Far-UV variability of theta CrB in 1985-86 : a progression toward higher velocities.

Abstract

New far UV observations of θ CrB obtained with the IUE in 1985 - 1986 are presented. They show that the far UV spectrum of that star has usually continued to exhibit the apparently low excitation state observed from mid-84 to mid-85. However, the C IV resonance lines are occasionally conspicuous and exhibit an even higher outflow velocity than during the preceding epochs of variation, when the C IV resonance lines were strong and frequently present. Such a long term progression toward higher expansion velocities has not yet been observed in any other Be star.