High cadence measurement of neutral sodium and potassium absorption during the 2009-2011 eclipse of epsilon Aurigae
The results of a spectroscopic survey of epsilon Aurigae during eclipse using a network of small telescopes are presented. The spectra have a resolution of 0.35 to 0.65Å and cover the period 2008 to 2012 with a typical interval of 4 days during eclipse. This paper specifically covers variations in the K I 7699Å, Na D and Mg II 4481Å lines. Absorption started increasing in the KI 7699Å line 3 months before the eclipse began photometrically and had not returned to pre eclipse levels by the end of the survey March 2012, 7 months after the brightness had returned to normal outside eclipse levels. The contribution of the eclipsing object to the KI 7699Å line has been isolated and the data show the excess absorption increasing and decreasing in a series of steps during ingress and egress. This is interpreted as an indication of structure within the eclipsing object. The F star is totally obscured by the eclipsing object at the Na D wavelength during eclipse. The radial velocity of the F star and the mean and maximum radial velocity of the eclipsing material in front of the F star at any given time have been isolated and tracked throughout the eclipse. The quasi-periodic variations seen in the F star RV outside eclipse continued during the eclipse. It is hoped that these results can be used to constrain proposed models of the system and its components.