2 RING NEBULAE AROUND BLUE SUPERGIANTS IN THE LARGE-MAGELLANIC-CLOUD

Ring nebulae are often found around massive stars such as Wolf-Rayet s tars, OB and Of stars and Luminous Blue Variables (LBVs). In this pape r we report on two ring nebulae around blue supergiants in the Large M agellanic Cloud. The star Sk-69 279 is classified as O9f and is surrou nded by a closed shell with a diameter of 4.5 pc. Our echelle observat ions show an expansion velocity of 14 km s(-1) and a high [NII]lambda 6583 Angstrom/H alpha ratio. This line ratio suggests nitrogen abundan ce enhancement consistent with those seen in ejectas from LBVs. Thus t he ring nebula around Sk-69 279 is a circumstellar bubble. The star Sk -69 271, a B2 supergiant, is surrounded by an Ha: are resembling an ha lf shell. Echelle observations show a large expanding shell with the a re being part of the approaching surface. The expansion velocity is si milar to 24 km s(-1) and the [NII]lambda 6583 Angstrom/H alpha is not much higher than that of the background emission. The lack of nitrogen abundance anomaly suggests that the expanding shell is an interstella r bubble with a dynamic age of 2 x 10(5) yr.