Far Ultraviolet Spectroscopic Explorer Atlas of OB Stars in the Magellanic Clouds

Abstract

An atlas of the 900-1200 {Å} region in the spectra of 47 OB stars inthe Large and Small Magellanic Clouds, observed at high resolution bythe Far Ultraviolet Spectroscopic Explorer (FUSE), is presented anddiscussed. The systematic trends in the numerous stellar-wind featuresin this region, some from species (and ionizations) not represented atlonger wavelengths, are charted as a function of the optical spectraltypes. The FUSE sample is by far the most powerful to date for thatpurpose. A special effort has been made to verify the spectral types ofall stars included in the atlas, in a number of cases with new opticalobservations that are also illustrated, to avoid uncertainties from thatsource in the stellar-wind trends. A new O2 star has been found in theprocess. Most of these stars have been previously observed at longerultraviolet wavelengths by the Hubble Space Telescope and in the opticalfrom the ground with high-resolution, digital instruments; thus verycomprehensive physical modeling of these OB atmospheres and winds nowbecomes possible. This atlas will serve as a guide to the FUSEMagellanic Cloud OB database for that purpose. The Magellanic Cloudsample provides a very important complement to the FUSE database ofGalactic OB counterparts (Pellerin et al. 2002), both because the lowerextinction and interstellar H_{2} absorption toward the Cloudstars allow a much clearer view of the stellar spectra below 1100{Å}, and because of the metallicity differences among the threegalaxies. In particular, most wind features in the SMC spectra are seento be significantly weaker than those in the LMC at the same spectraltypes. Based on observations made with the NASA-CNES-CSA Far UltravioletSpectroscopic Explorer. FUSE is operated for NASA by The Johns HopkinsUniversity under NASA contract NAS5-32985. Also based in part onobservations collected at the European Southern Observatory in program67.D-0238, and at the Australian National University/Siding SpringObservatory.