Far-ultraviolet observations of the variable radio star LS I +61 303.

Abstract

One short wavelength spectrum, 1200-1950 A, and two long wavelength spectra, 1900-3200 A, have been obtained from IUE observations of the radio star LSI plus 61 deg 303 in September 1980. Assuming an E(BV) value of 0.9, as given by the rectification of the 2200 A absorption dip, the ultraviolet continuum is found to be fitted by a model atmosphere corresponding to a supergiant of subclass b and spectral type around B1.5, at a distance of about 4 kpc. From Sept. 27-29, 1980, the profile of the Mg II (2800 A) line changed substantially, with the 2700-3100 A continuum flux varying by about 25 percent.