Stokes IQUV magnetic Doppler imaging of Ap stars – I. ESPaDOnS and NARVAL observations†

摘要: In this paper we describe and evaluate new spectral line polarization observations obtained with the goal of mapping surfaces magnetic Ap stars in great detail. One hundred complete or partial Stokes IQUV sequences, corresponding to 297 individual polarized spectra, have been for seven bright using Echelle SpectroPolarimetric Device Observation Stars (ESPaDOnS) NARVAL high-resolution spectropolarimeters. The targets span a range masses from approximately 1.8 3.4 M circle dot, rotation periods 2.56 6.80 ?d maximum longitudinal field strengths 0.3 over 4 kG. For three stars, dense phase coverage sampling entire rotational cycle. These data sets are suitable immediate chemical abundance surface Doppler imaging. remaining four has obtained, additional will be required order map these stars. median signal-to-noise ratio reduced is 700 per km?s-1 pixel. Spectra all show V Zeeman signatures essentially lines, most clear QU many lines. provide vastly improved set compared previous generations terms ratio, resolving power measurement uncertainties. Measurement demonstrates that internally consistent within computed uncertainties typically at 50-100 sigma level. Data also shown excellent agreement published qualitative predictions structure models. addition providing foundation next generation maps study establishes performance stability ESPaDOnS spectropolarimeters during period 2006-2010.