The SMC compact blob N 81 - A detailed multi-wavelength investigation

The physical characteristics of the compact Small Magellanic Cloud (SMC) H II region N 81 are investigated using several observational techniques with various telescopes at ESO, namely CCD, Image Dissector Scanner, and Reticon high, medium, and low resolution spectroscopy in the 3700-10,000 A range; CCD imaging; and UBVRI and JHK photometry. Compared to the SMC blobs N 88 A and the LMC N 160 A 1, N 81 was found to be neither dense nor reddened. It is suggested that the nebula N 81 is excited by one star of about 60 solar masses, the absolute visual magnitude of which was derived to be equal to -5.1. The high-resolution profile of N 81 at H-beta was decomposed into its various components, with the most probable three-dimensional turbulent velocity in N 81 estimated to be about 3 km/s. The chemical abundances of He, O, N, Ne, S, and Ar were computed and compared with the mean values available for the SMC.