The Discovery of a Very Massive Star in W49
  Very massive stars (M>100 M$_{\odot}$) are very rare objects, but have a strong influence on their environment. The formation of this kind of objects is of prime importance in star formation, but observationally still poorly constrained. We report on the identification of a very massive star in the central cluster of the star-forming region W49. We investigate near-infrared K-band spectroscopic observations of W49 from VLT/ISAAC together with JHK images obtained with NTT/SOFI and LBT/LUCI. We derive a spectral type of W49nr1, the brightest star in the dense core of the central cluster of W49. On the basis of its K-band spectrum, W49nr1 is classified as an O2-3.5If* star with a K-band absolute magnitude of -6.27$\pm$0.10 mag. The effective temperature and bolometric correction are estimated from stars of similar spectral type. After comparison to the Geneva evolutionary models, we find an initial mass between 100 M$_{\odot}$ and 180 M$_{\odot}$. Varying the extinction law results in a larger initial mass range of 90 - 250 M$_{\odot}$. 
Shi-Wei Wu, Arjan Bik, Thomas Henning, Anna Pasquali, Wolfgang   Brandner, Andrea Stolte
astro-ph.SR astro-ph.GA