THE CHEMICAL-COMPOSITIONS OF 3 MAIN-SEQUENCE B-TYPE STARS IN THE LARGE MAGELLANIC CLOUD

High-resolution observations of three B-type main-sequence stars in th e Large Magellanic Cloud (LMC) have been obtained with the UCL echelle spectrograph on the 3.9-m Angle-Australian Telescope. These spectra a nd IUE low-resolution spectroscopic data have been analysed using LTE model-atmosphere techniques, to derive stellar atmospheric parameters and chemical compositions. As these stars lie on the hy drogen burning main-sequence, their surface abundances should reflect those of the p resent-day interstellar medium. From a differential analysis of LH 104 -24 and PS 34-16 performed relative to the Galactic B-type stars tau S co and gamma Peg, we conclude that there exists a general heavy-elemen t underabundance of similar to 0.3 dex within the LMC, but there is so me evidence to suggest that these stars possess different oxygen and s ilicon abundances. The third star, PS 34-144, exhibits chemical anomal ies, with a helium underabundance of 0.5 dex and a mean metal deficien cy of approximately 0.8 dex. We classify this object as a Helium-weak star that is a member of the LMC. However, as additional processes suc h as diffusion may have occurred in its atmosphere, we do not believe that element abundances derived for PS 34-144 to be representative of the progenitor interstellar material.