The Massive Star Content of Circumnuclear Star Clusters in M83
  The circumnuclear starburst of M83 (NGC 5236), the nearest such example (4.6
Mpc), constitutes an ideal site for studying the massive star IMF at high
metallicity (12+log[O/H]=9.1$\pm$0.2, Bresolin & Kennicutt 2002). We analyzed
archival HST/STIS FUV imaging and spectroscopy of 13 circumnuclear star
clusters in M83. We compared the observed spectra with two types of single
stellar population (SSP) models, semi-empirical models, which are based on an
empirical library of Galactic O and B stars observed with IUE (Robert et al.
1993), and theoretical models, which are based on a new theoretical UV library
of hot massive stars described in Leitherer et al. (2010) and computed with
WM-Basic (Pauldrach et al. 2001). The models were generated with Starburst99
(Leitherer & Chen 2009). We derived the reddenings, the ages, and the masses of
the clusters from model fits to the FUV spectroscopy, as well as from optical
HST/WFC3 photometry.
