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We analyze far-ultraviolet spectra and ancillary data of the super starcluster SSC-N and its surrounding H II region in the nearby dwarf galaxy II Zw40. From the ultraviolet spectrum, we derive a low internal reddening of E(B-V)= 0.07 +/- 0.03, a mass of (9.1 +/- 1.0) x 10^5 Lsol, a bolometric luminosityof (1.1 +/- 0.1) x 10^9 Lsol, a number of ionizing photons of (6 +/- 2) x 10^52s^-1, and an age of (2.8 +/- 0.1) Myr. These parameters agree with the valuesderived from optical and radio data, indicating no significant obscured starformation, absorption of photons by dust, or photon leakage. SSC-N and itsnebulosity are an order of magnitude more massive and luminous than 30 Doradusand its ionizing cluster. Photoionization modeling suggests a high ionizationparameter and a C/O ratio where C is between primary and secondary. Wecalculate diagnostic emission-line ratios and compare SSC-N to localstar-forming galaxies. The SSC-N nebula does not coincide with the locusdefined by local galaxies. Rather, it coincides with the location of "GreenPea" galaxies, objects which are often considered nearby analogs of thegalaxies reionizing the universe. Most stellar features are well-reproduced bysynthetic spectra. However, the SSC-N cluster has strong, broad, stellar He II1640 emission that cannot be reproduced, suggesting a deficit of He-enhancedstars with massive winds in the models. We discuss possible sources for thebroad He II emission, including very massive stars and/or enhanced mixingprocesses.

Physical Properties of II Zw 40's Super Star Cluster and Nebula: New Insights and Puzzles from UV Spectroscopy