Stokes IQUV mapping of α² CVn & other Ap stars using ESPaDOnS and NARVAL

¹ Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, Ontario, K7L 3N6 Canada
² Department of Astronomy and Space Physics, Uppsala University, 751 20, Uppsala, Sweden
³ Department of Physics, Royal Military College of Canada, PO Box 17000, Station “Forces”, Kingston, Ontario, K7K 7B4 Canada

Abstract

New spectral line polarisation observations of 7 bright Ap stars have been obtained with the ESPaDOnS and Narval high resolution spectropolarimeters (Silvester et al. 2012). The aim of this data set is produce a series of surface magnetic field and surface chemistry maps for these Ap stars. We present new magnetic maps for the Ap star α² CVn using these new data and the MDI inversion code INVERS10. α² CVn is the first Ap star to be observed during two separate epochs using high resolution phase resolved spectropolarimetric IQUV observations and as such allows us an insight into how stable the surface magnetic structure is over a decade timescale. We show that the new maps give a magnetic field structure consistent with the previous maps obtained by Kochukhov and Wade (2010) from lower quality MuSiCoS spectra taken a decade ago and that the field topology cannot be described by a dipolar or quadrupolar field.