Paschen is Partially Back

TL;DR

This paper discusses the partial Paschen-Back effect in magnetic Ap stars, highlighting deviations from Zeeman splitting, appearance of ghost lines, and implications for stellar magnetic diagnostics.

Contribution

It provides a theoretical overview and modeling of the partial Paschen-Back effect, revealing new spectral features and diagnostic possibilities in magnetic star observations.

Findings

Deviations from Zeeman splitting in strong magnetic fields

Appearance of ghost lines in stellar spectra

Wavelength shifts in Paschen-Back regime

Abstract

We present a discussion of the partial Paschen-Back (PB) effect in magnetic Ap stars. An overview of the theory is illustrated with examples of how splittings deviate non-linearly from the simple Zeeman picture; normally forbidden ``ghost lines'' appear in strong fields. Resulting asymmetric stellar Stokes profiles for a dipolar magnetic geometry are shown for the FeII 6149 line and it is established that PB lines may be subject to wavelength shifts. Modelling of Stokes profiles in the PB regime opens exciting new diagnostics.