The anomalous atmospheric structure of the strongly magnetic Ap star HD166473

Abstract

High resolution spectropolarimetric observations of the strongly magnetic, super-slowly rotating rapidly oscillating Ap star HD166473 are used to investigate the implications of the presence of a variable strong magnetic field on the vertical and surface horizontal distribution of various chemical elements. The analysis of the calculated LSD Stokes $I$ and $V$ profiles confirms the previously reported detection of non-uniform horizontal surface distribution of several chemical elements. To test the vertical abundance stratification of iron peak and rare earth elements, magnetic field measurements were carried out using spectral lines of these elements belonging to neutral and ionised stages. We find clear indication of the existence of a relation between the magnetic field strength and its orientation and vertical element stratification: magnetic field values obtained for elements in different stages close to the magnetic equator are rather similar whereas the dispersion in field strengths is remarkably large in the regions close to magnetic field poles. At the phases of negative and positive extrema the mean longitudinal field strength determined from the analysis of the REE lines is usually stronger than when using Fe and Cr. The strongest mean longitudinal magnetic field, up to $-$4160$\pm$226 G, is detected using the La II line list at the negative extremum, followed by the measurements using the Pr III lines with $⟨B_z⟩$=$-$3740$\pm$343 G and the Ce II lines with $⟨B_z⟩$=$-$3372$\pm$247 G. The strongest mean longitudinal magnetic field of positive polarity, up to 3584$\pm$354 G is detected using the Pr III lines, followed by the measurement $⟨B_z⟩$=2517$\pm$249 G using the Ce II lines.

Accepted to be published in MNRAS

References in corpus (2)

• Non-LTE line formation for Pr II and Pr III in A and Ap stars
• The 10.5 year rotation period of the strongly magnetic rapidly oscillating Ap star HD 166473

Cited by in corpus (6)

• Constraining atmospheric parameters and surface magnetic fields with $\text{ZeeTurbo}$: an application to SPIRou spectra
• Are magnetic fields universal in O-type multiple systems?
• The rapidly oscillating Ap star gamma Equ: linear polarization as an enhanced pulsation diagnostic?
• Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879
• The magnetic field of the stripped primary in the upsilon Sgr system, a member of the rare class of hydrogen-deficient binaries
• Magnetic field measurements of sharp-lined Ap stars