Cygnus OB2-8A

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The correct title of this article is Cygnus OB2 #8A. The omission of the # is due to technical restrictions.
Cygnus OB2 #8A
Bica2 HST.jpg
Cygnus OB2 #8A to #8D (lower left) and other OB-type stars from the Hubble Space Telescope
Observation data
Epoch J2000       Equinox J2000
Constellation Cygnus [1]
Right ascension 20h 33m 15.07905s [2]
Declination +41° 18′ 50.4762″ [2]
Apparent magnitude  (V)9.06 [3]
Characteristics
Spectral type O6If + O5.5III(f) [4]
U−B color index +0.15 [5]
B−V color index +1.29 [5]
Astrometry
Radial velocity (Rv)125.56 [6] km/s
Proper motion (μ)RA: −2.664 [6] mas/yr
Dec.: −4.895 [6] mas/yr
Parallax (π)0.6058±0.0191  mas [6]
Distance 5,400 ± 200  ly
(1,650 ± 50  pc)
Absolute magnitude  (MV)−6.78 [7]
Orbit [8]
Period (P)21.9 days
Semi-major axis (a)71 R☉ [9]
Eccentricity (e)0.24
Semi-amplitude (K1)
(primary)		82.8 km/s
Semi-amplitude (K2)
(secondary)		95.8 km/s
Details [9]
Cyg OB2 #8A1
Mass 44.1  M☉
Radius 20  R☉
Luminosity 650,000  L☉
Surface gravity (log g)3.48  cgs
Temperature 36,800  K
Cyg OB2 #8A2
Mass 37.4  M☉
Radius 14.8  R☉
Luminosity468,000  L☉
Surface gravity (log g)3.67  cgs
Temperature 39,200  K
Age 2 [7]   Myr
Other designations
Schulte  8A, 1E  203127+4108.5, TYC  3161-1325-1, ADS  14000 A, 2E  4382, HIP  101425, UBV  17839, AG+41°1925, 2E  2031.4+4108, IDS  20297+4058, LS  III +41 37, Cyg OB2-8A, 1ES  2031+41.1, 2MASS  J20331508+4118504, BD+40 4227, GCRV  20036, PPM  60129, CCDM  J20332+4119A, 1RXS  J203315.8+411848, CGO  605, GOS  G080.22+00.79 01, SAO  49781, CSI+40 4227 1, GSC  03161-01325, Gaia DR2 2067784624247057920
Database references
SIMBAD data

Cygnus OB2 #8A is a double-lined spectroscopic binary located near the centre of the Cygnus OB2 association located 5,500 light years away.

Contents

Discovery

Until 1951 Cyg OB2 #8 had been known only as an anonymous catalogue entry in the Bonner Durchmusterung. Then it was identified as one of several highly luminous hot stars close together in Cygnus. Despite being commonly referred to as Schulte #8A, the number 8 was first published in an earlier paper. [10] Schulte identified the grouping as a massive stellar association and split star #8 into four components, including #8A. [11]

System

The Cygnus OB2 #8A system contains two massive luminous O class stars in a 21.9 day orbit. The primary is a 44 M☉ supergiant and the secondary is a 37 M☉ giant star. [8] The two stars are not thought to be exchanging mass and their luminosity classes match the main sequence turnoff in the Cyg OB2 association at around O6. [7] The nearby stars Cyg OB2 #8B, #8C, and #8D, originally thought to be a single star, are all massive and luminous class O stars.

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific . 99 (617): 695. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Constellation record for this object at VizieR.
  2. 1 2 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID   18759600.
  3. ↑ Caballero-Nieves, S. M.; Nelan, E. P.; Gies, D. R.; Wallace, D. J.; Degioia-Eastwood, K.; Herrero, A.; Jao, W.-C.; Mason, B. D.; Massey, P.; Moffat, A. F. J.; Walborn, N. R. (2014). "A High Angular Resolution Survey of Massive Stars in Cygnus OB2: Results from the Hubble Space Telescope Fine Guidance Sensors". The Astronomical Journal. 147 (2): 40. arXiv: 1311.5087 . Bibcode:2014AJ....147...40C. doi:10.1088/0004-6256/147/2/40. S2CID   22036552.
  4. ↑ Cazorla, Constantin; Nazé, Yaël; Rauw, Gregor (2014). "Wind collisions in three massive stars of Cygnus OB2". Astronomy & Astrophysics. 561: A92. arXiv: 1312.1871 . Bibcode:2014A&A...561A..92C. doi:10.1051/0004-6361/201322539. S2CID   53682076.
  5. 1 2 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  6. 1 2 3 4 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  7. 1 2 3 Negueruela, I.; Marco, A.; Herrero, A.; Clark, J. S. (2008). "New very massive stars in Cygnus OB2". Astronomy and Astrophysics. 487 (2): 575. arXiv: 0806.2879 . Bibcode:2008A&A...487..575N. doi:10.1051/0004-6361:200810094. S2CID   10915879.
  8. 1 2 De Becker, M.; Rauw, G.; Manfroid, J. (2004). "A Spectroscopic study of the non-thermal radio emitter Cyg OB2 #8A: Discovery of a new binary system". Astronomy and Astrophysics. 424 (3): L39. arXiv: astro-ph/0408027 . Bibcode:2004A&A...424L..39D. doi:10.1051/0004-6361:200400049. S2CID   16213357.
  9. 1 2 De Becker, M.; Rauw, G.; Sana, H.; Pollock, A. M. T.; Pittard, J. M.; Blomme, R.; Stevens, I. R.; Van Loo, S. (2006). "XMM-Newton observations of the massive colliding wind binary and non-thermal radio emitter CygOB2#8A [O6If + O5.5III(f)]" (PDF). Monthly Notices of the Royal Astronomical Society. 371 (3): 1280. Bibcode:2006MNRAS.371.1280D. doi: 10.1111/j.1365-2966.2006.10746.x .
  10. ↑ Münch, Luis; Morgan, W. W. (1953). "Notes: A Probable Clustering of Blue Giants in Cygnus". Astrophysical Journal. 118: 161. Bibcode:1953ApJ...118..161M. doi: 10.1086/145737 .
  11. ↑ Schulte, D. H. (1956). "New Members of the Association VI Cygni". Astrophysical Journal. 124: 530. Bibcode:1956ApJ...124..530S. doi:10.1086/146256.
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