same direction as the primary triple.^[10][11]