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$_{\odot}$.
