# The complex magnetic field topology of the cool Ap star 49 Cam

## TL;DR

This study reveals that the cool Ap star 49 Cam possesses a highly complex magnetic field topology with significant toroidal components, challenging simpler models and providing new insights into magnetic structures in chemically peculiar stars.

## Contribution

First detailed magnetic and chemical surface maps of 49 Cam showing complex field structures with spherical harmonic modes up to l=3, including toroidal components, using high-resolution spectropolarimetric data.

## Key findings

- Magnetic field exhibits significant complexity with modes up to l=3.
- No consistent correlation between magnetic field and element abundance distributions.
- Complex magnetic structures are common in Ap stars across temperature ranges.

## Abstract

49 Cam is a cool magnetic chemically peculiar star which has been noted for showing strong, complex Zeeman linear polarisation signatures. This paper describes magnetic and chemical surface maps obtained for 49 Cam using the INVERS10 magnetic Doppler imaging code and high-resolution spectropolarimetric data in all four Stokes parameters collected with the ESPaDOnS and Narval spectropolarimeters at the Canada-France-Hawaii Telescope and Pic du Midi Observatory. The reconstructed magnetic field maps of 49 Cam show a relatively complex structure. Describing the magnetic field topology in terms of spherical harmonics, we find significant contributions of modes up to l=3, including toroidal components. Observations cannot be reproduced using a simple low-order multipolar magnetic field structure. 49 Cam exhibits a level of field complexity that has not been seen in magnetic maps of other cool Ap stars. Hence we concluded that relatively complex magnetic fields are observed in Ap stars at both low and high effective temperatures. In addition to mapping the magnetic field, we also derive surface abundance distributions of nine chemical elements, including Ca, Sc, Ti, Cr, Fe, Ce, Pr, Nd, Eu. Comparing these abundance maps with the reconstructed magnetic field geometry, we find no clear relationship of the abundance distributions with the magnetic field for some elements. However, for other elements some distinct patterns are found. We discuss these results in the context of other recent magnetic mapping studies and theoretical predictions of radiative diffusion.