  Context: Worldwide interest in the recent eclipse of epsilon Aurigae resulted
in the generation of several extensive data sets, including those related to
high resolution spectroscopic monitoring. This lead to the discovery, among
other things, of the existence of a mass transfer stream, seen notably during
third contact. Aims: We explored spectroscopic facets of the mass transfer
stream during third contact, using high resolution spectra obtained with the
ARCES and TripleSpec instruments at Apache Point Observatory. Methods: One
hundred and sixteen epochs of data between 2009 and 2012 were obtained, and
equivalent widths and line velocities measured, selected according to reports
of these being high versus low eccentricity disk lines. These datasets also
enable greater detail to be measured of the mid-eclipse enhancement of the He I
10830A line, and the discovery of the P Cygni shape of the Pa beta line at
third contact. Analysis: We found evidence of higher speed material, associated
with the mass transfer stream, persisting between third and fourth eclipse
contacts. We visualize the disk and stream interaction using SHAPE software,
and use CLOUDY software to estimate that the source of the enhanced He I 10830A
absorption arises from a region with log n = 10 (/cm3) and temperature of
20,000 K consistent with a mid B type central star. Results and Next Steps: Van
Rensbergen binary star evolutionary models are somewhat consistent with the
current binary parameters for the case of a 9 plus 8 solar mass initial binary,
evolving into a 2.3 and 14.11 solar mass end product after 35 Myr. Prior to the
next eclipse, it is possible to make predictions which suggest that continued
monitoring will help resolve standing questions about this binary.
