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Y Cyg
	; A light curve for Y Cygni, plotted from TESS data
Observation data; Epoch J2000 Equinox J2000
Constellation	Cygnus
Right ascension	20h 52m 3.57718s
Declination	+34° 39′ 27.4861″
Apparent magnitude (V)	7.3 - 7.9
Characteristics
Primary
Spectral type	O9.5V
Apparent magnitude (U)	5.91[citation needed]
Apparent magnitude (B)	6.996[citation needed]
Apparent magnitude (V)	7.287
U−B color index	−1.086
B−V color index	−0.291
Secondary
Spectral type	O9.5V
Apparent magnitude (U)	5.883[citation needed]
Apparent magnitude (B)	6.974[citation needed]
Apparent magnitude (V)	7.265
U−B color index	−1.091
B−V color index	−0.291
Variable type	Algol
Astrometry
Proper motion (μ)	RA: +2.763 mas/yr ; Dec.: −15.981 mas/yr
Parallax (π)	0.6759 ± 0.0338 mas
Distance	4,900 ly ; (1,500 pc)
Absolute magnitude (MV)	−3.59/−3.62
Absolute bolometric; magnitude (Mbol)	−6.65±0.04/−6.7±0.04
Orbit
Primary	Y Cyg A
Companion	Y Cyg B
Period (P)	2.99633210±0.00000031 d
Semi-major axis (a)	28.72 R☉
Eccentricity (e)	0.14508
Inclination (i)	86.474±0.019°
Periastron epoch (T)	2,446,308.66407±0.0001
Argument of periastron (ω); (secondary)	312.514°
Argument of periastron (ω); (primary)	132.514±0.052°
Details
Primary
Mass	17.72±0.35 M☉
Radius	5.785±0.091 R☉
Luminosity	36,000 L☉
Surface gravity (log g)	4.161±0.014 cgs
Temperature	33,200±200 K
Rotational velocity (v sin i)	132 km/s
Age	2 Myr
Secondary
Mass	17.73±0.3 M☉
Radius	5.816±0.063 R☉
Luminosity	37,700 L☉
Surface gravity (log g)	4.157±0.01 cgs
Temperature	33,521±40 K
Rotational velocity (v sin i)	132 km/s
Age	2 Myr
Other designations
	Y Cyg, HD 198846, HIP 102999
Database references
SIMBAD	data

Y Cygni is an eclipsing and double-lined spectroscopic binary star system in the constellation of Cygnus. It is located about 4,900 light-years from Earth. The system was one of the first binaries with a convincing detection of the apsidal precession.^[4]

The two stars, being O-type main-sequence stars, orbit each other with a period of nearly 3 days.^[4]

Observation history

The early type of Y Cyg made it a popular target for astronomers in the past, and spectroscopic orbits have been historically computed numerous times.^[5] The first of these studies was published in 1920 by John Stanley Plaskett.^[6] Extensive spectroscopic studies of Y Cyg were carried out as early as 1930.^[7] Several follow-ups to these have been published in 1959,^[8] 1971,^[9]^[10] and 1980.^[11] The latter of these contained an estimate of the period of apsidal precession.

References

^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
^ ^a ^b ^c ^d ^e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ ^a ^b 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.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o Harmanec, P.; Holmgren, D. E.; Wolf, M.; Božić, H.; Guinan, E. F.; Kang, Y. W.; Mayer, P.; McCook, G. P.; Nemravová, J.; Yang, S.; Šlechta, M.; Ruždjak, D.; Sudar, D.; Svoboda, P. (March 2014). "Revised physical elements of the astrophysically important O9.5+O9.5V eclipsing binary system Y Cygni". Astronomy and Astrophysics. 563: A120. arXiv:1403.0721. Bibcode:2014A&A...563A.120H. doi:10.1051/0004-6361/201323230. ISSN 0004-6361. S2CID 118651473.
^ Hill, G.; Holmgren, D. E. (May 1995). "Studies of early-type variable stars. IX. Y Cygni". Astronomy and Astrophysics. 297: 127–134. Bibcode:1995A&A...297..127H.
^ Jones, Harold Spencer (1 November 1942). "John Stanley Plaskett, 1865-1941". The Royal Society. 4 (11): 67–82. doi:10.1098/rsbm.1942.0007.
^ Redman, R. O. (August 1930). "Y Cygni". Publications of the Astronomical Society of the Pacific. 42: 250. Bibcode:1930PASP...42..250R. doi:10.1086/124047. S2CID 250785748.
^ Struve, O.; Sahade, J.; Zabergs, V. (January 1959). "Y Cygni". Astrophysical Journal. 129: 59. Bibcode:1959ApJ...129...59S. doi:10.1086/146595.
^ Vitrichenko, E. A. (1971). "The improvement of the Spectroscopic orbit of Y Cyg". Società Astronomia Italiana. 43: 71. Bibcode:1972MmSAI..43...71V.
^ Vitrichenko, E. A. (1971). "The improvement of the Spectroscopic orbit of Y Cyg". Izv. Krym. Astrofiz. Obs. 43: 71–75. Bibcode:1971IzKry..43...71V.
^ Gimenez, A.; Costa, V. (December 1980). "Y CYG : photometry and apsidal motion". Publications of the Astronomical Society of the Pacific. 92: 782–784. Bibcode:1980PASP...92..782G. doi:10.1086/130747. S2CID 120757652.