We analyze archival HST /STIS/FUV-MAMA imaging and spectroscopy of 13 compact star clusters within the circumnuclear starburst region of M83 , the closest such example .
We compare the observed spectra with semi-empirical models , which are based on an empirical library of Galactic O and B stars observed with IUE , and with theoretical models , which are based on a new theoretical UV library of hot massive stars computed with WM-Basic .
The models were generated with Starburst99 for metallicities of Z = 0.020 and Z = 0.040 , and for stellar IMFs with upper mass limits of 10 , 30 , 50 , and 100 M _ { \odot } .
We estimate the ages and masses of the clusters from the best fit model spectra , and find that the ages derived from the semi-empirical and theoretical models agree within a factor of 1.2 on average .
A comparison of the spectroscopic age estimates with values derived from HST /WFC3/UVIS multi-band photometry shows a similar level of agreement for all but one cluster .
The clusters have a range of ages from about 3 to 20 Myr , and do not appear to have an age gradient along M83 ’ s starburst .
Clusters with strong P-Cygni profiles have masses of a few \times 10 ^ { 4 } M _ { \odot } , seem to have formed stars more massive than 30 M _ { \odot } , and are consistent with a Kroupa IMF from 0.1 - 100 M _ { \odot } .
Field regions in the starburst lack P-Cygni profiles and are dominated by B stars .