KY Cygni

KY Cygni
Location of KY Cygni in the Sadr region (circled, east is up)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 25m 58.04s
Declination +38° 21′ 07.7″
Apparent magnitude (V) 10.60 - 11.74
Characteristics
Evolutionary stage Red supergiant or hypergiant
Spectral type M3 Ia (M3.5 Ia)
U−B color index +2.91
B−V color index +3.39
Variable type Lc
Astrometry
Proper motion (μ) RA: −3.556 mas/yr
Dec.: −6.061 mas/yr
Parallax (π)0.6687±0.0517 mas
Distance4,680+350
−390 ly
(1,436+106
−119 pc)
Absolute magnitude (MV)−8.18
Details
Mass19 M☉
Radius1,032 R☉
Luminosity150,000 L☉
Surface gravity (log g)−0.5 cgs
Temperature3,500±100 K
Age>9 Myr
Other designations
RAFGL 2575, UCAC2 45230193, KY Cyg, TYC 3152-1140-1, GSC 03152-01140, IRAS 20241+3811, IRC +40415, 2MASS J20255805+3821076
Database references
SIMBADdata

KY Cygni is a variable red supergiant or hypergiant of spectral class M3Ia located in the constellation Cygnus. It is approximately 4,700 light-years away.

Observations

KY Cyg lies near the bright open cluster NGC 6913, but is not thought to be a member. The location is close to the bright star γ Cygni. It was identified as a variable star in 1930, and later named as KY Cygni. The spectrum was given the MK classification of M3 Ia, with only minor adjustments since.

KY Cygni is heavily reddened due to interstellar extinction, losing an estimated 7.75 magnitudes at visual wavelengths. It would be a naked eye star if no light was lost.

Properties

Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to estimates derived in 2005

KY Cygni is classified as a luminous red supergiant with a strong stellar wind. It is losing mass at around 4.9×10−6 M☉ and has been described as a cool hypergiant.

Its properties are uncertain, but the effective temperature is around 3,500±100 K. A model fit based on K-band infrared brightness gives a luminosity of 273,000+87,000
−66,000 L☉, corresponding to a radius of 1,420±284 R☉. Another model based on visual brightness gives an unexpectedly large luminosity of 1,107,000+352,000
−247,000 L☉, with the difference due mainly to the assumptions about the level of extinction. The radius corresponding to the higher luminosity would be 2,850±570 R☉. These parameters are larger and more luminous than expected for any red supergiant, making them doubtful. More recently, integration of the spectral energy distributions across a full range of wavelengths from U band to the 60 micron microwave flux gives an even lower luminosity of 138,000 L☉, and a 2020 paper published a luminosity of 150,000 L☉, which give a smaller radius of 1,032 R☉ using a spectral type of M4, which suggests an assumed effective temperature of 3,535 K.

A visual band light curve for KY Cygni, plotted from data published by Kochanek et al. (2017)

KY Cygni is a variable star with a large amplitude but no clear periodicity. At times, it varies rapidly, at others it is fairly constant for long periods. The photographic magnitude range is given as 13.5 - 15.5, while a visual range is 10.60 - 11.74.

See also

Notes

  1. ↑ Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
    .
  2. ↑ This is only the age at which the star enters the red supergiant phase.

References

  1. 1 2 3 4 5 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.
  2. 1 2 Alfonso-Garzón, J.; Domingo, A.; Mas-Hesse, J. M.; Giménez, A. (2012). "The first INTEGRAL-OMC catalogue of optically variable sources". Astronomy & Astrophysics. 548: A79. arXiv:1210.0821. Bibcode:2012A&A...548A..79A. doi:10.1051/0004-6361/201220095. S2CID 118428054.
  3. 1 2 3 4 5 6 7 8 9 10 Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901. S2CID 15109583.
  4. 1 2 Stickland, D. J. (1985). "IRAS observations of the cool galactic hypergiants". The Observatory. 105: 229. Bibcode:1985Obs...105..229S.
  5. 1 2 White, N. M.; Wing, R. F. (1978). "Photoelectric two-dimensional spectral classification of M supergiants". Astrophysical Journal. 222: 209. Bibcode:1978ApJ...222..209W. doi:10.1086/156136.
  6. 1 2 3 KY Cyg, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars Archived 2017-06-20 at the Wayback Machine, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 12, 2010.
  7. 1 2 3 4 Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993. S2CID 119276502.
  8. ↑ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
  9. 1 2 Comerón, F.; Djupvik, A. A.; Schneider, N.; Pasquali, A. (October 2020). "The historical record of massive star formation in Cygnus". Astronomy & Astrophysics. 644: A62. arXiv:2009.12779. Bibcode:2020A&A...644A..62C. doi:10.1051/0004-6361/202039188. S2CID 221970180.
  10. 1 2 Romano, G. (1969). "Researches with the Schmidt telescopes. III. Variable stars in the field of gamma Cygni". Memorie della Società Astronomia Italiana. 40: 375. Bibcode:1969MmSAI..40..375R.
  11. ↑ Hoffmeister, Cuno (1930). "Relative Koordinaten, Oerter und Karten neuer Veraenderlicher". Mitteilungen der Sternwarte zu Sonneberg. 17: 1. Bibcode:1930MiSon..17....1H.
  12. ↑ Ahnert, P.; Van Schewick, H.; Hoffmeister, C. (1941). "Die Veraenderlichen Sterne der noerdlichen Milchstrasse. Teil II". Kleine Veroeffentlichungen der Universitaetssternwarte zu Berlin Babelsberg. 6: 4.1. Bibcode:1941KVeBB...6....4A.
  13. ↑ Kochanek, C. S.; Shappee, B. J.; Stanek, K. Z.; Holoien, T. W. S.; Thompson, Todd A.; Prieto, J. L.; Dong, Subo; Shields, J. V.; Will, D.; Britt, C.; Perzanowski, D.; Pojmański, G. (October 2017). "The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0". Publications of the Astronomical Society of the Pacific. 129 (980): 104502. arXiv:1706.07060. Bibcode:2017PASP..129j4502K. doi:10.1088/1538-3873/aa80d9.