Is the Far-ultraviolet Flux of 21 Com Anticorrelated to its Optical Brightness?

Abstract

The comparison of 20 ultraviolet spectra of 21 Com taken over continuous 24 hr to the optical counts collected by the Fine Error Sensor on board IUE reveals that large variations observed shortwards of 1700 Å occur in anti-phase with the optical brightness for part of the observations but not all. In this data, the FUV flux at 1540 Å reaches a minimum at rotational phase 0.32 and increases afterwards while the FES counts continue to increase after this phase. The Fe ii resonance line at 1608.45 Å is Doppler shifted by 0.13 Å at phase 0.00 and −0.13 Å at phase of FUV flux minimum.