Astronomy:KY Cygni

From HandWiki
Short description: Star in the constellation Cygnus
KY Cygni
Sadr Region rgb.jpg
Red circle.svg
Location of KY Cygni (circled, east is up)
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
Distance4,900 ± 400 ly
(1,500 ± 100 pc)
Details
Radius1,033[6] – 1,420[7] R
Luminosity138,000[2] – 270,000[7][8] L
Surface gravity (log g)−0.5 (−0.9?)[7] cgs
Temperature3,550[9] K
Other designations
KY Cyg, GSC 03152-01140, IRAS 20241+3811, IRC+40415, TYC 3152-1140-1, RAFGL 2575, UCAC2 45230193, 2MASS J20255805+3821076
Database references
SIMBADdata

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

Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to estimates derived in 2005[7]

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]

A visual band light curve for KY Cygni, plotted from data published by Kochanek et al. (2017)[14]

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. 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. Bibcode2021A&A...649A...1G.  Gaia EDR3 record for this source at VizieR.
  2. 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. Bibcode2011A&A...526A.156M. 
  3. 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. Bibcode2012A&A...548A..79A. 
  4. 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. Bibcode1978ApJ...222..209W. 
  5. 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.
  6. 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. Bibcode2020A&A...644A..62C. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Cite error: Invalid <ref> tag; no text was provided for refs named levesque
  8. 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. Bibcode2020ApJ...902...24D. 
  9. 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. Bibcode2019AJ....158...20M. 
  10. 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. Bibcode1969MmSAI..40..375R. 
  11. Hoffmeister, Cuno (1930). "Relative Koordinaten, Oerter und Karten neuer Veraenderlicher". Mitteilungen der Sternwarte zu Sonneberg 17: 1. Bibcode1930MiSon..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. Bibcode1941KVeBB...6....4A. 
  13. Stickland, D. J. (1985). "IRAS observations of the cool galactic hypergiants". The Observatory 105: 229. Bibcode1985Obs...105..229S. 
  14. 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. Bibcode2017PASP..129j4502K. 

External links