Literature Review: "Epsilon Aurigae. Historical Sketch"

Literature Review

As part of my Ph.D. dissertation, I have been conducting a comprehensive review of literature on Epsilon Aurigae.  Each month I will select one paper to review or discuss, adding relevant information from more recent literature when necessary.

This month I have elected to summarize and discuss one paper published in the NASA conference proceedings during the 1985 workshop on Epsilon Aurigae.  This paper, entitled “Epsilon Aurigae. Historical Sketch,” was written by Frank Bradshaw Wood.  Frank was a professor at the University of Florida who organized the first photometric campaign of Epsilon Aurigae during the 1955 eclipse.  His paper provides an excellent short review of the historical research on eps Aur starting in the early 1800s and sets the stage for the remaining contents in the conference proceedings.

Wood attributes discovery of the variability of Epsilon Aurigae is attributed to an amateur astronomer named J.M. Fritsch who,  in 1824, discussed observing a minimum in the light from eps Aur in 1821.  Although follow-up observations were conducted, few publications resulted until H. Ludendorff (1903, 1912) collected the previous 70 years of unpublished data and produced a detailed discussion of the photometric observations.  These papers are written in German, but the Epsilon Aurigae campaign website contains translations of both papers.  It was about this time that a 0.3 magnitude out-of-eclipse variation was discovered by Shapley (1928).  Present estimates place the out-of-eclipse variations at 0.1 magnitude in V-band.  It was also in 1928 that Miss Payne analyzed the spectra of eps Aur and concluded that the star was “a typical if extreme supergiant,” an interpretation that still holds today.

During the '30s and '40s, the number of publications had subsided, but some work was still completed.  Spectrophotometry was conducted by Hall (1941, 1942) and egress equivalent widths were measured by Wright and van Dien (1949).  The then forthcoming eclipse in 1955 brought with it so many papers that Wood summarizes it as “too extensive to give in detail.”  Wood coordinated the first campaign on eps Aur, focusing on photometry.  Unfortunately, much photometry from this period was lost because it was not published.  Spectroscopic and photometric measurements from this time period lead to the Huang-Wilson model for eps Aur (see Huang 1965, 1974 and Wilson, 1971) consisting of a F-supergiant primary star with a secondary companion that is allegedly a disk-like object.  Although Huang and Wilson argue for either a physically thick or physically thin disk respectively, the concept of a disk-like object passing in front of the primary is still used as the dominant model for eps Aur today.

For further reference, please refer to:

“Epsilon Aurigae. Historical Sketch”
Frank B. Wood
http://adsabs.harvard.edu/abs/1985NASCP2384....1W
http://mysite.du.edu/~rstencel/NASAcp2384.pdf