KY Cygni
Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Cygnus |
Right ascension | 20h 25m 58.05s[1] |
Declination | +38° 21′ 07.6″[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: –3.574[6] mas/yr Dec.: –6.279[6] mas/yr |
Parallax (π) | 0.9151 ± 0.0920 mas[6] |
Distance | 1,068+120 −99[7] pc |
Absolute magnitude (MV) | –8.18[8] |
Details | |
Radius | 1,033[9] R☉ |
Luminosity | 138,000[2] – 270,000[8][10] L☉ |
Surface gravity (log g) | −0.5 (−0.9?)[8] cgs |
Temperature | 3,550[11] 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 3,480 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.[12] It was identified as a variable star in 1930,[13] and later named as KY Cygni.[14] 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 estimate 7.75 magnitudes at visual wavelengths. It would be a naked eye star if no light was lost.[8]
Properties
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Mukyv354.png/220px-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][15]
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.[8] 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☉.[11]
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.[12] The photographic magnitude range is given as 13.5 - 15.5,[5] while a visual range is 10.60 - 11.74.[3]
References
- ^ a b Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: University of Massachusetts and Infrared Processing and Analysis Center. Bibcode:2003yCat.2246....0C.
- ^ a b c d e f 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.
- ^ a b 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.
- ^ a b 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.
- ^ a b c 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.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Mantelet, G.; Andrae, R. (2018). "Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2". The Astronomical Journal. 156 (2): 58. arXiv:1804.10121. Bibcode:2018AJ....156...58B. doi:10.3847/1538-3881/aacb21. S2CID 119289017.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ a b c d e f 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.
- ^ 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.
- ^ 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. arXiv:2008.11723. Bibcode:2020ApJ...902...24D. doi:10.3847/1538-4357/abb318. S2CID 221340538.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ a b 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. arXiv:1905.03744. Bibcode:2019AJ....158...20M. doi:10.3847/1538-3881/ab1cbd. S2CID 148571616.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ a b 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.
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.