Observations of the MG II lines near 2800 A from Copernicus

Abstract

Observations of the Mg II resonance doublet lines at 2795 and 2802 A, and their respective subordinate lines at 2797 and 2790 A, have been made for some 40 stars in the spectral region O8-B8 employing the Princeton telescope-spectrometer on the Copernicus satellite. Equivalentwidth measures, determined by a new approach, are in agreement with the recent theoretical predictions made by Snijders and Lamers for most of the stars. Deviations from the theoretical predictions have been found for the earliest spectral types, where the rotational velocity effects, discussed recently by Collins, appear to make the equivalent widths greater. Evidence of emission has been found in a few stars of earliest and latest spectral type& studied. Subject headings: early-type stars - emission-line stars - ultraviolet