Long-Term Optical and Near-Infrared Spectroscopic Monitoring of ɛ Aurigae During the 2009-11 Eclipse

We present the results of a program to spectroscopically monitor the long-period (P ∼ 27 y) eclipsing binary ɛ Aurigae during the primary eclipse of 2009-11 with the ARC 3.5m telescope at Apache Point. Spectroscopic data from 3500-10000Å were obtained at a resolving power of R 38000 and from 0.9-2.5μm at R 3000 with a temporal cadence of approximately one week for the full duration of the eclipse. By noting the velocity centroids of certain weak metal lines (e.g., Na I D and K I 7699Å associated with the presumed optically-thick disk around the unseen secondary, we confirm a mid-eclipse epoch of HJD 2455384. The same lines indicate disk absorption with equivalent widths equal to or greater than the corresponding lines in the primary photosphere. The components of Hα and their evolution through the eclipse suggest the presence of weak ionized hydrogen, possibly distributed in a circumstellar ring or shell, and a separate, broad ionized component associated with the secondary disk in the form of a disk atmosphere or wind. Overall, our observations support the "consensus model'' of ɛ Aur, consisting of a 2 M⊙, F0 post-asymptotic giant branch primary and a dust-enshrouded, 6 M⊙ B8 dwarf. Variability of the profiles of certain lines such as Hα outside of eclipse encourages continued long-term synoptic monitoring of ɛ Aur between primary eclipses to better understand the circumstellar environment of the system.