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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
Epoch J2000 Equinox J2000
|Right ascension||20h 21m 21.8803s|
|Declination||36° 55′ 55.771″|
|Apparent magnitude (V)||8.4 - 9.9|
|Spectral type||M4 Iab|
|Proper motion (μ)|| RA: ±0.140−2.929 mas/yr |
Dec.: ±0.151−5.223 mas/yr
|Parallax (π)||0.7269 ± 0.0811 mas|
|Absolute magnitude (MV)||−6.78|
|Radius||850 - 1,240 R☉|
|Diameter||850 - 1,240 D☉|
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☉.
It is considered a member of the stellar Cygnus OB1 association, 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. Frequency analysis of its light curve shows no significant periods.
BI Cyg is one of largest known stars with a radius around 1,240 D☉ based on the assumption of an effective temperature of 3,575 K and a bolometric luminosity of 226,000 L☉. More recent studies derive lower luminosities below 130,000 L☉, suggesting an initial mass of 20 M☉, and consequently lower values for the radius.
- 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.
- Samus, N. N.Expression error: Unrecognized word "etal". (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.
- Brown, A. G. A. (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.
- 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. Bibcode 2011A&A...526A.156M. doi:10.1051/0004-6361/201013993.
- 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.
- 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.
- 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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