  Dynamical studies of superbubbles and Wolf-Rayet ring nebulae show
discrepancies from the standard, adiabatic model for wind-blown bubbles. We
therefore study the physical properties and kinematics of three candidate
bubbles blown by single O stars, to evaluate whether these discrepancies are
also found in these simpler objects. Our sample candidates are N44F, N44J, and
N44M, in the outskirts of the HII complex N44 in the Large Magellanic Cloud. We
have obtained ground-based and HST emission-line images and high dispersion
echelle spectra for these objects. From the Halpha luminosities and the
[OIII]/Halpha ratios of these nebulae, we estimate the spectral types of the
ionizing stars to be O7V, O9.5V and O9.5V for N44F, N44J, and N44M,
respectively. We find that the observed expansion velocity of 12 km/s for N44F
is consistent with the stellar wind luminosity expected from the central
ionizing star, as predicted by the standard bubble model. The observed upper
limits for the expansion velocities of N44J and N44M are also compatible with
the expected values, within the uncertainties. We also report the discovery in
N44F of strongly-defined dust columns, similar to those seen in the Eagle
Nebula. The photoevaporation of these dense dust features may be kinematically
important and may actually govern the evolution of the shell. The inclusion of
photoevaporation processes may thus undermine the apparent agreement between
the observed bubble dynamics and the simple adiabatic models.
