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Spectropolarimetry of the disk of epsilon Aurigae during the 2010 total eclipse

Published onJun 01, 2020
Spectropolarimetry of the disk of epsilon Aurigae during the 2010 total eclipse

We used spectro-polarimetry to pursue a detailed exploration of structure in HD 31964, the ε Aurigae system. As a single-line spectroscopic binary, it consists of a variable F-type supergiant star that is eclipsed by an accretion disk surrounding an unseen companion (probably a B-type star). A total eclipse occurs every 27 years and lasts for almost 2 years. We re-examined 50+ epochs of high dispersion optical spectro-polarimetric data from the ESPaDOnS instrument at the Canada-France-Hawaii Telescope, obtained before,during and after the most recent eclipse (2009-2011). Software was developed to optimize signal to noise, and to find the phase-dependent appearance of linear and circular polarization in spectral lines. Using a multi-point box kernel and requiring at least 6σ confidence above the coefficient of variation, we found the linear and circular polarization signal in these spectra. We present here spectral lines the wavelength region 461 to 468 nm as representative of intermediate strength lines in the spectra, and find a preponderance of circular polarization signal during early (2009) and late eclipse phases (2011), and a preponderance of the linear polarization signal during mid-eclipse (2010). Finally, we are grateful to the estate of William Herschel Womble for support of astronomy and astrophysics at the University of Denver.

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