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 N44 F , N44 J , and N44 M , in the outskirts of the H ii 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 H \alpha luminosities and the [ O iii ] /H \alpha ratios of these nebulae , we estimate the spectral types of the ionizing stars to be O7V , O9.5V and O9.5V for N44 F , N44 J , and N44 M , respectively .
We find that the observed expansion velocity of 12 km s ^ { -1 } for N44 F 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 N44 J and N44 M are also compatible with the expected values , within the uncertainties .
We also report the discovery in N44 F 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 .