NGC 3603-B

NGC 3603-B (HD 97950B) is a Wolf-Rayet star located at the centre of the HD 97950 cluster in the NGC 3603 star-forming region, about 25,000 light years from Earth. It has the spectral type WN6h and is among the most luminous and most massive stars known.

NGC 3603-B

B is the brightest star just left of the three barely-resolved A components at the centre in this HST image of the central region of HD 97950.
Credit: NASA, ESA and Wolfgang Brandner (MPIA), Boyke Rochau (MPIA) and Andrea Stolte (University of Cologne)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Carina
Right ascension 11h 15m 07.411s[1]
Declination −61° 15′ 38.58″[1]
Apparent magnitude (V) 11.33[1]
Characteristics
Spectral type WN6h[2]
B−V color index +1.01[1]
Astrometry
Proper motion (μ) RA: 2.4[3] mas/yr
Dec.: 2.8[3] mas/yr
Distance7,600[2] pc
Absolute magnitude (MV)−7.77[2]
Details
Mass132[2] M☉
Radius33.8[2] R☉
Luminosity2,900,000[2] L☉
Temperature42,000[2] K
Age1.5[2] Myr
Other designations
NGC 3603-B, CD-60°3452B, CPD-60°2732B, HD 97950B, HIP 54948B, WR 43b, NGC 3603 MDS 23
Database references
SIMBADdata

HD 97950 was catalogued as a star, but was known to be a dense cluster or close multiple star. In 1926, the six brightest members were given letters from A to F,[4] although several of them have since been resolved into more than one star. Star B turned out to be the brightest single star.[5]

HD 97950B is a Wolf-Rayet (WR) star, with spectra dominated by strong broadened emission lines. Type WN6 indicates that ionised nitrogen lines are strong in comparison to ionised carbon lines, and the suffix h indicates that hydrogen is also seen in the spectrum. This type of WR star is not the classical stripped helium-burning aged star, but a young highly luminous object with CNO cycle fusion products showing at the surface due to strong conventional and rotational mixing, and high mass loss rates from the atmosphere. The emission lines are generated in the stellar wind and the photosphere is completely hidden. The surface fraction of hydrogen is still estimated to be around 60%.[2]

HD 97950B is the most massive and most luminous star known in the NGC 3603 region, nearly three million times more luminous than the sun and 132 times more massive. Although the star is very young, around 1.5 million years old, it has already lost a considerable fraction of its initial masses. The initial mass is estimated to have been 166 M☉, meaning it has lost 34 M☉.[2]

References
  1. Melena, Nicholas W.; Massey, Philip; Morrell, Nidia I.; Zangari, Amanda M. (2008). "The Massive Star Content of NGC 3603". The Astronomical Journal. 135 (3): 878–891. arXiv:0712.2621. Bibcode:2008AJ....135..878M. doi:10.1088/0004-6256/135/3/878. ISSN 0004-6256. S2CID 16765414.
  2. Crowther, P. A.; Schnurr, O.; Hirschi, R.; Yusof, N.; Parker, R. J.; Goodwin, S. P.; Kassim, H. A. (2010). "The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M⊙ stellar mass limit". Monthly Notices of the Royal Astronomical Society. 408 (2): 731–751. arXiv:1007.3284. Bibcode:2010MNRAS.408..731C. doi:10.1111/j.1365-2966.2010.17167.x. S2CID 53001712.
  3. Zacharias, N.; et al. (2003). "The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2)". CDS/ADC Collection of Electronic Catalogues. 1289. Bibcode:2003yCat.1289....0Z.
  4. Van Den Bos, W. H. (1928). "Another nebulous multiple star". Bulletin of the Astronomical Institutes of the Netherlands. 4: 261. Bibcode:1928BAN.....4..261V.
  5. Moffat, Anthony F. J.; Drissen, Laurent; Shara, Michael M. (1994). "NGC 3603 and its Wolf-Rayet stars: Galactic clone of R136 at the core of 30 Doradus, but without the massive surrounding cluster halo". Astrophysical Journal. 436: 183. Bibcode:1994ApJ...436..183M. doi:10.1086/174891.
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