Epoch J2000.0 Equinox J2000.0
|Right ascension||20h 31m 4.6s|
|Declination||+40° 30′ 57.05″|
|Apparent magnitude (V)||10.45|
|Apparent magnitude (K)||4.466|
|Apparent magnitude (J)||5.469|
|Apparent magnitude (H)||4.833|
|B−V color index||1.68|
|Variable type||candidate LBV|
|Proper motion (μ)||RA: -3.8 mas/yr
Dec.: -2.8 mas/yr
|Absolute magnitude (MV)||-7.66|
|Luminosity (bolometric)||630,000 L☉|
BD+40° 4210, heavily reddened and extinguished by the interstellar dust of the Milky Way and little studied until now, has turned out to be one of the most luminous stars of the Cygnus OB2 association, with an absolute magnitude of -7.66 and a bolometric luminosity more than 600,000 times that of our Sun. It has been assigned a B1III spectral classification, but with peculiarities including unusually shallow lines and broad emission. Despite the giant luminosity class, the luminosity appears to be extremely high, placing it on or near the S Doradus instability strip occupied by quiescent luminous blue variables.
BD+40° 4210 is located at a projected 4.8 parsecs from the candidate luminous blue variable G79.29+0.46 and probably at a similar distance since both are assumed members of Cygnus OB2; however, unlike the latter which is surrounded by an extensive ring-shaped nebulosity, no nebula has been found around this star.
- . Bibcode:1988A&AS...74..449R. Missing or empty
- . Bibcode:2000A&A...355L..27H. Missing or empty
- Comerón, F.; Pasquali, A. (2012). "New members of the massive stellar population in Cygnus". Astronomy & Astrophysics 110: 2715. Bibcode:2012A&A...543A.101C. doi:10.1051/0004-6361/201219022.
- . Bibcode:-2003yCat.2246....0C. Missing or empty
- http://www.sciops.esa.int/SD/ESACFACULTY/docs/seminars/160212_Comeron.pdf In and around the rich association Cygnus OB2