Astronomy:KY Cygni
Observation data Equinox J2000.0]] (ICRS) | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 25m 58.04s[1] |
Declination | +38° 21′ 07.7″[1] |
Apparent magnitude (V) | 11.14[2] (10.60 - 11.74[3]) |
Characteristics | |
Spectral type | M3 Ia[4] (M3.5 Ia[5]) |
U−B color index | +2.91[2] |
B−V color index | +3.39[2] |
Variable type | Lc[5] |
Astrometry | |
Proper motion (μ) | RA: –3.556[1] mas/yr Dec.: –6.061[1] mas/yr |
Parallax (π) | 0.6687 ± 0.0517[1] mas |
Distance | 4,900 ± 400 ly (1,500 ± 100 pc) |
Details | |
Radius | 1,033[6] – 1,420[7] R☉ |
Luminosity | 138,000[2] – 270,000[7][8] L☉ |
Surface gravity (log g) | −0.5 (−0.9?)[7] cgs |
Temperature | 3,550[9] K |
Other designations | |
Database references | |
SIMBAD | data |
KY Cygni is a red supergiant of spectral class M3.5Ia located in the constellation Cygnus. It is approximately 5,000 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.[10] It was identified as a variable star in 1930,[11] and later named as KY Cygni.[12] The spectrum was given the MK classification of M3 Ia, with only minor adjustments since.[4]
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.[7]
Properties
![](/wiki/images/thumb/5/50/Mukyv354.png/250px-Mukyv354.png)
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.[2][13]
Its properties are uncertain, but the temperature is around 3,500 K. A model fit based on K-band infrared brightness gives a luminosity of 273,000 L☉, corresponding to a radius of 1,420 R☉. Another model based on visual brightness gives an unexpectedly large luminosity of 1,107,000 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 R☉. These parameters are larger and more luminous than expected for any red supergiant, making them doubtful.[7] 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☉,[2] and calculation of the bolometric luminosity based on its Gaia Data Release 2 parallax gives a luminosity below 70,000 L☉ with a corresponding radius of 672 R☉.[9]
![](/wiki/images/thumb/7/73/KYCygLightCurve.png/250px-KYCygLightCurve.png)
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.[10] The photographic magnitude range is given as 13.5 - 15.5,[5] while a visual range is 10.60 - 11.74.[3]
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics 526: A156. doi:10.1051/0004-6361/201013993. Bibcode: 2011A&A...526A.156M.
- ↑ 3.0 3.1 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. doi:10.1051/0004-6361/201220095. Bibcode: 2012A&A...548A..79A.
- ↑ 4.0 4.1 White, N. M.; Wing, R. F. (1978). "Photoelectric two-dimensional spectral classification of M supergiants". Astrophysical Journal 222: 209. doi:10.1086/156136. Bibcode: 1978ApJ...222..209W.
- ↑ 5.0 5.1 5.2 KY Cyg, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars , Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 12, 2010.
- ↑ Comerón, F.; Djupvik, A. A.; Schneider, N.; Pasquali, A. (October 2020). "The historical record of massive star formation in Cygnus". Astronomy & Astrophysics 644: A62. doi:10.1051/0004-6361/202039188. Bibcode: 2020A&A...644A..62C.
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Cite error: Invalid
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- ↑ Dorn-Wallenstein, Trevor Z.; Levesque, Emily M.; Neugent, Kathryn F.; Davenport, James R. A.; Morris, Brett M.; Gootkin, Keyan (2020). "Short Term Variability of Evolved Massive Stars with TESS II: A New Class of Cool, Pulsating Supergiants". The Astrophysical Journal 902 (1): 24. doi:10.3847/1538-4357/abb318. Bibcode: 2020ApJ...902...24D.
- ↑ 9.0 9.1 Messineo, M.; Brown, A. G. A. (2019). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal 158 (1): 20. doi:10.3847/1538-3881/ab1cbd. Bibcode: 2019AJ....158...20M.
- ↑ 10.0 10.1 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.
- ↑ Hoffmeister, Cuno (1930). "Relative Koordinaten, Oerter und Karten neuer Veraenderlicher". Mitteilungen der Sternwarte zu Sonneberg 17: 1. Bibcode: 1930MiSon..17....1H.
- ↑ 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.
- ↑ Stickland, D. J. (1985). "IRAS observations of the cool galactic hypergiants". The Observatory 105: 229. Bibcode: 1985Obs...105..229S.
- ↑ Kochanek, C. S.; Shappee, B. J.; Stanek, K. Z.; Holoien, T. W. S.; Thompson, Todd A.; Prieto, J. L.; Dong, Subo; Shields, J. V. et al. (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. doi:10.1088/1538-3873/aa80d9. Bibcode: 2017PASP..129j4502K.
External links
- http://jumk.de/astronomie/big-stars/ky-cygni.shtml
- http://www.astronomy.com/asy/default.aspx?c=a&id=2772
- List of Largest Stars Gets 3 New Chart Toppers, Robert Roy Britt, space.com, 10 January 2005. Accessed on line November 12, 2010.
![]() | Original source: https://en.wikipedia.org/wiki/KY Cygni.
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