Physical structure of small Wolf-Rayet ring nebulae

We have selected the seven most well-defined Wolf-Rayet (WR) ring nebulae i n the Large Magellanic Cloud (LMC), Br 2, 10, 13, 40a, 48, 52, and 100, to study their physical nature and evolutionary stages. New CCD imaging and ec helle observations have been obtained for five of these nebulae; previous p hotographic imaging and echelle observations are available for the remainin g two nebulae. Using the nebular dynamics and abundances, we find that the Br 13 nebula is a circumstellar bubble, and that the Br 2 nebula may repres ent a circumstellar bubble merging with a fossil main-sequence interstellar bubble. The nebulae around Br 10, 52, and 100 all show influence of the am bient interstellar medium. Their regular expansion patterns suggest that th ey still contain significant amounts of circumstellar material. Their nebul ar abundances would be extremely interesting, as their central stars are WC 5 and WN3-WN4 stars whose nebular abundances have not been derived previous ly. Intriguing and tantalizing implications are obtained from comparisons o f the LMC WR ring nebulae with ring nebulae around Galactic WR stars, Galac tic LBVs, LMC LBVs, and LMC BSGs; however, these implications may be limite d by small-number statistics. A SNR candidate close to Br 2 is diagnosed by its large expansion velocity and nonthermal radio emission. There is no in dication that Br 2's ring nebula interacts dynamically with this SNR candid ate.