Disk Origin Narrow Metallic Absortion Lines Observed during the 2009–2011 Eclipse of ∊ Aurigae

Abstract

Frequent high-resolution spectroscopic observations of $\epsilon$ Aur during the 2009–2011 eclipse revealed temporal appearances of low-excitation absorption lines of neutral iron peak elements. Several 0 eV lines of Fe I were detected near the end of the first half of the eclipse. They had migrated toward shorter wavelength, became much strong after the third contact, and then disappeared after the fouth contact. Curiously, the widths of these temporal absorption lines became broader for about a 100-d period just before the third contact. The radial velocity measured for these lines follows that of the K I line at 7699 Å, implying that these lines originated in a rotating disk around the secondary star, which occulted the primary star. Weak and sharp absorption lines of low excitation neutral metals, such as Sc I, Ti I, V I, Cr I, and Mn I, were observed only for a short period from the third contact to the fourth contact, and they were all blue-shifted by $\sim$ 40 km s$^{-1}$. These observations show that the rotating disk around the secondary star is not axially symmetric, but suggest that a clump of cool gas concentrated in a region observed projected on the primary star near at the end of the eclipse.