High cadence measurement of neutral sodium and potassium absorption during the 2009-2011 eclipse of epsilon Aurigae

TL;DR

This study presents high-cadence spectroscopic observations of epsilon Aurigae during its 2009-2011 eclipse, revealing detailed absorption line variations that suggest complex structure within the eclipsing object.

Contribution

It provides the first detailed, time-resolved analysis of specific absorption lines during the eclipse, highlighting structural features of the eclipsing body.

Findings

Absorption in KI 7699Å increased 3 months before eclipse

Excess absorption shows step-like changes during ingress and egress

F star is fully obscured at Na D wavelength during eclipse

Abstract

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 0.65{\AA} 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 7699{\AA}, Na D and Mg II 4481{\AA} lines. Absorption started increasing in the KI 7699{\AA} 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 7699{\AA} 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.