Spectrally-polarized features of ε Aurigae: In and out of eclipse Graduate colloquium May 6, 2013 Spectrally-polarized features of ε Aurigae: In and out of eclipse Presented by Kathy Geise Thank you to Robert Stencel, University of Denver Nadine Manset, CFHT, Kamuela, Hawaii Canada-France-Hawaii telescope

Research goals Hypothesis Methods Broader impacts The eclipsing disk material originates from the visible star in this binary stellar system Methods Differential (time series) analysis of spectropolarimetric data before, during and after eclipse Broader impacts Unique “laboratory” to study a planet-forming disk and binary system evolution

Outline System overview Polarization refresher QU frame to stellar frame of reference ESPaDOnS observations (50+ epochs) Data rotation, radial velocity correction Automated spectral (absorption) line fitting Automatic Routine for line Equivalent widths in stellar Spectra (ARES) Sousa et al. (2007) Results: Polarized atomic species

Epsilon Aurigae, system overview Spectroscopic single lined binary Line polarization intrinsic to F star Additional spectropolarimetric features during eclipse AJC April 17, 2013

Stokes parameters Stokes vector Before I show you a sample of the data, I need to explain the Stokes parameters. Light can be represented by 4 parameters – One for the Intensity (all photons) – Two for linear polarization – One more for circular polarization • Those parameters are called Stokes parameters Often represented as a 4 vector Linear polarization is usually caused by scattering (on electrons, or dust grains) in an asymmetric envelope Circular polarization is usually caused by magnetic fields Stokes vector

Calculate %p and P.A. from Stokes parameters Bagnulo et al. (2009)

Stokes frame to stellar reference frame

Rotation angle Motion along a line with a position angle of 296.82 ± 6.85 degrees Rotate observations 27 degrees into the stellar frame Kloppenborg et al. 2010 AJC April 17, 2013

Rotation angle Simulated rotation

Rotated QU data Fe II Fe II rotated Rotation matrix from Code, A. & Whitney B. (1995)

Sousa et al. (2007)

20080825 Fitted with single Gaussian

IDL Routine Polarization peaks ≥ 4σ Hack line list ARES output file species

IDL Routine

IDL Routine

IDL Routine

Next Steps Expand line list to include full range of wavelengths All epochs Eclipse species? Analyze position angle Analyze scattering behavior when the F star is not uniformly eclipsed

Thank you This research used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency.