Stokes IQUV Magnetic Doppler Imaging of Ap stars II: Next Generation Magnetic Doppler Imaging of α2 CVn?

Abstract

We present updated magnetic field maps of the chemically peculiar B9p star α2 CVn created using a series of time resolved observations obtained using the high resolution spectropolarimeters ESPaDOnS and Narval. We compare these new magnetic field maps with the original magnetic Doppler imaging maps based on spectra recorded with the MuSiCoS spectropolarimeter and taken a decade earlier. These new maps are inferred from line profiles in all four Stokes parameters using the magnetic Doppler imaging code INVERS10. With the addition of new lines exhibiting Stokes IQUV signatures we have a unique insight into how the derived magnetic surface structure may be affected by the atomic lines chosen for inversion. We report new magnetic maps of α2 CVn created using strong iron lines (directly comparable to the published MuSiCoS maps), weak iron lines and chromium lines, all of which yield a magnetic field structure roughly consistent with that obtained previously. We then derive an updated magnetic structure map for α2 CVn based on the com-plete sample of Fe and Cr lines, which we believe to produce a more representativ