The Ultraviolet Spectra of Alpha Draconis Recorded by IUE

Abstract

Abstract The comparison of all unpublished archival IUE spectra of the bright spectroscopic binary α Draconis shows that the far-ultraviolet flux has remained constant over the 18 yr of the mission, except possibly for one spectrum which shows significantly less flux below 1800 Å. The Si ii lines undergo large radial velocity variations which are due to the orbital motion of α Draconis around the center of mass of the system. The far-UV energy distribution of α Draconis has more flux than that of Sirius A (α CMa) which reflects the weaker abundances of the metals in α Draconis compared to Sirius A.