BI Cygni

BI Cygni
BI Cygni is the small very red dot right on the left edge of this image. The bright star at the centre is γ Cygni and north is to the right.
Credit: Erik Larsen
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 21m 21.8803s[1]
Declination 36° 55′ 55.771″[1]
Apparent magnitude (V) 8.4 - 9.9[2]
Characteristics
Spectral type M4 Iab[2]
Variable type Lc[2]
Astrometry
Distance1,580[3] pc
Absolute magnitude (MV)−6.78[4]
Details
Radius850[5] - 1,240[4] R☉
Luminosity123,000[3]-226,000[4] L☉
Temperature3,575[4][3]-3,720[5] K
Other designations
BI Cygni, BD+36 4025, IRC+40408, 2MASS J20212192+3655555, IRAS 20194+3646, WDS J20214+3656, AAVSO 2017+36B
Database references
SIMBADdata

BI Cygni (BI Cyg, IRC +40408, BD+36 4025) is a red supergiant in the constellation Cygnus. It is an irregular variable star with a maximum brightness of magnitude 8.4 and a minimum of magnitude 9.9. It has a current mass of 20 M☉.[5]

It is considered a member of the stellar Cygnus OB1 association,[4] its distance is 1,580 parsecs (5,150 light-years) of the Solar System. It is less than a degree south of another variable red supergiant, BC Cygni.

BI Cyg is a slow irregular variable star classified as type Lc, an irregular supergiant. Its brightness changes between extremes of magnitude 8.4 and 9.9.[2] Frequency analysis of its light curve shows no significant periods.[6]

BI Cyg is one of largest known stars with a radius around 1,240 R☉ based on the assumption of an effective temperature of 3,575 K and a bolometric luminosity of 226,000 L☉.[4] More recent studies derive lower luminosities below 130,000 L☉, suggesting an initial mass of 20 M☉, and consequently lower values for the radius.[3][5]

See also

References

  1. 1 2 Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
  2. 1 2 3 4 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. Bibcode:2009yCat....102025S.
  3. 1 2 3 4 Nicolas Mauron; Eric Josselin (2010). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369 [astro-ph.SR]. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993. Cite uses deprecated parameter |class= (help)
  4. 1 2 3 4 5 6 Table 4 in Levesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (August 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.
  5. 1 2 3 4 Josselin, E.; Plez, B. (2007). "Atmospheric dynamics and the mass loss process in red supergiant stars". Astronomy and Astrophysics. 469 (2): 671–680. arXiv:0705.0266. Bibcode:2007A&A...469..671J. doi:10.1051/0004-6361:20066353.
  6. ↑ Kiss, L. L; Szabó, Gy. M; Bedding, T. R (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
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