The eclipse of epsilon Aurigae in the ultraviolet.

Abstract

Ultraviolet low-resolution spectra of Epsilon Aurigae (F0Ia +) have been taken with IUE during the partial and total phase of the present eclipse; they are compared with a set of corresponding pre-eclipse spectra. The following conclusions are derived. A hot component, dominant in far UV, is associated with the extended body that eclipses the primary. Far UV variability, observed also out of eclipse, may originate from this component or from the extended object itself; possible mechanisms are suggested. The eclipsing body cannot be made of dust, since no deepening of the lambda 2200 feature is observed during the eclipse. Electron scattering is thus supposed to be responsible for the grayness of the eclipse; an additional contribution by blending of absorption lines in the eclipsing body is possible. The system is embedded in a large rarefied gaseous envelope, which is responsible for the O I lambda 1304 emission, remaining practically unaffected by the eclipse.